Does protein help with hair growth and hair loss?

For people who already eat enough protein, the answer is unknown, because it has not been tested. A systematic review in JAMA Dermatology, searching up to October 2021, looked at 30 studies of nutrition and hair loss, 17 of them randomized trials, and found no study that tested a diet, eating more protein included. Where protein is genuinely short, the picture is different. After weight-loss surgery 57% of patients lose hair, and in a cohort of 555 of them, those with hair loss had lower blood markers of protein and iron. That is an association and it does not show that protein would fix it.

Unsettled. The trials people cite for protein and hair tested branded multi-ingredient products: marine protein, keratin or fish collagen mixed with vitamins, minerals and amino acids. Some showed gains on hair-cycle measures. None can tell you whether the protein did anything, because it was never tested alone.

What the trials found

Hair supplements, pooled

A 2026 meta-analysis of 14 studies with 967 adults with hair loss or thinning tested branded products including Viviscal, Nutrafol, Nourkrin, Lambdapil and Cynatine HNS. Against placebo, anagen hair density, the density of hairs in the growing phase, rose by 10.48 (95% CI 8.81 to 12.14). Total hair count, the number most people care about, did not change significantly (p = 0.06). The analysis mixes randomized trials with open-label and proof-of-concept studies, and its authors call for independent research.

A 2025 network meta-analysis of 19 randomized trials with 1,658 people with pattern hair loss compared 16 supplements. The ones that raised hair density against placebo were a standardized plant extract (Nutrafol), apple extract, tocotrienols, pumpkin seed oil and an extract of Cistanche and Laminaria. Marine extracts and amino acids were in the comparison and were not among the products that raised hair density.

Single trials of protein-based products

In an assessor-blinded randomized trial on 83 people with pattern hair loss or chronic telogen effluvium, a daily tablet of hydrolyzed fish collagen (300 mg) with taurine, cysteine, methionine, iron and selenium was added to drug treatment for 12 weeks. The global hair score reached 1.67 against 0.66 on drugs alone, and 50% against 23% reached a score of 2 or more. There was no placebo, and the tablet also carried iron and selenium.

In a 1992 trial on 40 young men with pattern baldness, the marine-protein supplement Viviscal raised non-vellus hair by 38% over 6 months against 2% on a fish extract tablet. The comparator was another fish product, the trial was small, and later trials have not reproduced a result of that size.

A placebo-controlled trial on 50 women gave 500 mg of keratin with vitamins and minerals, or maltodextrin, for 90 days. The abstract gives no effect sizes, so this trial cannot say how much, if anything, the capsule changed.

When protein is missing

The clearest link between protein and hair comes from weight-loss surgery. Across 18 observational studies, 57% of patients lost hair after surgery (95% CI 42 to 71%), more often those with lower zinc, folic acid and ferritin. Protein status was not pooled in that review. In a cohort of 555 bypass and sleeve patients, protein and iron markers in the blood were lower in those losing hair, and hair loss fell from 65% in the first year to 35% at three years or more. Most of them took multivitamins, and the markers are blood levels rather than intake. In 67 sleeve gastrectomy patients, a smaller rise in serum albumin one month after surgery predicted moderate or severe hair loss at three months (OR 0.687). Albumin also moves with inflammation and hydration, so it is a rough stand-in for protein.

Who should be careful

Not for everyone. Many hair formulas pair protein with selenium, and chronically high selenium causes the problem you are trying to fix. NIH lists hair loss and brittle or lost nails as the most common signs of selenium excess and sets the adult upper limit at 400 mcg a day. Biotin, often found in dietary supplements, can distort blood tests. The FDA warns it can cause incorrect results that may go undetected, in a notice about troponin, the test used to diagnose a heart attack.

Side effects of the supplements themselves were mild in the trials that reported them: bloating, diarrhea and itching, recorded for 11 of the interventions in the 19-trial network, and the authors note that many trials reported safety incompletely. People who have had weight-loss surgery are the group where hair loss and low protein markers go together, and hair loss there is a question for the team that follows them after surgery. This page has no evidence on high protein intake and kidney disease, because the search found none tied to hair. Nothing here is a reason to eat more protein for hair, and that matters most for anyone whose protein intake is set by a doctor.

What expert bodies say

We found no agency or professional body that takes a position on protein for hair loss. The two agency statements on this page are about other ingredients that ride along in hair products: the NIH Office of Dietary Supplements on selenium excess, and the FDA on biotin and lab tests.

