By Megan Nunn, PharmD 

Updated on November 15, 2023

 Medically reviewed by Allison Herries, RDN

Hair loss, or alopecia, affects almost half of all people over age 50.¹² It can be reversible or permanent. Reversible hair loss happens when the hair cycle undergoes changes, but hair follicles are not destroyed. Permanent hair loss occurs when scar tissue replaces hair follicles.³

Supplements may help correct low levels of specific nutrients required for healthy hair growth.³

This article discusses how much of these nutrients your body needs each day and when supplementing might be helpful.

Important Nutrients for Hair Growth

The hair follicle cycle is mainly made up of micronutrients (vitamins and minerals).³

Hair loss caused by a nutrient deficiency may be reversed by supplementing with that vitamin or mineral.

Here's a look at the evidence behind some popular supplements used for hair loss.

Supplement use should be individualized and vetted by a healthcare professional, such as a registered dietitian or registered dietitian nutritionist (RD or RDN), pharmacist, or healthcare provider. No supplement is intended to treat, cure, or prevent disease.

Protein

Hair is primarily made of proteins like keratin, so boosting protein intake could theoretically promote growth.⁴ But there's not much evidence yet.

To function correctly, the body generally needs at least 0.8 grams (g) of protein for every kilogram (kg) of body weight (g/kg). However, the following groups of people need more protein per day:

• Infants

• Athletes

• People who are malnourished

• People fighting infections

• People who've undergone surgery⁵

Taking keratin directly won't help with hair loss because it can't be absorbed in the body. Some products marketed for hair growth contain amino acids like cysteine made into keratin in the body.⁶ More research is needed before these can be recommended.

Small trials have shown that a product of fish protein can limit hair shedding and increase hair thickness in women with thinning hair.⁷

 Female brushing her curly hair with comb in bathroom mirror.

Taras Grebinets / Getty Images

Collagen

Collagen is a popular supplement for hair, skin, and nails. But there's not much evidence it lives up to the hype.⁸

Taking 2.5 g a day of collagen peptides increased hair follicles and hair thickness in a small study of 44 healthy females.⁹

A combination product that contained collagen, peptides, lipids, and hyaluronic acid made hair softer and shinier after eight weeks.¹⁰ However, because multiple ingredients were used, it's unclear how much of the effect was due to collagen alone.

Omega-3 Fatty Acids

Loss of eyebrows and hair lightening have been associated with low levels of omega-3 fatty acids.¹¹

A product that included omega-3 fatty acids, plus other fatty acids and antioxidants, reported improvement in hair thickness and less hair loss for women who took the supplement.¹² Again, because this was a combination product, it's impossible to know how much of the effect was caused by omega-3 fatty acids alone.

Zinc

Low zinc levels may cause a specific form of hair loss called telogen effluvium, which is typically reversible.¹³ But there's not enough data to know if supplementing with zinc prevents or reverses hair loss or what an optimal dose is.

It's been studied at 50 milligrams (mg) daily for women with hair loss. In this trial, about half of the women who took zinc reported improvement in hair loss.

Recommended daily levels of zinc for adults are as follows:¹⁴

• 11 mg for males

• 8 mg for females

• 11 mg during pregnancy

• 12 mg during breastfeeding

Foods high in zinc include the following:

• Oysters

• Beef¹⁴

Too much zinc could cause side effects like vomiting and diarrhea.¹¹ Additionally, taking large doses of zinc for an extended period of time (usually weeks) can result in the following:

• Copper deficiency

• Anemia

• Reduced immune function¹⁵

Biotin

Many people use biotin (vitamin B7) to prevent or treat hair loss. It's aggressively marketed for this, but there's very little evidence it works unless you have a biotin deficiency.³

In fact, the evidence for using biotin for hair growth is limited to case studies in children with a rare condition called familial uncombable hair syndrome. who used 5 mg of biotin a day.¹⁶

Adults over age 19 require 30 micrograms (mcg) of biotin daily and 35 mcg during breastfeeding.¹⁷ Protein-rich foods like meat and eggs are good sources of biotin.

Biotin deficiencies are very rare in people who eat a balanced diet. Along with hair loss, other symptoms of low biotin levels are rashes and brittle nails.³

Remember that biotin supplements may also cause false lab results in heart problems and thyroid disease tests.¹⁸ Consult with your healthcare provider if you decide to take biotin.

Iron

Iron is essential in cells that rapidly divide, like hair follicles. Low levels of iron are associated with hair loss.³

Adults need the following amounts of iron daily, according to the Food and Nutrition Board (FNB) at the Institute of Medicine (IOM) of the National Academies:¹⁹

• 8 mg for males

• 18 mg for females between 19 and 50 years old

• 8 mg for females over age 51

• 27 mg during pregnancy

• 9 mg during breastfeeding

Taking iron supplements may help if your hair loss is due to an iron deficiency. However, there's not enough evidence to prove that it helps promote hair growth when you don't have an iron deficiency.³

Selenium

Interestingly, having either too little selenium or too much of it may cause hair loss.³

Sources of selenium in the diet include the following:

• Seafood

• Brazil nuts

The recommended dietary allowance of selenium for adults is:²⁰

• 55 micrograms (mcg) daily

• 60 mcg daily during pregnancy

• 70 mcg daily during breastfeeding

Selenium has been studied for people with hair loss caused by chemotherapy. However, the effectiveness is unclear since other vitamins were also taken during the trial.²¹

Selenium also has been researched at a dose of 5 mcg/kg daily in infants with alopecia.²²

Hair loss is a common side effect of selenium toxicity (having too much in your body). So, it's not recommended to supplement with selenium for hair loss if you have enough levels in your body.³

In the United States, the Food and Drug Administration (FDA) does not regulate supplements the way it regulates prescription drugs. That means some supplement products may not contain what the label says. When choosing a supplement, look for third-party tested products and consult a healthcare provider, registered dietitian nutritionist (RD or RDN), or pharmacist.

What Conditions Cause Hair Loss?

The following can cause hair loss:³

• Low levels of vitamins or minerals

• Skin disorders

• Malnutrition

• Hormonal imbalances

• Drug use

• Stress

• Depression

• Cancer treatments (chemotherapy)

• Childbirth

• Thyroid dysfunction

• Immune system attacking the hair follicles (alopecia areata)

What Medications Cause Hair Loss?

Some medications can contribute to hair loss as well. These include the following:³

• Blood pressure medicines

• Cholesterol medicines (statins)

• Seizure medicines

• Blood thinners

• Acid reflux medicines

Appropriate treatment of hair loss may differ depending on what's causing it.

What Treatments Are Available for Hair Loss?

The FDA has approved the following treatments for hair loss:

• Minoxidil

• Finasteride

• Light therapy²³

Hair transplantation, a type of surgery to restore hair, is also available.

Summary

If you are concerned about hair loss, a dermatologist can help you determine what's causing your hair loss.

Many of the nutrients involved in the hair cycle are found in a healthy diet. Some people may be deficient in one, like iron, zinc, or biotin. If you have low levels of one of these vitamins or minerals, supplementing with that nutrient may help hair growth. But if you already have normal levels of these vitamins and minerals in your body, these supplements are unlikely to treat or prevent hair loss.

Keep in mind that taking supplements you don't need could do more harm than good, causing unwanted side effects or even worsening hair loss.