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Obesity Linked to the Return of Prostate Cancer
Men who have been treated for prostate cancer are less likely to have a recurrence if they maintain a healthy weight, according to a recent study in the journal Urology. University of California researchers analyzed data on 2,131 prostate cancer patients from 1989 to 2002, using the Cancer of the Prostate Strategic Urologic Research Endeavor (CaPSURE) database.
Obese men, defined as those with a body mass index (BMI) greater than 30, were found to have a 30 percent increased risk of cancer recurrence, compared with those with lower body weights. Very obese patients (BMI greater than 35) had the overall greatest risk of recurrence—about 70 percent higher than thinner men. Results emphasize the importance of maintaining a healthy weight.
Other research has shown that the average person following a vegetarian diet weighs about 10 percent less than the average meat-eater and that low-fat vegetarian diets are effective in helping people achieve and maintain a healthy weight. Furthermore, vegetarians are also less likely to develop cancer when compared with their meat-eating counterparts.
Bassett WW, Cooperberg MR, Sadetsky N, et al. Impact of obesity on prostate cancer recurrence after radical prostatectomy: data from CaPSURE. Urology. 2005;66:1060-1065.
Fish Consumption Multiplies Prostate Cancer Risk
Studies looking at the specific components of a traditional Asian diet have concluded that the high vegetable and soy content as well as the low fat and animal protein composition may all play beneficial roles in prostate cancer prevention and survival. Researchers further explored this idea by tracking the diets and prostate cancer diagnoses of 18,115 Japanese men. They found that fish intake was the only dietary factor significantly associated with increased risk of developing prostate cancer. Men who ate fish products four or more times per week had a 54 percent increased risk of developing prostate cancer compared to men who consumed fish products fewer than two times per week.
Allen NE, Sauvaget C, Roddam AW, et al. A prospective study of diet and prostate cancer in Japanese men. Cancer Causes Control. 2004;15:911-20.
Vegan Diet and Lifestyle Changes Slow Prostate Cancer
A new study by Dean Ornish, M.D., shows the power of diet and lifestyle changes to improve cancer survival. In a group of men with prostate cancer, prostate-specific antigen (PSA) levels—a marker that tracks prostate cancer growth—decreased by 4 percent after one year on a low-fat vegan diet, complemented by moderate aerobic exercise and stress management. (The diet was supplemented with soy, omega-3 fatty acids, vitamin E, selenium, and vitamin C.) It is unusual for PSA levels to decrease without treatment. A control group saw its PSA levels rise by 6 percent. In addition, six of the men in the control group needed treatment during the one-year study period because their prostate cancer was progressing, but no one in the experimental group needed treatment. Previous studies have shown that the consumption of dietary fat and dairy products increases prostate cancer risk, while compounds in tomatoes, soy, and cruciferous vegetables protect against the disease.
Ornish D, Weidner G, Fair WR, et al. Intensive lifestyle changes may affect the progression of prostate cancer. J Urol. 2005;174:1065-1070.
Dairy Products Linked to Prostate Cancer
A long-term study suggests an association between consumption of dairy products and the risk of prostate cancer. Researchers tracked more than 20,000 male physicians for 11 years and found a moderate elevation in prostate cancer risk associated with higher intake of five dairy products, including milk, cheese, and ice cream.1
Men who drank more than six glasses of milk per week had lower levels of vitamin D, which has been shown to protect the prostate. Milk-drinking also raises the amount of insulin-like growth factor (IGF-1) in the blood, which is linked to cancer risk.
Consumption of animal foods, protein, and calcium in relation to risk of prostate cancer was studied as part of the European Prospective Investigation into Cancer and Nutrition (EPIC). Researchers found a high intake of dairy protein was associated with an increased risk of prostate cancer. An estimated 35 gram per day increase in consumption of dairy protein was associated with a 32 percent increase in the risk of prostate cancer. Calcium from dairy products was also positively associated with risk, but not calcium from other foods. These results support the hypothesis that a high intake of protein or calcium from dairy products may increase the risk for prostate cancer.2
1. Chan JM, Stampfer MJ, Ma J, et al. Dairy products, calcium, and prostate cancer risk in the Physician's Health Study. Presented at the 91st Annual Meeting of the American Association for Cancer Research, April 2000.
2. Allen NE, Key TJ, Appleby PN. Animal foods, protein, calcium and prostate cancer risk: the European Prospective Investigation into Cancer and Nutrition. Br J Cancer. 2008;98(9):1574-1581.
New Study: Soy Improves Prostate Cancer Outlook
A new Australian study suggests that soy products can help decrease the risk of prostate cancer progression. The study, published in the September issue of Urology, included 29 Australian men with prostate cancer who were waiting to undergo a radical prostatectomy. The researchers divided the men into three groups to test how soy affects levels of hormones and prostate-specific antigen (PSA, which is used to screen for and track prostate cancer).
One group was asked to eat specially prepared bread made with soy grits (which contain 50 grams of natural phytoestrogens). A second group also consumed high phytoestrogen bread but it was made with 50 grams of soy grits plus 20 grams of linseed. The third group consumed wheat bread, which is naturally low in phytoestrogens. All three groups were instructed to consume four pieces of bread daily until surgery. The group consuming the soy-only enriched bread had a statistically significant drop in PSA levels (-12.7%) compared with the wheat bread control group whose PSA levels rose 40 percent. The PSA levels of the group consuming the soy-plus-linseed bread increased 21.3 percent, indicating that the addition of linseed may not only have no beneficial effect on PSA levels, but may actually increase prostate cancer progression. Although the study was small, it suggests that isoflavones in soy may be protective against prostate cancer.
China and Japan have some of the lowest rates of prostate cancer in the world, possibly due to the typically soy-rich diets in these countries. Isoflavones and phytoestrogens found in soybeans as well as the phytoestrogens and omega-3 fatty acids found in linseed oil have all been shown to have protective roles in prostate cancer development and progression.
Dalais FS, Meliala A, Wattanapenpaiboon N, Frydenberg M, Suter DA, Thomson WK, Wahlqvist ML. Effects of a diet rich in phytoestrogens on prostate-specific antigen and sex hormones in men diagnosed with prostate cancer. Urology. 2004 Sep;64(3):510-5.