Mixed nuts: 105 trials, no weight gain, and one number to watch

Across 105 randomised trials searched to December 2020, diets enriched with nuts did not raise body weight in 6768 adults. The same pooling found no increase in body mass index in 2918 people, in waist circumference in 5045 or in body fat in 1226, with hazelnut-enriched diets the single exception for waist circumference. The energy side has been pooled too, and it is small. Resting energy expenditure rose by 28.6 kcal a day across 1121 adults from 27 studies, and the confidence interval runs from minus 10.7 to plus 67.8, so zero sits inside it. In people who already have atherosclerotic cardiovascular disease, adding nuts moves the standard markers barely at all. Across 5 randomised trials of 6 to 12 weeks in 436 such adults, at a median dose of 30 g a day, systolic blood pressure differed by 1.16 mmHg with a confidence interval from minus 5.68 to plus 3.35, which crosses zero. The number the title points at is selenium. A cup of unroasted mixed nuts weighs 142 g in the US survey record and carries 208.9 mcg of it, against an adult tolerable upper intake level of 400 mcg a day that falls to 45 mcg for the youngest children, and Brazil nuts at 68 to 91 mcg each are what tips a tin towards it.

The numbers, per 100 g

How much is actually in it

• A cup of unroasted mixed nuts weighs 142 g and carries 208.9 mcg of selenium, which is half the adult upper limit in that one cup. — USDA FNDDS household measures for Mixed nuts, unroasted (fdc_id 2707505) and Mixed nuts, NFS (fdc_id 2707504) Evidence E source
  1 cup = 142 g; 1 package = 50 g; unspecified quantity = 28 g. Selenium 147.1 mcg per 100 g unroasted and 73.8 mcg per 100 g NFS, giving 208.9 mcg and 104.8 mcg per cup

What cooking and storage change

• Roasting nuts and seeds costs about 20% of the folate, vitamin C and phosphorus and about 15% of the thiamin, while iron, zinc, copper, magnesium and potassium stay put. — USDA retention factors for the food group Nut and Seed Products, method NUTS,ROASTED Evidence E source
  Folate, vitamin C and phosphorus retained 80%; thiamin 85%; riboflavin, niacin, vitamin B6 and sodium 95%; calcium, iron, magnesium, potassium, zinc, copper, choline and vitamin B12 100%

