Whey protein: a real effect on muscle, and a small one

Whey protein makes muscle build protein faster after exercise, and the gains it adds over months are small. A meta-analysis of randomized trials in healthy adults found that whey with exercise raised the rate of muscle protein synthesis by a large standardized effect, Hedges g 1.24 (95% CI 0.71 to 1.77), rising with doses from 10 g to 60 g. That is a short-term marker taken from muscle biopsies, mostly in men. In 261 young adults doing resistance training, a meta-analysis of 12 studies found whey raised bench press by 8.87 and squat by 9.60, in units the abstract does not name, with no significant gain in lean body mass. In older people with sarcopenia, whey added to resistance training raised handgrip strength by 5.1 lb (95% CI 0.02 to 10; metric: 2.31 kg, 0.01 to 4.6) across 7 trials with 591 people, below the size that counts as clinically meaningful, at low to very low certainty. In women, 13 trials found 0.82 lb (0.37 kg) more lean mass (95% CI 0.06 to 0.67), mostly in trials that also cut calories. The gain disappeared when only trials with resistance training were pooled. The EU refused the claim that whey taken after resistance exercise supports muscle growth.

Every statement here is tied to a source. The badge says what kind of evidence stands behind it: A is a meta-analysis or systematic review, E is the position of an expert body without its own analysis. How we verify →

We have no USDA entry for whey protein itself in this cohort. The evidence below stands on published studies rather than on a composition table, and we would rather say that than show you a number for something else.

How much is actually in it

USDA lists whey protein powder isolate at 58 g protein, 3.49 ug vitamin B12 and 1.16 mg copper per 3.5 oz (100 g). — one USDA SR Legacy record Evidence E source
Per 100 g: protein 58.14 g (116% DV); vitamin B12 3.49 ug (145% DV); copper 1.163 mg (129% DV)

What a real portion looks like

A meta-analysis of 15 RCTs found whey with exercise raised muscle protein synthesis (Hedges g 1.24), dose-dependently between 10 and 60 g. — healthy adults in 21 RCTs, 15 meta-analyzed (n = 21 RCTs) Evidence A source
Myofibrillar FSR Hedge's g = 1.24 (0.71-1.77); 1.3 to 1.6-fold after exercise; dose-dependent 10-60 g
In the US dietary survey database, one scoop of whey protein powder weighs about 20 g and a tablespoon 10 g. — FNDDS record Nutritional powder mix (EAS Whey Protein Powder) Evidence E source
1 scoop 20 g; 1 tablespoon 10 g; quantity not specified 39 g

What your body absorbs

Pooled data from 18 RCTs show about 57% of whey protein phenylalanine reaches the blood within 5 hours, more than casein (45%) but less than milk protein (65%), and less in older adults. — 18 randomized controlled trials with a total of 602 participants (n = 602) Evidence A source
Whey 57% +/- 10%, casein 45% +/- 11%, milk 65% +/- 13%; older 45% vs young 51%

What it does to your health

A meta-analysis of 62 randomized trials of animal-source protein in mothers and young children found that supplementing mothers in pregnancy raised birth weight by about 60 g. — mothers, preterm infants and young children in 62 RCTs of animal protein supplementation across 5 continents (n = over 30,000 (all 62 trials)) Evidence A source
Maternal supplementation birth weight +0.13 lb (0.06 kg)
In young adults aged 18 to 30 who trained, whey did not change lean body mass in 12 studies, though it improved bench press by about 8.9 and squat by about 9.6 (units not stated). — trained or untrained adults aged 18 to 30 in resistance training, whey or soy concentrate or isolate (n = 261) Evidence A source
Lean body mass no significant effect; bench press MD 8.87 (95% CI 5.95 to 11.79); squat MD 9.60 (5.61 to 13.60)
When whey was compared only with equal-calorie placebo in 8 trials of active people, it did not change fat-free mass, though fat mass fell by about 2.1 lb (0.96 kg). — healthy athletes and physical activity practitioners, about 64.5 days of training (n = 246) Evidence A source
Fat-free mass no significant effect in any scenario (p > 0.05); fat mass WMD -2.1 lb (-3 to -1.2; metric: -0.96 kg, -1.37 to -0.55)
Over 9 months of supervised training, untrained adults taking whey gained 7.3 lb (3.3 kg) of lean mass against 5.1 lb (2.3 kg) on a carb drink and 4 lb (1.8 kg) on soy. — non-resistance-trained men and women, 96 workouts, isocaloric daily supplements (n = 63) Evidence B source
Lean body mass gain whey 3.3 +/- 1.5 kg, carbohydrate 2.3 +/- 1.7 kg, soy 1.8 +/- 1.6 kg (p < 0.05); daily protein 1.4 vs 1.1 g/kg
Across 49 trials of protein supplements with weight training, gains in lean mass stopped at a total protein intake of about 1.6 g per kg a day, so extra shakes beyond that add nothing. — healthy adults in 49 randomized trials of protein supplementation with resistance training of 6 weeks or more (n = 1863) Evidence A source
No further fat-free mass gain above 1.62 g/kg/day total protein; overall FFM +0.66 lb (0.2 to 1.1; metric: 0.30 kg, 0.09 to 0.52)
In the same 2024 meta-analysis, whey protein improved lower body strength only when combined with resistance exercise, by a small amount. — older adults in 11 RCTs combining whey protein with resistance exercise (n = 11 trials) Evidence A source
Lower body strength SMD 0.25 (95% CI 0.05 to 0.45), I2 0%
A 2023 meta-analysis of 7 trials with 591 older people with sarcopenia found whey added to resistance training gave a small muscle gain, at low to very low certainty. — sarcopenic adults aged 60 or older doing resistance exercise training with whey protein versus training with or without placebo (n = 591) Evidence A source
Appendicular muscle index SMD 0.24 (95% CI 0.05 to 0.42); handgrip +5.1 lb (0.02 to 10; metric: 2.31 kg, 0.01 to 4.6), below the minimally important clinical difference
A 2024 network meta-analysis of 78 trials ranked whey first among six protein sources for adding muscle mass on top of resistance training in middle-aged and older adults. — untrained community-dwelling, hospitalized or institutionalised middle-aged and older adults doing resistance training (n = 5272) Evidence A source
Whey plus resistance training muscle mass SMD 1.29 (95% CI 0.96 to 1.62), SUCRA 0.86; handgrip SMD 1.46 (0.92 to 2.00)
A 2025 meta-analysis of 150 trials across adults found milk protein supplements, whey included, added about 0.88 lb (0.4 kg) of lean body mass. — adults in 150 RCTs of milk protein, casein or whey supplementation (n = 150 trials) Evidence A source
Lean body mass WMD 0.9 lb (95% CI 0.42 to 1.4; metric: 0.41 kg, 0.19 to 0.62); fat-free mass 1.5 lb (0.88 to 2.1; metric: 0.67 kg, 0.40 to 0.94); no considerable effect on muscle mass
A 2018 meta-analysis of 9 RCTs in overweight and obese adults found whey groups lost about 1.3 lb (0.6 kg) more weight and 2.4 lb (1.1 kg) more fat than controls. — individuals who are overweight or obese in RCTs comparing whey protein to placebo or control (n = 9 trials) Evidence A source
Body weight MD 1.2 lb (95% CI 0.66 to 1.8; metric: 0.56 kg, 0.30 to 0.81), fat mass MD 2.5 lb (1.7 to 3.2; metric: 1.12 kg, 0.77 to 1.47) and lean mass MD 1.7 lb (1.3 to 2.1; metric: 0.77 kg, 0.59 to 0.96), all favoring whey
A 2025 meta-analysis of 150 RCTs of milk proteins, whey included, found 1.5 lb (0.66 kg) less fat and 0.88 lb (0.4 kg) more lean mass but no change in body weight or BMI. — randomized controlled trials of milk protein, casein or whey supplementation (n = 150 trials) Evidence A source
Fat mass WMD -1.5 lb (95% CI -2 to -0.9; metric: -0.66 kg, -0.91 to -0.41); lean body mass +0.9 lb (0.41 kg); waist -0.27 in (-0.69 cm); no considerable effect on body weight or BMI
A meta-analysis of 10 RCTs with 596 adults found whey added 2 lb (0.9 kg) of lean mass but did not change body mass, fat mass or body fat percentage. — adults in randomized clinical trials of whey or soya protein supplementation (n = 596) Evidence A source
Lean body mass WMD 2 lb (95% CI 0.33 to 3.7; metric: 0.91 kg, 0.15 to 1.67); no significant change in body mass, fat mass or body fat percentage
In a 12-week RCT of 70 overweight and obese adults, whey isolate did not change body composition compared with casein or glucose, though fasting lipids and insulin fell. — overweight and obese men and women, mean age 48.4 years and mean BMI 31.3, randomized to whey, casein or glucose for 12 weeks (n = 70) Evidence B source
No significant change in body composition; lower triglycerides, total and LDL cholesterol and fasting insulin with whey
A meta-analysis of 21 RCTs found whey protein combined with exercise lowered LDL cholesterol by 5.38 units (unit not named), with no relevant effect on blood pressure. — adults in 21 RCTs (n = 21 RCTs) Evidence A source
LDL MD -5.38 (95% CI -8.87 to -1.88) with exercise; total cholesterol MD -8.58 (-14.32 to -2.83); no clinically relevant effect on BP or HOMA-IR
A meta-analysis of 20 RCTs with 1,638 adults found whey protein lowered triglycerides by 12 mg/dL and raised HDL by 2.6 mg/dL, without changing LDL. — 20 randomized clinical trials (n = 1638 participants) (n = 1638) Evidence A source
TG WMD -12.21 mg/dL (-20.16, -4.26); HDL-c WMD +2.59 mg/dL (1.11, 4.07); no significant effect on TC or LDL-c
In young adults doing resistance training, a meta-analysis of 12 studies found whey raised bench press by 8.9 and squat by 9.6 units without increasing lean body mass. — 12 studies with 261 participants aged 18-30 years engaged in RET (n = 261) Evidence A source
Bench press MD 8.87 (5.95-11.79); squat MD 9.60 (5.61-13.60); no significant effect on LBM

