The Alpha Omega of Carotenoids

vegetables Beta carotene has long been in the news for its antioxidant effect and its possible effect on a number of degenerative diseases. Many speak of it as a cure-all: A nutrient bullet that does the trick. There may be some truth to this, but this attitude tends to narrow our focus to one particular element as opposed to a synergetic whole. Many fruits and vegetables, carrots, pumpkins, spinach, tomatoes, oranges, hot chili peppers, contain at least one member, if not more, of the carotene family (known as carotenoids), and all of them are potentially beneficial to us.

There are believed to be some 500 members of the carotenoid family, and 50 to 60 are in our foods. They literally are food coloring that gives many fruits and vegetables their yellow, orange, and red coloring. They also are found in green, leafy vegetables, but the color is masked by the green of chlorophyll. Of the 50 or 60 carotenoids found in fruits and vegetables, some of the key carotenoids identified thus far are alpha carotene, beta carotene, lycopene, lutein, and zeaxanthin.

Alpha Carotene

Although alpha comes before beta, alpha carotene only recently has drawn the attention of researchers. According to an article in NCI Cancer Weekly, Michiaki Murakoshi, who leads a team of biochemists at Japan's Kyoto Prefectural University of Medicine, contends that alpha carotene may be more powerful than beta carotene, its more well-known relative, in inhibiting processes that may lead to tumor growth. Murakoshi indicated that neuroblastoma (cancer) cells coated with carotenoids experienced a drop in N-myc activity compared to untreated cells. N-myc is a gene that codes for cell-growth stimulating proteins and can contribute to cancer formation and growth. Alpha carotene was found to be about ten times more inhibitory toward N-myc activity than beta carotene. Murakoshi concludes that all types of carotenoids should be studied for possible health benefits.

Beta Carotene

Beta carotene, at least to the general public, is the star of the carotenoids. It is beta carotene that makes the headlines, beta carotene that appears on television newsmagazines and daytime TV, and beta carotene that takes the falls.

It's hard not to say too much about beta carotene. The popular press is full of accounts on its wonders, and many studies are examining its benefits as a free-radical fighting antioxidant. Free radicals, of course, may be responsible for cell membrane damage, DNA mutation, and lipid (fat) oxidation, all of which may be responsible for arthritis, hardening of the arteries, strokes, cataracts, heart disease, and many of the diseases we call "degenerative."

In January 1996, beta carotene made the news in a way that brought dismay to many. In a press conference, the National Cancer Institute (NCI) released the results of two anticipated antioxidant/beta carotene studies: the Carotene and Retinol Efficacy Trial (CARET) and the Physicians' Health Study. The press release noted that in the studies, beta carotene (and vitamin E) did not appear to have any effect on health, and that in the CARET study, it appeared to increase the likelihood of cancer.

However, this is not the whole story. In the CARET study, the 14,254 participants were smokers or former smokers and 4,060 had been exposed to asbestos on the job_two major causes of lung cancer. The smokers and former smokers had smoked at least a pack a day for 20 years or the equivalent. The other participants had had extensive occupational asbestos exposure for 15 years. In other words, the participants in the study were in a very high-risk group. Also keep in mind that the vitamin A and beta-carotene used in these studies were in the form of synthetic supplements, and in the many epidemiological studies that show positive results, these vitamins were in the form of fresh fruits and vegetables.

So what should we think about beta carotene? Dr. Charles Hennekons, a professor of medicine at the Brigham and Women's Hospital in Boston, said that the results of a similar trial (The Finnish ATBC trial; also with smokers) may indicate that when the smokers took vitamins for five to eight years, it was too little, too late to protect them: The damage had already been done. The CARET study may reinforce this and suggest that smokers should avoid taking beta carotene supplements.

We also should consider the years of positive results of beta carotene tests; the many human studies that show that beta carotene might, along with other substances found in plants, protect against tumors and heart disease; and the National Cancer Institute's advice that, for those who wish to reduce their risk of cancer, it is prudent to adopt a low-fat diet containing plenty of fruits, vegetables, and grains. In other words, use natural products.

