Biotin, a B vitamin, is essential for the health of your hair, skin, and nails. A biotin deficit can result in brittle, easily splitting nails. Biotin-rich foods include eggs, almonds, cauliflower, cheese, mushrooms, sweet potatoes, and spinach. Dehydration can have a big influence on your nails, making them brittle and more likely to split. Drinking enough of water throughout the day helps keep nails flexible and strong