Safety, limits and interactions

In the same 62-woman trial, daily whey protein through the third trimester caused no more stomach or bowel side effects and no difference in obstetric outcomes than placebo. — women with gestational diabetes given 20 g whey protein isolate or placebo daily in the third trimester (30 and 25 completers) (n = 55) Evidence B source
No between-group differences in gastrointestinal side effects or obstetrical outcomes
In that trial, newborn birthweight did not differ between the whey and placebo groups, while cord blood C-peptide was non-significantly higher with whey. — newborns of women with gestational diabetes given whey protein (30) or placebo (25) in the third trimester (n = 55) Evidence B source
Birthweight 3461 g vs 3611 g, difference -150 g (95% CI -399 to 100), p=0.235; cord blood C-peptide p=0.093
A Cochrane review found high-protein supplements in pregnancy raised the risk of a small-for-gestational-age baby by 58% in one trial of 505 women and concluded they may harm the fetus. — pregnant women given high-protein supplementation, one trial (n = 505) Evidence A source
Small for gestational age RR 1.58 (95% CI 1.03 to 2.41), moderate-quality evidence
In the same 4-week whey trial in 100 older adults, no serious side effects occurred, and 2 people on whey stopped because of mild nausea. — adults aged 60 and over with functional constipation, 15 g a day dried whey vs placebo (n = 100) Evidence B source
No serious adverse events; 2 withdrawals for mild nausea on whey, 1 for abdominal pain on placebo
In a randomized crossover trial in 13 runners, a 0.4 g/kg whey shake before a 10 km run raised bloating severity versus 0.15 g/kg, but no other gut symptom. — recreational runners (8 women, 5 men), whey shake 60 minutes before a 10 km treadmill run at 85% race pace (n = 13) Evidence B source
Bloating severity 1.23 vs 0.54 (p = 0.03); total symptoms not affected by protein dose (p = 0.85)
In an 8-week RCT in 67 nursing home residents, high-protein drinks (18 to 20 g protein) were well tolerated, and two versions differed only in flatulence. — nursing home residents needing oral nutritional supplements; 6.8 fl oz (200 ml) (20 g protein) vs 4.2 fl oz (125 ml) (18 g protein) high-protein drink daily for 8 weeks (n = 67) Evidence B source
Stool frequency, consistency and gut symptoms: no clinically relevant differences between versions, except flatulence
In the same 8-week trial in 67 nursing home residents, daily high-protein drinks did not affect kidney function, including in people with stage 3 chronic kidney disease. — nursing home residents, including stage 3 chronic kidney disease, 18 to 20 g protein drink daily for 8 weeks (n = 67) Evidence B source
No difference in eGFR or urinary albumin/creatinine ratio between groups or over time
A systematic review found only 11 documents on whey harms, and most tied kidney and liver effects to chronic heavy use. — experimental and randomized studies of whey protein supplementation (n = 11 documents) Evidence C source
Harms linked to chronic, excessive use: kidney and liver, also acne and microbiota changes
The US NIDDK lists whey among food label words that mean a product contains lactose, which matters for people with lactose intolerance. — people with lactose intolerance reading food labels Evidence E source
Whey named as a lactose-containing ingredient
In adults without kidney disease, high-protein diets raised estimated kidney filtration (SMD 0.39) without changing creatinine in 22 trials, but long-term effects are unknown and people with kidney disease were excluded. — adults without chronic kidney disease, high-protein diets of about 25-35% of energy or at least 2.0 g/kg/day (n = 1044) Evidence A source
EGFR SMD 0.39 (0.09 to 0.69); serum creatinine SMD 0.08 (-0.09 to 0.25; 19 trials, n=1044)
Whey is a milk protein, and the US FDA lists milk among the nine major food allergens, so whey powders are not for people with cow's milk allergy. — people with food allergy in the United States (n = -) Evidence E source
Milk listed as a major food allergen requiring declaration on labels
In a 12-week trial of 39 older adults with type 2 diabetes doing resistance training, whey did not add strength beyond training and slightly raised blood urea. — older adults with non-insulin-dependent type 2 diabetes in resistance training, 33 g whey twice a week (n=19) or placebo (n=20) (n = 39) Evidence B source
Strength gains in both groups, whey not superior; blood urea slightly higher with whey (p = .05) but within normal limits
A 2018 meta-analysis of 28 trials with 1358 healthy adults found higher-protein diets did not change kidney filtration over time. — adults without kidney disease in RCTs comparing higher protein (at least 1.5 g/kg or 100 g/day) with normal or lower protein intake (n = 1358) Evidence A source
Change in GFR SMD 0.11 (95% CI -0.05 to 0.27), not different between diets
In people with chronic kidney disease, a 2018 meta-analysis of 19 trials with 2492 patients found a low-protein diet cut the odds of kidney failure by about 40%. — adults with chronic kidney disease in RCTs comparing protein intake levels for at least 24 weeks (n = 2492) Evidence A source
Kidney failure OR 0.59 (95% CI 0.41 to 0.85); end-stage renal disease OR 0.64 (0.43 to 0.96)
In a 6-month double-blind trial of 49 young men with mild to moderate acne, 30 g of whey a day did not worsen acne lesions compared with a non-whey supplement. — men with mild to moderate facial and/or truncal acne, mean age about 20 years (n = 49) Evidence B source
Facial total lesions MD -5.99 (95% CI -13.18 to 1.19), truncal -2.18 (-11.83 to 7.48); noninferior
In a Jordanian case-control study of 201 young men at gyms, 47% of those with acne took whey supplements against 27.7% of those without. — male teenagers and young adults attending fitness centers in Irbid, Jordan (n = 201) Evidence C source
Whey use in previous 3 months 47% in acne cases vs 27.7% in controls (p = 0.0047), significant after multivariate analysis
In 5 teenage athletes, acne that began after starting whey cleared in 4 once they stopped, and returned in 1 who restarted it. — male patients aged 14 to 18 years using whey protein supplements (n = 5) Evidence C source
Lesions cleared in 4 of 5 after stopping whey; flare on rechallenge in 1
A systematic review found only 11 documents on whey harms, and most tied kidney and liver effects to chronic heavy use. — experimental and randomized studies on adverse effects of whey protein supplements (n = 11 documents) Evidence C source
Kidneys and liver the main organs affected with chronic and abusive use; also acne, aggression and microbiota changes reported
No upper intake level has been set for protein because the data were insufficient. The US reference values put the RDA at 0.8 g per kg a day and the acceptable range at 10 to 35 percent of calories. — general healthy population covered by the US and Canadian DRIs Evidence E source
No tolerable upper intake level for protein (data insufficient); RDA 0.8 g/kg/day; AMDR 10 to 35 percent of calories
The US kidney institute (NIDDK) says some people with chronic kidney disease may need moderate amounts of protein so waste does not build up in the blood, while people on dialysis may need more, and too little protein can lead to malnutrition. — people with chronic kidney disease, including people on dialysis Evidence E source
Some people with CKD may need moderate protein so waste does not build up; people on dialysis may need more; too little risks malnutrition
The FDA says the allergen labeling law, which requires labels to name the food source of every major allergen, applies to most packaged foods and includes dietary supplements. — US consumers with food allergy; packaged foods and dietary supplements Evidence E source
Milk is a major food allergen; FALCPA labeling applies to most packaged foods and includes dietary supplements
A 2022 USDA evidence scan notes reports of higher urinary calcium with 27 g whey a day and of acne flare-ups with high protein intake, from systematic reviews. — evidence scan of reviews on high protein intake Evidence E source
Increased urinary calcium and decreased urinary pH with 27 g/day whey for 3 days; acne exacerbation at high protein for 60 days

