What is Vitamin A?
Vitamin A is a fat-soluble vitamin that acts as an antioxidant. Antioxidants are chemicals which may help reduce risk of cancer. Since vitamin A is fat-soluble it is not needed in daily, large quantities. Fat-soluble vitamins are stored in the body in organs such as the liver. Most of the vitamin A that we consume goes to the liver to be stored until it is needed by another part of the body. Therefore, our intake of vitamin A should be enough to replenish our liver stores.
Vitamin A, like many other nutrients, is found in different forms. The vitamin A that we obtain from animal products is called retinoids and can be used by our bodies without any modification. The form of vitamin A found in fruits and vegetables is known as carotenoids. The most common type of carotenoid is ß-carotene (beta carotene). These carotenoids are used to build the type of vitamin A used by our body.
Vitamin A, also called retinol, helps your eyes adjust to light changes when you come in from outside and also helps keep your eyes, skin and mucous membranes moist. Vitamin A mostly comes from animal foods, but some plant-based foods supply beta-carotene, which your body then converts into Vitamin A. It also has antioxidant properties that neutralize free radicals in the body that cause tissue and cellular damage.
Early information from scientific studies suggests that beta-carotene
might help people who already have Coronary Artery Disease (CAD). The
American Heart Association doesn't recommend taking supplements of
beta-carotene until more is known, however. Nutritionists categorize vitamins by the materials that a vitamin will dissolve in. There are two categories: water-soluble and fat-soluble vitamins. Fat-soluble vitamins—vitamins A, D, E and K—are stored in the fat tissues of the body for a few days to up to six months. If you get too much of a fat-soluble vitamin, it can be stored in your liver and may sometimes cause health problems. Vitamin A is a fat-soluble vitamin.
Some people take mega-doses of fat-soluble vitamins, which can lead to toxicity. Eating a normal diet of foods rich in these vitamins won't cause a problem. Remember, you only need small amounts of any vitamin. In the case of vitamin A, overconsumption has been linked with an increased risk of fractures in postmenopausal women.
Some health problems can make it hard for a person's body to absorb these vitamins. If you have a chronic health condition, ask your doctor about whether your vitamin absorption will be affected.
How Much Vitamin A Is Enough?
It's recommended that women consume 800 mcg and men consume 1000 mcg of vitamin A daily.
Sources of Vitamin A
Top sources of vitamin A include:
- Beef liver
- Egg yolk
- Cheddar cheese
- Fortified milk
- Sweet potato
- Carrots
- Pumpkin
- Cantaloupe
- Broccoli
- Apricots
- Spinach and collard greens
Vitamin A deficiency is rare in the United States, but it can cause night blindness, eye inflammation, diarrhea and other problems. Overconsumption of vitamin A can cause nausea, irritability and blurred vision in its mild form. In addition, the palms of the hands and the bottoms of the feet can turn orange if a person has a high intake of Vitamin A.
Too much vitamin A in the body is known as hypervitaminosis A. This occurs when vitamin A becomes toxic to the body and causes harmful effects. High levels of vitamin A can cause birth defects, osteoporosis, liver problems, and central nervous system problems. The amount of vitamin A needed to cause toxicity can vary depending on the type of vitamin A eaten. It is suggested that men and women above the age of 19 should consume less than 75,000 IU of vitamin A per day to prevent toxicity.
Vitamin Storage
If you want to get the most vitamins possible from your food, refrigerate fresh produce, and keep milk and grains away from strong light. Vitamins are easily destroyed and washed out during food preparation and storage. If you take vitamin supplements, store them at room temperature in a dry place that's free of moisture.
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