The brush filling up, the ponytail thinning: hair loss is concerning, and the supplement aisle promises much. Studies are more precise. Among 5,110 women aged 35 to 60 followed in a French cohort, 9% described excessive hair loss, and among them 59% had low iron reserves, compared to 48% in the rest of the cohort. The best hair supplement therefore depends on the cause of hair loss, and first on what a blood test reveals.
This comparison reviews studies identified via PubMed, nutrient by nutrient, then medical treatments that serve as a point of comparison, before a table of evidence levels, a choice by profile and a realistic timeline, as hair takes three to four months to respond.
The cause first : diffuse hair loss three to four months after childbirth, illness, a diet or shock is most often telogen effluvium, which resolves on its own; progressive thinning of the crown suggests androgenetic alopecia; round patches suggest alopecia areata. A blood test (ferritin, zinc, vitamin D, thyroid) settles the question of deficiencies.
Supplements with supporting data : iron when ferritin is low, zinc when serum zinc is low (9 out of 15 patients with alopecia areata who were deficient regrew hair in 12 weeks, a statistically non-significant result), vitamin D when it is lacking (deficiency 3.1 times more common in hair loss). Biotin only helps in cases of proven deficiency, which is rare; collagen has trials on skin and nails, none on hair. An omega-3 and antioxidant complex improved density in 6 months, a keratin complex reduced hair loss by 34% versus placebo in 90 days. For androgenetic alopecia, minoxidil remains the reference standard.
- Before choosing: identifying the cause of hair loss
- When to consult, and what tests to request
- Iron and ferritin: the first deficiency to check
- Zinc: the best-documented mineral in those with deficiency
- Vitamin D: solid associations, few trials
- Biotin and B vitamins: useful only in cases of deficiency
- Collagen and keratin: what the trials really measure
- Omega-3 and antioxidants
- Plants, selenium, vitamin A: what helps and what harms
- The comparison point: minoxidil and medical treatments
- Which supplement for which profile, and in how long
- Frequently asked questions
Before choosing: identify the cause of hair loss
Telogen effluvium is the leading cause of diffuse hair loss. According to a 2015 review, hair loss appears 3 to 4 months after the triggering event (fever, surgery, childbirth, crash diet, medication, shock) without revealing its cause: blood tests should rule out endocrine, nutritional, or autoimmune origin. Typical case, the postpartum period : in a study comparing 116 women at four stages (pregnancy, 4th month and first year after childbirth), the proportion of growing hair was lowest at the 4th month postpartum, and the variations remained moderate in most cases.
Androgenetic alopecia (female-pattern hair loss in women) is a progressive thinning: hair growth cycles shorten and thick hair is replaced by fine hair. It affects nearly 50% of men and women by age 50. In 178 postmenopausal women aged 50 to 65, its prevalence reached 52.2%, most often at a mild stage, and a body mass index of 25 or higher multiplied the risk by 2.65: an association, not a cause.
The thyroid acts directly on the hair follicle: on human follicles cultured in the laboratory, thyroxine prolongs the growth phase and stimulates matrix cell multiplication. Both excess and deficiency of thyroid hormones can therefore cause hair loss, hence TSH in the blood work. Stress and season also play a role: see our articles on cortisol and stress and autumn hair loss.
When to consult, and what blood work to request
Reviews converge: supplements only have evidence in people with deficiencies. Guo and Katta (2017) recommend asking patients about their medical history, diet, and risk factors for deficiency, ordering blood work in the presence of these factors, and correcting any identified deficiency; some supplements in excess worsen hair loss.
Ferritin is the first marker to check. The review by Trost and colleagues (Cleveland Clinic, 2006) reminds us that hemoglobin detects iron deficiency but ferritin confirms it, that it can be falsely elevated in case of infection or inflammation, and that the cause must be sought: heavy menstrual periods and pregnancy before menopause, digestive bleeding or malabsorption in men and after menopause. These authors systematically screen for iron deficiency in their hair loss patients, while acknowledging that formal evidence is lacking. Serum zinc, 25-hydroxyvitamin D, and TSH complete the basic blood work.