What people believe that the data does not support

A Cochrane review of 5 trials with 952 women found that avoiding foods like cow milk in pregnancy is unlikely to prevent allergy in the child and may harm maternal or fetal nutrition. — pregnant women at high risk of having an atopic child, prescribed avoidance of cow milk, egg or other antigens (n = 952) Evidence A source
No protective effect on atopic eczema in the first 18 months; slightly lower gestational weight gain with the restricted diet
A 2020 USDA systematic review judged with moderate evidence that cutting cow milk products in pregnancy does not reduce the child's risk of eczema. — pregnant women and their children, RCTs and cohort studies Evidence C source
Moderate evidence: restricting cow milk products in pregnancy does not reduce child atopic dermatitis risk; evidence for food allergy insufficient
WHO does not recommend high-protein supplementation for pregnant women in undernourished populations to improve maternal and perinatal outcomes. — pregnant women in undernourished populations Evidence E source
Recommendation against high-protein supplementation (WHO ANC guideline 2016)
A 2026 network meta-analysis of 19 RCTs ranked fruit-based foods first for constipation severity, ahead of fiber supplements and placebo, with moderate certainty. — people with functional constipation in randomized trials of dietary interventions (n = 19 trials) Evidence A source
Fruit-based foods superior to fiber supplements and placebo for severity (moderate certainty); no protein intervention among the ranked options
For constipation, the US NIDDK advises eating enough fiber and drinking plenty of liquids, and avoiding low-fiber foods such as meat and processed foods. — people with constipation Evidence E source
Fiber 22 to 34 g a day for adults, depending on age and sex
Europe allows labels to say that protein contributes to a growth in muscle mass, a claim for protein in general and not for whey as such. — - (n = -) Evidence E source
Claim authorized for protein
According to the PROT-AGE study group, people over 65 should get at least 1.0 to 1.2 g of protein per kg of body weight a day to keep muscle and function. — older people over 65 years Evidence E source
At least 1.0-1.2 g/kg/day; at least 1.2 g/kg/day if exercising; 1.2-1.5 g/kg/day with acute or chronic disease
The same PROT-AGE position paper makes an exception for older people with severe kidney disease not on dialysis, who may need to limit protein. — older people with estimated GFR below 30 mL/min/1.73 m2 not on dialysis Evidence E source
Exception to the higher-protein advice; protein intake may need to be limited
The EU allows foods that are at least a source of protein to say that protein contributes to the maintenance of muscle mass. — foods sold in the EU that are at least a source of protein Evidence E source
Claim status: authorized
A meta-analysis of RCTs found whey protein had no significant effect on CRP, IL-6, TNF-alpha or oxidative stress markers in adults. — adults in RCTs searched up to March 2022 Evidence A source
No significant effect on inflammatory factors and oxidative stress vs control
The EU did not authorize the claim that whey protein taken after resistance exercise supports muscle growth. — EU Register entry POL-HC-8187 Evidence E source
Non-authorized

