Vitamins are a key factor in making bodily processes run effectively and healthily, and nails are no exception. A lack of iron and zinc can harm nail health, and a basic multivitamin is often the solution. Try something with staples like niacin, iron, calcium and vitamins A and C.
A vitamin B complex containing biotin is often cited as important for nail health. Besides being present in certain vitamin supplements, biotin can be found in oatmeal, bananas, mushrooms, peanuts, soy and, if you can stomach it, some animal organs. It's not really clear how effective biotin is in strengthening nails or by what mechanism it operates, though the vitamin has been successful in strengthening horse hooves. In one test, women who took 2.5 milligrams of biotin a day for six months or more ended up with 25 percent thicker nails [source: Healthnotes].
Biotin is found in many foods, so most people normally ingest enough, except in certain cases, such as people with alcoholism, people who eat excessive quantities of raw egg whites or those who use antibiotics for an extended period. Many pregnant women have a biotin deficiency, which can lead to birth defects, making prenatal vitamins essential [source: Healthnotes]. Some healthy women who aren't pregnant take prenatal vitamins for their reputed benefits for hair and nail health.
Much information about supplement-nail relationships is anecdotal rather than scientifically established. There is some evidence to suggest that glucosamine, often used for the treatment of osteoarthritis, is beneficial. Gelatin and an herb known as horsetail are often used for treating brittle nails, though there's little or conflicting evidence that they actually help [source: Healthnotes]. (Gelatin is derived from animal hooves and connective tissue and is a favorite of many nail salons.)