The best supplement for hair growth, according to a dietician

Many supplements are marketed as the best for hair growth. But do any of them work?

Research on the benefits of hair growth supplements has produced mixed results. Nutrition as a whole is vital for hair growth. However, supplements of specific vitamins and minerals may be warranted in some cases to correct nutrient deficiencies associated with hair loss.

This article discusses how much zinc you need per day for hair growth and whether supplements are appropriate.

Zinc for hair growth

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

Zinc is a mineral that the body needs in small amounts (micronutrients). Zinc helps with immune function, cell renewal and wound healing.

Zinc helps keep hair healthy by supporting the hair follicle cycle. Hair loss (alopecia) is a symptom of low zinc levels, and some research suggests that zinc supplementation may promote hair regrowth in people with hair loss. Zinc supplements can reduce hair loss by bringing low levels of the nutrient back into the normal range. However, not all research supports this.

There is some evidence to support 50 milligrams (mg) of zinc supplements for reducing hair loss. One study among women with hair loss found that 50 mg of zinc daily improved hair thickness.

Another study among women with normal zinc levels and polycystic ovary syndrome (PCOS) observed less hair loss in women who consumed 50 mg of zinc supplements daily for eight weeks than those who took a placebo (an ineffective substance given to a control group). Hair loss can be a side effect of PCOS.

Ultimately, there is insufficient information to support zinc supplementation to prevent or reverse hair loss in people without low levels or underlying health problems associated with zinc status.

Comb hair in hand.

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The average daily amount of zinc needed to meet the nutrient needs of most healthy adults (the Recommended Dietary Allowance or RDA) includes the following:

Zinc can be obtained from food. It is found naturally in meat, fish and seafood and is added to many breakfast cereals. Foods that contain the most zinc include:

  • Oysters: 32 mg per 3 ounces
  • Beef: 3.8 mg per 3 ounces
  • Breakfast cereals and oats: 2.3 mg per cup
  • Pumpkin seed: 2.2 mg per ounce

You only absorb between 5% and 50% of the zinc in food. This amount can vary depending on the food source of zinc and the composition of the meal.

Plant foods contain less zinc than animal foods. In addition, certain substances found in plants (phytates) affect the absorption of zinc. Therefore, absorbing zinc from a plant-based diet can be more challenging.

Zinc deficiency is less common in the United States, as most people meet requirements through food or supplements. Insufficient zinc levels are more common in low- and middle-income countries.


It’s possible that zinc supplementation can do more harm than good, especially if you take too much. Always consult your doctor before starting a new supplement.

In the United States, the Food and Drug Administration (FDA) does not regulate supplements the way it regulates prescription drugs. This means that some supplements may not contain what they say on the label. When choosing a supplement, look for third-party tested products and consult with a health care professional, registered dietitian nutritionist (RD or RDN), or pharmacist.

Preventive measures

Avoid zinc if you are allergic to it or its components (parts). Seek immediate medical attention if you have a severe allergic reaction (itching, hives, shortness of breath).

People with Wilson’s disease (hepatolenticular degeneration, copper overload condition) should be consulted with a health care professional before starting zinc supplementation.

  • The Food and Nutrition Board (FNB) at the Institute of Medicine (IOM) has set tolerable upper limit of intake for zinc at 40 mg per day for any adult, including those who are pregnant or breastfeeding

The Tolerable Upper Limit (UL) reflects the maximum daily amount that someone can take without risking adverse health effects for most individuals.

FNB does not recommend taking doses of 50 mg zinc or more over a long period of time. Too much zinc can affect copper absorption and reduce immune function.


Too much zinc can cause side effects. Although it is difficult to exceed recommendations with diet alone, toxicity is possible with zinc supplements.

Side effects include the following:

Long-term side effects such as reduced immune function are also possible.

Excessive zinc supplementation can also affect the absorption of other vital micronutrients such as copper and iron.