Who this works differently for

In a randomized trial of 62 women with gestational diabetes, 20 g of whey protein isolate taken 30 minutes before breakfast through the third trimester cut the 1-hour glucose after breakfast by 15 to 20% versus placebo. — women with gestational diabetes, normotensive, aged 18 or over, singleton pregnancy, given 20 g whey protein isolate or placebo daily 30 min before breakfast throughout the third trimester, Denmark (n = 62) Evidence B source
1 h postprandial glucose after breakfast -20% (95% CI -28% to -11%) early and -15% (95% CI -24% to -5%) late third trimester under controlled conditions
In a crossover trial of 24 pregnant women, 20 g of whey 30 minutes before a glucose drink lowered the glucose peak by 18 mg/dL (1.0 mmol/L) in those with gestational diabetes and by 13 mg/dL (0.7 mmol/L) in those without. — 12 women with gestational diabetes and 12 pregnant women with normal glucose tolerance at 20-36 weeks' gestation (n = 24) Evidence B source
Peak glucose -18 mg/dL (95% CI -29 to -7.2; metric: -1.0 mmol/L, -1.6 to -0.4) with GDM, -13 mg/dL (-23 to -1.8; metric: -0.7 mmol/L, -1.3 to -0.1) without; at home 30 g whey up to -36 mg/dL (-45 to -27; metric: -2.0 mmol/L, -2.5 to -1.5)
In the Cochrane review, balanced energy and protein supplements lowered the risk of a small-for-gestational-age baby by 21% across 7 trials with 4408 women. — pregnant women given balanced energy and protein supplementation, mostly in low-income settings (n = 4408) Evidence A source
Small for gestational age RR 0.79 (95% CI 0.69 to 0.90), I2 16%, moderate-quality evidence
A 2026 individual-data meta-analysis of 8 trials with 10,252 women in low- and middle-income countries found balanced energy-protein supplements cut the risk of a term, small, low-birthweight baby by 20%. — pregnant women in low- and middle-income countries, 8 RCTs of prenatal balanced energy and protein supplements (n = 10252) Evidence A source
Term-SGA-LBW RR 0.80 (95% CI 0.72 to 0.90); preterm-SGA-LBW RR 0.70 (0.53 to 0.91)
In undernourished women in low- and middle-income countries, a meta-analysis of 7 trials with 2367 women found balanced protein energy supplements improved birthweight, with a small effect size of 0.20. — undernourished pregnant women in low- and middle-income countries, 7 RCTs (n = 2367) Evidence A source
Birthweight SMD 0.20 (95% CI 0.03 to 0.38); no benefit for birth length or head circumference
The US protein RDA in pregnancy is 71 g a day, which FDA adopted as the label reference for pregnant and lactating women. — pregnant and lactating women, US labeling Evidence E source
RDA 71 g/day protein in pregnancy (IOM)
In a 4-week RCT in 100 adults over 60 with functional constipation, 15 g a day of a traditional dried whey cut hard stools from 48 people to 0, against 46 to 13 on placebo. — adults aged 60 and over with functional constipation (Rome III), Iran, 15 g a day Ma'aljobon whey powder vs placebo of lactose, calcium carbonate, maltodextrin and sugar; 94 completed (n = 100) Evidence B source
Hard stools (Bristol types 1 and 2): 48 to 0 with whey vs 46 to 13 with placebo; all constipation scores better than placebo (p < 0.001)
In an 8-week RCT in 46 older adults with gastric cancer on chemotherapy, constipation worsened in the group without high-protein drinks, not in the group taking them. — patients aged 65 or older with locally advanced gastric cancer on neoadjuvant chemotherapy; high-protein oral supplement plus standard care vs standard care (n = 46) Evidence B source
Constipation symptoms worsened significantly in the non-supplement group by week 8 (p = 0.008)
In NHANES data on 14,048 US adults, women in the top fifth of protein intake had twice the odds of constipation of women in the bottom fifth. — US women aged 20 and over, NHANES 2005-2010, constipation by Bristol stool types 1 and 2 (n = 14,048) Evidence C source
Women Q5 vs Q1 OR 2.00 (95% CI 1.09 to 3.68); Q4 OR 1.54 (1.02 to 2.34)
In the same NHANES data, men in the top fifth of protein intake had half the odds of constipation of men in the bottom fifth. — US men aged 20 and over, NHANES 2005-2010 (n = 14,048) Evidence C source
Men Q5 vs Q1 OR 0.50 (95% CI 0.28 to 0.91), fully adjusted
Across 21 trials averaging 13 weeks of weight training, whey added about 1 lb (0.46 kg) of lean mass, 1.4 lb (0.62 kg) less fat and a small strength gain (SMD 0.25) over placebo, in healthy people only. — healthy adults and people with a pathological condition doing resistance training with whey or placebo (n = 837) Evidence A source
Lean mass MD +1 lb (-0.04 to 2.1; metric: 0.46 kg, -0.02 to 0.94); fat mass MD -1.4 lb (-2.3 to -0.42; metric: -0.62 kg, -1.05 to -0.19); strength SMD 0.25 (0.11 to 0.38); no benefit in people with a pathological condition; lean-mass gain fell with age
In people already lifting weights, whey-containing supplements gave small extra gains in lean mass (g 0.30) over equal-calorie carb or other-protein drinks, across 9 trials. — resistance-trained adults, 6 weeks or more of training, whey alone or in multi-ingredient formulas vs isoenergetic contrast supplements (n = 192) Evidence A source
Fat-free or lean body mass g = 0.301 (95% CI 0.032 to 0.571); whey alone g = 0.217 (-0.113 to 0.547), multi-ingredient g = 0.468 (0.003 to 0.934)
In adults over 60, whey against placebo did not change lean body mass (SMD 0.02) in 11 trials, and with weight training it added only a small gain in leg strength (SMD 0.25). — adults aged 60 and older, whey vs placebo with or without training (n = 2105) Evidence A source
Lean body mass SMD 0.02 (-0.13 to 0.17); handgrip SMD 0.18 (-0.13 to 0.49); lower-body strength with resistance exercise SMD 0.25 (0.05 to 0.45)
In older people diagnosed with sarcopenia, whey raised appendicular muscle mass index (SMD 0.47) and walking speed (SMD 1.13) against placebo or usual care in 10 trials. — older community or hospital patients with sarcopenia by EWGSOP or AWGS criteria (n = 1154) Evidence A source
Appendicular skeletal muscle mass index SMD 0.47 (0.23 to 0.71); appendicular skeletal muscle mass SMD 0.28 (0.11 to 0.45); gait speed SMD 1.13 (0.82 to 1.44); no effect on weight or fat mass
A network analysis of 78 trials in middle-aged and older adults ranked whey first of six protein sources added to weight training for muscle mass (SMD 1.29) and grip strength. — untrained community-dwelling, hospitalized or institutionalised middle-aged and older adults doing resistance training (n = 5272) Evidence A source
Muscle mass SMD 1.29 (0.96 to 1.62; SUCRA 0.86); handgrip SMD 1.46 (0.92 to 2.00); walking speed SMD 0.73 (0.39 to 1.07)
In older lifters, whey at 10 to 15 g did worse than control supplements for lean mass in four of five studies (-1.1 lb / -0.49 kg), while whole milk protein helped. — older adults, mean age 60 or more, resistance training with milk-based protein vs control supplements (n = 17 studies) Evidence A source
Whey vs control lean mass -1.1 lb (95% CI -1.5 to -0.64, I2 14%; metric: -0.49 kg, -0.69 to -0.29); milk protein 10-15 g sufficient to augment lean mass; strength gains only at milk protein doses of 22 g or more (+1.5 lb (0.66 kg))
In 38 trials of healthy adults over 50, weight training alone raised strength nearly as much as training plus protein (SMD 2.53 vs 2.74), so the exercise does most of the work. — healthy adults aged 50 and older randomized to protein supplementation, resistance training or both (n = 2610) Evidence A source
Muscle strength vs control: combined SMD 2.74 (0.76 to 4.74), training alone SMD 2.53 (0.29 to 4.84); lean body mass combined vs protein alone SMD 0.44 (0.05 to 0.95)
A 2024 meta-analysis of 30 trials with 2105 people aged 60 and over found whey protein did not change lean body mass, grip strength or walking tests. — adults aged 60 and older in RCTs of whey protein supplement versus placebo, with or without training (n = 2105) Evidence A source
Lean body mass SMD 0.02 (95% CI -0.13 to 0.17); handgrip SMD 0.18 (-0.13 to 0.49); gait speed SMD -0.08 (-0.43 to 0.28); appendicular muscle mass SMD 0.39 (0.28 to 0.51) from only 2 studies
A 2024 meta-analysis of 10 trials with 1154 older adults with sarcopenia found whey protein increased appendicular muscle mass and gait speed versus placebo. — older patients from community or hospital diagnosed with sarcopenia by EWGSOP or AWGS criteria (n = 1154) Evidence A source
Appendicular skeletal muscle mass index SMD 0.47 (95% CI 0.23 to 0.71); appendicular skeletal muscle mass SMD 0.28 (0.11 to 0.45); gait speed SMD 1.13 (0.82 to 1.44)
A 2023 meta-analysis found whey protein improved lean mass and function in older adults with sarcopenia or frailty but had no positive effect in healthy older people. — healthy and sarcopenic or frail older adults in RCTs of whey protein with or without vitamin D Evidence A source
No effect on lean mass or strength overall; in sarcopenic or frail adults lean mass SMD 0.982 (95% CI 0.228 to 1.736, 11 comparisons)
A 2022 meta-analysis of women aged 55 and over found whey protein raised leg lean mass only with resistance training, and did nothing for muscle without it. — postmenopausal women aged 55 and above in RCTs of whey protein with or without resistance training (n = 10 studies) Evidence A source
With resistance training lower-limb lean mass SMD 1.103 (95% CI 0.632 to 1.574); without training no significant effect on strength or lean mass
In a 24-week trial of 128 healthy adults aged 65 and over, whey protein that raised total protein intake to 1.5 g/kg a day did not change muscle power, physical performance or muscle mass. — healthy free-living adults aged 65 or older, mean age 74, baseline protein intake 0.85 g/kg/d, in a 2 x 2 factorial trial of whey protein and potassium bicarbonate (n = 128) Evidence B source
Leg press power difference 4.7 W (95% CI -21.1 to 30.5) versus placebo; no group differences in physical performance or muscle mass; IGF-1 +14.2 ng/mL
In a 10-week blinded trial of 45 older Korean adults, 38 g a day of fermented whey protein raised skeletal muscle index more than a placebo. — community-dwelling Korean adults aged 65 and older, BMI 18.5-30, given 38 g/day lactic acid bacteria-fermented whey protein (n=22) or dextrin placebo (n=23) (n = 45) Evidence B source
Skeletal muscle mass index gain greater by 1.5 (P = .004); eSPPB +1.4 (P = .017)
A 2026 systematic review of 14 RCTs found whey mainly helps adults with obesity keep fat-free mass while dieting, mostly with resistance exercise, and the certainty of evidence was often downgraded. — adults with obesity receiving whey protein as part of a hypocaloric diet, compared with placebo or standard care (n = 14 trials) Evidence A source
Maintenance or modest gain of fat-free mass, especially with resistance exercise; several trials neutral without structured exercise
After bariatric surgery, a 2026 meta-analysis of 5 RCTs with 267 patients found whey may soften the drop in weight by preserving fat-free mass, with evidence rated moderate to very low. — patients after bariatric surgery in randomized trials of whey protein (n = 267) Evidence A source
Whey may alleviate the reduction in body weight (p = 0.017) and BMI (p = 0.027), with lower fat mass (p = 0.024) and preserved fat-free mass (p = 0.003)
A 2025 meta-analysis of 21 RCTs found whey lowered LDL cholesterol by about 5 mg/dL only when combined with exercise, and had no relevant effect on blood pressure or insulin resistance. — adults in RCTs of whey protein versus placebo or a carbohydrate control (n = 21 trials) Evidence A source
LDL-cholesterol MD -5.38 (95% CI -8.87 to -1.88) with exercise; total cholesterol MD -8.58 with exercise; no clinically relevant effect on blood pressure or HOMA-IR
In older people with sarcopenia, a meta-analysis of 7 RCTs found whey protein added to resistance training raised handgrip strength by 5.1 lb (2.31 kg), a small effect. — Seven randomized clinical trials (591 participants), sarcopenic adults aged 60 or older (n = 591) Evidence A source
Handgrip MD +5.1 lb (95% CI 0.02 to 10; metric: 2.31 kg, 0.01 to 4.6); muscle index SMD 0.24 (0.05 to 0.42); below minimal clinically important difference
In people with type 2 diabetes, a meta-analysis of 5 RCTs found whey protein before a meal lowered blood glucose by 48 mg/dL (2.67 mmol/L) at 60 minutes. — Five RCTs involving 134 persons with mild or well-controlled T2DM (n = 134) Evidence A source
Glucose WMD -48 mg/dL (-65 to -31; metric: -2.67 mmol/L, -3.62 to -1.72) at 60 min; -29 mg/dL (-52 to -5; metric: -1.59 mmol/L, -2.91 to -0.28) at 120 min
In women, a meta-analysis of 13 RCTs found whey protein added 0.82 lb (0.37 kg) of lean mass without changing fat mass, with no lean-mass gain when combined with resistance training alone. — women in thirteen randomized controlled trials with 28 groups (n = 13 RCTs) Evidence A source
Lean mass WMD +0.82 lb (0.13 to 1.5; metric: 0.37 kg, 0.06 to 0.67); fat mass -0.44 lb (-1.5 to 0.6; metric: -0.20 kg, -0.67 to 0.27); with RT only 0.51 lb (-0.37 to 1.4; metric: 0.23 kg, -0.17 to 0.63)
In 116 tube-fed neurocritical patients, whey protein powder raised daily protein intake to 1.7 g/kg but did not improve serum albumin at 14 days. — 116 out of 597 patients who required enteral nutrition for at least 7 days (n = 116) Evidence B source
No difference in albumin or mRS; protein intake 1.7 (IQR 1.6-1.8) vs 1.5 g/kg/day

