The B Vitamin Series, Vitamin B7

Vitamin B7, also known as biotin, is a water-soluble vitamin and is part of the vitamin B complex group. The discovery of vitamin B7 goes back to 1927, when it was observed during a research project that rats who were fed egg whites developed dermatitis and lost their hair. This was known as “egg white injury”, and it was noted that egg whites were deemed toxic to animals and had the ability to cause skin lesions. The same year, a doctor named M.A Boas found that a nutrient mainly found in liver could successfully cure “egg white injury”, and he named the substance “protective factor x”. In 1940, a biochemist called Vincent Du Vigneaud finally made the breakthrough and identified that the protective factor was a vitamin which became labelled vitamin B7. It was a protein contained in the raw egg whites that interfered with the uptake of B7 from food, causing the symptoms in the animals. Vitamin B7 is now often referred to as the beauty vitamin because of its beneficial effects for hair and fingernails.

What is the prevalence of vitamin B7 deficiency?

Vitamin B7 deficiency rarely occurs within healthy populations because it is prevalent amongst many foods, the recommended daily amount is low, and we can synthesize the vitamin from our intestinal bacteria if deprived over long periods. Furthermore, B7 deficiency is listed as a "rare disease" by the Office of Rare Diseases (ORD) of the National Institutes of Health (NIH), affecting less than 1% of the population in modernised societies.

However, cases of deficiency are still documented in modernised societies, predominantly for two main reasons. First is the consumption of raw egg whites for multiple weeks or longer. Avidin, a substance found in egg whites, binds to biotin and blocks absorption. Heating of the egg denatures avidin, however 30-40% is still present after frying or boiling [1]. Secondly, deficiency is seen in pregnant women, as they have an increased rate of B7 catabolism and leads to 50% of pregnant women having some degree of notable deficiency, despite adequate dietary intake [2].

Less common, yet documented, causes of deficiency are individuals who are treated with anticonvulsants, antiseizure medications or antibiotics [3], those with genetic disorders such as intestinal malabsorption from short bowel syndrome, or individuals that have excessive alcohol intakes.

What foods contain vitamin B7?

The best plant-based sources are barley, brewer’s yeast, fortified cereals, corn, soy, wheat bran, avocado, bread, broccoli, cauliflower, legumes, mushrooms, nuts, potatoes and spinach. Animal-based sources are fish, milk, cheese, chicken and pork.

Vitamin B7 bioavailability lacks research, and details are unknown. Researchers in previous studies speculate that the minimum estimates of B7 bioavailability is 24-58%, but more data is needed [4].

What are the symptoms of vitamin B7 deficiency?

The main symptoms of B7 deficiency include hair loss and a scaly red rash around the eyes, nose, mouth, and genitals. B7 deficiency may also cause mental issues, such as depression, lethargy, hallucinations, numbness and tingling. Researchers have also noted a phenomenon called the “biotin deficient facies”, where the face has a strange fat distribution, sometimes alongside a facial rash [5]. Those with metabolic disorders affecting B7 metabolism may also experience seizures, impaired immune system function, and increased susceptibility to bacterial and fungal infections [6].

How much do you need per day?

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What are the health benefits of vitamin B7?

Similar to the other B vitamins, B7 plays a role in energy production. Several enzymes need B7 to function properly, known as carboxylases which are critical for the functioning of important metabolic pathways, such as gluconeogenesis, fatty acid synthesis, and amino acid catabolism. [8]. These pathways are responsible for glucose production from sources other than carbohydrates, as well as the metabolism of leucine which is essential for protein synthesis and muscle retention or growth [9].

One of the most well-known health benefits of B7 is the effect it has on promoting hair growth, especially in those with temporarily thinning hair. A double-blind study found that women who supplemented B7 for 180 days noted a significantly improved overall hair volume, scalp coverage, hair thickness, hair shine, skin moisture retention, and skin smoothness, compared to placebo [7]. Other studies are available that support this, noting a deficiency may lead to accelerated hair loss [10], although a true deficiency needs to be measured for supplementation to show beneficial effects [11].

Vitamin B7 may also strengthen nails, and improve brittle nails that are easily cracked or broken. A study of 25 adults showed 2.5mg/day of biotin for 6-15 months improved nail thickness by 25%, and reduced the frequency of nail splitting compared to placebo [12]. Another study demonstrated a 25% increase in nail plate thickness in patients with brittle nails who received 2.5mg biotin supplementation for 6 months [13].

Multiple sclerosis is a disease that may be clinically improved by high dose B7 supplementation. Multiple sclerosis is an autoimmune disease, where the protective shield (myelin) of nerve fibers in the brain, spinal cord and eyes is damaged or destroyed. Vitamin B7 has been found to be essential for myelin production. High dose B7 supplementation (100-300mg/day) for 2-36 months conveyed in one study to improve symptoms of progressive multiple sclerosis in over 90% of the 23 patients involved [14]. More data is needed to assess this link.

Vitamin B7 is found mainly in barley, fortified cereals, corn, soy, wheat bran, avocado, bread, potatoes, spinach, fish, milk, cheese, chicken and pork. It has benefits on energy metabolism, hair growth, nail strength, and may improve symptoms of progressive multiple sclerosis. A lack of B7 can cause hair loss, a scaly red rash around the eyes, nose, mouth, and genitals, and mental issues such as depression, lethargy and hallucinations. Deficiency is rare in healthy populations, but still seen in pregnant women, or those who consume excessive amounts of alcohol and/or raw eggs.

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