Zinc can interact with certain medications, and medications can affect zinc levels. These medications include the following:

  • Antibiotics: Antibiotics treat or prevent bacterial infections. Some antibiotics can interact with zinc supplements in the digestive tract, affecting the absorption of both drugs.
  • Cuprimin (penicillamine): Penicillamine removes high levels of heavy metals from the body. It can treat rheumatoid arthritis and Wilson’s disease, a condition in which copper levels in the body are too high. Zinc supplements may reduce the absorption and effect of penicillamine. Taking zinc and penicillamine at least one hour apart may reduce this interaction.
  • Diuretics: Diuretics prevent accumulation and help remove excess fluid from the body. Specific types of diuretics can increase urinary zinc excretion, contributing to lower levels of the nutrient.

    It is essential to read the supplement’s ingredient list and Nutrition Facts panel carefully to know which ingredients are included and how much of each ingredient is included. Review the supplement label with your doctor to discuss potential interactions with food, other supplements, and medications.

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Other nutrients contribute to healthy hair. However, limited research supports taking these hair growth supplements only if you are not deficient in these nutrients.


Hair is primarily composed of protein. Not getting enough protein can contribute to hair loss.

It is not clear whether supplementation with a particular amino acid (protein molecule) can improve hair loss. Many studies on amino acids include other nutrients, so it is difficult to draw a clear link between individual amino acids and hair loss.

The RDA for protein is at least 0.8 grams (g) of protein per kilogram (kg) of body weight (g/kg). However, some individuals may need more protein.

Foods rich in protein include the following:

  • Animal flesh
  • Seafood
  • Dairy
  • Tofu
  • Tempeh
  • Legumes


Hair loss is linked to iron levels. Hair cells are among the most active in the body and require adequate levels of iron to function properly. However, there is not much evidence to support the benefits of iron supplements for hair growth without low iron levels.

FNBat IOM of the National Academies recommends the following daily iron intake for adults:

  • 8 mg for men
  • 18 mg for women aged 19 to 50
  • 8 mg for women older than 51 years
  • 27 mg for pregnant women
  • 9 mg for people who are lactating

Food sources of iron include lean meats, seafood, and fortified cereals and grains.

Omega-3 fatty acids

Deficiency of omega-3 fatty acids is associated with loss of hair and eyebrows. One randomized controlled trial among women with hair loss found that a supplement containing 460 mg of fish oil (a source of omega-3 fatty acids) reduced hair loss and improved hair thickness. But the supplement also contained antioxidants, in which fish oil is weak, and the added antioxidants may have contributed to the beneficial results.

There is no established recommended dietary allowance for omega-3 fatty acids. However, it is recommended that adults consume the following amounts of omega-3 fatty acids daily to ensure nutritional adequacy:

  • 1.6 g for men
  • 1.1 g for females
  • 1.4 g for pregnant women
  • 1.3 g for people who are lactating

Foods rich in omega-3 fatty acids include the following:


If you are concerned about hair loss, talk to a health care professional to identify the underlying cause.

A healthy diet with sufficient nutrients and protein provides the best support for hair growth. Sometimes nutrient deficiencies can contribute to hair loss. If you have low zinc or iron levels, taking a supplement can help restore nutrient levels and promote hair growth. But if your levels of these minerals are already in the normal range, then the supplement probably won’t support hair growth or prevent hair loss.

Taking zinc when not needed can do more harm than good, contributing to unwanted side effects and affecting the absorption of other minerals essential to health.

Frequently asked questions

  • Do any hair growth supplements work?

    Depends. Supplements that correct nutrient deficiencies can reduce hair loss. However, the data do not support hair growth supplements in people who are already getting enough of these nutrients.

  • What is the best supplement for hair growth?

    There is no best supplement for hair growth. Instead, overall nutrition from a balanced diet is fundamental to hair growth. See your doctor to discuss whether your hair loss may be due to an underlying problem or nutrient deficiency.

  • What is the best biotin supplement for hair regrowth?

    Despite its popularity, there is limited evidence to support the use of biotin for hair regrowth. In healthy individuals, biotin does not promote hair growth. However, biotin supplements can promote hair growth in people with low biotin levels.

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