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By Mark Anthony, Ph.D. | 08/01/2006
According to the American Cancer Society, the best diet advice for preventing cancer is, essentially, to eat lots of fruits and vegetables and avoid obesity. Although we’d love for the advice to be more specific – more formulaic – the truth is the diet-cancer relationship is hard to pin down because of the inherent confounding variables. The variety and action of reputed anti-cancer compounds in food are matched only by the complexity and unpredictable nature of the disease itself.
Cancer is varied and complex because it is not one disease. As defined by the American Cancer Society, “Cancer is a group of diseases characterized by uncontrolled growth and spread of abnormal cells.”
Normal cells have a programmed life span, but cancer cells remain perpetually youthful, highly energetic rebels that endlessly proliferate. They restlessly migrate using the blood or lymphatic system as their means of transportation. To support their wanderlust, they give off chemicals that increase the blood supply and eat away at the membranes of the tissues they randomly invade. This “metastasis” is what makes cancer so insidious.
In whatever new location the deviant cells set up shop, they continue their incessant replication, displacing healthy, well-behaving cells and impairing vital function.
Damage to genes that determine cellular life span converts healthy cells into mutant ones. This damage may happen as a result of exposure to radiation, pollutants and dangerous chemicals that cause oxidative damage, or even viral infections. Mutations also may happen spontaneously. All these factors can take advantage of a genetic predisposition to cancer.
This first stage of cancer is called “initiation” or “transformation.” Transformed cells do not automatically become malignant tumors; they still need to avoid detection by the immune system, which normally destroys aberrant cells. The cells then go through a “promotion” stage where conditions in the body must favor their tendency to reproduce. This phase may occur over a few months or it may take many years.
For diet to head off cancer, it must make an impact at the initiation and promotion phases, where nutrients and phytochemicals may prevent the DNA damage while enhancing the power of the immune system to pick off mutant cells before they enter the promotion phase. Certain nutritional components also may help slow the promotion phase to prevent cancer from entering its final stage. The final stage, progression, accelerates as cancer cells quickly multiply, disrupting body functions and leading to death.
|The list of potential anti-cancer agents that occur naturally in fruits, vegetables, spices and herbs is impressive and growing, as scientists learn more about these phytochemicals. They are categorized by structure and include polyphenols, terpenes, alkaloids, flavonoids, phenolics and many others.|
On the other hand, a deficiency of nutrients critical to normal DNA synthesis and repair could also increase cancer risk. For example, the B vitamin folate provides the single-carbon units for the synthesis of nucleic acids – a critical step in DNA synthesis (see “To B or Not to B”, also from the August 2006 issue of Wellness Foods).
Poor folate status is associated with cancers of the brain, breast, cervix, lung, esophagus, pancreas and lower GI tract. A folate deficiency can lead to breaks in the DNA strand, which increases the rate of mutations and hampers the synthesis and repair of DNA.
Folate is abundant in green vegetables, orange juice and many legumes (the name comes from “foliage”). It’s also in liver. Still, many people rely on fortification of processed foods to supply their needs.
Factors other than intake and absorption are at work in folate metabolism. A deficiency of vitamin B12 can weaken DNA, and without B12, folate remains trapped in a form that cannot be used for DNA synthesis.
Reducing cancer risk by preventing oxidation is a strategy that grew out of the observation that fruits and vegetables contain numerous natural antioxidants, such as vitamin C. The connection between C and cancer prevention is unclear.
Several studies show a lowered risk of various cancers with a vitamin C intake of 80 to 200 mg per day – greater than the current RDA of 60 mg, but certainly not a megadose. However, low intake of vitamin C can also indicate low intake of fruits and vegetables, a risk factor for health in general.
A placebo-controlled intervention study designed to look at the effect of another antioxidant vitamin, alpha-tocopherol (vitamin E) supplementation on lung cancer in smokers showed the vitamin E group had a 34 percent lower rate of prostate cancer. It also prompted interest in how vitamin E may act in conjunction with selenium, an antioxidant mineral.
“Selenium, especially in organic form, is one of the most versatile antioxidants,” says Vladimir Badmaev, Ph.D., vice president of medical and scientific affairs at Sabinsa Corp. (www.sabinsa.com), Piscataway, N.J. He adds, “Selenium is an essential trace element in nutrition for the prevention of disease in humans. Epidemiological studies indicate an association between low nutritional selenium and increased risks of cardiomyopathy, cardiovascular disease and carcinogenesis in various sites in the body.”
Sabinsa currently supplies its Selenium Select for the National Cancer Institute’s Selenium and Vitamin E Cancer Prevention Trial. The study, which began in 2001 on 35,000 men from the U.S., Canada and Puerto Rico, is examining how selenium and vitamin E, both separately and together, can protect against prostate cancer.
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