In March 2019 researchers from Saudi Arabia and the USA published their review of the medical scientific literature to assess the role of vitamins and minerals in hair loss. A total of 125 studies met the search criteria and and were included in the review. The researchers stated that the human scalp contains approximately 100,000 hair follicles, of which 90% are in the anagen phase (ie the active growth phase of hair follicles during which the root of the hair is dividing rapidly, adding to the hair shaft, and the hair grows about 1 cm every 28 days). Androgenetic alopecia (male pattern hair loss), telogen effluvium (overall hair shedding) and alopecia areata (when hair is lost from some or all areas of the body, frequently resulting in a few small bald spots on the scalp) are the three most common types of non-scarring alopecia.
It is known that a vitamin or mineral deficiency may contribute to hair loss with a severe reduction in carbohydrate intake also appearing to result in hair loss. The following vitamins and minerals have been implicated.
Vitamin A level of under 0.70 μmol/L signifies vitamin A insufficiency. In most cases, a balanced diet will provide sufficient vitamin A. However, consuming too much or over-supplementing with vitamin A can cause hair loss. An intake of vitamin A exceeding the recommended daily intake (10,000 IU/day) can lead to vitamin A toxicity, and cause hair loss.
The vitamin B complex includes thiamine (B1), riboflavin (B2), niacin (B3), pantothenic acid (B5), vitamin B6, biotin (B7), folate and vitamin B12. The recommended daily intake of these vitamins can be reached by eating a balanced diet, with the exception of biotin, which is the only B vitamin produced by the body. Of these B vitamins, only riboflavin, biotin, folate, and vitamin B12 deficiencies have been associated with hair loss.
Biotin: An adequate intake of biotin is 30 mcg/day. Biotin toxicity has never been reported and therefore there is no recommended upper limit for biotin intake. However a high biotin intake can cause inaccurate laboratory test results. Many supplements for hair, skin and nails far exceed the recommended daily intake of biotin.
A biotin deficiency is usually genetic or acquired as the average dietary intake of biotin in Western countries is generally considered adequate. Genetic causes of biotin deficiency can be either neonatal or infantile and involves scalp hair loss, and loss of eyebrows and eyelashes. Acquired biotin deficiency can be due to increased raw egg consumption, malabsorption, alcoholism, pregnancy, prolonged use of antibiotics and some medications. In fact, current evidence suggests that up to 50% of pregnant women may be deficient in biotin. Signs of acquired biotin deficiency include hair loss, skin rashes and brittle nails, but large-scale studies where biotin supplementation has been given to individuals with a deficiency have not proved effective. However, there are some single case reports where individuals have reported an improvement in their hair shedding following biotin supplementation. In addition, children with uncombable hair syndrome have improved after biotin supplementation (3–5 mg daily) for 3-4 months. It has also been noted that a group of individuals from India, aged under 20 years, with premature greying of hair were found to have a deficiency of vitamin B12 and folic acid as well as lower levels of biotin without any obvious biotin deficiency.
Folate: The recommended daily intake of food folate is 400 mcg daily for adults which, in some countries, is supported by the fortification of some foods. While most individuals consume adequate amounts of folate, certain groups are at risk for deficiency which is usually in association with poor diet, alcoholism or a malabsorption disorder. It is known that a folate deficiency can also cause hair, skin, and nail changes. One study involving individuals who had alopecia areata involving over 20% of the scalp found that they had significantly lower levels of folate and that the folate levels were lower still in individuals with alopecia totalis/alopecia universalis when compared to individuals with patchy hair loss.
Vitamin B12: The recommended daily intake of vitamin B12 for adults is 2.4 mcg. However, there is no upper limit for vitamin B12 intake, as there is only a low potential for toxicity. One study reported a reduction in vitamin B12 levels in females with androgenetic alopecia which was being treated with ethinyl estradiol and cyproterone acetate (Diane/Dianette and Androcur). This medication reduced vitamin B12 levels and resulted in vitamin B12-related anxiety, causing some individuals to stop treatment. However, 200 µg vitamin B12 daily supplement corrected the reduced B12 levels.
Folate and Vitamin B12: Two studies involving individuals with alopecia areata and healthy controls found no significant differences in serum folate and vitamin B12 levels between the the two groups. Neither was there any association between the levels and duration or activity of the disease. One study assessing the folate and vitamin B12 levels in individuals with an acute/chronic telogen effluvium found that 2.6% of individuals had a vitamin B12 deficiency although none had a folate deficiency. However, there was no control group for comparison in this study.
Vitamin C, or ascorbic acid, is a water-soluble vitamin and plays an essential role in helping to reduce the gastrointestinal side effects of taking iron. Therefore vitamin C intake is important in patients with hair loss associated with iron deficiency. Although vitamin C deficiency is typically associated with body hair abnormalities, there are no data linking vitamin C levels and hair loss.
Vitamin D is a fat-soluble vitamin and may be involved in alopecia areata. A review of 14 studies involving a total of 1255 individuals with alopecia areata and a control group of 784 individuals revealed that the average vitamin D level was significantly lower in the alopecia areata group than the control group. In fact there was such a high incidence of vitamin D deficiency in the individuals with alopecia areata that the researchers suggested that the vitamin D level should be assessed in all individuals with alopecia areata. Although, this review did not find any clear association between the amount of hair loss and vitamin D levels, there are studies which have shown that lower vitamin D levels can be associated with a greater disease severity. Results from studies assessing vitamin D levels in individuals with female pattern hair loss and a telogen effluvium are contradictory and further studies are required to clarify the role of vitamin D in these medical conditions.