Bald patches, red, painful or scaly scalp, hair loss lasting more than six months, marked fatigue, very heavy menstrual periods, unexplained weight changes. The dermatologist distinguishes effluvium, androgenetic alopecia, and alopecia areata by pull test, trichogram, and dermoscopy. If you are taking biotin, inform your doctor: according to Almohanna's review (2019), it can interfere with laboratory tests.
Iron and ferritin: the first deficiency to check
Iron deficiency is the most common nutritional deficiency worldwide and primarily affects menstruating women. Its link with hair loss has been studied almost exclusively in women, with conflicting results.
In 5,110 women aged 35 to 60 who completed a standardized questionnaire and had their ferritin measured, 43% reported no hair loss, 48% moderate hair loss, and 9% excessive hair loss. Among women with excessive hair loss, 59% had ferritin below 40 µg/L, compared to 48% in the rest of the population. In multivariate analysis, low iron reserves represented a risk factor for hair loss in non-menopausal women.
Deloche C, Bastien P, Chadoutaud S, et al. Eur J Dermatol 2007;17(6):507-512. DOI: 10.1684/ejd.2007.0265
This study, conducted by researchers from a cosmetics group and INSERM (SU.VI.MAX cohort), is based on a questionnaire and shows an association, not a cause. Conversely, a controlled study of 381 women with female-pattern alopecia or chronic effluvium and 76 controls found no significant difference: ferritin below 40 µg/L in 58.8% and 63.8% of patients before menopause, versus 72.3% of controls. Between the two, 80 women aged 18 to 45 had an average ferritin of 14.7 µg/L (effluvium) and 23.9 µg/L (female alopecia), compared to 43.5 µg/L in 40 controls.
Almohanna, Ahmed, Tsatalis and Tosti's review (2019) notes that the definition of deficiency ranges from 15 to below 70 µg/L depending on the study, that a threshold of 30 µg/L detects iron deficiency with 92% sensitivity and 98% specificity, and that some authors recommend maintaining ferritin above 40 µg/L, others above 70 µg/L, to reverse severe effluvium. Evidence for iron's effectiveness on effluvium is still considered insufficient.
Two populations deserve attention: women with heavy menstrual periods, and vegetarians, whose ferritin is on average 29.71 µg/L lower than that of non-vegetarians according to a meta-analysis of 24 studies (a difference of 17.70 µg/L in women before menopause, of 61.88 µg/L in men).
If your ferritin is low, iron should be taken with medical monitoring: an excess causes overload, which is dangerous in case of hemochromatosis. Our Iron bisglycinate provides 14 mg of iron, 80 mg of vitamin C and 200 µg of vitamin B9 per capsule; it is reserved for people whose blood test confirms the deficiency, and is not recommended during pregnancy, breastfeeding and in case of hemochromatosis. See our guides on iron deficiency and hair loss, low ferritin and iron bisglycinate.
Zinc: the best-documented mineral in those with deficiencies
Zinc participates in hundreds of enzymes and in the Hedgehog pathway, involved in follicle formation. Hair loss is a classic sign of established deficiency; the question remains what happens in common hair loss.
In 312 patients with alopecia areata, male pattern baldness, female pattern baldness or telogen effluvium, mean serum zinc was 84.33 µg/dL, compared to 97.94 µg/dL in 30 healthy controls, a significant difference, whereas copper did not differ. Each type of hair loss had lower zinc. The proportion of patients below 70 µg/dL was significantly higher in alopecia areata (odds ratio 4.02) and telogen effluvium.
Kil MS, Kim CW, Kim SS. Ann Dermatol 2013;25(4):405-409. DOI: 10.5021/ad.2013.25.4.405
Two meta-analyses on alopecia areata agree: 10 articles and 764 subjects in 2017, lower serum zinc and selenium, no difference for copper, iron, ferritin or magnesium; 34 articles and 4,931 participants in 2025, lower zinc (standardized difference of −0.69, a medium effect) and lower vitamin D. These are associations: low zinc accompanies the disease, without knowing whether it precedes it.