What it does to your health

• Each extra 28 g of nuts per week was linked to a 10% lower risk of cardiovascular death and an 8% lower risk of death from any cause across 63 prospective studies. — adults in 63 prospective cohort studies pooled from 33 publications (n = 63 studies) Evidence C source
  RR per 28 g/week 0.90 (95% CI 0.86-0.94) for CVD mortality and 0.92 (95% CI 0.90-0.94) for all-cause mortality
• In people who already have atherosclerotic disease, adding nuts changed systolic blood pressure by 1.16 mmHg at most, and the confidence interval crosses zero. — 436 adults with atherosclerotic cardiovascular disease, 5 randomised trials, 6 to 12 weeks, median dose 30 g/day (n = 436) Evidence A source
  Systolic MD -1.16 mmHg (95% CI -5.68 to 3.35); diastolic MD 0.10 mmHg (95% CI -2.30 to 2.51)
• Across 5 randomised trials in people with atherosclerotic disease, nuts moved only the atherogenic index, by 0.32 units, and left every other lipid marker unchanged. — 439 adults with atherosclerotic cardiovascular disease, 5 randomised trials, 6 to 12 weeks, doses 5 g to 85 g/day (n = 439) Evidence A source
  Atherogenic index MD -0.32 (95% CI -0.58 to -0.06), I2 = 0%
• Eating nuts raised resting energy expenditure by about 29 kcal a day, a figure whose confidence interval still includes zero. — 1121 adults from 27 studies, 16 on energy intake and 10 on energy expenditure (n = 1121) Evidence A source
  Weighted mean difference in resting energy expenditure 28.6 kcal/d (95% CI -10.7 to 67.8)
• Across 105 randomised trials with 6768 people weighed, nut-enriched diets did not raise body weight, body mass index, waist circumference or body fat. — 6768 adults for body weight, 2918 for BMI, 5045 for waist circumference and 1226 for body fat, 105 randomised trials to December 2020 (n = 6768) Evidence A source
  No significant increase in any adiposity measure, with hazelnut-enriched diets the single exception for waist circumference
• Adding 30 g of mixed nuts a day to a cardioprotective diet for 16 weeks after a heart attack left LDL cholesterol 3.48 mg/dL apart from the control, which is no difference. — 388 adults over 40 years old, 2 to 6 months after myocardial infarction, 9 Brazilian centres, 10 g each of peanuts, cashew and Brazil nuts daily for 16 weeks (n = 388) Evidence B source
  LDL cholesterol intervention minus control 3.48 mg/dL (95% CI -3.45 to 10.41), P = 0.32
• A single drink with 45 g of cashew and Brazil nuts raised fat burning over the next 3 hours from 27.93 to 47.53 mg per minute, but 8 weeks of daily intake changed nothing. — adult women with overweight or obesity at cardiometabolic risk, acute arm with a 30 g cashew plus 15 g Brazil nut beverage, chronic arm 45 g/day for 8 weeks on a 500 kcal deficit (n = not reported in abstract) Evidence B source
  Postprandial fat oxidation piAUC 47.53 plus or minus 5.78 mg/min versus 27.93 plus or minus 6.98 mg/min, p = 0.048
• Pooling 21 trials, a Mediterranean diet topped up with mixed nuts gave lower systolic blood pressure than the same diet topped up with olive oil, while lipids and diastolic pressure matched. — adults at cardiovascular risk in 21 randomised trials with 25 effect sizes, searched to April 2024 (n = 21 trials) Evidence A source
  Olive oil arm had higher systolic blood pressure than the mixed nuts arm, p < 0.001; no significant difference in lipid indices or diastolic pressure

Safety, limits and interactions

• The tolerable upper intake level for selenium is 400 mcg a day for adults and as low as 45 mcg for the youngest children. — adults, and infants, children and adolescents by age band, United States Food and Nutrition Board Evidence E source
  Upper limit 400 mcg/day for adults, 45 mcg to 400 mcg for infants through adolescents
• Brazil nuts carry 68 to 91 mcg of selenium each, which is why a mix that leans on them can reach the daily upper limit from food alone. — general population advice from the United States National Institutes of Health Evidence E source
  68 to 91 mcg of selenium per Brazil nut, with regular intake named as a route to selenium toxicity

Who this works differently for

• In adults aged about 65 with excess weight, 60 g of mixed nuts a day for 16 weeks lowered LDL cholesterol by 0.24 mmol/L and systolic blood pressure by 5 mmHg. — 28 healthy adults aged 65 plus or minus 3 years with BMI 27.9 kg/m2, crossover, 60 g/day of walnuts, pistachio, cashew and hazelnuts for 16 weeks (n = 28) Evidence B source
  LDL cholesterol -0.24 mmol/L (95% CI -0.44 to -0.04, P = 0.019); systolic blood pressure -5 mm Hg (95% CI -8 to -1, P = 0.006); intrahepatic lipid -0.7 percentage point (95% CI -1.3 to -0.1, P = 0.027)
• In 19 adults with lipid transfer protein allergy, a supervised challenge with 2 to 4 nuts at once was negative in every case and cut testing time from 208 to 76 hours. — 19 patients with lipid transfer protein syndrome, 73.7% male, median age 32.5 years, 52 individual nuts tested (n = 19) Evidence C source
  All challenges negative; oral food challenges reduced by 63%, from 52 to 19; testing time from 208 to 76 hours

What is still unknown

• A 2025 review of 28 nut trials found only a modest effect on gut health, with propionate the one outcome that moved favourably and fecal moisture moving the wrong way. — adults aged 18 and over in 28 intervention trials, 6 of them using a mixture of different nuts, at least 1 week of intake (n = 28 trials) Evidence A source
  No effect on fecal pH or intestinal permeability, positive effect on propionate, unfavourable effect on fecal moisture