What is still unknown

In the same Cochrane review, adding protein without extra calories did not change birthweight in two trials with 184 women. — pregnant women given isocaloric protein supplementation, two trials (n = 184) Evidence A source
Birthweight MD 108.25 g (95% CI -220.89 to 437.40); weekly weight gain MD 110.45 g (-82.87 to 303.76), very low-quality evidence
A meta-analysis of 23 diet trials in 1,714 adults with chronic constipation found no trial of protein or whey. Fruit, rye bread and mineral water were the foods with evidence. — adults with chronic constipation in intervention trials of foods, drinks and diets (n = 1,714) Evidence A source
Studies covered kiwifruit, mineral water, prunes, rye bread, mango, fig, cereal, oat bran, yogurt, water, prune juice, high-fiber and no-fiber diets; none tested protein
A 2023 meta-analysis of whey protein in older adults with sarcopenia concluded whey did not improve any of the sarcopenia measures tested. — elderly people with sarcopenia in RCTs of whey protein supplementation (n = 10 studies) Evidence A source
No improvement in any sarcopenia-linked parameter overall; study duration and age modified handgrip and chair-stand results

The bottom line

Effects on blood fats are modest. Across 20 trials with 1,638 adults, whey lowered triglycerides by 12.21 mg/dL (95% CI 4.26 to 20.16) and raised HDL by 2.59 mg/dL, without changing LDL, with doses and durations that varied widely. A second meta-analysis of 21 trials found LDL fell by 5.38 (95% CI 1.88 to 8.87) when whey was combined with exercise, in units the abstract does not name, and blood pressure did not change in any clinically relevant way. The two analyses disagree on LDL. In people with mild or well-controlled type 2 diabetes, whey taken before a meal lowered blood glucose by 48 mg/dL (2.67 mmol/L) at 60 minutes and by 29 mg/dL (1.59 mmol/L) at 120 minutes. That comes from 5 small trials with 134 people testing single meals, with no long-term data. The idea that whey calms inflammation was tested in a meta-analysis of randomized trials, and it had no significant effect on CRP, IL-6, TNF-alpha or oxidative stress markers. About 57% of the phenylalanine in whey reached the blood within 5 hours, pooled from 18 trials with 602 people. That sits between casein at 45% and milk protein at 65%, in a comparison made across different studies. Older adults took up less than young ones, 45% against 51%. A scoop weighs about 20 g in USDA survey data, from one brand. The single USDA record for whey protein powder isolate lists 58 g of protein per 3.5 oz (100 g), one record with no range, so the label on your tub is the better guide. In 116 tube-fed patients in neurocritical care, adding whey protein powder raised protein intake to 1.7 g/kg a day against 1.5 g/kg, and serum albumin at 14 days did not differ, in a post hoc analysis of a pilot trial. Who should be careful. Whey is a milk protein, and the US FDA lists milk among the nine major food allergens, so whey powders are not for people with cow's milk allergy. The US allergen labeling law, which requires labels to name the food source of every major allergen, covers dietary supplements too. The NIDDK names whey among the label words that mean a product contains lactose. No upper intake level has been set for protein, because the data were insufficient. That means no number was set, not that any amount is safe. The US RDA is 0.8 g per kg a day. Kidney disease changes the picture. In people with chronic kidney disease, a meta-analysis of 19 trials with 2,492 patients found a low-protein diet cut the odds of kidney failure by about 40 percent. The NIDDK says some people with the disease may need moderate amounts of protein so waste does not build up, while people on dialysis may need more, and too little protein risks malnutrition. In adults without kidney disease, high-protein diets raised estimated kidney filtration without changing creatinine across 22 trials, and the long-term effects are unknown. A systematic review found only 11 documents on whey harms, and most tied kidney and liver effects to chronic heavy use. On acne the evidence is mixed. In 49 young men with acne, 30 g of whey a day for 6 months did not worsen it against a non-whey supplement, while a case-control study of 201 young men at gyms and a series of 5 teenage athletes linked whey use to acne. A 2022 USDA evidence scan adds higher urinary calcium and lower urinary pH with 27 g of whey a day for 3 days, from a short exposure with no size of risk given. In pregnancy, a Cochrane review found that high-protein supplements, not whey specifically, raised the risk of a small-for-gestational-age baby by 58 percent in one trial of 505 women, and WHO does not recommend high-protein supplementation for pregnant women in undernourished populations. In one trial of women with gestational diabetes, 20 g of whey a day through the third trimester caused no more gut side effects than placebo. We found no long randomized trials of kidney or liver effects in healthy people at usual doses, so this page cannot tell you whether long-term use is safe for those organs.

