The antioxidant vitamin A, also referred to as retinol, is a fat-soluble vitamin necessary for the immune system, healthy eyes, teeth, bones, soft tissues and skin. Animal sources of vitamin A are high in cholesterol and saturated fat and include eggs, dairy, meat, cod and liver. Other sources of vitamin A come from micronutrients called carotenoids that convert into vitamin A inside the body.
Carotenoids
Fruits and vegetables are a rich source of carotenoids, especially those of orange, red or dark-green color such as carrots, pumpkins, apricots, cantaloupe, spinach, kale and tomatoes. There are six major carotenoids: alpha-carotene, beta-carotene, beta-cryptoxanthin, lutein, trans-lycopene and zeaxanthin. Beta-carotene converts to vitamin A more effectively than the other carotenoids, according to the CDC.
Effects of Cooking
Vitamin loss may when cooking in the microwave, but this depends on the temperature and cooking time. The hotter and longer foods are cooked, the more nutrient are lost. A study published in the August 2010 issue of the "Journal of Zhejiang University Science" compared various cooking methods and their affect on the nutrients in broccoli. The methods tested were steaming, microwaving, boiling and stir frying. The results showed that while all methods reduced vitamin C content, only boiling, and stir frying followed by boiling, caused a total loss of carotenoids. Steaming was the method that maintained the highest nutrient content.
Recommended Daily Allowance
The recommended daily allowance for adults is 700 to 900 μg/day. Children need between 300 and 600 μg/day, however, because of the risk of toxicity, see your child's pediatrician before giving him a supplement. The Office of Dietary Supplements, a service of the National Institutes of Health, states there are no recommendations for carotenoids but suggests that 3 to 6 mg daily of beta-carotene is "associated with a lower risk of chronic diseases." This amount equates to at least 5 servings of fruits and vegetables daily.
Considerations
Vitamin A deficiency is rare in the U.S, but it can occur with alcohol abuse or people with digestive conditions that limit the absorption of nutrients in foods. Large amounts of vitamin A supplementation can be toxic. Consult a qualified health care professional before taking a supplement. A balanced diet with a wide variety of fruits and vegetables provide the best source of vitamin A and carotenoids.
References
- MedlinePlus: Vitamin A
- Office of Dietary Supplements: Vitamin A and Carotenoids
- University of Maryland Medical Center: Vitamins-Carotenoids
- American Dietetic Association: Does Microwaving Food Destroy the Vitamins?
- MayoClinic.com: Vitamin A (Retinol)
- "Journal of Zhejiang University Science"; Effects of Different Cooking Methods on Health-Promoting Compounds of Broccoli; Geo-feng Yaun, et al; August 2010
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