How we searched

What would change this answer

• A placebo-controlled trial of protein alone, whey or collagen without added vitamins and minerals, in people with telogen effluvium who already eat enough, counting hairs with a phototrichogram. That would answer the question on this page directly. The trials registry lists no such trial.
• A trial of protein repletion after weight-loss surgery with hair loss as an outcome. The cohorts point there and nobody has tested it.
• Independent trials of the branded products, so it becomes clear whether their effects come from protein, from other ingredients, or from small trials linked to the makers.

Sources

1. ev-prh-01 · Meta-analysis or systematic review · systematic review and meta-analysis including RCTs and open-label trials · n = 967
   Meta-analysis demonstrated significant improvements with oral supplements versus placebo: reduced telogen hair density (mean difference [MD] -5.91, 95% confidence interval [CI] -6.74 to -5.08, p < 0.00001), increased anagen hair density (MD 10.48, 95% CI: 8.81 to 12.14, p < 0.00001), and reduced telogen proportion (MD 3.08, 95% CI: -3.35 to -2.81, p < 0.00001).
   
   Who: adults with alopecia or hair thinning in 14 studies, mostly RCTs of 12 weeks to 12 months, testing Ceramosides, Nutrafol, Nourkrin, Lambdapil, Viviscal, Forti5, GFM and Cynatine HNS
   Effect: anagen hair density MD 10.48 (95% CI 8.81 to 12.14); telogen hair density MD -5.91 (-6.74 to -5.08); total hair count no significant difference (p = 0.06)
   Certainty: mixes RCTs with open-label and proof-of-concept studies; multi-ingredient branded products, so no effect can be assigned to protein; the authors call for independent research
   J Cosmet Dermatol, 2026 · checked 2026-10-06 · we read the abstract
2. ev-prh-02 · Meta-analysis or systematic review · systematic review of RCTs and clinical studies · n = 30 studies
   No diet-based interventional studies met inclusion criteria.
   
   Who: people with alopecia or hair loss without a known baseline nutritional deficiency; databases searched to October 2021
   Effect: 17 RCTs, 11 non-randomized studies and 2 case series of supplements; zero diet-based interventional studies eligible
   Certainty: Oxford CEBM quality grading; English-language only; the absence is a finding about the literature
   JAMA Dermatol, 2023 · checked 2026-10-06 · we read the abstract
3. ev-prh-03 · Meta-analysis or systematic review · systematic review and network meta-analysis of RCTs · n = 1658
   Results showed that compared with placebo, standardized plant extracts (Nutrafol), apple extract (AMSbzs, AMS), tocotrienols, pumpkin seed oil (PSO), and a compound extract of Cistanche and Laminaria (MK-R7) significantly improved hair density.
   
   Who: patients with androgenetic alopecia in 19 randomized controlled trials of 16 dietary supplements, 16 to 32 weeks
   Effect: hair density vs placebo: Nutrafol SMD 0.90 (0.48 to 1.33), apple extract 0.81 to 0.85, tocotrienols 0.86, pumpkin seed oil 0.59, MK-R7 0.58
   Certainty: GRADE applied; small trials, many single-study nodes; marine extracts and amino acids were in the network but not among products that raised hair density
   Front Nutr, 2025 · checked 2026-10-06 · we read the abstract
4. ev-prh-04 · Meta-analysis or systematic review · systematic review and network meta-analysis of RCTs, adverse events · n = 1658
   The results showed that among the 19 studies included in the analysis, 11 interventions reported adverse events, all of which were mild symptoms such as bloating, diarrhea, and itching.
   
   Who: patients with androgenetic alopecia in 19 randomized controlled trials of dietary supplements
   Effect: 11 interventions reported adverse events, all mild (bloating, diarrhea, itching), resolving without treatment
   Certainty: the authors note safety reporting was incomplete in many trials
   Front Nutr, 2025 · checked 2026-10-06 · we read the fulltext
5. ev-prh-05 · Observational data · systematic review and meta-analysis of observational studies · n = 18 studies
   The pooled results showed that the incidence of hair loss after MBS was 57% (95% CI 42-71%).
   
   Who: patients after metabolic and bariatric surgery in 18 observational studies
   Effect: pooled incidence of hair loss 57% (95% CI 42 to 71%), falling with longer follow-up; lower serum zinc, folic acid and ferritin in those with hair loss
   Certainty: observational data; protein status was not pooled; associations, not proof that a deficiency causes the hair loss
   Obes Surg, 2021 · checked 2026-10-06 · we read the abstract
6. ev-prh-06 · Observational data · prospective cohort · n = 555
   In subjects with hair loss, blood parameters of protein and iron metabolism were significantly lower than in subjects without hair loss, both in the ST and LT.
   
