Beta Carotene

"The most famous of the Carotenoids"

What is it?

The carotenoids give the yellow and orange color to plants such as carrots and squash, in which they are especially abundant. However, some of them are green in color and you can find them in most plants. They have numerous biologic effects and are very active free radical scavengers.

Beta-carotene and the carotenoids

Until recently, beta-carotene got all the press because it was the only carotenoid manufactured in great bulk, and therefore easily available to the vitamin manufacturers and researchers. In addition, it can be converted into twice as much vitamin A as any other carotenoid.

However, we are learning that other carotenoids, such as lycopene, lutein, and zeaxanthin are extremely important, too. Lycopene has been shown to decrease the incidence of certain cancers. Lutein and zeaxanthin protect us from macular degeneration, the leading cause of blindness in the aged.  These often appear on the supplement label as mixed carotenoids.

Who should take beta-carotene? And how much?

This is why it's best to obtain your beta-carotene (and all your other carotenoids) through the daily consumption of yellow vegetables such as squash, pumpkin and carrots and green vegetables such as spinach and broccoli. There are many beneficial substances in our food besides vitamins; attempting to obtain all our nutrients from a supplement is unwise. For the average person I do not recommend beta-carotene supplementation. Having said that, I've never found a daily vitamin that didn't include it.

Beta-carotene and vitamin A

Beta-carotene is a very effective free-radical scavenger and vitamin A is less so. Beta-carotene, in addition, can be transformed by the body into vitamin A, and thus provide us with a safe source of vitamin A activity. This conversion into vitamin A can only occur if we have proper thyroid function and an adequate intake of protein, zinc and vitamin C. Beta-carotene will not be transformed into vitamin A unless we are deficient in vitamin A. Therefore, one can take large amounts of beta-carotene without fear of vitamin A toxicity.

There are conditions, such as retinitis pigmentosa (an eye disease), that respond to vitamin A and not beta-carotene.

Prevention with beta-carotene

Those who consume at least five servings of green leafy vegetables a week (rich in lutein and zeaxanthin) have one fifth the chance of developing visual loss due to macular degeneration. Macular degeneration is the leading cause of blindness in the aged.

A study in the Archives of Ophthalmology (1988;106:337) suggested that people with high levels of at least 2 of the 3 antioxidant vitamins (beta-carotene, vitamin E, and vitamin C) have only a fifth of the chance of developing a cataract as those people with low levels. The British Medical Journal in 1992 (305:335) confirmed that beta-carotene and vitamin C were protective against cataracts. Spinich was noted to be a particularly protective food.   So many studies have confirmed these findings that many ophthalmologists sell such supplements in their office.

The Proceedings of the National Academy of Sciences in 1984 (81:7627) reported that in comparing species of mammals, those with the highest levels of beta-carotene have the longest life span. And that this relationship is especially strong for human beings.

Adverse effects of beta-carotene

People who eat large amounts of beta-carotene (as in carrots or squash) can develop a yellowish color around the nose, on the palms and soles, or even more extensively. This does not affect the whites of the eyes. Most frequently this is seen in children. It causes no harm and slowly diminishes once intake of beta-carotene is diminished.

Male smokers who take large doses of beta-carotene suffer higher rates of lung cancer. I believe the explanation is that higher doses of beta-carotene have been shown to interfere with lycopene, which has an anti-cancer effect. The higher doses may have interfered with other protective carotenoids as well.