Carotenemia

Well-known as an antioxidant that snuffs out free radicals - those unpaired electrons that can damage and alter DNA in cells and, over time, contribute to the start of cancer - beta-carotene and hundreds of other plant pigments go far beyond that initial function to protect us from cancer. These colorful pigments also limit the effectiveness of enzymes which metabolize tumors.

In plain English, beta-carotene, a vitamin A precursor (a substance from which another substance is formed), does its best to deprive the cancer of nourishment so that it can't survive. In contrast, preformed vitamin A, alone, cannot accomplish this. The advantages which the precursor form of vitamin A (such as beta-carotene) has in this regard was established by evidence from rat experiments, as stated in an article by Thomas E. Edes, M.D., in the Nutrition Report.

There may even be another advantage of beta-carotene and the 500 other carotenoids over preformed vitamin A. Despite growing restrictions on smoking in public places, we are all exposed to some cigarette smoke and, particularly, to one of its major cancer-causing ingredients: benzopyrene. This carcinogen depletes our tissues of protective vitamin A, even if our diet includes enough of this vitamin, leaving us vulnerable to illness and disease. The good news is that a high intake of beta-carotene and the other carotenoids seems to prevent such depletion.

Some biochemists believe that beta-carotene and other carotenoids may be more effective ill preventing lung cancer than has been preformed vitamin A. Make no mistake, vitamin A is a necessary cancer-preventive, too, but it guards us against this disease in different ways. Essential to cell differentiation, vitamin A appears to be able to reverse malignant characteristics of cells - particularly in promyelocytic leukemia, states an article in Nutrition Report.

Over and above the positive influences of vitamin A, beta-carotene guards our health by serving as an antioxidant, by stimulating our immune system, and by degrading metabolic products. The almost Siamese twin-like partnership of vitamin A and beta-carotene has been revealed in many research projects.

Stanley Levenson, M.D., professor of surgery at Albert Einstein College of Medicine, states that, in its ability to suppress cancer, beta-carotene exerts its protective effects longer than does vitamin A.

A few years ago, a disconcerting study of lifetime smokers conducted in Finland seemed to indicate that beta-carotene contributed to an increased risk of developing lung cancer. Researchers were stunned, then puzzled, because hundreds of previous studies had revealed the great benefits of beta-carotene for this type of cancer, as well as for many others.

Now most biochemists - even those who conducted the Finnish study - doubt the validity of these findings, and with good reasons.

First, the volunteers had smoked for more than B years, secondly, a great many of them drank heavily. (Alcohol is often a negative influence on liver function and, consequently, on the body's ability to detoxify itself. In addition, beta-carotene is, converted to vitamin A in the liver, which accounts for its ineffectiveness here). Further, since cancers often take 20 years to develop, the damage apparently had already been done, in the opinion of Jeffrey Blumberg, Ph.D., of Tufts University, one of the nation's most respected scientists in. nutrition and biochemistry.

Many authorities feel that the Finnish study was also flawed because synthetic beta-carotene was used, rather than the natural form. Then, too, the daily dosage was far smaller than that which is usually recommended. Additionally, the beta-carotene was colored with quinoline yellow, a cancer-causing agent.

Various studies stress that beta-carotene is indeed helpful for preventing cancer. Garrison and Somers, in The Nutrition Desk Reference (Keats Publishing, Inc.), make the statement that "...beta-carotene might be more related to the prevention of certain types of cancer than vitamin A. The carotenoids also, appear to be more effective against the early stages of cancer, whereas vitamin A is more effective in the later stages."

They make still another point: that while vitamin A in huge amounts may be toxic, beta-carotene is not (because it is not stored in the liver). In fact, according to Shari Lieberman in her classic, The Real Vitamin & Mineral Book, "Since beta-carotene is a naturally-occurring pigment, the only adverse effect of eating too much beta-carotene is the possibility of carotenemia, a harmless condition in which the skin turns a slight orange color." She often tells her patients that, if this condition occurs, to simply reduce their intake of beta-carotene, since this pigmentation indicates that the body has converted as much beta-carotene to active A as it can.

Garrison and Somers also cite the fact that "researchers at the University of Toronto found that beta-carotene reduces harmful lipid peroxidation induced by free radicals in cigarette smoke that initiate the cascade of events leading to the development of lung and other cancers."

Excess lipid (fat) peroxidation (break down) can be harmful because a whole array of carcinogenic environmental toxins (DDT, dioxin, etc.) that have wound up in semi-permanent storage within fat cells are then released, at dangerous levels.

Studies by researchers at Yale University School of Medicine show that a daily intake of beta-carotene and other carotenoids might help to prevent lung cancers in both smokers and abstainers (often "second-hand" smokers).

Experiments at Albert Einstein School of Medicine reveal that low blood levels of beta-carotene appear to relate to an increased risk of lung, stomach, and colon cancer. Measuring the beta-carotene in epithelial tissues (the surface membrane) of the cervix and vagina, they concluded that low levels appear to invite cervical cancer.

These same researchers discovered that a regular and generous inverse the condition called oral leukoplakia - white patches on the mouth's mucous membranes which often precedes oral cancer.

