Diet and Cancer

Over the past 50 years, deaths from heart disease, stroke and infectious diseases have decreased significantly, but the same cannot be said of cancer.

By Mark Anthony, Ph.D.

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A wealth of other antioxidants, such as vitamin A and related carotenoids, anthocyanins and other phytochemicals, have been and are still being studied for their abilities to protect cells against damage that influences cancer development and growth.

 

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Hot peppers - photo courtesy of Wikipedia
The same phytochemical that gives these peppers their fire – capsaicin – has a protective, anti-inflammatory effect on human cells. Photo courtesy of wikipedia.com.

The vast majority of the dietary elements that hold promise for preventing cancer are not essential nutrients, but rather phytochemicals that nature puts in plants to enhance their survival. (See “Phytochemical A-B-Cs”, also from the August 2006 issue of Wellness Foods).

For example, most peppers contain capsaicin, a fat-soluble chemical responsible for the strong burn of hot peppers. Most mammals (except for enlightened chili freaks) find this unpleasant. Both the heat and bright colors (anthocyanins) turn out to be protective.

These compounds can act in a number of ways, neutralizing free radicals or suppressing inflammatory processes that lead to transformation and the proliferation of cancer cells. They may also interfere with cell-signaling pathways that direct cancer’s rapid and uncontrolled growth. Some may even slow metastasis by making it harder for the growing cancer to obtain its blood supply.

Plant Advantage

Another example of how plant chemicals may work against cancer is their effect on a substance called nuclear factor-kappa B (NF-KB). According to Bharat Aggarwal, Ph.D., of the University of Texas M.D. Anderson Cancer Center, Houston, NF-KB describes a family of proteins that can bind to a specific DNA site.

Once activated by free radicals, inflammatory stimuli, carcinogens, UV light or X-rays, NF-KB migrates to the cell nucleus. It can then switch on more than 200 genes shown to suppress normal cell death, thus transforming the cells into potentially aggressive (pre)cancerous cells.

Many proteins regulate the cell cycle. Loss of this regulation virtually defines cancer. Isothiocyanates (found in cherries and berries), resveratrol (grapes), genistein (soybeans, chickpeas), apigenin (seeds and many vegetables), and silibinin (artichokes) have been shown to prevent aberrations of the cell cycle.

P53 is a protein that protects genes from damage. But damage to the gene that makes p53 removes a natural tumor suppressor, increasing the risk for many different cancers.

Phytochemicals such as epigallocatechin gallate (EGCG) from green tea, indole-3-carbinol and silibinin have been shown to affect the activity of this critical protein. EGCG has also displayed many favorable effects on the proteins that govern cell signaling and inflammation.

The list of potential anti-cancer agents in fruits, vegetables, spices and herbs is impressive and growing. They are categorized by structure and include polyphenols, terpenes, alkaloids, flavonoids, phenolics and many others. In addition to their potential to prevent cell transformation and promotion, some may slow metastasis by hindering angiogenesis, the proliferation of blood vessels that aid cancer cells in their invasion of healthy tissues.

Evidence that diet may prevent a large number of cancer deaths is encouraging. “Hippocrates’ quote ‘let food be thy medicine’ is now being more widely adopted and the benefits of natural and organic foods continue to be recognized,” says Gerry Amantea, Ph.D., vice president of technical service for Melville, N.Y.-based The Hain Celestial Group Inc.

But the diversity of phytochemicals and the complexity of their interactions means that no single diet, individual food, or ingredient emerges as a superhero all of the time. There are just too many complicating factors.

Macroingredients

The USDA may have just come around to whole grains in its latest version of the Food Guide Pyramid, but Nature’s Path Foods Inc., of Blaine, Wash., has been banking on this healthy tradition for more than two decades. The company provides a complete line of organic whole-grain cold and hot cereals, breads, pastas, baking mixes and energy bars.

Numerous case-control studies link a lower risk of more than 20 different types of cancers with increased consumption of whole grains. Known mostly for their fiber contribution to the diet, whole grains contain compounds called lignans.

Lignans are similar to isoflavones in that they have weak estrogenic and antioxidant activity. But unlike isoflavones, lignans must be activated. Lignan precursors in the plant fiber are converted to the animal lignans enterolactone and enterodiol by bacteria in the colon.

Diet & Cancer: Salmon photo
Wild-caught salmon is among the best sources of healthful omega-3 fatty acids.

Some studies have implicated the consumption of red meat as a risk factor for cancer. The results are far from conclusive. More than half a million people ages 35 to 70, from 10 European countries, participated in The European Prospective Investigation into Cancer and Nutrition.

People who ate the most red and processed meats had a higher risk of colon cancer, compared with those who ate the least. Fish eaters’ risks were the opposite. Cancer was lower among people who ate the most fish compared with those who ate the least. No link was apparent between poultry consumption and colon cancer risk.

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