1.   In high doses, vitamin A can cause brittle nails, hair loss, headaches and liver damage.

2.   It also produces dry skin, wrinkled skin, sparse dry hair, small brittle nails and cone-shaped teeth.

3.   The symptoms of anemia include not only fatigue, but may also include headache, dizziness and brittle pale nails.

4.   More than this amount could cause selenosis, a toxic reaction marked by hair loss and brittle nails.