Supplementation trials are small. In 15 patients with alopecia areata and low serum zinc, 12 weeks of zinc at 50 mg per day in gluconate form increased serum zinc from 56.9 to 84.5 µg/dL, with regrowth in 9 out of 15 patients (66.7%), not statistically significant; zinc increased more in responders (p = 0.003). Five patients with zinc deficiency effluvium were all cured or improved by oral zinc (polaprezinc). Conversely, a double-blind trial in 1981 with 220 mg of zinc sulfate twice daily for 3 months showed no benefit in alopecia areata. Supplementation makes sense when serum zinc is low (proposed threshold: 70 µg/dL); nothing demonstrates benefit without deficiency.
| Study | Population | Result on zinc |
|---|---|---|
| Kil, 2013, case-control | 312 patients, 4 types of hair loss, 30 controls | 84.33 vs 97.94 µg/dL; low zinc more frequent in alopecia areata and effluvium |
| Wu, 2025, meta-analysis | 34 articles, 4,931 participants, alopecia areata | Lower zinc (−0.69) and lower vitamin D; copper no difference |
| Park, 2009, open trial | 15 patients, alopecia areata, low serum zinc | Regrowth in 9 out of 15 after 12 weeks of 50 mg zinc per day in gluconate form, not significant |
Who risks zinc deficiency? Heavy consumers of whole grains and legumes (phytates slow absorption), light meat and fish eaters, people with digestive illness. In vegetarians, a meta-analysis of 26 studies measures serum zinc lower by 0.93 µmol/L, especially in women and vegans.
In Park's trial, tablets provided 50 mg of zinc per day in gluconate form, in patients with alopecia areata and deficient, under medical supervision. Our Zinc provides 104.4 mg of zinc gluconate, or 14.16 mg of elemental zinc (141.6% of reference nutritional values) and 2 mg of vitamin B6 in two capsules during meals: a nutritional dose, approximately 3.5 times lower than that of the trial, the pill organizer covering two months of a first cycle. It is not recommended for pregnant or breastfeeding women. Excess zinc is not trivial: digestive disorders, interference with iron and long-term immune defense decline, according to Guo and Katta. See also the benefits of zinc.
Vitamin D: solid associations, few trials
Vitamin D plays a role in the hair follicle cycle, whose receptor is more highly expressed during the growth phase. In humans, data are abundant but observational.
In 3,374 patients with non-scarring alopecia (alopecia areata, female pattern hair loss, androgenetic alopecia, telogen effluvium) compared to 7,296 controls, serum 25-hydroxyvitamin D was lower by an average of 7.29 ng/mL, and vitamin D deficiency was 3.11 times more frequent (95% confidence interval 2.29 to 4.22).
Chen Y, Dong X, Wang Y, et al. J Cosmet Dermatol 2024;23(4):1131-1140. DOI: 10.1111/jocd.16093
A 2024 meta-analysis details by diagnosis: deficiency in 51.94% of patients with alopecia areata, 50.38% in female pattern hair loss, 47.38% in male pattern hair loss, and 53.51% in telogen effluvium. Compared to controls, the association was significant only for alopecia areata (deficiency 2.84 times more frequent) and female pattern hair loss (5.24 times, wide confidence interval 1.50 to 18.33), not for male pattern hair loss.
This body of evidence justifies measuring and correcting vitamin D when levels are low. What is missing are randomized trials measuring hair regrowth under vitamin D supplementation: we identified none in PubMed. Supplementation corrects a documented deficiency, not hair loss itself. Our guide vitamin D in IU per day specifies the dose; our Plant-based Vitamin D3 in drops, derived from lichen, provides 1,000 IU per drop, 2 drops daily for adults.
