Fruits and Vegetables
There is good reason to believe that getting an adequate amount of fruits and vegetables in the diet may reduce the risk of prostate cancer. Men who consume primarily vegetarian diets have been shown to have lower rates of prostate cancer, but there is no good evidence to establish if it is due to the fruit and vegetables or some other component of the diet. In the best long-term prospective study currently available of risk factors for various diseases, the Health Professionals Follow-Up Study, researchers examined the relationship between consuming 46 different fruits and vegetables or related products and the risk of prostate cancer. The only fruits and vegetables that they found independently associated with prostate cancer risk were related to tomatoes.
Most diets that include significant amounts of fruits and vegetables are low in fat, especially animal fat, and higher in fiber, and either or both of these could be the main factors related to prostate cancer risk. But plant foods also contain small amounts of natural substances called phytochemicals or phytoestrogens. These micronutrients protect plants from the stresses of sunlight as well as disease, and they also are believed to protect against cancer in humans. There are three main classes of phytoestrogens -- isoflavanoids, flavonoids, and lignans. Plant foods contain varying amounts of these.
In addition to these cancer-fighting substances, it also has been shown that plant-based diets result in lower testosterone levels than diets with a large component of higher fat, animal-based foods. Higher amounts of fiber also may contribute to lower testosterone levels through greater excretion in the feces. Lower testosterone levels are generally associated with a lower risk of prostate cancer.
There is little conclusive evidence, besides that regarding tomato-based products, that a low consumption of fruits and vegetables increases the risk of prostate cancer, or that higher consumption reduces risk, but this is primarily due to the fact that a good quality study that examines the question has not been done. Another report from the Health Professionals Follow-Up Study added more controversy to the evidence supporting dietary fruits and vegetables. It showed that higher fructose consumption was related to reduced risk of advanced prostate cancer, but it did not matter whether the fructose came from fruit or nonfruit sources.
But, despite this, there are many healthy reasons to adopt a lower-fat, higher plant-based diet, and there are good reasons to believe that this will help prevent prostate cancer. Eat at least 3 to 5 servings of vegetables a day, including 3 servings of colorful, nonstarchy vegetables and at least 2–to 4 servings of fruit per day. Cruciferous vegetables, such as cabbage, broccoli, and Brussels sprouts and dark leafy greens; and orange, red, and yellow vegetables, such as carrots and peppers, are best. Many cancer-fighting substances and other nutrients found in vegetables are best absorbed when they are accompanied by small amounts of fat. The monounsaturated fats found in olive oil and canola oil are the healthiest fats, so they are good choices to include in salad dressings and other preparations. Avocados, nuts, and soy are other good sources of monounsaturated fats.
