Biotin is a water-soluble member of the vitamin B group that is best known for its benefits on skin, hair and nails. At least eight different forms of biotin are known, but only D-biotin occurs naturally and has full biological activity in cells. Biotin is sometimes referred to as vitamin B7.
Biotin is involved in energy production in cells. It is essential for the action of four enzymes that synthesise fatty acids and glucose and breakdown certain amino acids. Biotin may also be involved in the expression of some genes, and for stimulating the release of insulin from pancreatic beta-cells. Biotin may also improve insulin sensitivity of muscle and fat cells. Biotin is best known for its role in promoting healthy hair and skin and strengthening nails, however.
Within the EU, the European Food Safety Authority have authorised health claims that biotin contributes to:
- Normal energy-yielding metabolism
- Normal functioning of the nervous system
- Normal macronutrient metabolism
- Normal psychological function
- The maintenance of normal hair
- The maintenance of normal mucous membranes
- The maintenance of normal skin.
Biotin Food Sources
Biotin is widely found in the diet and is also produced by probiotic bacteria in the bowel, from which you can absorb useful amounts. Good sources of biotin include:
- Offal, especially liver and kidney
- Lean meat
- Oily fish
- Egg yolk
- Legumes, especially soybeans and lentils
- Vegetables, especially spinach and mushrooms
- Yeast extract
Biotin is obtained from both animal and plant-based foods, and is also made by bacteria in the gut from which it can be absorbed, so biotin deficiency is relatively rare. An estimated one in every 120 people inherits an error of biotin metabolism which reduces immunity against yeast infections and may be linked with recurrent Candida (thrush). High-dose biotin supplements will solve a recurrent thrush problem if biotin deficiency is to blame.
Low biotin intakes can occur when following a very low-calorie weight loss diet without taking a multivitamin supplement. Biotin deficiency can also develop if you eat large amounts of raw egg white over a long period which is popular among body-builders. Raw egg white contains a protein, avidin, which binds biotin in the gut and prevents its absorption. Cooked egg white does not have this effect.
People on long-term antibiotic treatment are also at risk of deficiency due to loss of the normal probiotic bowel bacteria that secrete biotin.
Lack of biotin affects the function of some metabolic enzymes and may result in hypoglycaemia between meals and raised blood levels of ammonia.
Symptoms that may be due to a mild biotin deficiency
- dry, scaly, flaky skin
- rash around the eyes, nose and mouth
- brittle hair and nails
- loss of appetite
- withdrawn behaviour.
Symptoms that may be due to major biotin deficiency
- patchy hair loss (alopecia)
- reversible baldness
- muscle pains and wasting
- recurrent Candida yeast infection.
Biotin and glucose control
Biotin is needed for the action of glucokinase, an enzyme involved in glucose metabolism. Biotin is believed to stimulate insulin secretion from pancreatic beta-cells, increase the breakdown of glucose in the liver and stimulate the conversion of glucose to fats and glycogen (a starchy, energy storage molecule). It may also have an effect on the glucose receptors (known as GLUT 4) that are needed to transport glucose into cells under the influence of insulin.
Blood levels of biotin are lower in people with Type 2 diabetes than in those without, and biotin supplements have also been shown to improve the results of oral glucose tolerance tests in some people with diabetes when taken together with chromium picolinate.
Biotin and nail strength
Biotin supplements can increase nail plate thickness by 25% in women with brittle nails. In a study in which 71 people were given 2.5mg biotin per day, 91% showed definite improvement in nail firmness and hardness after 6 months treatment. In another study, however, around one in three women showed no significant improvements, suggesting that biotin deficiency is not always involved in poor nail quality.
How much biotin do you need?
The EU RDA for biotin is 50mcg daily. The US DV is 300mcg.
Requirements may increase during pregnancy and lactation.
The average Western diet supplies just 33 mcg biotin per day.
For maintaining healthy skin, hair and nails, intakes of around 1000 mcg (1 mg) a day are needed. Two out of three people respond, with nails growing significantly thicker and stronger.
Biotin is relatively non-toxic as excess is excreted in the urine. The European Food Safety Authority felt unable to determine a tolerable upper intake for biotin due to lack of evidence relating to toxicity.
For guidance purposes only, however, the UK Expert Group on Vitamins and Minerals suggested an upper tolerable intake of 900 mcg.
Do You Need A Multivitamin? My Quick Nutrition guide (46 pages) is currently free via this link
|My Essential Guide to Vitamins, Minerals and Herbal Supplements offers a complete overview of each vitamin, mineral, dietary oils and herbal remedy.|
Image credits: william_ismael/flickr