B vitamins help the body convert the food that we eat into energy, although the vitamins themselves don’t actually give us energy (we energy from carbohydrate, protein, and fat). Read on to learn about one of the members of this vitamin family, vitamin B7, also known as biotin.
What is vitamin B7?
Vitamin B7 is most commonly known as biotin, but it also goes by the name “vitamin H” (the H stands for Haar und Haut, which is German for “hair and skin”). It’s a water-soluble vitamin that’s naturally found in some foods and is also available in dietary supplements. Bacteria in the intestines also make biotin.
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What does vitamin B7 do?
Like all of the B vitamins, vitamin B7 helps to derive energy from the food that we eat. In the case of vitamin B7, it is a cofactor for enzymes that are involved in critical steps in the metabolism of glucose, amino acids, and fatty acids. Vitamin B7 in foods is mostly bound to protein, and enzymes in the gut break down protein-bound vitamin B7 into a form that is absorbed in the small intestine. Most of this vitamin is stored in the liver.
In addition to playing a role in energy metabolism, vitamin B7 is needed for:
- Maintaining normal skin and mucous membranes
- Maintaining healthy hair
- Normal functioning of the nervous system
- Supporting the growth and development of the fetus
This B vitamin is most known for promoting healthy hair, skin, and nails, and it’s added to many cosmetics and hair care products. However, while a deficiency of vitamin B7 can result in hair loss, skin problems, and brittle nails, the evidence for supplementation is not particularly strong.
But what about all of the hype about taking biotin to counteract hair loss and regrow hair? A meta-analysis published in May 2017 in the Journal of Drugs and Dermatology determined that there is no evidence to support using biotin to “improve hair quantity or quality.” Anecdotal reports of biotin helping with hair growth (as well as promoting strong nails) abounds, however; it’s important to realize that many supplements aimed at healthy hair and/or nails contain other nutrients that may play a role in supporting hair and nails.
Vitamin B7 is sometimes used to help improve symptoms of peripheral neuropathy, and is being studied for use in the treatment of multiple sclerosis as well as restoring a loss of taste.
What foods have vitamin B7?
Vitamin B7 is found in a variety of foods. The main sources are:
- Beef liver
- Eggs
- Salmon
- Pork
- Hamburger
- Sunflower seeds
- Nuts and nut butters
- Sweet potatoes
- Legumes
Raw egg whites contain a protein called avidin. Avidin binds to vitamin B7 in foods and prevents it from being absorbed. Cooking denatures avidin, however, allowing absorption.
Vitamin B7 is found in some multivitamin/mineral supplements, in B complex supplements, and supplements containing just this vitamin. Many dietary supplements that promote healthy nails, hair, and skin contain this vitamin as well.
How much vitamin B7 do you need?
The Recommended Daily Allowance for vitamin B7 is as follows:
- For men and women age 19 and older: 30 micrograms (mcg)
- For pregnancy: 30 mcg
- For lactation: 35 mcg
What are signs of vitamin B7 deficiency?
Vitamin B7 deficiency is rare. The average intake of this vitamin from foods is about 35 to 70 mcg per day, indicating that most people consume enough.
According to the Office of Dietary Supplements of the National Institutes of Health (NIH), people who are most likely to have an inadequate vitamin B7 status include:
- People with a biotinidase deficiency, which is a rare autosomal recessive disorder that can lead to coma or death if not treated. Newborns in the U.S. are screened for this disorder. The condition is treated with oral vitamin B7.
- People with alcoholism, since alcohol can block the absorption of vitamin B7.
- Pregnant and breastfeeding women. At least one third of pregnant women develop a marginal biotin deficiency, and breastmilk concentrations of the vitamin decrease in breastfeeding women.
- People receiving dialysis for kidney disease.
- People receiving intravenous nutrition.
- People who smoke.
Long-term antibiotic use may lower vitamin B7 levels as a result of destroying bacteria in the gut, and antiseizure or anticonvulsant medications taken for a long period of time can lower vitamin B7 levels in the body.
Signs and symptoms of vitamin B7 deficiency are:
- Hair loss
- Skin rashes and scaly skin around the eyes, nose, and mouth
- Cradle cap (seborrheic dermatitis) in infants
- Brittle nails
What are signs of vitamin B7 toxicity?
There’s no evidence that high intakes of vitamin B7 is toxic. And because this is a water-soluble vitamin, any excess intake will be excreted in the urine.
Other things to know about vitamin B7
Although vitamin B7 is advertised as helping to stop hair loss and regrow hair, and to grow healthy nails, evidence is lacking. On the other hand, you might argue that, since this vitamin is not known for any toxicity, why not give it a try?
One of the downsides of taking biotin supplements is that high doses can interfere with some laboratory blood tests. In November of 2017, reports The Nutrition Source of the Harvard T.H. Chan School of Public Health, “The U.S. Food and Drug Administration (FDA) issued a warning based on reports of biotin supplements interfering with laboratory blood tests, causing incorrect results.” For example:
- People taking 10-300 milligrams of biotin daily can falsely indicate Graves’ disease and severe hyperthyroidism.
- High doses may cause a falsely low troponin result. Troponin is a biomarker to help diagnose a heart attack.
As a precaution, if you take high doses of biotin and are due to have blood work, talk with your health care provider ahead of time. They may recommend that you temporarily stop taking the supplement so as to avoid false results.