Lycopene

In late 1995, newspapers around the country ran articles linking tomato sauce, tomatoes, and pizza to decreased incidences of prostate cancer. This was based on a December 6, 1995, article in the Journal of the National Cancer Institute. The article stated that a carotenoid found in tomatoes, lycopene, correlated inversely to prostate cancer. Participants with high amounts of lycopene in blood plasma had 21 percent less cancer risk than those with small amounts of lycopene. When lycopene in tomato sauce was considered, this figure rose to 34 percent. The difference is believed to be because lycopene is fat-soluble, and when the tomato sauce is cooked with oil, bioavailability improves. The authors of the article concluded that "Our studies are consistent with current recommendations to increase consumption of vegetables and fruits to reduce mortality from cancer but suggest that consumption of tomato-based foods may be especially beneficial in reducing the risk of prostate cancer. Further work is required to understand if and how lycopene or other compounds in tomatoes influence prostate carcinogenesis."

Other studies have indicated a link between low levels of lycopene and increased levels of bladder cancer. All of these studies looked at whole foods, not supplements. Although lycopene supplements are available, eating foods that contain this phytochemical probably would be more beneficial to your health.

Lutein and Zeaxanthin

Lutein and zeaxanthin, two carotenoids found in green, leafy vegetables, have been considered recently for potential benefits to our sight. Susan E. Hankinson reported in the January 20, 1993, issue of the Journal of the American Medical Society that a study concluded that dietary carotenoids and vitamin C may decrease the risk of cataracts severe enough to require extraction. Spinach, which contains these two carotenoids, was the food item most consistently associated with a lower relative risk. More recently, a 1994 study at Harvard Medical School suggests that these two carotenoids might protect the eyes from macular degeneration, a cause of irreversible blindness, often occurring in people age 65 and older.

Johanna Seddon, who was involved in the study, is quoted as saying, "People who ate spinach or collard greens two to four times a week had half the estimated risk of those who ate them less than once a month," (as reported in The Natural Way, Jan/Feb 1996).

All for One, One for All

When discussing carotenoids, many people ask, "But which one is best?" We believe that no specific carotenoid is the best, but that they are all equal. Nor is it, perhaps, wise to isolate individual carotenoids in extracts. We believe that what is important is not so much the individual substances, but the combined power of all substances.

When we look closely at many of the epidemiological studies on carotenoids, we find that we are talking about fruits and vegetables_in other words, everything, not an isolated part. In a ten-year study in Japan, the diets of 250,000 people were examined, and those who ate daily servings of green and yellow vegetables had cancer of the lung, cervix, colon, prostate, and stomach far less often than those who did not eat so many colorful veggies. Another study shows that men with high blood levels of carotenoids, a variety of carotenoids, not one or two, had a one-third lower risk of heart disease than other men even when their blood cholesterol levels were high.

Finally, a study concerning age-related macular degeneration (the chief cause of blindness among the elderly) found that people who consumed the highest levels of carotenoids had a 43 percent lower risk of the disorder than those who ate the least amount of carotenoids. People who ate greens, such as collards and spinach, at least five times a week had an 86 percent lower risk than those who seldom or never ate greens.

What does this mean? It seems clear. Eat whole foods, not part of a whole food. Don't consider beta carotene the end all and be all; remember that all the carotenoids, working together in natural proportions, could result in the best health of all.

Further Reading

Langer, Stephen. "Carotenoids may prevent cancer growths." Better Nutrition, March 1990.

Seddon, Johanna M., et al. "Dietary carotenoids, vitamins A, C, and E, and advanced age-related macular degeneration." JAMA, The Journal of the American Medical Association, Nov. 9, 1994.

Maureen, Ternus. "Don't count out 'other' carotenoids; they may offer big health bonus." Environmental Nutrition, June 1994.

Hankinson, Susan E. and Meir J. Stampfer. "All that glitters is not beta carotene." (Editorial) JAMA, The Journal of the American Medical Association, Nov. 9, 1994.

"Bran and beta carotene may check colon cancer," in Better Nutrition for Today's Living. May 1995.

Salynn, Boyles. Report on "Inhibitory effects on alpha- carotene on proliferation of the human neuroblastoma cell line." NCI Cancer Weekly, Nov. 13, 1989.

Giovannucci, Edward, et al. "Intake of Carotenoids and Retinol in Relation to Risk of Prostrate Cancer." Journal of the National Cancer Institute. 1995 Vol. 87, No. 23.

Liebman, Bonnie. "Beyond Beta Carotene." The Natural Way. January/February 1996.

Murakoshi, M., et al. "Inhibitory effects of alpha-carotene on proliferation of the human neuroblastoma cell line." Journal of the National Cancer Institute, 1989: 81.

The article "Carotenoids" is reproduced with the permission of AIM International.
©1997 by AIM International

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