Jewish World Review August 30, 2004 / 13 Elul, 5764

Carbs & breast cancer risk; statins & cancer; eat your brussels sprouts & broccoli!; antioxidants may reduce prostate cancer risk

By Robert A. Wascher, M.D., F.A.C.S. | Today's column features several new studies related to cancer prevention. Some experts have estimated that between 50 and 80 percent of all cases of cancers might be preventable if everyone ate a healthy diet, exercised regularly, avoided tobacco, and minimized alcohol intake. So, it is not surprising that a great deal of research, looking for more effective methods of preventing cancer, is underway….

Cancer Research: There is a great deal of ongoing research looking at the effects of antioxidants on the risk of prostate cancer. Previous research has shown that diets rich in lycopene, an antioxidant chemically related to vitamin A, may be associated with a reduction in the risk of prostate cancer. Several studies, using prostate cancer cells in culture, have shown that lycopene and vitamin E can actually induce tumor cell death.

A new study has assessed the impact of the antioxidants lycopene, selenium and vitamin E on the diet of mice genetically altered to spontaneously develop prostate cancer. Following administration of lycopene, selenium and vitamin E in the diets of these prostate cancer-prone mice, the incidence of prostate cancer dropped dramatically. Among the mice fed a standard rodent chow diet without the three antioxidant supplements, 74 percent developed prostate cancer during the study.

Interestingly, 100 percent of the mice fed a high-fat rodent chow diet, also without the antioxidant supplements, developed prostate cancer (in humans, obesity is considered a risk factor for prostate cancer as well). When the three antioxidants were added to the standard rodent chow diets, only 11 percent of the mice developed prostate cancer, while only 16% of the mice fed a high-fat diet with the added antioxidants developed the disease. The results of this study strongly support the findings of earlier studies suggesting that selected antioxidants may be protective against prostate cancer. At the present time, 32,400 men are enrolled in the very large SELECT trial (The Selenium and Vitamin E Cancer Prevention Trial).

The goal of this study is to evaluate the effects, if any, of dietary supplementation with selenium and vitamin E. (It will take 10 to 12 years before the final results of the SELECT trial are known.)

Carcinogenesis: I have previously reported on research suggesting that a diet rich in cruciferous vegetable may be associated with a reduced risk of developing cancer.

(The cruciferous family of vegetables includes broccoli, cauliflower, Brussels sprouts, bok choy, radishes, cabbage, chard, collard and mustard greens, arugula, kohlrabi, turnips, watercress, kale and rutabagas.)

There is also evidence, albeit still debated, that high levels of red meat consumption in the diet may be associated with an increased risk of colon and rectal cancer. The proposed mechanism whereby cooked red meat might increase the risk of colorectal cancer involves the heat-induced production of carcinogenic compounds. Now, it appears, the cancer-reducing effects of cruciferous vegetables may, at least in part, derive from their ability to enhance the body's metabolism of these carcinogenic substances into non-carcinogenic metabolites. A new study evaluated the effects of increasing and decreasing levels of cruciferous vegetable consumption in 20 nonsmoking adult male subjects.

At the end of each 12-day study phase, the subjects were fed a meal containing cooked red meat, and urine samples were then collected and studied. This study revealed that the research volunteers excreted significantly higher levels of nontoxic metabolites from cooked meat-associated carcinogens after eating cruciferous vegetables for 12 days when compared to the levels excreted after 12 days without cruciferous vegetables.

While this finding does not prove that this is the exact mechanism whereby cruciferous vegetables may reduce cancer risk, it is nonetheless very interesting, and may point the way towards additional important research in cancer prevention.

The Journal of Clinical Oncology: Regular readers of this column are already knowledgeable about the remarkable heart-protective effects of the class of drugs referred to as statins. The statin drugs significantly reduce elevated blood levels of cholesterol and fat, which is thought to be only one of several mechanisms involved in their ability to reduce the risk of heart attacks and other manifestations of cardiovascular disease. There have been numerous studies published, recently, suggesting that statin drugs may also have powerful antioxidant and antiinflammatory effects. This has, naturally, caused some researchers to wonder if the statin drugs might have cancer prevention effects as well. A new study looks at just this issue.

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The pharmacy records for the residents of 8 Dutch cities identified 3,129 patients who were taking medications for cardiovascular diseases, as well as 16,976 patients who were on medications for non-cardiovascular diseases, only. These patients were then followed over a period of 13 years. Every attempt was made to match the two groups of patients in order to reduce the likelihood that some factor, or factors, other than the use of statin drugs might have affected the study's results.

When the study's data was analyzed, it was discovered that statin use was associated with a 20 percent overall reduction in the incidence of cancer. Among those patients who used statin drugs for more than 4 years, the risk of cancer was reduced by an impressive 36 percent. When the researchers looked at statin use in terms of total daily doses taken, they found that the patients who had, by their calculations, taken more than 1350 daily doses of statins (or, the equivalent of at least 3.7 years of daily medication) experienced a very substantial 40 percent reduction in the incidence of cancer.

Although one weakness of so-called observational studies, such as this, is the possibility that researchers might have missed other factors that might be affecting the observed results, this intriguing study still strongly suggests that statins may be associated with a reduction in the risk of developing cancer. In order to confirm these findings, however, it will be necessary to undertake a large scale prospective, randomized, double-blinded study comparing statin use to placebos.

Cancer Epidemiology Biomarkers & Prevention: Atkins Diet proponents aside, it is well understood that excessive calories in the diet are associated with an increased risk of obesity, cardiovascular disease, diabetes and, perhaps, some cancers. The evidence that obesity may be associated with an increased risk of breast cancer is already substantial. Evidence that high carbohydrate intake, specifically, is associated with an increase in the risk of developing breast cancer is not, however, well defined. A new study, performed in Mexico, looked at dietary carbohydrate intake as a risk factor for developing breast cancer.

A total of 1,866 women participated in the study, and carbohydrate intake was calculated for each woman using dietary surveys. This study found that increasing levels of dietary carbohydrate intake were associated with increasing risks of breast cancer. When comparing women with the lowest and highest reported levels of dietary carbohydrate intake, the women who consumed the highest amounts of carbohydrate experienced a 122 percent increase in the relative risk of developing breast cancer. This finding was true for both premenopausal women and women who were postmenopausal. When looking at the types of carbohydrates that were the most strongly associated with an increased breast cancer risk, sucrose (common table sugar) and fructose took the honors.

Interestingly, this study did not find any correlation between dietary fat intake and the risk of breast cancer, contrary to multiple previous epidemiological studies. This is an interesting study that is certain to fuel the low carbohydrate craze currently sweeping the globe. However, my advice, to all patients, is still to eat a healthy balanced diet rich in fruits, vegetables, nuts and fiber, and low in meat products and fat.

JWR contributor Dr. Robert Wascher is an oncologic surgeon, professor of surgery, oncology research scientist, and author. He lives in Honolulu with his wife and two daughters. Comment by clicking here.



© 2004, Dr. Robert A. Wascher