Scanning a popular health and nutrition magazine, you encounter an advertisement for a pill touted as the "the natural way to beat cancer." You read further and find the advertisement is promoting use of a supplement containing carotenoids, a group of chemicals found naturally in carrots, tomatoes, sweet potatoes and other foods. Significantly, recent scientific studies have indeed linked a diet high in carotenoids with a reduced cancer risk. So is it time to go to your local health food store and stock up?
What Are Carotenoids?
Carotenoids are among the most widespread pigments in the natural world. Carotenoids play a large role in the colorful appearance of many plants and animals, including red peppers, tomatoes, paprika, flamingos, canaries, ladybugs and salmon. The color-producing properties of carotenoids are so powerful that many manufactured products, such as soft drinks, use carotenoids as coloring (although in such low concentrations that they don't produce much nutritional benefit).
The most common individual carotenoid found naturally is beta-carotene, a yellow-orange pigment that lends its color to carrots, sweet potatoes and other fruits and vegetables. Beta-carotene is a provitamin-A carotenoid. That means that the body easily converts it into vitamin A, a nutrient associated with the prevention of cataracts and other vision problems.
A variety of carotenoids are possibly associated with the prevention of several different kinds of cancer. One study suggested a link between lutein (a carotenoid found in large proportions in spinach, broccoli, lettuce, tomatoes, oranges and orange juice, carrots, celery and greens) and a reduced risk of colon cancer. Another study showed that men who ingest higher amounts of lycopene (a carotenoid found in tomato-based foods) appear to have a reduced risk of prostate cancer.
A Groundbreaking Harvard Study
Another study focused on the relationship between carotenoids and the risk of lung cancer. In a paper published in the October 2000 issue of The American Journal of Clinical Nutrition, researchers from the Harvard School of Public Health, Brigham and Women's Hospital and Harvard Medical School tracked the diets of more than 124,000 men and women from 1984 to 1996. They found that a diet featuring a variety of carotenoids was associated with a 32 percent drop in the incidence of lung cancer, some of the strongest evidence so far linking carotenoids with a reduced lung cancer risk. Significantly, this study focused on consumption of alpha-carotene, as opposed to beta-carotene, which had been the focus of earlier studies.
From Medical Journals To Health Food Stores
It's no surprise that individual carotenoid supplements are now appearing on store shelves. Beta-carotene pills, lutein pills and others can now be found at health food stores and supermarkets alongside such familiar products as vitamin C, echinacea and folic acid. For people at high risk of lung cancer, such as smokers and former smokers, a bottle of beta-carotene pills may seem like a smart investment. But it's not.
Words Of Caution
Despite the positive associations of foods rich in carotenoids and lower cancer risk, the same is not true for carotenoid supplements in pill form.
Exactly how carotenoids work as preventative agents is still an open question. The recent Harvard lung cancer study reinforces what researchers have known for several years: that a diet rich in fruits and vegetables may help prevent a wide variety of cancers.
What's more, the need for caution is reinforced by ambiguous results of other studies of the effects of carotenoids, especially studies of beta-carotene. For example, a study focusing on the use of beta-carotene and alpha-tocopherol (a form of vitamin E), conducted primarily at the National Public Health Institute of Helsinki, Finland, and published in the New England Journal of Medicine in 1994, showed negative results. In this study, more than 29,000 male smokers were randomly given beta-carotene, alpha-tocopherol, a combination of the two or a placebo (an inactive substance used as a control in an experiment). Smokers who received beta-carotene supplements had an 8 percent higher mortality and an 18 percent higher incidence of lung cancer than did smokers who received placebo. Similar findings occurred in another study that examined the effects of beta-carotene and retinol, a form of vitamin A.
Smokers: Don't Get Distracted
Supplements may also distract people from the most important element of preventing lung cancer: quitting smoking. And the sooner one quits, the better. A smoker's risk of lung cancer returns close to baseline (meaning that the risk returns to the level of those who have never smoked) only after 20 to 25 years. Clearly the most important thing you can do to prevent lung cancer, quit smoking.
Former Smokers: Eat Healthy, Live Healthy
The 45 million Americans who have quit smoking may take additional steps to potentially reduce the dangers of lung cancer. One possible step is to participate in screening studies conducted at teaching hospitals that seek to catch lung cancer at early stages.
A more certain step is to maintain a healthy lifestyle with a diet featuring large amounts of fruits and vegetables — thereby gaining the greatest possible benefits from carotenoids and other potential cancer-preventing nutrients.
No Magic Pill
So what about supplements? Despite the ads, there's no magic pill to prevent lung cancer. Based on recent studies, you might try adding carrots or tomatoes to your diet to help lower your risk of cancer. But your best bets are to get help to quit smoking and to maintain a healthy lifestyle.