Biotin and B vitamins: useful only in case of deficiency
Biotin deficiency (vitamin B8) causes hair loss, skin rash, and brittle nails, but it is rare: the intestinal flora produces it, and it occurs mainly only in cases of congenital enzymatic deficiency, prolonged anticonvulsant or antibiotic treatments, or excess raw egg white consumption.
In reviewing published cases and randomized trials, the authors identified 18 cases of biotin used for hair or nail disorders. In all cases, patients had an underlying condition, and all improved on biotin. The authors conclude that these situations are rare and evidence is lacking to recommend biotin to healthy people.
Patel DP, Swink SM, Castelo-Soccio L. Skin Appendage Disord 2017;3(3):166-169. DOI: 10.1159/000462981
Almohanna's review adds that only cases of children with uncombable hair syndrome, improved by 3 to 5 mg daily for 3 to 4 months, support its use, and that biotin is not supported for androgenetic alopecia, telogen effluvium, or alopecia areata. According to Guo and Katta, its presence in hair supplements comes mainly from its results on brittle nails. See our article on biotin.
Other B vitamins follow the same logic: pellagra (B3 deficiency) is accompanied by alopecia but has become rare, no difference in folates (B9) was measured in 91 patients with diffuse hair loss, and data on B12, B2, and folates are too limited to recommend testing.Pantothenic acid (B5) appears in combined formulas whose individual effect cannot be isolated.
For someone with limited dietary variety, the reasonable goal is to meet reference intakes, not to multiply doses. Our Multivitamins provide in two capsules 100% of the daily reference intakes of 12 vitamins, including 50 µg of biotin and 5 µg of vitamin D3, as well as 10 mg of zinc and 10 mg of iron. A ferritin test remains preferable before starting regular iron supplementation.
Collagen and keratin: what trials actually measure
Hydrolyzed collagen is well studied in dermatology, not for hair. A meta-analysis of 19 double-blind randomized trials (1,125 participants, 95% women) concludes that 90 days of hydrolyzed collagen improve skin hydration and elasticity and reduce wrinkles compared to placebo. For nails, one open-label trial without placebo in 25 participants taking 2.5 g of peptides daily for 24 weeks measured a 12% increase in growth and a 42% reduction in broken nails; two co-authors worked for the manufacturer.
For hair, we identified no randomized trial in PubMed measuring hair density or loss under collagen alone. Collagen provides glycine and proline, but hair is made of keratin, rich in cysteine: nothing allows us to claim that collagen thickens or promotes hair regrowth. See our article collagen, hair and nails.
Studies on skin and nails used 2.5 to 10 g of peptides daily. Our capsules provide 1,208 mg; for the scale of the studies, our Marine collagen in powder provides 10 g of collagen, 210 mg of hyaluronic acid and 80 mg of vitamin C per day. In both cases, the documented benefit concerns skin and nails. Pregnant or breastfeeding women: consult a health professional.
Oral keratin has, for its part, a trial on hair. Fifty women aged 40 to 71 with damaged hair received 500 mg per day of a hydrolyzed sheep's wool keratin associated with 15 mg of zinc, copper, biotin and B vitamins, or placebo, for 90 days in a double-blind study. In the pull test, hair loss decreased by 46.6% at 90 days, or 34.4% less than placebo; the ratio of growing hair to resting hair improved by 9.2%, resistance to breakage by 5.9%. Two caveats: the product and placebo were supplied by the ingredient manufacturer, one of whose authors is an employee, and the formula combined zinc and vitamins, which prevents attributing the effect to keratin alone. Our article keratin in capsules details this trial.
Omega-3 and antioxidants
A deficiency in essential fatty acids (omega-6 and omega-3), observed during inadequate parenteral nutrition or malabsorption, causes loss of hair and eyebrows. Outside these cases, the most cited trial concerns a complex combining omega-3, omega-6 and antioxidants.
In 120 healthy women, 6 months of supplementation with omega-3, omega-6 and antioxidants improved hair density evaluated on standardized photographs compared to the control group (p less than 0.001), reduced the proportion of hair in the resting phase on trichogram and increased the proportion of growing hair greater than 40 µm in diameter. At 6 months, 89.9% of supplemented women reported reduced hair loss, 86.1% improved diameter and 87.3% improved density.
