Beta-carotene: more than a nutrient, more than an antioxidant, more than a defense against night blindness, could be a potent weapon in the war against cancer.

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Few people have known about beta-carotene until recently Even scientific researchers looked upon it as merely a substance interchangeable with vitamin A. Recent discoveries herald the substance as a possible weapon against life-threatening diseases.

Q: How are beta-carotene and vitamin A linked?

A: Beta-carotene is known as a precursor to vitamin A; it is converted to vitamin A in the liver and the mucous membranes of the small intestines. Beta-carotene is safer because it will not become toxic to the body. (Vitamin A has been reported to be possibly toxic in very large quantities.)

Q: Otherwise, given its safety features, what properties does beta-carotene possess that vitamin A does not?

A: Beta-carotene penetrates more vital organs of the body than vitamin A and remains in the system for longer periods of time, providing more protection against invaders.

Q: What is the composition of betacarotene?

A: Beta-carotene is a yellowish compound present in yellow, orange, and green vegetables. It is related to the carotenoids (alpha-carotene, gamma-carotene, and cryptoxanthin), which also appear in these vegetables but do not as much vitamin A.

Q: By what process is beta-carotene prevented from becoming toxic like vitamin A?

A: Whatever beta-carotene is not converted to vitamin A during absorption is stored in the liver until needed; significant quantities also circulate in the bloodstream and in fatty areas of all cells.

Q: Individuals who take large quantifies of beta-carotene often develop a yellow cast on the skin and palms of the bands. What process causes the change?

A: As noted above, beta-carotene penetrates the fatty tissues, which reflect the yellowish color of the substance. No danger exists from this phenomenon, and it can be diminished by reducing dosage if desired.

Q: Do beta-carotene and vitamin A have the same activity?

A: As beta-carotene converts to vitamin A, the latter invigorates the epithelial cells, which form the tissues of the outer layer of skin and the mucous membranes, which line the mouth, digestive tract, respiratory tract, and genitourinary tract. It is supposed that such enrichment provides barriers against invasion by bacteria, cancer-causing carcinogens, and viruses. A deficiency of the vitamin could lower resistance to diseases.

Beta-carotene also functions to protect the thymus gland (a part of the immune system) from atrophy. Its ability to maintain night vision is well known.

Among the most recent discoveries is the vitamin's ability to act as an antioxidant, which helps to protect cell membranes against oxidation. Other attributes include its ability to maintain the health of the adrenal glands and aid in bone development and membrane integrity.

Q: What are some of the deficiency symptoms that can serve as warning signs?

A: Lack of tear secretion can indicate glandular problems. Individuals who are highly susceptible to colds could be suffering from beta-carotene deficiency. Constant diarrhea is another warning sign.

Ordinarily, laboratory tests can reveal deficiencies; not so in the case of beta-carotene. Many months of deficiency are required before laboratory studies reflect incipient problems.

Q: Who would be especially vulnerable to deficiencies of the vitamin?

A: Topping the list of those who are most vulnerable to vitamin A (beta-carotene) deficiencies are pregnant women, breast-feeding mothers, those who abuse alcohol or drugs, and people who are undergoing excess stress for long periods of time. Patients who suffer from gastrointestinal problems require an adequate supply of the vitamin.

Q: Besides night blindness, what are the dangers of deficiencies related to the eyes?

A: Vitamin A is essential to normal function of the retina.

Q: What are the best sources of betacarotene?

A: Beta-carotene is abundant in vegetables and fruits. The vitamin can also be purchased in the form of a food supplement. In using the latter, do not chew or crush the tablets. Individuals should take these supplements with food to decrease possibility of stomach irritation.

Q: If beta-carotene is not available, what are the symptoms of a vitamin A overdose?

A: Bleeding gums could be one symptom. Diarrhea, double vision, headache, irritability, dry skin, hair loss, vomiting, and seizures are others. Vitamin A toxicity has been known to diminish upon withdrawal of the vitamin. If not, consult your doctor.

Q: Could the use of beta-carotene supplementation optimize recovery after surgery?

A: Beta-carotene can significantly reduce the immune-depressive effects of radiation treatment and cancer chemotherapy, reports The Doctor "s Vitamin and Mineral Encyclopedia (Fireside Edition, Simon and Schuster, 1991).

A group of researchers has proposed looking into the use of vitamin A/beta-carotene in the treatment of AIDS and cancer patients, the authors of the encyclopedia say.

The encyclopedia enumerates many successful studies in which beta-carotene has been employed in dealing with cancers of the bladder, larynx, esophagus, stomach, rectum, and prostate.

Also noted are successful experiments in which beta-carotene was used to counter the effects of such infections as Candida albicans (yeast infections commonly known as "thrush").

In contrast, instead of using small quantities of vitamin A, they could increase the "kill" rate by using beta-carotene in higher doses.

Q: Since beta-carotene is also known to increase wound healing, is there any reason why diabetics, who are usually plagued by this problem, should not take beta-carotene?

A: There is no known reason for diabetic patients to avoid the use of beta-carotene (but they should always consult their physicians before beginning any new regimen of food or supplements).

Several researchers have reported favorably on beta-carotene supplementation among diabetic patients and patients recovering from surgery.

Foods Containing Beta-Carotene

Alfalfa 

Apples

Apricots

Asparagus

Bananas

Beet greens

Bell peppers

Broccoli

Brussels sprouts

Bulghur 

Cabbage

Cantaloupe 

Carrots

Cauliflower

(hard

Cherries

Corn grits

Corn kernels

Collard greens 

Cranberries

Dandelion 

Garlic

Grapefruit

Green beans

Green peas

Kale 

Kidney beans

Kiwi fruit

Lentils

Mangoes

Oatmeal

Oranges

Papaya 

Peaches

Potatoes

Prunes

Pumpkin

Romaine Lettuce

Shredded wheat

Spinach

Strawberries

Sweet potatoes

Tangerines

Tomatoes

Turnip greens

Watermelon 

Winter squash

Zucchini

(Editor's Note: This article originally appeared in Nutrition Health Review, Issue #64.)

Editor's Note: The following questions and answers have been amassed from interviews and research among leading dietitians, nutritionists, and physicians, along with worldwide literature dealing with degenerative diseases.