Questions about whey protein, answered from the trials

Related foods

Whey: it makes you stronger without making you bigger

Sources

whyr8-13 · USDA FoodData Central SR Legacy, dataset
Beverages, Whey protein powder isolate (FDC 173177, SR Legacy, Beverages): protein 58.14 g per 100 g = 116% DV; vitamin B12 3.49 ug = 145% DV; copper 1.163 mg = 129% DV
USDA FoodData Central, SR Legacy (2018), FDC 173177 · checked 2026-10-03
whyr8-08 · meta-analysis of RCTs
The combination of whey protein supplementation and exercise has been shown to significantly enhance FSR (Hedge's g = 1.24, 95% CI: 0.71-1.77; p < 0.001), with increases ranging from 1.3 to 1.6 folds when consumed immediately after exercise and up to 2.5 folds when given 45 min prior to multiple-set resistance exercise. A dose-dependent increase in FSR was observed in response to whey protein supplementation, ranging from 10 to 60 g.
Nutrients, 2025 · checked 2026-10-03
whyr8-14 · FNDDS 2021-2023, dataset
Nutritional powder mix (EAS Whey Protein Powder) (FNDDS 95201200): 1 scoop EAS Whey 20 g; 1 tablespoon 10 g; Quantity not specified 39 g
USDA FNDDS 2021-2023, FNDDS 95201200, FDC 2710731 · checked 2026-10-03
whyr8-09 · meta-analysis of RCTs
Casein ingestion resulted in a smaller (45% ± 11%), whey protein ingestion in an intermediate (57% ± 10%), and milk protein ingestion in a greater (65% ± 13%) fraction of dietary protein-derived phenylalanine appearing in the circulation (P < 0.001).
J Nutr, 2020 · checked 2026-10-03
ev-whpreg-09 · meta-analysis of RCTs
Maternal supplementation increased birth weight by 0.06 kg, and both formula and food-based supplementation in term infants/young children increased weight by ≤0.14 kg.
Am J Clin Nutr, 2019 · checked 2026-10-07
ev-wpm-03 · meta-analysis of randomized controlled trials
The analysis found no significant effect of either whey or soy protein supplementation on LBM. However, protein supplement increased peak plasma total EAA with whey protein significantly improved bench press (mean difference [MD] 8.87; 95% CI: 5.95-11.79) and squat performance (MD 9.60; 95% CI: 5.61-13.60), with low to no heterogeneity.
J Diet Suppl, 2026 · checked 2026-10-06
ev-wpm-08 · meta-analysis of randomized controlled trials
There was no significant effect on FFM in any of the scenarios investigated (p > 0.05).
Nutrients, 2019 · checked 2026-10-06
ev-wpm-10 · randomized controlled trial
Lean body mass gains were significantly (p < 0.05) greater in whey (3.3 ± 1.5 kg) than carb (2.3 ± 1.7 kg) and soy (1.8 ± 1.6 kg).
J Am Coll Nutr, 2013 · checked 2026-10-06
ev-wpm-11 · meta-analysis of randomized controlled trials
Protein supplementation beyond total protein intakes of 1.62 g/kg/day resulted in no further RET-induced gains in FFM.
Br J Sports Med, 2018 · checked 2026-10-06
ev-wpom-02 · meta-analysis of RCTs
In interventions incorporating RE, statistically significant positive effects of WPS on lower body strength were observed (n = 11, SMD: 0.25; 95%CI: 0.05, 0.45; I2 = 0%).
Clin Nutr, 2024 · checked 2026-10-07
ev-wpom-05 · meta-analysis of RCTs
However, the effect sizes were small, and the MD did not exceed the minimally important clinical difference.
Nutrients, 2023 · checked 2026-10-07
ev-wpom-06 · network meta-analysis of RCTs
Among the six protein sources identified in this NMA, namely whey, milk, casein, meat, soy, and peanut, whey supplement yielded the most effective treatments augmenting efficacy of RT on muscle mass (SMD = 1.29, 95% CI: 0.96, 1.62; SUCRA = 0.86), handgrip strength (SMD = 1.46, 95% CI: 0.92, 2.00; SUCRA = 0.85), and walking speed (SMD = 0.73, 95% CI: 0.39, 1.07; SUCRA = 0.84).
Nutrients, 2024 · checked 2026-10-07
ev-wpom-09 · meta-analysis of RCTs
MP supplementation substantially increased lean body mass (LBM) (weighted mean difference (WMD): 0.41 kg; 95% CI: 0.19, 0.62; p < 0.001) and fat-free mass (FFM) (WMD: 0.67 kg; 95% CI: 0.40, 0.94; p < 0.001).
Nutrients, 2025 · checked 2026-10-07
ev-wpwl-01 · meta-analysis of RCTs
There was a significant reduction of body weight (MD = 0.56, 95% CI: 0.30-0.81), lean mass (MD = 0.77, 95% CI: 0.59-0.96), and fat mass (MD = 1.12, 95% CI: 0.77-1.47) favoring the whey protein group.
J Am Coll Nutr, 2018 · checked 2026-10-06
ev-wpwl-02 · meta-analysis of RCTs
No considerable effects were observed for muscle mass (MM), body mass index (BMI), and body weight (BW).
Nutrients, 2025 · checked 2026-10-06
ev-wpwl-03 · meta-analysis of RCTs
We observed no significant change between whey protein supplementation and body mass, fat mass and body fat percentage.
Br J Nutr, 2022 · checked 2026-10-06
ev-wpwl-05 · RCT
Subjects supplemented with whey protein had no significant change in body composition or serum glucose at 12 weeks compared with the control or casein group.
Br J Nutr, 2010 · checked 2026-10-06
whyr8-02 · meta-analysis of RCTs
This meta-analysis included 21 RCTs. Whey protein supplementation had no effect on HDL-cholesterol concentration but did elicit a reduction in LDL-cholesterol in individuals aged <50 years (P < 0.01) and when combined with exercise (MD: -5.38, 95 % confidence interval (95 % CI): -8.87 to -1.88, I2 = 0 %, P < 0.01). ... There was no clinically relevant effect of whey protein supplementation on blood pressure and HOMA-IR, however, changes pertinent to HDL-cholesterol, total cholesterol, and triglyceride reduction were primarily displayed in healthy adults.
Clin Nutr, 2025 · checked 2026-10-03
whyr8-03 · meta-analysis of RCTs
Overall, 20 randomized clinical trials (n = 1638 participants) met our inclusion criteria. The current meta-analysis demonstrates a significant reduction in TG (WMD: -12.21 mg/dL; %95CI: -20.16, -4.26; P = 0.003). Pooled analysis of 19 studies on HDL-c indicated a significant increase (WMD: 2.59 mg/dL; %95CI: 1.11, 4.07; P = 0.001).
Nutr Metab Cardiovasc Dis, 2025 · checked 2026-10-03
whyr8-07 · meta-analysis of RCTs
A total of 12 studies with 261 participants were included after full-text screening with the main reason for exclusion being wrong population. The analysis found no significant effect of either whey or soy protein supplementation on LBM. However, protein supplement increased peak plasma total EAA with whey protein significantly improved bench press (mean difference [MD] 8.87; 95% CI: 5.95-11.79) and squat performance (MD 9.60; 95% CI: 5.61-13.60), with low to no heterogeneity.
J Diet Suppl, 2026 · checked 2026-10-03
ev-whpreg-02 · RCT
There were no differences in gastrointestinal side effects or obstetrical outcomes (ESM Fig. 1, ESM Table 4).
Diabetologia, 2026 · checked 2026-10-07
ev-whpreg-03 · RCT
Newborn birthweight and z score did not differ between groups.
Diabetologia, 2026 · checked 2026-10-07
ev-whpreg-05 · Cochrane systematic review
High-protein supplementation does not seem to be beneficial and may be harmful to the fetus.
Cochrane Database Syst Rev, 2015 · checked 2026-10-07
ev-wpc-04 · RCT
Of the six participants who withdrew, two from the intervention group cited mild nausea as the reason for discontinuation.
Health Sci Rep. 2026. Effect of Ma'aljobon (Whey) Consumption on Functional Constipation in Older Adults: A Randomized Double-Blind Controlled Trial · checked 2026-10-07
ev-wpc-05 · randomized crossover trial
A significant increase in bloating severity was observed following the moderate-protein shake as compared to the low-protein shake during the run (0.54 vs 1.23; p = 0.03), but no other symptoms assessed were significantly impacted by the shake composition.
J Int Soc Sports Nutr, 2026 · checked 2026-10-07
ev-wpc-07 · RCT
No clinically relevant and, except for flatulence, no statistically significant differences in gastro-intestinal tolerance were observed between groups.
J Nutr Health Aging, 2016 · checked 2026-10-07
ev-wpc-08 · RCT
High protein ONS seems to be well-tolerated and safe; there is no indication that it affects renal function in nursing home residents, including patients with stage 3 chronic kidney disease, under the conditions tested.
J Nutr Health Aging, 2016 · checked 2026-10-07
ev-wpc-11 · systematic review
The majority of the papers associated the damaging effect with the chronic and abusive use of whey protein, with the kidneys and liver being the main organs affected.
Appl Physiol Nutr Metab, 2021 · checked 2026-10-07
ev-wpc-13 · agency guidance
The following words mean that the product contains lactose: milk, lactose, whey, curds, milk by-products, dry milk solids, nonfat dry milk powder
NIDDK (NIH), Eating, Diet, & Nutrition for Lactose Intolerance · checked 2026-10-07
ev-wpm-12 · meta-analysis of randomized controlled trials
High-protein diets were associated with increases in eGFR without consistent biochemical evidence of renal injury in adults without chronic kidney disease.
Diabetes Obes Metab, 2026 · checked 2026-10-06
ev-wpm-13 · expert body statement
The major food allergens are milk, eggs, fish, Crustacean shellfish, tree nuts, peanuts, wheat, soybeans, and sesame.
Food Allergies, US Food and Drug Administration, 2026 · checked 2026-10-06