Vitamin E is involved in the oxidant/antioxidant balance and helps to protect against free-radical damage and several studies have implicated an oxidant/antioxidant discrepancy in individuals with alopecia areata. One study assessed the serum and tissue vitamin E levels in individuals with alopecia areata and found significantly lower levels of vitamin E in these individuals when compared to a control group. However, these results were not confirmed by another study which found no statistical difference in plasma vitamin E levels between individuals with alopecia areata and healthy controls. There is also no data to support the role of vitamin E in androgenetic alopecia or a telogen effluvium.
The most common nutritional deficiency in the world is iron deficiency, which contributes to a telogen effluvium. The serum ferritin (iron-binding protein) level is considered to be a good indicator of total body iron stores and is relied upon as an indicator in hair loss studies. Menstruation is the biggest cause of iron deficiency in otherwise healthy premenopausal women. Contrary to this, serum ferritin levels may be raised in patients with inflammatory, infectious, and neoplastic conditions and in those with liver disorders.
Iron deficiency is common in females with hair loss, and several studies assessing the relationship between iron deficiency and hair loss have focused on non-scarring alopecia in women. Most studies have suggested that iron deficiency may be related to a telogen effluvium, alopecia areata and androgenetic alopecia, although there are those that have not. In addition, a study looking at the incidence of iron deficiency in individuals with either male or female pattern hair loss found that the iron deficiency was related to gender rather than to type of hair loss. One study carried out in India on 35 students, aged under 20 years, who had premature greying of hair, showed that serum calcium, serum ferritin, and vitamin D3 levels may all play a role in premature greying of the hair. Despite the studies highlighted, the role of iron during the hair cycle has not been well studied and further research is required.
However, most researchers agree in supplementing iron in individuals with iron deficiency and/or low ferritin levels. Although there is no consensus on “normal ferritin” levels, most authors prescribe supplements when the ferritin level is under 40 ng/dL, with some researchers recommending that a serum ferritin level of 70 ng/dL is maintained. The role of essential amino acids in anemia is well known, but just how amino acids affect iron uptake and therefore on hair growth is the subject of ongoing research. L-lysine is limited primarily to fish, meat and eggs and little is known about the influence of l-lysine on iron uptake. However, one study found that whilst some women achieved a modest increase in serum ferritin level following iron supplementation, adding l-lysine (1.5–2 g/day) to their existing iron supplementation resulted in a significant increase in the average serum ferritin level. In fact, l-lysine supplementation is recommended for vegan individuals with iron deficiency. However, it is also important to note that too much iron can cause side effects, such as iron poisoning and even organ and tissue damage.
Selenium is an essential trace element and a selenium deficiency can occur in low-birthweight infants and in individuals requiring total parenteral nutrition. It can also occur among people living in a location where the soil lacks selenium. The recommended daily intake is 55 μg daily for those aged over 14 years. The availability of selenium in a variety of foods, eg meat, vegetables and nuts, should be sufficient to meet the daily requirement. An intake of selenium of above 400 μg daily may cause toxicity. Symptoms of acute or chronic selenium toxicity include nausea, vomiting, nail brittleness and discolouration, hair loss, fatigue, irritability and foul smelling breath. One article reported severe hair loss due to selenium toxicity caused by a liquid dietary supplement that contained 200-times the labeled level of selenium.
One study described how four patients receiving parenteral nutrition experienced loss of hair pigmentation, which started to re-pigment after 6–12 months intravenous selenium. Similar findings were seen in 6 infants receiving nutritional support. In this instance the infants, who had alopecia with pseudoalbinism, were given daily selenium therapy following which their selenium serum levels returned to the normal range and the alopecia and pseudoalbinism improved. A further study involved individuals with ovarian cancer who experienced hair loss and other gastrointestinal symptoms whilst undergoing chemotherapy. They were started on selenium supplementation following which there was a significant decrease in hair loss and other gastrointestinal symptoms. The researchers of this study therefore concluded that taking selenium may be a supportive element in chemotherapy.
Zinc is an essential trace element, which means that the body cannot generate zinc on its own and must be supplied through the diet. The main dietary sources of zinc are fish and meat. Zinc deficiency can occur when large amounts of cereal grain is consumed, in those with poor meat intake and in infants on milk formula. Other causes of zinc deficiency include anorexia nervosa, inflammatory bowel disease, jejunal bypass surgery and cystic fibrosis. Alcohol, malignancy, burns, infection and pregnancy may all cause an increased excretion of zinc.
Hair loss is a well-known symptom of zinc deficiency with hair regrowth frequently occurring with zinc supplementation. One study, involving 115 individuals diagnosed with a telogen effluvium, found that 10% of individuals had zinc deficiency, whilst a further study involving individuals with male and female pattern baldness and a telogen effluvium showed a strong association between zinc deficiency and hair loss. A literature review has found that in 4 out of 6 studies individuals with alopecia areata had low zinc levels. In fact a further study found a strong association between zinc deficiency and severity of alopecia areata. However, there are other studies which have shown no significant association between zinc level and alopecia areata. Whether there is a role for zinc supplementation is open to debate. One study has shown that zinc supplementation produced no improvement in alopecia areata whilst another study produced good results in over 50% of individuals.
There are reports in the medical scientific literature where individuals have developed a telogen effluvium after 2-5 months of starting a vigorous weight reduction programme. It is thought that such a severe reduction in carbohydrate intake (ie calorie restriction) with subsequent inadequate energy supply of the hair matrix may be the cause for this.
Given the role of vitamins and minerals in normal hair follicle development and in immune cell function, large studies are required to assess the effect of micronutrient supplementation on hair growth in those patients with both micronutrient deficiency and non-scarring alopecia.
Almohanna HM et al. The Role of Vitamins and Minerals in Hair Loss: A Review.