Le Floc'h C, Cheniti A, Connétable S, et al. J Cosmet Dermatol 2015;14(1):76-82. DOI: 10.1111/jocd.12127
Several authors of this trial worked for the laboratory that marketed the product, it was conducted without placebo (40 control women taking nothing, versus 80 supplemented), and the dose of EPA and DHA is not specified (460 mg of fish oil and 460 mg of blackcurrant seed oil per day); Guo and Katta draw only limited conclusions from it, the formula combining several fatty acids and antioxidants. As for antioxidants, at high doses polyphenols can produce free radicals instead of neutralizing them: fruits, vegetables and cereals are considered safer than high isolated doses.
No trial has tested EPA and DHA alone on hair loss. If you eat little oily fish, our Omega 3 Omegavie provides 1,200 mg of omega-3, including 640 mg of EPA and 440 mg of DHA, in four capsules. See the proven effects of omega-3.
Plants, selenium, vitamin A: what helps and what harms
Saw palmetto (saw palmetto), studied for its anti-androgenic action, is the best documented plant extract. A 2020 systematic review pooled 5 randomized trials and 2 cohorts on oral or topical supplements dosed from 100 to 320 mg: depending on studies, improvement of 60% in hair quality, 27% in hair count, increased density in 83.3% of patients and stabilization in 52%, without serious adverse effects, but without robust data, the products tested often combining several ingredients. Other plants have only isolated trials.
Selenium : recommended intake of 55 µg per day, toxicity beyond 400 µg. In 2008, a liquid supplement containing 200 times the indicated concentration caused 201 cases of poisoning in the United States, at a median estimated dose of 41,749 µg per day: diarrhea (78%), fatigue (75%), hair loss (72%), damaged nails (61%), and hair loss persisting at 90 days in 29% of people. See our article on selenium. Vitamin A : beyond approximately 10,000 IU per day, excess causes alopecia and skin, visual and bone disorders. Vitamin E : excess is also associated with hair loss. Guo and Katta wonder why very popular hair supplements contain these three nutrients at high doses.
The comparison point: minoxidil and medical treatments
For androgenetic alopecia, no supplement reaches the level of evidence of medical treatments, which shows what can be expected from a nutrient.
In 5,290 women with female alopecia, topical minoxidil achieved moderate to marked regrowth in 157 out of 593 participants, compared to 77 out of 555 under placebo (relative risk 1.93), with a gain of 13.18 hairs per cm² compared to placebo in eight studies (1,242 participants). Concentrations of 2% and 5% showed no difference between them, and finasteride at 1 mg did not perform better than placebo in women.
van Zuuren EJ, Fedorowicz Z, Schoones J. Cochrane Database Syst Rev 2016;2016(5):CD007628. DOI: 10.1002/14651858.CD007628.pub4
In men, a network meta-analysis of 23 studies (JAMA Dermatology, 2022) compared minoxidil, finasteride, and dutasteride: at 24 weeks, dutasteride at 0.5 mg per day increased total hair count the most, and oral minoxidil at 5 mg per day increased terminal hair count the most, with 29.3 to 29.8 more hairs per cm² than its topical forms. In 1,404 patients on low-dose oral minoxidil, the most frequent adverse effect was hair growth (15.1%); systemic effects (dizziness 1.7%, water retention 1.3%) led to treatment discontinuation in 1.2% of patients. These treatments require medical prescription and monitoring.
Correcting iron, zinc, or vitamin D deficiency remains relevant when using minoxidil: these deficiencies are more common in cases of hair loss, regardless of the cause.
