Vitamin A is actually a group of related compounds including retinol, retinal and retinoic acid. Sometimes provitamin A carotenoids, compounds such as beta-carotene that can be converted into retinol in the body, are included in this group. While vitamin A is necessary for a variety of bodily processes, excess vitamin A can be toxic.
Importance
Vitamin A is vital to proper functioning of the eyes, as retinol acts on the retina to aid night vision. Retinoic acid acts as a hormone in the body that controls gene expression. Vitamin A also operates in the immune system, where it promotes the development of white blood cells. Another function of vitamin A is to mobilize hemoglobin, the oxygen-carrying component of blood. In the developing fetus, retinol and retinoic acid are vital in the formation of the baby's heart, eyes and ears.
Recommendations
Normal males age 14 and older should get 900 micrograms of vitamin A daily, while females of this age should get 700 mcg. Preteens of both genders between the ages of 9 and 13 should get a minimum of 600 mcg daily. The recommended daily intake for children between 4 and 8 is 400 mcg. Children between 1 and 3 need 300 mcg daily. Babies under the age of 1 typically get vitamin A through breast milk or fortified infant formula, about 500 mcg every day when between 7 months and 1 year old and 400 mcg for babies 6 months and younger. The recommended intake of vitamin A, when taken daily, can provide up to four months of stored vitamin A within the body.
Special Circumstances
Pregnant women under 18 need 750 mcg of vitamin A each day, while pregnant women over 18 need 770 mcg. Lactating mothers require 1,200 mcg if under 18 and 1300 mcg if over 18. Some people get the majority of their vitamin A intake in the form of carotenoids. No recommended daily intake of beta-carotene or other carotenoids exists, but according to the National Institutes of Health's Office of Dietary Supplements, 3 to 6 mg of beta-carotene can provide the equivalent of 833 IU to 1,667 IU of vitamin A; 300 mcg of vitamin A is equal to about 1,000 IU.
Excessive Intake
Too much vitamin A can cause reduced bone mineral density, liver problems and birth defects. The tolerable upper limit for vitamin A is set at 3,000 mcg for individuals over age 19, including pregnant and lactating women, and 2,800 mcg for anyone between the ages of 14 and 18. Preteens between 9 and 13 should take no more than 1,700 mcg daily, and children between 4 and 8 should limit their vitamin A consumption to below 900 mcg. The tolerable upper limit of vitamin A for children under 3 years old, including infants, is 600 mcg.
Sources
Cod liver oil contains high levels of vitamin A. Other good food sources include fortified breakfast cereals (with milk), sweet potatoes, carrots, cantaloupe, spinach and kale. Vitamin A is also often included in multivitamins in doses of 750 to 1,500 mcg.
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