Vitamin A and Carotenoids: Antioxidants for Sight

Vitamin A is an antioxidant that you can get from animal sources such as liver or butter, or from plants that contain carotenoids. So what exactly are carotenoids? They're simply red and yellow pigments in plants and animals. In addition to providing color, they also act as antioxidants, and your body converts certain ones (beta-carotene is most common) into vitamin A as well. Vitamin A is essential for eye health, and certain carotenoids, such as lutein and zeaxanthin, appear to be beneficial as well.

Let's look at how vitamin A helps your eyes. For one thing, it prevents night blindness. If the vitamin A deficiency causing night blindness isn't corrected, it can lead to xerophthalmia, with dryness in the eyes, corneal ulcers and swollen eyelids. Untreated, xerophthalmia can lead to blindness. In fact, vitamin A deficiency is one of the leading causes of blindness in developing countries. Vitamin A has been reported to prevent cataracts from forming and may have a role in preventing blindness from macular degeneration, the leading cause of blindness in the world.

Cataracts Macular degeneration

How much vitamin A do you need? The U.S. RDA (recommended daily allowance) for males age 11+ is 1,000 Retinol Equivalents (RE); the RDA for females age 11+ is 800 RE. Vitamin A is also measured in International Units (IU): 1 RE = 10 IU for plant products and 1 RE = 3.3 IU for animal products.

If you smoke or drink, plan on taking in extra vitamin A, because tobacco keeps your body from absorbing it and drinking depletes what you already have in your body. However, watch out for beta-carotene supplements: studies suggest that they increase smokers' incidence of lung cancer. Instead, get your vitamin A from food sources.

The following is a sampling of foods that are good sources of vitamin A*:

The above values are for raw foods. Cooking can change the values, as heat will destroy vitamin A and beta-carotene in foods. Also, if you don't pick up fresh food, select frozen rather than canned, as canning strips away much more of the vitamin A in food.

Various studies have found that lutein and zeaxanthin may reduce the risk of developing cataracts. They may reduce the risk of developing age related macular degeneration as well: some studies have found a link, while others have not.

One recent study released in November 2005 from the USDA Human Nutrition Research Center on Aging at Tufts University indicated a strong link between the prevention of cataracts and age-related macular degeneration with an increase of foods rich in lutein and zeaxanthin, such as green and yellow vegetables and egg yolks.

Lutein and zeaxanthin are closely related: they often appear together in fruits and vegetables, and your body can convert lutein into zeaxanthin.

There is currently no RDA for either, but you need to get some every day, because your body can't make them.

The best source of lutein and zeaxanthin is green, leafy vegetables, particularly spinach. Kale and collard greens are also good choices. You can also find lutein and zeaxanthin in yellow and orange fruits and vegetables, such as corn.

Cooked vegetables are a better source of lutein than raw, as cooking breaks down the cell walls to release the lutein.**