Health Options Alan Titchenal  & Joannie Dobbs                    Saturday , June 30, 2007

Too much Vitamin A can be toxic

MORE THAN 150 years ago, blindness and eye disease in Africa was thought to be due to a dietary deficiency. About 60 years later, vitamin A was found to be the deficient component.

Even now, an estimated half-million children worldwide annually suffer from vitamin A deficiency. This not only causes serious eye problems, but also death from common illnesses like measles due to impaired immune functions.

Question: What does vitamin A do in the body?

Answer: In addition to eye health, vitamin A is needed for normal growth, reproduction, bone health, blood cell production, skin health and immune function. The carotenoid forms of vitamin A also function as antioxidants.

Q: What foods provide vitamin A?

A: In ancient Greece, Hippocrates found that eating liver successfully treated night-blindness. This worked because liver is extremely high in the most active form of vitamin A called retinol. Another form of vitamin A, sometimes called provitamin A, is found in a variety of fruits and vegetables that are yellow, orange or green. Provitamin A is composed of specific types of carotenoids like beta-carotene. This is the compound that gives carrots their characteristic orange color and can be converted into retinol in the body.

Q: How much vitamin A does the body need?

A: Daily needs are less than one milligram of retinol per day. This tiny amount is present in a fourth of an ounce of beef liver (about 2 teaspoons). To meet daily vitamin A needs with plant food sources, the average person needs to eat one of the following: 1/2 cup of sweet potato or baby carrots, a large mango or papaya, one cup of cooked spinach or chopped red bell pepper, or a fourth of an average cantaloupe.

Q: Can you consume too much vitamin A?

A: Yes. Vitamin A (especially the retinol or retinyl forms) is one of the most toxic vitamins. Ongoing consumption of two to three times the current recommended intake of vitamin A in the retinol or retinyl form is associated with increased bone loss and bone-fracture risk as people age. Also, there is evidence that pregnant women may increase the risk of birth defects in their offspring by consuming too much vitamin A during pregnancy.

Q: Are dietary supplements with vitamin A safe to take?

A: It depends on the amount of vitamin A in a person's diet and how everything adds up. Just remember that due to outdated labeling regulations, if a supplement label indicates 100% of the "Daily Value" for vitamin A, it contains about double the current recommended intake (RDA) of vitamin A for adults.