Changes in your nails can often be one of the first signs of a problem with your diet or a vitamin or nutrient deficiency. Nail changes may signify a number of disorders elsewhere in the body. These changes may indicate illness even before the rest of the body does.
    
The following is a list of disorders that often show up in the nails:
  
Brittle nails signify possible iron deficiency and thyroid problems, impaired kidney function, and circulation problems