Biotin, also known as vitamin B7, is a water-soluble nutrient essential for converting food into energy and supporting keratin production - a protein that forms the structure of hair, skin, and nails. As biotin supplements become more common in hair care products and dietary regimens, their actual effectiveness for improving hair growth has come under scrutiny. This review looked at 18 case reports and a handful of small trials to assess the clinical outcomes of biotin use for hair loss and nail strength (Patel et al., 2017).

In every reported case where biotin supplementation improved hair or nail condition, an underlying pathology was present. These included inherited enzyme deficiencies like biotinidase deficiency, dietary restrictions, medication side effects, and brittle nail syndrome. Doses in these studies ranged widely - from 300 μg to 30,000 μg daily - and all showed clinical improvements, particularly in cases involving alopecia linked to biotin deficiency. However, in healthy individuals with no confirmed deficiency, no strong evidence supports biotin’s role in promoting hair growth or preventing hair loss.

Although some studies found that up to 38% of women with hair loss symptoms had low biotin levels, these were often linked to external factors such as medications, pregnancy, or gastrointestinal issues. Furthermore, in vitro studies showed that biotin had no effect on normal keratinocyte proliferation, suggesting it may not enhance hair growth in individuals with sufficient baseline levels.

Despite the popularity of biotin in supplements and shampoos, there are no controlled trials proving its benefit in non-deficient individuals. Most people in Western countries already consume 35–70 μg of biotin daily through food sources like eggs, meats, and nuts, meeting or exceeding the recommended adequate intake of 30 μg/day.