Which supplement for which profile, and how long it takes
The table summarizes evidence level, trial doses, and relevant profile. Strong: randomized trials or meta-analyses with effects on hair. Moderate: small trials, open-label, or manufacturer-linked. Associative: blood level comparisons. Weak: isolated cases.
| Nutrient | Evidence Level | Dose in Trials | Relevant Profile |
|---|---|---|---|
| Iron | Associative in women, small and contradictory trials | 50 mg elemental iron twice daily, with L-lysine, in a study cited by Almohanna's review | Confirmed low ferritin, heavy menstruation, vegetarians |
| Zinc | Moderate in deficient cases (9 out of 15 in alopecia areata, not significant), null without deficiency | 50 mg zinc per day as gluconate, 12 weeks | Low serum zinc, alopecia areata, telogen effluvium, vegetarians |
| Vitamin D | Associative, several meta-analyses, no hair regrowth trials | Not studied on hair; correction of measured deficiency | Low levels, alopecia areata, female alopecia |
| Biotin | Weak, 18 cases with underlying pathology | 3 to 5 mg per day, 3 to 4 months, in deficient children | Confirmed deficiency only |
| Collagen | Strong on skin, moderate on nails, absent on hair | 2.5 to 10 g of peptides per day, 90 days to 24 weeks | Skin and nails objective |
| Keratin (complex) | Moderate, one trial linked to the ingredient manufacturer | 500 mg per day with zinc, copper, biotin, and B vitamins, 90 days | Damaged hair, moderate diffuse hair loss |
| Omega-3, omega-6, and antioxidants | Moderate, one trial without placebo, authors linked to the laboratory | 460 mg fish oil and 460 mg blackcurrant oil per day, 6 months | Diffuse hair loss without deficiency, fine hair |
| Saw Palmetto | Moderate, 5 small trials, combined products | 100 to 320 mg per day | Mild androgenetic alopecia, with medical supervision |
| Selenium, vitamin A, vitamin E | Documented toxicity in excess | Do not exceed: 400 µg and 10,000 IU per day | Non-deficient individuals |
Confirmed iron deficiency : iron, ferritin monitoring at 3 months and investigation of the underlying cause; see when to take iron. Vegetarian or vegan : ferritin and serum zinc are on average lower; comprehensive testing is necessary before choosing between zinc and iron.
Postpartum : hair shedding from the 3rd to 6th month after delivery is most often telogen effluvium that resolves within a year; ferritin testing is warranted. During breastfeeding, our Zinc and Iron bisglycinate are not recommended; only the physician or midwife decides on supplementation. Menopause : in a study of 178 postmenopausal women, more than half presented female pattern alopecia, most often mild; among women with female pattern alopecia regardless of age, vitamin D deficiency is 5.24 times more frequent. Vitamin D and ferritin testing, then minoxidil discussed with the dermatologist if hair thinning progresses; see our article on menopause.
Fine hair without deficiency : the profile with the weakest evidence. Omega-3 and antioxidant complexes (6 months) and keratin (90 days) are the only ones to have measured improvement in women without deficiency, with disclosed ties to their manufacturers; collagen has evidence for skin and nails, not for hair density.
Zinc gluconate combined with vitamin B6, in vegetable capsules. Two capsules daily with meals provide 104.4 mg of zinc gluconate, or 14.16 mg elemental zinc, and 2 mg of vitamin B6, in a bottle of 120 capsules, lasting two months. Not recommended for pregnant or nursing women.
View ZincOur analysis of 8 active ingredients studied for hair loss completes this comparison.
Frequently asked questions
What is the best hair supplement?
The one that corrects what you're lacking: iron if ferritin is low, zinc when serum zinc is low (9 out of 15 patients with alopecia areata and deficiency regrew hair in 12 weeks, a statistically non-significant result), vitamin D when it's deficient. Without deficiency, only omega-3 and antioxidant complexes (6 months) or keratin (34 percent less shedding versus placebo in 90 days) have trials, linked to their manufacturers. A blood test guides the choice.
What is the best zinc for hair?
Published trials used 50 mg of zinc daily in gluconate form for 12 weeks in patients with alopecia areata and zinc deficiency, with regrowth in 9 out of 15, a statistically non-significant result; no study compares zinc forms for hair. What matters: low serum zinc at baseline, a reasonable dose with meals, and monitoring at 3 months.