The bottom line

Selenium is the number to watch in a mixed tin. A cup of unroasted mixed nuts weighs 142 g and carries 208.9 mcg of selenium in the USDA survey record. The adult tolerable upper intake level set by the US Food and Nutrition Board is 400 mcg a day, and it falls to 45 mcg for the youngest children. Brazil nuts are what tips it, at 68 to 91 mcg of selenium each by the National Institutes of Health, which names regular intake of them as a route to selenium toxicity. Those last two are agency documents rather than measurements in people eating mixed nuts. How close any tin comes to that limit depends on how many Brazil nuts are in it: across the 10 USDA records for mixed nuts, selenium runs from 3.7 to 421.5 mcg per 100 g. On nut allergy this page has one small study, and it is about testing rather than about eating. In 19 patients with lipid transfer protein syndrome, median age 32.5 years, a supervised challenge with 2 to 4 nuts at once was negative in every case and cut testing time from 208 to 76 hours across 52 individual nuts. That is a hospital procedure. The association data is larger than the trial data and says something weaker. Each extra 28 g of nuts a week went with 10 percent lower cardiovascular mortality (RR 0.90, 95% CI 0.86 to 0.94) across 63 prospective cohort studies. All-cause mortality in the same pooling came out 8 percent lower (RR 0.92, 95% CI 0.90 to 0.94). Those are observational cohorts, so the figure is an association. The trials that actually added nuts found less. In 388 adults over 40 who were 2 to 6 months past a heart attack, 10 g each of peanuts, cashew and Brazil nuts daily for 16 weeks left LDL cholesterol 3.48 mg/dL from control (95% CI minus 3.45 to 10.41, P = 0.32). In 439 adults with atherosclerotic disease across 5 trials, the only lipid marker that moved was the atherogenic index, by 0.32 units (95% CI minus 0.58 to minus 0.06). One group did better than that. In 28 healthy adults aged 65 plus or minus 3 years with a BMI of 27.9, a crossover gave 60 g a day of walnuts, pistachio, cashew and hazelnuts for 16 weeks. LDL cholesterol fell by 0.24 mmol/L (95% CI minus 0.44 to minus 0.04) and systolic blood pressure by 5 mmHg (95% CI minus 8 to minus 1). Roasting costs about 20 percent of the folate, vitamin C and phosphorus and about 15 percent of the thiamin by the USDA retention factors for nut and seed products, while iron, zinc, magnesium, potassium and copper are listed at full retention. Gut health is the open question. A 2025 review of 28 intervention trials, six of them using a mixture of nuts, found no effect on fecal pH or intestinal permeability, a favourable move in propionate and an unfavourable move in fecal moisture.