ev-wpom-12 · RCT
WP supplementation slightly increased blood urea compared with the placebo group (p = .05), but values remained within normal limits.
J Aging Phys Act, 2025 · checked 2026-10-07
ev-wpom-13 · meta-analysis of RCTs
The change in GFR did not differ between interventions (SMD: 0.11; 95% CI: -0.05, 0.27; P = 0.16).
J Nutr, 2018 · checked 2026-10-07
ev-wpom-14 · meta-analysis of RCTs
A low protein diet reduced the risk of kidney failure (odds ratio (OR) = 0.59, 95% CI: 0.41 to 0.85) and end-stage renal disease (ESRD) (OR = 0.64, 95% CI: 0.43 to 0.96)
PLoS One, 2018 · checked 2026-10-07
ev-wpwl-08 · RCT
The mean differences in the facial and truncal total acne lesions for the WP and non-WP group were -5.99 (95% confidence interval [CI], -13.18 to 1.19, p = 0.09) and -2.18 (95% CI, -11.83 to 7.48, p = 0.65), respectively.
Journal of Dermatology, 2024, Whey protein and male acne: A double-blind, randomized controlled trial · checked 2026-10-06
ev-wpwl-09 · case-control
However, considerably more participants in the acne group (47%) were taking whey protein supplements than in the control group (27.7%)
Dermatology Research and Practice, 2024, The Effect of Whey Protein Supplements on Acne Vulgaris among Male Adolescents and Young Adults: A Case-Control Study from North of Jordan · checked 2026-10-06
ev-wpwl-10 · case series
Lesions fully cleared in 4 patients after discontinuation of whey protein supplementation, but 1 patient's acne flared after reinitiation of the whey protein supplement.
Cutis, 2012, Whey protein precipitating moderate to severe acne flares in 5 teenaged athletes · checked 2026-10-06
ev-wpwl-11 · systematic review of adverse effect reports
The majority of the papers associated the damaging effect with the chronic and abusive use of whey protein, with the kidneys and liver being the main organs affected.
Appl Physiol Nutr Metab, 2021 · checked 2026-10-06
hf2-whey-1 · agency evidence review background
In the DRI publication, the protein intake recommendations for the general population were set at 0.66 and 0.8 g/kg/day as the EAR and RDA, respectively. ... However, data was insufficient to establish a tolerable upper intake level for protein. The AMDR for protein was set at 10 to 35 percent of calorie intake.
Agency for Healthcare Research and Quality, The Effect of Protein Intake on Health: A Systematic Review (2024), Protein Dietary Reference Intakes · checked 2026-10-08
hf2-whey-2 · agency advice
As your body uses protein, the protein breaks down into waste. Your kidneys remove this waste from the blood. Some people with CKD may need to consume moderate amounts of protein so waste doesn’t build up in the blood. However, too little protein may lead to malnutrition ... People with CKD who are on dialysis may need to eat more protein because the dialysis treatment removes protein from the blood.
NIDDK, Eating & Nutrition for Chronic Kidney Disease (last reviewed January 2025) · checked 2026-10-08
hf2-whey-3 · agency advice
The FDA enforces the provisions of this law in most packaged food products. This includes dietary supplements but does not include meat, poultry, and egg products ... The law requires that food labels identify the food source of all major food allergens used to make the food.
US FDA, Food Allergies: What You Need to Know (content current as of 03/11/2026) · checked 2026-10-08
whyr8-11 · agency evidence scan
Another SR reported changes in urinary biomarkers (increased urinary calcium and decreased urinary pH) with 27 g per day of whey protein for 3 days.5 The same SR reported exacerbation of acne lesions when consuming a high level of protein for 60 days.5
USDA 2022, Dietary Protein Intake: A Series of Evidence Scans · checked 2026-10-03
ev-whpreg-11 · Cochrane systematic review
Prescription of an antigen avoidance diet to a high-risk woman during pregnancy is unlikely to reduce substantially her child's risk of atopic diseases, and such a diet may adversely affect maternal or fetal nutrition, or both.
Cochrane Database Syst Rev, 2012 · checked 2026-10-07
ev-whpreg-12 · systematic review of mixed designs
Moderate evidence indicates that lower or restricted consumption of cow milk products during pregnancy does not reduce the risk of atopic dermatitis/eczema in the child.
USDA Nutrition Evidence Systematic Review, 2020, Maternal Diet during Pregnancy and Lactation and Risk of Child Food Allergies and Atopic Allergic Diseases: A Systematic Review · checked 2026-10-07
ev-whpreg-13 · Agency recommendation
In undernourished populations, high-protein supplementation is not recommended for pregnant women to improve maternal and perinatal outcomes
WHO, 2016, WHO recommendations on antenatal care for a positive pregnancy experience (eLENA: high-protein supplementation during pregnancy) · checked 2026-10-07
ev-wpc-02 · network meta-analysis
Regarding the severity of constipation, fruit-based foods (category 1) ranked first, superior to fiber supplements (moderate certainty) and placebo (moderate certainty).
Am J Clin Nutr, 2026 · checked 2026-10-07
ev-wpc-12 · agency guidance
Eat enough fiber. Drink plenty of liquids to help the fiber work better.
NIDDK (NIH), Eating, Diet, & Nutrition for Constipation · checked 2026-10-07
ev-wpm-14 · regulatory register entry
POL-HC-6446 Protein Protein contributes to a growth in muscle mass Authorised
EU Register on nutrition and health claims, claim POL-HC-6446, snapshot 2026-09-21 · checked 2026-10-06
ev-wpom-15 · consensus statement
To help older people (>65 years) maintain and regain lean body mass and function, the PROT-AGE study group recommends average daily intake at least in the range of 1.0 to 1.2 g protein per kilogram of body weight per day.
J Am Med Dir Assoc, 2013 · checked 2026-10-07
ev-wpom-16 · consensus statement
Older people with severe kidney disease (ie, estimated GFR <30 mL/min/1.73 m(2)), but who are not on dialysis, are an exception to this rule; these individuals may need to limit protein intake.
J Am Med Dir Assoc, 2013 · checked 2026-10-07
ev-wpwl-12 · regulatory register entry
POL-HC-6447 Protein Protein contributes to the maintenance of muscle mass Authorised
EU Register on nutrition and health claims, claim POL-HC-6447, snapshot 2026-09-21 · checked 2026-10-06
whyr8-04 · meta-analysis of RCTs
The results of the present study demonstrated that WP supplementation had no significant effect on the modulation of inflammation and oxidative stress compared with the control.
Nutr Rev, 2025 · checked 2026-10-03
whyr8-12 · EU claims register
POL-HC-8187 Whey Protein Taken after resistance exercise, whey protein supports muscle growth Non-authorised
EU Register on nutrition and health claims, claim POL-HC-8187, snapshot 2026-09-21 · checked 2026-10-03
ev-whpreg-01 · RCT
In the WP group, the 1 h postprandial glucose following breakfast was -20% (95% CI -28%, -11%) lower in the early and -15% (95% CI -24%, -5%) lower in the late third trimester compared with the placebo group under controlled conditions.
Diabetologia, 2026 · checked 2026-10-07
ev-whpreg-04 · RCT
Intake of premeal whey resulted in lowered peak glucose by -1.0 mmol/L (95% CI -1.6 to -0.4) in women with GDM and -0.7 mmol/L (95% CI -1.3 to -0.1) in women without GDM compared with placebo.
Diabetes Care, 2025 · checked 2026-10-07
ev-whpreg-07 · Cochrane systematic review
There was also a significant reduction in the risk of small-for-gestational age (RR 0.79, 95% CI 0.69 to 0.90, I² = 16%, seven trials, 4408 women, moderate-quality evidence).
Cochrane Database Syst Rev, 2015 · checked 2026-10-07
ev-whpreg-08 · IPD meta-analysis of RCTs
In the 10-group categorization of SVNs, on average, prenatal BEP supplementation led to a 30% lower risk of preterm-SGA-LBW (RR: 0.70; 95% CI [0.53, 0.91]; P = 0.009), a 25% lower risk of preterm-AGA-LBW (RR: 0.75; 95% CI [0.60, 0.93]; P = 0.009), and a 20% lower risk of term-SGA-LBW (RR: 0.80; 95% CI [0.72, 0.90]; P < 0.001).
PLoS Med, 2026 · checked 2026-10-07
ev-whpreg-10 · meta-analysis of RCTs
Balanced protein energy supplementation significantly improved birthweight (seven randomised controlled trials, n = 2367; d = 0.20, 95% confidence interval, 0.03-0.38, P = 0.02).
Matern Child Nutr, 2015 · checked 2026-10-07
ev-whpreg-14 · Regulatory reference value
In the preamble to the proposed rule (79 FR 11879 at 11943), we noted that the IOM established 71 grams/day protein as the RDA for pregnant and lactating women based on the needs for maternal and fetal development and human milk production.
FDA, 2016, Food Labeling: Revision of the Nutrition and Supplement Facts Labels, final rule (FR Doc. 2016-11867) · checked 2026-10-07
ev-wpc-03 · RCT
Notably, the number of participants reporting hard stools (types 1 and 2) decreased from 48 to 0 in the intervention group, compared to a decrease from 46 to 13 in the control group.
Health Sci Rep. 2026. Effect of Ma'aljobon (Whey) Consumption on Functional Constipation in Older Adults: A Randomized Double-Blind Controlled Trial · checked 2026-10-07