Should you take iron for hair loss?
Only if a blood test shows low ferritin. In 5,110 women, ferritin below 40 micrograms per liter was a risk factor for excessive shedding, but a study of 381 women found no greater deficiency in those losing hair than in controls. Excess iron is dangerous, especially in hemochromatosis.
Is biotin effective for hair?
Only in case of deficiency, which is rare. A 2017 review found only 18 published cases, all with an underlying condition, all improved. No trial shows an effect in healthy people, and biotin can skew laboratory tests.
Does vitamin D make hair grow?
Meta-analyses show that vitamin D deficiency is 3.1 times more common in people losing hair, and 5.2 times in female alopecia. No randomized trial has measured hair regrowth with vitamin D: correcting a low level is justified, expecting regrowth has no data to support it.
Is collagen good for hair?
Evidence concerns skin (19 randomized trials: hydration, elasticity, and wrinkles improved in 90 days) and nails (growth increased by 12 percent, brittle nails reduced by 42 percent in 24 weeks). No randomized trial measures hair shedding or density with collagen alone.
How long before a supplement works on hair?
Three months minimum, six months to assess density. Telogen effluvium appears 3 to 4 months after its trigger and takes equally long to resolve. In trials, regrowth with zinc was assessed at 12 weeks, shedding with keratin at 90 days, density with omega-3 and antioxidants at 6 months.
Which supplement for hair after childbirth?
Usually none: hair loss from the 3rd to 6th month after delivery is a telogen effluvium that resolves within a year; in a study of 116 women at four stages, the proportion of growing hair was lowest at 4 months postpartum. Ferritin testing is useful. During breastfeeding, our Zinc and our Iron bisglycinate are not recommended; only the doctor or midwife decides on supplementation.
Which supplement for hair at menopause?
In a study of 178 menopausal women, more than half had female alopecia, usually mild; in women with female alopecia, across all ages, vitamin D deficiency is 5.2 times more common. Testing and correcting vitamin D and ferritin is the first step; if thinning progresses, minoxidil, discussed with a dermatologist, has the most solid evidence.
Which supplements can worsen hair loss?
Selenium beyond 400 micrograms daily (shedding in 72 percent of 201 people poisoned by an overdosed supplement in 2008), vitamin A beyond approximately 10,000 IU daily, and vitamin E at very high doses. Excess iron or zinc is equally harmful.
Sources
The studies cited below were identified via PubMed.
- Deloche C, Bastien P, Chadoutaud S, et al. Low iron reserves: a risk factor for excessive hair loss in non-menopausal women. European Journal of Dermatology, 2007;17(6):507-512. DOI
- Guo EL, Katta R. Diet and hair loss: effects of nutritional deficiencies and supplement intake. Dermatology Practical and Conceptual, 2017;7(1):1-10. DOI
- Malkud S. Telogen effluvium: a review. Journal of Clinical and Diagnostic Research, 2015;9(9):WE01-WE03. DOI
- Gizlenti S, Ekmekci TR. Changes in the hair cycle during pregnancy and the postpartum period. Journal of the European Academy of Dermatology and Venereology, 2014;28(7):878-881. DOI
- Chaikittisilpa S, Rattanasirisin N, Panchaprateep R, et al. Prevalence of female alopecia in postmenopausal women: a cross-sectional study. Menopause, 2022;29(4):415-420. DOI
- van Beek N, Bodó E, Kromminga A, et al. Thyroid hormones directly modify the functions of the human hair follicle: prolongation of anagen and stimulation of matrix keratinocyte proliferation and pigmentation. The Journal of Clinical Endocrinology and Metabolism, 2008;93(11):4381-4388. DOI
