The Conflict with Carotenoids

Carotenoids, the pigments responsible for the vivid plumage of flamingos and bright orange of carrots, are causing quite a stir. Found in nearly all brightly colored fruits and vegetables, carotenoids serve as photoprotectants, which are antioxidants that protect cells from free radicals, and modulators of gene activity resulting in protection from inflammatory damage and neoplastic transformation. Of 700 carotenoids identified thus far, the major players seem to be beta-carotene, lycopene, lutein, cryptoxanthin, alpha-carotene and zeaxanthin. Beta-carotene, the most-common carotenoid found naturally, is the most-studied carotenoid, however lycopene and lutein are receiving a fair share of attention.

Under the microscope
Of late, carotenoids have received mixed reviews. A large body of research examined beta-carotene's role in the prevention of age-related diseases. By the 1980s, epidemiological and laboratory evidence supported the theory that beta-carotene plays a role in preventing human cancer. But the "Beta-Carotene and Retinol Efficacy Trial" conducted by Gary E. Goodman, et al of Fred Hutchinson Cancer Research Center, Seattle, WA, which tested the effects of daily beta-carotene and retinyl palmitate on the incidence of lung cancers, other cancers, and death in 18,314 participants with high risk for lung cancer, was stopped ahead of schedule in 1996. Participants who received the active intervention experienced a 28% increase in lung cancer, a 17% increase in death and a higher rate of cardiovascular-disease mortality compared with placebo groups.

Three comprehensive reports soon followed. First, the World Cancer Research Fund, London, and American Institute for Cancer Research, Washington, D.C., called on a panel of 16 international scientists to look at the putative carotenoid-cancer relationship. They concluded that carotenoid intake probably decreases the risk of lung cancer and possibly decreases cancers of the esophagus, stomach colon, rectum, breast and cervix, but insufficient evidence exists for effects on larynx, ovary, endometrium and bladder cancers. The panel's final word: The evidence for the role of vegetables and fruits in most cancer sites is stronger than for carotenoids. A committee on carotenoids from the International Agency for Cancer Research, Lyon, France, concluded that it is unclear how results showing activities of beta-carotene against animal cancers might be related to human cancers, and cited a lack of evidence for cancer prevention with supplemental beta-carotene. Finally, a panel by the National Research Council's Dietary Reference Intake Panel on Antioxidants, Washington, D.C., evaluated not only the putative relationship between beta-carotene and lung cancer, but also the relationship between lutein and age-related macular degeneration, and lycopene and prostate cancer, and ruled inadequate evidence for the role of carotenoids in disease exists. Thus, DRIs for carotenoids and beta-carotene were not established.

Some scientists pose a few questions about the results of the "Beta-Carotene and Retinol Efficacy Trial".   They argue that the study was restricted to smokers and that the amount of beta-carotene in the blood levels of subjects was higher than in other studies, such as the Physician's Health Study, which displayed no adverse effects from beta-carotene supplementation. Two smaller studies reported no effect of beta-carotene with respect to cardiovascular, cancer and mortality.

Many recent studies focus on supplemental carotenoids. In the Dec. 2004 issue of Journal of Nutrition, scientists at Cornell University, Ithaca, NY, proposed that additive and synergistic effects of phytochemicals in whole fruits and vegetables create their potent antioxidant and anticancer activities. They concluded that eating 5 to 10 daily servings of a variety of fruits and vegetables is an appropriate strategy for significantly reducing chronic-disease risk. The USDA Grand Forks Human Nutrition Research Center, ND, proposed that the evidence of efficacy is weak for carotenoids and that enriching foods with them is premature. Most agree that the gaps in understanding these bioactive compounds and their health benefits should motivate further research.

On the ingredient list
Still, the global market for carotenoids is expected to cross $935 million by 2005, according to a Business Communications Company, Inc., Norwalk, CT. Chemical synthesis still dominates the production of carotenoids, although efforts are underway to produce them by fermentation or extraction. Some carotenoids are used as coloring agents, but more companies are introducing them into foods and supplements as functional ingredients. Foods might even be boosted with carotenoids through genetic engineering. U.K. scientists developed a new genetically modified strain of golden rice that produces 23 times more beta-carotene than previous varieties.

"Food processors are better understanding the health benefits of carotenoids," says Herb Woolf, Ph.D., technical marketing manager, BASF Corporation, Florham Park, NJ. "In many cases, manufacturers are using carotenoids as a nature-identical colorant. They are using carotenoids to clean up the label and get rid of synthetic chemicals." Woolf reports the beverage and nutrition-bar industry express the greatest interest in carotenoids as ingredients.

Since tomatoes contain lycopene, companies are making the best use of their product's natural state of functionality. LycoRed Natural Products Industries, Ltd., Be'er-Sheva, Israel, has developed a tomato extract called Lyc-O-Mato®, which capitalizes on the fact that natural lycopene is an approved food colorant in European countries and Japan.

Sharon Palmer is a registered dietitian with 16 years of experience in health-care and foodservice management. She writes on food and nutrition for newspapers, magazines, websites and books. Palmer makes her home in Southern California.

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