Brittle nails

An under-active thyroid and iron deficiency can cause dry skin and brittle nails. Upping dietary protein and supplementing with biotin can help.

Peeling nails

This common problem indicates your diet may be lacking conjugated linoleic acid, abundant in vegetable oils.

Spoon-shaped nails

Nails that are slightly raised at the tip and curve down in the middle (the opposite of what they should be) are a sign of iron deficiency or anemia.