ev-wpc-06 · RCT
Additionally, constipation symptoms worsened significantly in the non-ONS group by week 8 (p = 0.008).
Support Care Cancer, 2025 · checked 2026-10-07
ev-wpc-09 · cross-sectional
After comprehensive adjustment for covariates in model 3, women in Q5 had a significantly higher risk of constipation compared to Q1 (OR = 2.00, 95% CI: 1.09, 3.68, p = 0.0247), with a significant effect observed also in Q4 (OR = 1.54, 95% CI: 1.02, 2.34, p = 0.0423).
Front Nutr. 2024;11:1393596. Gender differences in the association between dietary protein intake and constipation: findings from NHANES · checked 2026-10-07
ev-wpc-10 · cross-sectional
In the fully adjusted model 3, the ORs of constipation in Q5 remained 0.50 times that of Q1 (95% CI: 0.28, 0.91, p = 0.0235).
Front Nutr. 2024;11:1393596. Gender differences in the association between dietary protein intake and constipation: findings from NHANES · checked 2026-10-07
ev-wpm-01 · meta-analysis of randomized controlled trials
In comparison with the placebo-RT group, WP-RT exhibited improved lean mass (MD 0.46 kg [-0.02, 0.94]; p = 0.01), fat mass (MD -0.62 kg [-1.05, -0.19]; p = 0.004) and muscular strength (SMD 0.25 [0.11, 0.38]; p = 0.0003) in healthy individuals but not in individuals with a pathological condition.
Food Funct, 2019 · checked 2026-10-06
ev-wpm-02 · meta-analysis of randomized controlled trials
Overall, with respect to the ingestion of contrast supplements, whey protein supplementation, administered alone or as part of a multi-ingredient, in combination with resistance training, was associated with small extra gains in fat-free mass or lean body mass, resulting in an effect size of g = 0.301, 95% confidence interval (CI) 0.032-0.571.
Sports Med, 2016 · checked 2026-10-06
ev-wpm-04 · meta-analysis of randomized controlled trials
The present meta-analysis indicates that WPS, when combined with resistance training (RT), can enhance lower body strength but does not seem to have a significant beneficial effect on handgrip strength, physical performance, or body composition.
Clin Nutr, 2024 · checked 2026-10-06
ev-wpm-05 · meta-analysis of randomized controlled trials
In WP group versus (vs.) Isocaloric placebo (PLA)/Routine consultation (RC) group, WP significantly increased the appendicular skeletal muscle mass index (SMD: 0.47, 95%CI: 0.23, 0.71), appendicular skeletal muscle mass (SMD: 0.28, 95%CI: 0.11, 0.45) and gait speed (SMD: 1.13, 95%CI: 0.82, 1.44) in older patients with sarcopenia.
J Nutr Health Aging, 2024 · checked 2026-10-06
ev-wpm-06 · network meta-analysis of randomized controlled trials
Among the six protein sources identified in this NMA, namely whey, milk, casein, meat, soy, and peanut, whey supplement yielded the most effective treatments augmenting efficacy of RT on muscle mass (SMD = 1.29, 95% CI: 0.96, 1.62; SUCRA = 0.86), handgrip strength (SMD = 1.46, 95% CI: 0.92, 2.00; SUCRA = 0.85), and walking speed (SMD = 0.73, 95% CI: 0.39, 1.07; SUCRA = 0.84).
Nutrients, 2024 · checked 2026-10-06
ev-wpm-07 · meta-analysis of randomized controlled trials
Intriguingly, four out of five studies show negative effect of whey protein supplementation at the same dose range (or even higher) compared with control supplementation (-0.49 kg, 95% CI: -0.69, -0.29, I2 = 14%, Z = 4.82, p < 0.001).
Nutrients, 2021 · checked 2026-10-06
ev-wpm-09 · network meta-analysis of randomized controlled trials
The combined intervention (SMD: 2.74; 95% CI: 0.76, 4.74) and resistance training alone (SMD: 2.53, 95% CI: 0.29, 4.84) significantly improved muscle strength compared with controls.
J Nutr, 2025 · checked 2026-10-06
ev-wpom-01 · meta-analysis of RCTs
The meta-analysis of 26 RCTs showed no significant positive effect of WPS on HS (n = 11, SMD: 0.18; 95% CI: -0.13, 0.49; I2 = 69%), 6MWT (n = 5, SMD: -0.08; 95%CI: -0.31, 0.16; I2 = 0%), GS test (n = 4, SMD: -0.08; 95%CI: -0.43, 0.28; I2 = 36%), TUG test (n = 9, SMD: 0.0, 95% CI -0.15, 0.14; I2 = 0%), LBM (n = 11, SMD: 0.02; 95%CI: -0.13, 0.17; I2 = 0%), FM (n = 15, SMD: -0.04; 95%CI: -0.18, 0.10; I2 = 0%).
Clin Nutr, 2024 · checked 2026-10-07
ev-wpom-03 · meta-analysis of RCTs
In WP group versus (vs.) Isocaloric placebo (PLA)/Routine consultation (RC) group, WP significantly increased the appendicular skeletal muscle mass index (SMD: 0.47, 95%CI: 0.23, 0.71), appendicular skeletal muscle mass (SMD: 0.28, 95%CI: 0.11, 0.45) and gait speed (SMD: 1.13, 95%CI: 0.82, 1.44) in older patients with sarcopenia.
J Nutr Health Aging, 2024 · checked 2026-10-07
ev-wpom-04 · meta-analysis of RCTs
Whey protein supplementation improved LM and function in sarcopenic/frail older adults but had no positive effect in healthy older persons.
Adv Nutr, 2023 · checked 2026-10-07
ev-wpom-08 · meta-analysis of RCTs
Without RT, WP has no significant benefit on muscle strength or lean mass.
Nutrients, 2022 · checked 2026-10-07
ev-wpom-10 · RCT
No group differences were noted in physical performance or muscle mass.
Am J Clin Nutr, 2026 · checked 2026-10-07
ev-wpom-11 · RCT
Compared with controls, the intervention group showed greater gains in skeletal muscle mass index (Δ = 1.5, P = .004) and eSPPB scores (Δ = 1.4, P = .017).
J Med Food, 2026 · checked 2026-10-07
ev-wpwl-04 · systematic review of RCTs
Whey protein supplementation generally supported the maintenance or modest improvement of fat-free mass, particularly when combined with resistance exercise or anabolic-enriched formulations such as leucine or vitamin D.
Nutrients, 2026 · checked 2026-10-06
ev-wpwl-06 · meta-analysis of RCTs
The results of the meta-analysis concerning anthropometry and body composition suggested that whey protein supplementation may alleviate the reduction in body weight (p = 0.017) and body mass index (p = 0.027), which may be attributable to decreases in fat mass (p = 0.024) and the preservation of fat-free mass (p = 0.003).
Front Nutr, 2026 · checked 2026-10-06
ev-wpwl-07 · meta-analysis of RCTs
Whey protein supplementation had no effect on HDL-cholesterol concentration but did elicit a reduction in LDL-cholesterol in individuals aged <50 years (P < 0.01) and when combined with exercise (MD: -5.38, 95 % confidence interval (95 % CI): -8.87 to -1.88, I2 = 0 %, P < 0.01).
Clin Nutr, 2025 · checked 2026-10-06
whyr8-01 · meta-analysis of RCTs
Seven randomized clinical trials (591 participants) were included, and five of them provided data for quantitative synthesis. ... The overall pooled mean difference (MD) estimate showed a significant difference of +2.31 kg (MD = 2.31 kg; 95% CI, 0.01 to 4.6; p = 0.05; I2 = 81%, p < 0.001) in handgrip strength in the RET plus WP group compared with the RET group with or without placebo.
Nutrients, 2023 · checked 2026-10-03
whyr8-05 · meta-analysis of RCTs
Five RCTs involving 134 persons were included. Postprandial glycemia was significantly lower at 60 minutes (weighted mean difference: -2.67 mmol/L; 95% confidence interval, -3.62 to -1.72 mmol/L) and 120 minutes (-1.59 mmol/L; -2.91 to -0.28 mmol/L) in WP group than in placebo group.
Nutr Res, 2022 · checked 2026-10-03
whyr8-06 · meta-analysis of RCTs
Thirteen randomized controlled trials with 28 groups met the inclusion criteria. Results: Globally, WP supplementation increased lean mass (WMD, 0.37 kg; 95% confidence interval [CI], 0.06 to 0.67) while not influencing changes in fat mass (-0.20 kg; 95%CI, -0.67 to 0.27) relative to non-WP control. The beneficial effect of WP on lean mass was lost when only studies with RT were included in the analysis (n = 7 comparisons; 0.23 kg; 95%CI, -0.17 to 0.63).
Nutr Rev, 2018 · checked 2026-10-03
whyr8-10 · RCT
No significant differences were observed in serum albumin levels or mRS scores (P > 0.05). Complication rates from EN and changes in inflammatory and biochemical markers were comparable between groups.
Nutr Clin Pract, 2026 · checked 2026-10-03
ev-whpreg-06 · Cochrane systematic review
Isocaloric protein supplementation (two trials, 184 women) had no significant effect on birthweight (MD 108.25, 95% CI -220.89 to 437.40) and weekly gestational weight gain (MD 110.45, 95% CI -82.87 to 303.76, very low-quality evidence).
Cochrane Database Syst Rev, 2015 · checked 2026-10-07
ev-wpc-01 · meta-analysis
We included 23 studies (17 RCTs, 6 uncontrolled; 1714 participants): kiwifruit (n = 7), high-mineral water (n = 4), prunes (n = 2), rye bread (n = 2), mango, fig, cereal, oat bran, yoghurt, water supplementation, prune juice, high-fibre diet, no-fibre diet (n = 1).
Aliment Pharmacol Ther, 2024 · checked 2026-10-07
ev-wpom-07 · meta-analysis of RCTs
The present meta-analysis demonstrated overall that whey supplementation does not improve any of the tested sarcopenia-linked parameters.
Nutrients, 2023 · checked 2026-10-07

Review. Reviewed on 2026-10-08 for evidence level, dose and population context, and claims a reader could misread. Bioma Learn has no human medical reviewer at this time, and we say so rather than invent one. Methodology. This is information, not medical advice.