What Is It?
Beta-carotene is probably the best known of the carotenoids, those red, orange, and yellow
pigments that give color to many fruits and vegetables. The body converts beta-carotene into vitamin A, a nutrient first identified in the 1930s and now recognized as vital to the growth and development of the human body.
As a potent immune-system booster and a powerful antioxidant--it counters the effects of cell-damaging molecules called free-radicals--beta-carotene has an important role to play in human health.
Consuming plenty of fruits and vegetables is an excellent way to supply your body with beta-carotene. In addition, beta-carotene is now sold in supplement form.
Scientists have long hoped that supplements could provide concentrated sources of beta-carotene and thus provide increased protection against heart disease and even against certain cancers. Recent findings, however, indicate that single, high-dose beta-carotene supplements may actually do more harm than good--possibly increasing (rather than decreasing) the number of cell-damaging free-radicals in the body.
Until more information is available, it's probably wise to get beta-carotene in supplement form only as part of a mixed complex, along with other health-promoting carotenoids. Look for products that combine beta-carotene with other carotenes such as alpha-carotene, lycopene, lutein, zeaxanthin, and cryptoxanthin.
In addition to the numerous studies on beta-carotene's effectiveness for heart disease and cancer, researchers have been exploring the nutrient's potential for treating chronic fatigue syndrome, Alzheimer's disease, fibromyalgia, male infertility, and psoriasis. Interestingly, low levels of beta-carotene and other antioxidants have been linked to the development of cataracts, a clouding of the eye's lens that impairs vision.
And preliminary studies point to a possible connection between too little beta-carotene (along with low levels of vitamins A and E) and subsequent development of lupus, an autoimmune disorder.
Specifically, beta-carotene, when taken in a comprehensive antioxidant program may help to:
Guard against heart disease. Beta-carotene may have a role to play in staving off heart disease, apparently a function of its ability to keep harmful LDL cholesterol from damaging the heart and coronary arteries. In a preliminary study done in 1982 of more than 300 doctors taking part in the Harvard University Physicians' Health Study, researchers found that ingesting 50 mg (85,000 IU) of beta-carotene daily cut in half the subsequent risk of risk of heart attack or stroke, or death from cardiovascular disease.
However, subsequent studies using beta-carotene alone and involving larger numbers of participants were not able to duplicate these results. It's possible that to directly benefit the heart, beta-carotene must be taken along with other antioxidants. Or it must be consumed through vegetables or fruits; these plant foods provide antioxidants, dietary fiber, folate, and a host of other heart-healthy compounds that have yet to be fully understood.
Interestingly, in a follow-up to the Harvard study published in 2001 and involving more than 15,000 male physicians, investigators found that a high intake of vegetables rich in beta-carotene made a big difference on heart health. Participants who consumed at least two and a half servings of vegetables a day over the 12-year study were far less likely to develop coronary heart disease than those who consumed less than one vegetable serving a day.
Prevent certain cancers. Beta-carotene's antioxidant actions make it valuable in protecting against, and in some cases even reversing, precancerous conditions affecting the breast, mucous membranes, throat, mouth, stomach, prostate, colon, cervix, and bladder.
To provide anti-cancer actions, however, beta-carotene must be taken as part of an antioxidant supplement formula featuring other carotenoids, vitamins C and E, and selenium. In fact, large studies indicate that beta-carotene taken as a single supplement offers no cancer-protective actions at all.
To confuse matters, an increased risk for lung cancer has actually been linked to beta-carotene supplements in smokers. In one highly publicized study, researchers in Finland found that more cases of lung cancer developed in male smokers (including former smokers) who were taking high doses of the supplement, particularly those who smoked 20 cigarettes or more a day.
Several factors were considered responsible for this finding. Smokers typically have low levels of vitamin C, for example, which--when combined with an excess of beta-carotene--creates an imbalance that may result in an increase (rather than decrease) in the formation of cell-damaging free radicals.
In treating cancer with chemotherapy or radiation--both of which can damage healthy cells as they attack cancer cells--beta-carotene taken with other carotenoids, such as lycopene, and antioxidants such as vitamins C and E, may help to protect the body.
No RDA has yet been established for beta-carotene, but about 10,000 IU of this nutrient fulfills the RDA for vitamin A.
If You Get Too Little
Symptoms of a beta-carotene deficiency mimic those of a vitamin A deficiency: dry skin, night blindness, susceptibility to infection. Such deficiencies are seldom seen, however, even in people who don't eat fruits or vegetables or take supplements, because so many other foods supply the nutrient.
If You Get Too Much
It is nearly impossible to overdose on beta-carotene because the body excretes what it doesn't need. However, if you ingest high levels of beta-carotene from foods (such as carrot juice) or supplements, the palms of your hands and the soles of your feet may turn orange. If this occurs, consult your doctor. In most cases, the coloration is harmless and will gradually fade if you reduce your beta-carotene intake.
How to Take It
--By far the best source of beta-carotene is fresh fruits and vegetables. Excellent sources include carrots, cantaloupe, and myriad other yellow, orange, and red fruits and vegetables. Green vegetables are also a good source. Choose dark ones such as broccoli, romaine lettuce, and spinach; the darker color indicates a higher beta-carotene content.
--In terms of supplements, the most effective and economical way to take beta-carotene is as part of a formula containing other significant health-promoting carotenoids, such as alpha-carotene, lycopene, lutein, zeaxanthin, and cryptoxanthin. Many products supply these carotenoids in one pill.
As part of a program to prevent heart disease, cancer, and other conditions associated with free-radical damage: Take one dose daily of a mixed-carotenoid supplement that provides 25,000 IU vitamin A activity. If you are at particularly increased risk for heart disease or cancer, or are trying to minimize the effects of cancer treatment on healthy cells, consider increasing your dose to two mixed-carotenoid pills daily.
Guidelines for Use
Take beta-carotene and all other carotenoid supplements with food.
There are no known drug or nutrient interactions associated with beta-carotene.
If you have a sluggish thyroid (hypothyroidism), liver or kidney disease, or an eating disorder, consult your doctor before trying beta-carotene supplements.
Many experts caution smokers to avoid beta-carotene supplements. The supplements are even riskier for smokers who also drink significant amounts of alcohol.
If you ingest high levels of beta-carotene from either foods or supplements, the palms of your hands and the soles of your feet may turn orange. If this occurs, consult your doctor. In most cases, the coloration is harmless and will gradually fade if you reduce the amount of beta-carotene you're taking.
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