What is Vitamin A?
Vitamin A is introduced into our bodies in two ways: as retinoids which are animal sources of vitamin A, and as carotenoids which are plant sources of vitamin A. Vitamin A has many important functions in our bodies, but the one that most people are familiar with is the health of our eyes. We require vitamin A to form light-sensitive nerve cells, called photoreceptors, in the retina, which gives us the ability to see at night and in dark areas. However, vision is not the only role this vitamin plays in our eyes. It also helps maintain the cornea of our eye - this is the clear layer around our eyeball that is one of the major barriers which protects us against things in our environment that can harm our eyes, such as dirt and germs.
Vitamin A also plays a role in maintaining the health and function of major organ systems, including our skin, and the lining of our lungs, digestive tract, and urinary tract. Lastly, vitamin A helps support our immune system to help us fight off infections.
Most adults can get half of their RDA by eating 5 servings of fruits and vegetables a day. Good animal sources of vitamin A include fish liver oils, liver, egg yolks, butter, cream, and fortified milk, while good plant sources include sweet potatoes, carrots, spinach, and apricots.
For adults, the RDA for vitamin A varies by gender: males 900 mcg/day, females 700 mcg/day, pregnant females 750-770 mcg/day, breastfeeding females 1,200-1,300 mcg/day. Too much vitamin A can be harmful and, since this vitamin is stored in fat, can reach toxic levels in our bodies. Symptoms of too much vitamin A include headaches, vomiting, confusion, joint pain, and skin that is dry and has a yellow-orange discoloration. Taking too much vitamin A supplements can have negative effects on bone density, liver health, and increase the risk of certain birth defects.