By what mechanisms does beta-carotene, a major player among the already identified members of the carotenoid family, prevent and, sometimes, even reverse cancers?

Japanese biochemists led by Michiaki Murakoshi at Japan's Kyoto Prefectural University of Medicine, offer at least part of the answer.

These researchers exposed cultured human cancer cells to various carotenoids - among them, beta-carotene - and discovered that many of these pigments fight cancers in two major ways: 1) by keeping potentially carcinogenic cells in a sleeping state, and 2) by suppressing a gene that promotes tumor growth and metastasization (spreading).

Murakoshi indicates that ingested carotenoids temporarily keep the cancer cells in suspension. Then more carotenoids must be taken in to keep the cancer permanently suspended.

Observing the N-myc gene

Infinitesimal amounts of either beta- or alpha-carotene dramatically blocked the growth and spread of human neuroblastoma (cancer) cells, Murakoshi found. To learn what was going on, he and his team observed the action of a gene, called N-myc, that codes for cell growth-stimulating proteins.

This gene is a part of healthy and mature cells. However, it is not active unless damaged or switched on by faulty signals, at which point it can contribute to cancer formation and growth.

Three hours after the neuroblastoma cells were treated with carotenoids, the N-myc activity dropped 24 percent lower than in cancer cells not treated. Eighteen hours later, the gene activity decreased to 18 percent, compared with untreated cells.

Findings by Dr. Joel Schwartz, a tumor immunologist at Harvard University's School of Dental Medicine, lend credibility to the discoveries in Japan.

Experimenting with another type of cancer, Schwartz and associates learned that beta-carotene not only prevented the N-myc gene from turning on, but also stopped the spread of existing cancer by blocking malignant cells from going through their usual developmental stages and division.

One of the most convincing studies to show the cancer-prevention power of beta-carotene is that conducted by Richard Shekelle and associates at the Rush-Presbyterian Virgule St. Luke's Medical Center in Chicago.

Over a 19-year period, they noted the intake of beta-carotene by male volunteers from the following dietary sources: carrots, broccoli, kale pumpkin, spinach, squash, sweet potatoes, tomatoes, turnips, and yams. They compared their health status with individuals who ate little beta-carotene.

Beta-carotene reduces risk

of lung cancer

Those who took in the most beta-carotene had only one-seventh the amount of lung cancer as did those who took in the least beta-carotene. Conversely, those who ate the least beta-carotene had seven times more lung cancer than did the others.

A surprise to Shekelle was that beta-carotene protected even long-time smokers from lung cancer, but not to the degree that it guarded non-smokers. Did it take a large amount of beta-carotene insurance? "No," says Shekelle, as little as the equivalent of a half cup of carrots daily.

Blood levels of beta-carotene can indicate the degree of protection we are receiving, according to the findings of Dr. Marilyn Menkes, of Johns Hopkins University School of Hygiene and Public Health.

Dr. Menkes and co-workers measured the beta-carotene levels in blood specimens gathered in 1874 from volunteers. Then the same donors were tracked down nine years later for new blood tests. Ninety-nine volunteers who had developed lung cancer were found to have lower blood levels of beta-carotene than did the cancer-free individuals.

From comparative measurements, she concluded that volunteers with the lowest blood levels of beta-carotene were twice as likely as the others to be stricken with lung cancer.

Another similar study disclosed that people who ate green vegetables, such as broccoli, kale, and spinach, just three times weekly, were twice as likely to develop lung cancer as those who ate them every day.

A monumental, 10-year study of 250,000 volunteers in Japan confirms this finding and goes even further. Individuals who ate beta-carotene-rich produce not only had far less lung cancer than those who didn't, but also less cancer of the cervix, colon, prostate, and stomach.

Unfortunately, in our "too-much-to-do-in-too-little-time, society, we can't always include all the carotenoid-rich foods we wish in our daily diet. That's where a beta-carotene/carotenoid supplement comes to our rescue!

REFERENCES

"Aging and Vitamin A Status: A Review," The Nutrition Review, October 1991. Barilla, Jean, ed. The Nutrition Superbook, The Antioxidants. New Canaan, Conn.: Keats Publishing, Inc., 1995. Carper, Jean. Nutrition Pharmacy. New York: Bantam Books, 1988. Edes, Thomas E., M.D. "Beta-carotene and Vitamin A: Casting Separate Shadows," The Nutrition Report, 10(2) February 1992. Lieberman, Shari and Bruning, Nancy. The Real Vitamin S, Mineral Book. Garden City Park, N.Y.: Avery Publishing Group, 1990, p. 57. Mayer, Jean and Goldberg, Jeanne. "Vegetable Beta-carotene Being Studied as a Cancer inhibitor," Los Angeles Times, May 26, 1983. Raloff, Janet. "Carotenoids: Colorful Cancer Protection," Science News, November 4, 1989. Salaman, Maureen and Scheer, James F. Foods That Heal. Menlo Park, Calif.: Statford Publishing, 1989.

COPYRIGHT 1996 PRIMEDIA Intertec, a PRIMEDIA Company. All Rights Reserved.
COPYRIGHT 2004 Gale Group