- Trost LB, Bergfeld WF, Calogeras E. Diagnosis and treatment of iron deficiency and its potential relationship with hair loss. Journal of the American Academy of Dermatology, 2006;54(5):824-844. DOI
- Almohanna HM, Ahmed AA, Tsatalis JP, Tosti A. The role of vitamins and minerals in hair loss: a review. Dermatology and Therapy, 2019;9(1):51-70. DOI
- Olsen EA, Reed KB, Cacchio PB, Caudill L. Iron deficiency in female alopecia, chronic telogen effluvium and in controls. Journal of the American Academy of Dermatology, 2010;63(6):991-999. DOI
- Rasheed H, Mahgoub D, Hegazy R, et al. Serum ferritin and vitamin D in female hair loss: do they play a role? Skin Pharmacology and Physiology, 2013;26(2):101-107. DOI
- Haider LM, Schwingshackl L, Hoffmann G, Ekmekcioglu C. Effect of vegetarian diets on iron status in adults: systematic review and meta-analysis. Critical Reviews in Food Science and Nutrition, 2018;58(8):1359-1374. DOI
- Kil MS, Kim CW, Kim SS. Analysis of serum zinc and copper concentrations in hair loss. Annals of Dermatology, 2013;25(4):405-409. DOI
- Jin W, Zheng H, Shan B, Wu Y. Changes in serum trace elements in patients with alopecia areata: a meta-analysis. The Journal of Dermatology, 2017;44(5):588-591. DOI
- Wu R, Li Y, Peng H, et al. Association between serum trace element levels and alopecia areata: systematic review and meta-analysis. Journal of Cosmetic Dermatology, 2025;24(1):e16740. DOI
- Park H, Kim CW, Kim SS, Park CW. Therapeutic effect and serum zinc changes after zinc supplementation in patients with alopecia areata with low serum zinc. Annals of Dermatology, 2009;21(2):142-146. DOI
- Karashima T, Tsuruta D, Hamada T, et al. Oral zinc in telogen effluvium related to zinc deficiency. Dermatologic Therapy, 2012;25(2):210-213. DOI
- Foster M, Chu A, Petocz P, Samman S. Effect of vegetarian diets on zinc status: systematic review and meta-analysis of studies in humans. Journal of the Science of Food and Agriculture, 2013;93(10):2362-2371. DOI
- Chen Y, Dong X, Wang Y, et al. Serum 25-hydroxyvitamin D in non-scarring alopecia: systematic review and meta-analysis. Journal of Cosmetic Dermatology, 2024;23(4):1131-1140. DOI
- Yongpisarn T, Tejapira K, Thadanipon K, Suchonwanit P. Vitamin D deficiency in non-scarring and scarring alopecia: systematic review and meta-analysis. Frontiers in Nutrition, 2024;11:1479337. DOI
- Patel DP, Swink SM, Castelo-Soccio L. Review of the use of biotin in hair loss. Skin Appendage Disorders, 2017;3(3):166-169. DOI
- de Miranda RB, Weimer P, Rossi RC. Effects of hydrolyzed collagen supplementation on skin aging: systematic review and meta-analysis. International Journal of Dermatology, 2021;60(12):1449-1461. DOI
- Hexsel D, Zague V, Schunck M, et al. Oral supplementation with specific bioactive collagen peptides improves nail growth and reduces symptoms of brittle nails. Journal of Cosmetic Dermatology, 2017;16(4):520-526. DOI
- Beer C, Wood S, Veghte RH. Clinical trial on the effect of a keratin complex on hair and nail parameters. The Scientific World Journal, 2014;2014:641723. DOI
- Le Floc'h C, Cheniti A, Connétable S, et al. Effect of a nutritional supplement on hair loss in women. Journal of Cosmetic Dermatology, 2015;14(1):76-82. DOI
- Evron E, Juhasz M, Babadjouni A, Mesinkovska NA. Natural hair supplement, friend or foe? Saw palmetto, a systematic review in alopecia. Skin Appendage Disorders, 2020;6(6):329-337. DOI
- MacFarquhar JK, Broussard DL, Melstrom P, et al. Acute selenium intoxication associated with a dietary supplement. Archives of Internal Medicine, 2010;170(3):256-261. DOI
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