   Who: adults after Roux-en-Y gastric bypass or sleeve gastrectomy, 555 studied at 1 year or less and 494 at 3 years or more
   Effect: hair loss 65% short term vs 35% long term; protein and iron parameters significantly lower in those with hair loss; zinc and B vitamins not different
   Certainty: association only; most patients took multivitamins; protein markers are blood levels, not intake
   Obes Surg, 2020 · checked 2026-10-06 · we read the abstract
7. ev-prh-07 · Observational data · prospective cohort · n = 67
   Logistic regression analysis showed that the changes in serum albumin (OR = 0.687, P < 0.05) and calcium (OR = 0.821, P < 0.05) at 1 month postoperatively were independent factors for the occurrence of hair loss.
   
   Who: patients with obesity after laparoscopic sleeve gastrectomy, single center, followed 3 months with dermoscopy
   Effect: change in serum albumin at 1 month OR 0.687 and calcium OR 0.821 as independent factors for hair loss
   Certainty: small single-center cohort; albumin also reflects inflammation and hydration, not only protein intake
   Int J Surg, 2026 · checked 2026-10-06 · we read the abstract
8. ev-prh-08 · Randomized controlled trial(s) · randomized assessor-blinded controlled trial, no placebo · n = 83
   At week 12 the GAS score in Group A was statistically significant higher in comparison with Group B (1.67 ± 0.16 and 0.66 ± 0.20, p < 0.001; Mann-Whitney test).
   
   Who: 83 subjects with androgenetic alopecia or chronic telogen effluvium, 1 tablet a day of hydrolyzed fish collagen (300 mg) with taurine, cysteine, methionine, iron and selenium plus drug treatment, vs drug treatment alone, 12 weeks
   Effect: global assessment score at week 12: 1.67 vs 0.66 (p < 0.001); score 2 or more in 50% vs 23%
   Certainty: no placebo, open to participants; product also contains iron and selenium, so the effect cannot be given to protein
   Skin Res Technol, 2023 · checked 2026-10-06 · we read the abstract
9. ev-prh-09 · Randomized controlled trial(s) · randomized double-blind parallel-group trial with active comparator · n = 40
   After 6 months' treatment, patients receiving ViviScal showed a mean increase in non-vellus hair of 38% compared with a 2% increase in the fish extract treatment group (P < 0.0001).
   
   Who: young males with hereditary androgenic alopecia, 20 on ViviScal and 20 on fish extract tablets daily for 6 months
   Effect: non-vellus hair +38% vs +2% (P < 0.0001)
   Certainty: old, small, active comparator not placebo; most had used minoxidil before; an extreme result (95% cure) that later trials have not reproduced at that size
   J Int Med Res, 1992 · checked 2026-10-06 · we read the abstract
10. ev-prh-10 · Randomized controlled trial(s) · randomized double-blind placebo-controlled trial · n = 50
    The active group (n = 25) received 2 capsules containing Cynatine HNS, comprised of Cynatine brand keratin (500 mg) plus vitamins and minerals, per day, and the placebo group (n = 25) received 2 identical capsules of maltodextrin per day for 90 days.
    
    Who: 50 females, 2 capsules a day of Cynatine HNS (500 mg keratin plus vitamins and minerals) or maltodextrin placebo for 90 days
    Effect: the quoted passage gives the design only; effect sizes not given in the abstract
    Certainty: small, product-specific, no numbers in the abstract; vitamins and minerals in the same capsule
    ScientificWorldJournal, 2014 · checked 2026-10-06 · we read the abstract
11. ev-prh-11 · Position of an expert body · agency fact sheet · n = —
    The most common clinical signs of chronically high selenium intakes, or selenosis, are hair loss and nail brittleness or loss.
    
    Who: general population; selenium from foods and supplements
    Effect: selenosis signs: hair loss and nail brittleness or loss; UL 400 mcg/day adults, 45 to 400 mcg for younger ages
    Certainty: agency summary of the DRI evidence; many hair formulas combine protein with selenium
    NIH Office of Dietary Supplements, Selenium Fact Sheet for Health Professionals · checked 2026-10-06 · we read the section
12. ev-prh-12 · Position of an expert body · agency safety notice · n = —
    Health care providers, lab personnel, and lab test developers should be aware that biotin, often found in dietary supplements, can significantly interfere with certain lab tests and cause incorrect test results which may go undetected.
    
    Who: people taking biotin-containing dietary supplements who have blood tests
    Effect: incorrect lab results that may go undetected; notice issued for troponin assays
    Certainty: about biotin, not protein; relevant because hair protein shakes and supplements commonly contain high-dose biotin
    US FDA, Biotin Interference with Troponin Lab Tests, 2022 · checked 2026-10-06 · we read the section