Sources

1. mxnt-r5-15 · dataset
   Mixed nuts, unroasted [fdc_id 2707505]: Selenium, Se 147.1 UG per 100 g; 1 cup 142 g = 208.9 UG; 1 package 50 g = 73.5 UG; Quantity not specified 28 g = 41.2 UG
   USDA FNDDS, Food and Nutrient Database for Dietary Studies, fdc_id 2707505 · checked 2026-09-24
2. mxnt-r5-14 · dataset
   NUTS,ROASTED / Retn_Code 2203 / Nut and Seed Products: folate_total_ug 80%, vitamin_c_mg 80%, phosphorus_mg 80%, thiamin_mg 85%, riboflavin_mg 95%, niacin_mg 95%, vitamin_b6_mg 95%, sodium_mg 95%, calcium_mg 100%, iron_mg 100%, magnesium_mg 100%, potassium_mg 100%, zinc_mg 100%, copper_mg 100%
   USDA Table of Nutrient Retention Factors, Release 6, 2007, retention code 2203 · checked 2026-09-24
3. mxnt-r5-01 · meta-analysis of cohorts
   With per 28-g increases in weekly nut intake, the RRs (95% CIs) for CHD, stroke, CVD, CVD mortality and all-cause mortality were 0.96 (0.95-0.97), 0.99 (0.97-1.01), 0.98 (0.97-0.99), 0.90 (0.86-0.94) and 0.92 (0.90-0.94), respectively.
   Arch Cardiovasc Dis, 2026 · checked 2026-09-24
4. mxnt-r5-02 · meta-analysis of RCTs
   They also had no effect on systolic (mean difference [MD]: -1.16 mmHg [95% CI, -5.68 to 3.35], I2 = 0%-moderate certainty of evidence) or diastolic (MD: 0.10 mmHg [95% CI, -2.30 to 2.51], I2 = 0%-high certainty of evidence) blood pressure.
   Nutr Rev, 2025 · checked 2026-09-24
5. mxnt-r5-03 · meta-analysis of RCTs
   Compared to nut-free diets, nut intake did not have a statistically significant effect on lipid profile biomarkers, except on the atherogenic index (MD: -0.32 [95% CI -0.58 to -0.06], I2 = 0% - moderate certainty of the evidence).
   Eur J Nutr, 2024 · checked 2026-09-24
6. mxnt-r5-04 · meta-analysis of RCTs
   The meta-analyses identified a nonsignificant increase in REE associated with nut consumption (weighted mean difference: 28.6 kcal/d; 95% CI: -10.7, 67.8 kcal/d).
   Adv Nutr, 2023 · checked 2026-09-24
7. mxnt-r5-05 · network meta-analysis of RCTs
   In the comparisons of nut consumption versus a control diet, there was no significant increase observed in any of the adiposity-related measures examined except for hazelnut-enriched diets, which raised WC.
   Nutrients, 2021 · checked 2026-09-24
8. mxnt-r5-07 · randomised controlled trial
   no significant difference was found between the groups in low-density lipoprotein cholesterol concentrations (intervention-control difference: 3.48 mg/dL [-3.45 to 10.41], P = 0.32)
   Nutr J, 2024 · checked 2026-09-24
9. mxnt-r5-08 · randomised controlled trial
   In the postprandial period, fat oxidation was higher in the MNG than in the CTG (piAUC: 47.53 ± 5.78 mg/min vs. 27.93 ± 6.98 mg/min; p = 0.048).
   Nutr Metab Cardiovasc Dis, 2026 · checked 2026-09-24
10. mxnt-r5-10 · meta-analysis of RCTs
    Evidence indicates no significant difference in serum lipid profile and DBP between the MED diet supplemented with olive oil and that with mixed nuts in participants at risk of CVD. However, mixed nuts significantly reduce SBP compared to olive oil.
    Nutr Metab Cardiovasc Dis, 2025 · checked 2026-09-24
11. mxnt-r5-11 · agency fact sheet
    The Tolerable Upper Intake Level for selenium is 400 mcg for adults, and it ranges from 45 mcg to 400 mcg for infants, children, and adolescents, depending on age.
    NIH Office of Dietary Supplements, Selenium Fact Sheet for Health Professionals · checked 2026-09-24
12. mxnt-r5-12 · agency fact sheet
    As discussed earlier, Brazil nuts contain very high amounts of selenium (68–91 mcg per nut) and could cause selenium toxicity if consumed regularly.
    NIH Office of Dietary Supplements, Selenium Fact Sheet for Health Professionals · checked 2026-09-24
13. mxnt-r5-06 · randomised crossover trial
    Intrahepatic lipid content (-0.7%-point; 95% CI: -1.3%-point to -0.1%-point; P = 0.027), serum low-density lipoprotein cholesterol concentration (-0.24 mmol/L; 95% CI: -0.44 to -0.04 mmol/L; P = 0.019), and systolic blood pressure (-5 mm Hg; 95% CI: -8 to -1 mm Hg; P = 0.006) were lower after the mixed nut intervention.
    Am J Clin Nutr, 2024 · checked 2026-09-24
14. mxnt-r5-13 · observational challenge study
    Nineteen patients (73.7% male; median age 32.5 years) underwent MixNut, testing 52 individual nuts. All challenges were negative. The MixNut approach reduced the number of OFC by 63% (from 52 to 19) and total testing time from 208 to 76 h.
    Nutrients, 2025 · checked 2026-09-24
15. mxnt-r5-09 · meta-analysis of RCTs
    In summary, the available evidence indicates that nuts have modest effect on gut health, but the substantial heterogeneity between studies may hinder further conclusions.
    Adv Nutr, 2025 · checked 2026-09-24