Dietary Prevention With Fruit, Vegetables, and a Low-fat Diet
Results from studies of the association between dietary intake of fruits and vegetables and risk of prostate cancer are not consistent. A study evaluated 1,619 prostate cancer cases and 1,618 controls in a multicenter, multiethnic population. The study found that intake of legumes and yellow-orange and cruciferous vegetables was associated with a lower risk of prostate cancer.
The European Prospective Investigation into Cancer and Nutrition examined the association between fruit and vegetable intake and subsequent prostate cancer. After an average follow-up of 4.8 years, 1,104 men developed prostate cancer among the 130,544 male participants. No statistically significant associations were observed for fruit intake, vegetable intake, cruciferous vegetable intake, or the intake of fruits and vegetables combined.
One study of dietary intervention over a 4-year period with reduced fat and increased consumption of fruit, vegetables, and fiber had no impact on serum PSA levels. It is unknown whether dietary modification through the use of a low-fat, plant-based diet will reduce prostate cancer risk. While this outcome is unknown, multiple additional benefits may be gleaned by such a diet, to include a lower risk of hyperlipidemia, better control of blood pressure, and a lower risk of cardiovascular disease—all of which may merit adoption of such a diet.
While several agents, including alpha-tocopherol, selenium, lycopene, difluoromethylornithine,[14,15,16,17,18] vitamin D,[19,20,21] and isoflavonoids,[22,23] have shown potential in either clinical or laboratory studies for chemoprevention of prostate cancer, the correlations of cancer prevention with these agents are increasingly of concern given the statistically increased risk of prostate cancer with alpha-tocopherol in the SELECT trial and the lack of preventive effect (actually, a non-significant increase in prostate cancer risk) with selenium.
Chemoprevention with selenium and vitamin E
The Selenium and Vitamin E Cancer Prevention Trial (SELECT [NCT00006392]) was a large randomized placebo-controlled trial of vitamin E and selenium. It showed no reduction in prostate cancer period prevalence, but an increased risk of prostate cancer with vitamin E alone.
Compared with the placebo group in which 529 men developed prostate cancer, there was a statistically significant increase in prostate cancer in the vitamin E group (620 cases), but not in the selenium plus vitamin E group (555 cases) or in the selenium group (575 cases). The magnitude of increase in prostate cancer risk with vitamin E alone was 17%. Of interest, the statistically increased risk of prostate cancer among men receiving vitamin E was seen after study supplements had been discontinued suggesting a prolonged effect of this agent.
Chemoprevention with lycopene
Evidence exists that a diet with a high intake of fruits and vegetables is associated with a lower risk of cancer. Which, if any, micronutrients may account for this reduction is unknown. One group of nutrients often postulated as having chemoprevention properties is the carotenoids. Lycopene is the predominant circulating carotenoid in Americans and has a number of potential activities, including an antioxidant effect. It is encountered in a number of vegetables, most notably tomatoes, and is best absorbed if these products are cooked and in the presence of dietary fats or oils.