About Vitamin A
Vitamin A is important for healthy skin, teeth, bones and organs—including the heart, lungs and kidneys. It plays a role in growth and development and is critical for good vision—especially in low light. Vitamin A also promotes a healthy immune system and good reproductive health and is important for women who are breastfeeding.
Vitamin A is a group of fat-soluble vitamins called retinoids (e.g., retinol, retinal, retinoic acid, retinyl esters) that act as antioxidants—substances that help protects the body's cells from damage caused by free radicals. Free radicals are produced when the body breaks down food or from environmental exposure to smoke, radiation, etc. Vitamin A is stored in the liver.
Sources of Vitamin A
Vitamin A can come from plant or animal sources in the diet. Plant sources of vitamin A include colorful fruits and vegetables—leafy, dark green vegetables and orange and yellow fruits and vegetables. Animal sources, which are often high in saturated fat and cholesterol, include dairy products, fish and fish oil, and meat (especially liver). Many cereals are also fortified with vitamin A.
The following foods are good sources of vitamin A:
- Beef liver
- Black-eyed peas
- Cheese (some types)
- Fortified cereal
- Pink grapefruit
- Pumpkin, pumpkin pie
- Sweet potato
- Tomatoes, tomato juice, tomato products
Vitamin A Recommendations
Although vitamin A deficiency is rare in the United States, it's more common in developing countries where people have limited access to foods that contain this essential vitamin. Babies who are born prematurely (before completion of the 37th week of gestation), alcoholics, vegetarians, and people with certain medical conditions, such as cystic fibrosis, liver disease, celiac disease, absorption disorders, pancreatitis, Crohn's disease, and others are at increased risk for vitamin A deficiency.
The Recommended Daily Allowance (RDA) for vitamin A varies according to age, gender, overall health and other factors. Talk to you health care provider about your vitamin A intake and about whether you should take a supplement to make sure you’re getting enough of this important vitamin.
RDA for vitamin A (mcg/day):
- From birth to 6 months of age400 mcg (micrograms)
- Ages 7 months to 1 year500 mcg
- Ages 13300 mcg
- Ages 48400 mcg
- Ages 913600 mcg
- Males over the age of 14900 mcg
- Females over the age of 14700 mcg
- Women who are pregnant750 mcg in those 18 or younger; 770 mcg in those over the age of 19
- Women who are nursing1,200 mcg in those 18 or younger; 1,300 mcg in those over the age of 19
Vitamin A Deficiency and Effects of Vitamin A
The most common symptom of vitamin A deficiency is dry eyexerophthalmiawhich leads to an inability to see well in low light or darkness (night blindness). People with inadequate vitamin A levels have a higher risk for infections, diarrhea and low blood iron (anemia), and may experience additional vision problems. Vitamin A deficiency also can cause problems during pregnancyfor the mother and the unborn baby. Growth and development may be impaired in babies born to mothers who have low levels of vitamin A.
Studies are being conducted to determine if vitamin A levels may play a role in certain medical conditions, including various types of cancer (e.g., lung cancer, prostate cancer), age-related macular degeneration (AMD), measles and bone loss leading to increased fracture risk. So far, results of these studies have been mixed and inconclusive, but research is ongoing.
A high intake of carotenoids (form of vitamin A found in brightly-colored fruits and vegetables, grains and oils) usually is not associated with any known health risks (other than yellow-orange skin), extremely high levels of vitamin Amost often from supplementscan cause liver damage and result in a serious condition called hypervitaminosis A. Symptoms include intracranial pressuredizziness, nausea, headaches, blurred visionbone, muscle and joint pain, fatigue and skin rashes or irritation. In severe cases, liver damage caused by hypervitaminosis A is not reversible and may lead to coma and death.
Women who are or may become pregnant should not take high doses of vitamin A or use topical retinoids. High levels of vitamin A can cause birth defects, including eye, skull, lung and heart malformations. Past or current smokers, people who have been exposed to asbestos, and those who take certain medications, such as orlistat for weight loss (Alli®, Xenical®) or retinoids to treat psoriasis or another health condition, should talk to their health care provider before taking vitamin A supplements.
Measuring Vitamin A Levels
People who are at increased risk for vitamin A deficiencydue to a medical condition, for exampleand those with signs and symptoms of a deficiency or of hypervitaminosis A may have a blood test to measure their vitamin A level. In some cases, this test may be performed regularly to monitor levels of vitamin A in the blood.
Source: National Institutes of Health (NIH)