          
               VITAMIN A
          
               Vitamin A (retinoid) is a fat-soluble vitamin found 
          mainly in animal foods in the vitamin form and in plant 
          foods primarily as carotenes, substances that are formed 
          into vitamin A chiefly in the small intestine.
          
               Function: Essential for growth and for keeping skin 
          and other tissues healthy; helps eyes to adapt to dim light 
          and perceive colors; essential for normal tooth 
          development.
          
               Sources: Beef, chicken and pork livers; whole and 
          vitamin A-fortified milk; cheddar cheese; butter; 
          margarine; egg yolk; deep green, yellow or orange 
          vegetables and fruits (including carrots, spinach, 
          collards, broccoli, kale, nectarines, apricots, mangoes, 
          cantaloupe, pumpkins, winter squash, turnip greens, sweet 
          potatoes, and watermelon).
          
               Deficiency: Vitamin A deficiency is reare in the 
          United States; it mainly occurs among some people in 
          developing countries. Some signs include skin changes, 
          stunted growth, night blindness, and serious eye problems 
          (such as drying, thickening, wrinkling, and muddy 
          pigmentation of the mucous membrane lining the eyelid and 
          eyeball, which eventually can destroy the eye). Inadequate 
          intakes of foods containing vitamin A have been associated 
          with some types of cancer, but the effect, if any, appears 
          related to lack of carotene.
          
               Excess: Because vitamin A is fat soluble, it is stored 
          in the body. As a result, continued high doses (several 
          times the U.S. RDA) have toxic effects. Signs of toxicity 
          include dry and itching skin, headaches, and nausea and 
          diarrhea. High vitamin A intake during pregnancy also may 
          cause birth defects, but it is not known at what level this 
          can occur. Excessive amounts of carotene are not known to 
          be toxic, but will cause the skin to turn deep yellow. The 
          color disappears when the amount of carotene in the diet is 
          decreased.
          
          
