The Worst Diet Mistakes for Your Hair and Nails...

Suffer from limp hair or brittle nails? These unhealthy habits may be to blame!

Just like your skin, your hair and nails are affected by the foods you choose to eat.  And we're not talking about the sheen of those lustrous waves or a hangnail. Both hair and nails can become brittle and dry, and hair can thin or fall out without the right range of nutritious picks in your diet.

"Both are a barometer of how well (or how poorly) you're feeding the body," says dermatologist Jessica Wu, M.D., author of Feed Your Face and skin and beauty expert for Daily Glow, "as well as your overall health."

Both hair and nails are made from the same protein, called keratin, so it makes sense that similar diet choices would affect them both, she explains. Of course, a number of other lifestyle choices also play a role, including smoking, she says, since it reduces circulation and may cut down on the amount of biotin in the blood. Biotin, often added to hair and nail products, seems to strengthen both.

Less research exists to document the impact of various foods on hair and nail health than to illustrate the role of diet in healthy skin. But there are still a few foods to be careful of if you're concerned about brittle nails or thinning hair; fish high in mercury, sugar, high-glycemic foods, high doses of vitamin A, too little protein and a lack of iron and zinc.