|Vitamin A (Retinol)|
Vitamin A is a fat-soluble compound that is found naturally in many foods. There are two categories of vitamin A, depending on whether the food source is animal or plant. Vitamin A plays an important role in vision, bone growth, reproduction, cell division, and cell differentiation. It also helps regulate the immune system by making white blood cells and promoting healthy surface linings of the eyes and the respiratory, urinary, and intestinal tracts.
Night blindness is one of the first signs of vitamin A deficiency as well as, corneal drying (xerosis), triangular gray spots on eye (Bitot's spots), corneal degeneration and blindness. It also causes impaired immunity, hypokeratosis (white lumps at hair follicles) and softening of the cornea (keratomalacia). Both vitamin A excess and deficiency are known to cause birth defects. During fetal development, retinol plays a role in limb development and formation of the heart, eyes, and ears.
As vitamin A is fat-soluble, excessive vitamin A can result in toxicity. Symptoms include nausea, jaundice, irritability, vomiting, blurry vision, headaches, muscle and abdominal pain and weakness, drowsiness and altered mentality.
Good sources of vitamin A include fortified foods, darkly colored fruits and vegetables, full fat milk, margarine, butter, eggs, sweet potatoes, apple, mango, lemon and pumpkin.
*DV = Daily Value. DVs were developed by the U.S. Food and Drug Administration (FDA) to help consumers compare the nutrient contents of products within the context of a total diet. The DV for vitamin A is 5,000 IU for adults and children age 4 and older. Foods providing 20% or more of the DV are considered to be high sources of a nutrient. The U.S. Department of Agriculture's (USDA's) Nutrient Database Web site  lists the nutrient content of many foods and provides a comprehensive list of foods containing vitamin A in IUs and foods containing beta-carotene in mcg.