Q. Is there a vitamin or mineral one can take to prevent or cure splitting fingernails?

A. Supplement makers commonly market biotin, a B vitamin, for nail health, based on two small studies published in the 1990s that found that most patients had stronger, thicker nails within several months of beginning a biotin supplement. However, neither study included a control group, so any improvements may have been a result of changes in diet or nail care.

Biotin helps the body use carbohydrates, fat and protein and is found naturally in many foods, including nuts, eggs, avocados, meat, fish and vegetables. The Institute of Medicine says adults need about 30 micrograms of the B vitamin a day, an amount easily obtained from diet. In contrast, the nail studies used doses of 2,500 to 3,000 micrograms, 100 times the recommended amount.

At those levels, “you’re giving it in doses that could not possibly be obtained from food without extraordinary effort or special selection, so this is kind of using it as somewhat of a drug,” said Dr. Paul Thomas, a registered dietitian and scientific consultant at the National Institutes of Health’s Office of Dietary Supplements. Because the Food and Drug Administration regulates dietary supplements as food, not pharmaceuticals, they are not reviewed for safety or efficacy before hitting store shelves, though the limited safety data on biotin is reassuring. As a water-soluble vitamin, excess biotin appears to be readily excreted in the urine.

Dr. Monica Lawry, a dermatologist at Sutter Medical Group in Davis, Calif., is skeptical of the various cocktails of vitamins, minerals and often proprietary blends of herbal ingredients commonly marketed for nail health. There’s no evidence that they work, she said, and “they’re very overpriced.”

Nail problems may also be a sign of a medical problem, so it’s worth having a dermatologist assess them, Dr. Lawry said. “People with brittle, thin, weak, splitting nails often have Raynaud’s syndrome,” marked by poor blood flow to the fingers and toes, which may be caused by a more serious underlying medical condition, she said. Other possible causes include thyroid disease and iron-deficiency anemia.


Most brittle nails are caused by dryness, Dr. Lawry said. To keep hands hydrated, she recommends applying a simple moisturizer containing alpha hydroxy acid to the nails themselves; soaking the nails in a paraffin wax bath for 10 to 20 minutes afterward can help the nails absorb extra moisture. Limit manicures and, if possible, avoid frequent hand-washing and use of alcohol-based hand-sanitizers, which can further dry out the nails, she said.