Biotin is a water-soluble vitamin also called Vitamin B7 or Vitamin H. It helps the body get nutrients from fats, carbohydrates and proteins and it's also involved in energy production.
Biotin deficiency is so rare that there's not enough evidence to conclude a Recommended daily Allowance. The Daily adequate intake is 30 mcg a day and most healthy individuals meet these requirements through their diet. Biotin is the only B vitamin produced in the body by bacteria in the large intestine, that's why severe biotin deficiency in healthy individuals has never been reported. On the other hand, high doses of biotin intake have been reported to cause falsely high or falsely low laboratory test results, mainly affecting results of thyroid function, gonadotrophins, vitamin D and a biomarker for heart attacks called troponin.
Who might be at risk of biotin deficiency:
Pregnant and breastfeeding women.
People dealing with gastrointestinal problems or malnutrition.
High alcohol and intravenous drug use.
People that consume raw eggs (they contain avidin which prevents biotin absorption).
Prolonged use of antibiotics.
Smokers.
Taking the medication isotretinoin for acne.
Biotinidase deficiency (genetic disorder that affects biotin metabolism).
Best food sources of biotin include:
Eggs
Legumes
Nuts and seeds
Liver
Sweet potatoes
Avocados
Broccoli
Since biotin is responsible for protein metabolism and hair is primarily made up of keratin (a protein), scientists theorize that biotin helps improve protein synthesis and keratin structure, but there isn't enough evidence to support these claims.
Hair growth requires many nutrients: antioxidants, vitamins, minerals, amino acids and fatty acids. Given that the hair cycle is a constant process of cell division and replication, these cells need a constant supply of nutrients to keep the process going. A nutritional imbalance can interfere with your hair cycle and cause hair loss, but biotin deficiency is very rare, it is needed in small amounts, it is produced by normal gut flora and being a water-soluble vitamin, excess biotin is excreted in the urine so there is really no need for biotin supplementation unless directed by your doctor.
Here is some of the medical literature on biotin use for hair, nails and skin:
…” Otherwise, indications for supplementation remain unnecessary in healthy individuals”
…” To date, there have been no trials supporting claims of biotin supplementation being used to im
prove hair quality or quantity, or nail growth” Biotin - StatPearls - NCBI Bookshelf (nih.gov)
…” A review of the fingernails literature reported brittle nail improvement as evidence from two pre-1990 clinical trials that had administered an oral dietary supplement of 2.5 mg/day for several months, without a placebo control comparison group” Nutrition and nail disease - PubMed (nih.gov)
…” We found 18 reported cases of biotin use for hair and nail changes. In all cases, patients receiving biotin supplementation had an underlying pathology for poor hair or nail growth” Skin Appendage Disorders SAD462981.indd (karger.com)
… “Despite these data, there have been no randomized, controlled trials to prove the efficacy of supplementation with biotin in normal, healthy individuals.” Skin Appendage Disorders SAD462981.indd (karger.com)