According to HowStuffWorks, dry and brittle toenails are commonly thought to be caused by a lack of moisture or a lack of protein. They can also be a symptom of a fungal infection or of a more severe disease such as heart disease, hepatitus, jaundice or lupus.
HowStuffWorks states that brittle nails are often a natural component of the aging process. Brittle nail syndrome is a relatively benign condition that often afflicts people as they age. Whether dry nails are a result of age, protein deficiency, moisture deficiency or something more severe, they can usually be treated.
One of the best ways to improve nail health is through vitamins. HowStuffWorks lists biotin as one of the best ways to fight against brittle nails. Biotin can be found in vitamin B supplements, as well as in bananas, oatmeal and mushrooms. In one study, women who ingested 2.5 milligrams of biotin every day for a period of six months were shown to have 25 percent thicker nails than women who did not.
Iron and zinc are also important for promoting nail health. HowStuffWorks suggests that taking a multivitamin full of iron, calcium, and vitamins A and C can be instrumental to stronger nail growth.