Prostate Cancer: Nutritional Considerations

Prostate cancer appears to be increasing worldwide, a trend that may be due in part to the advancing Westernization of eating habits. Increased meat and dairy intake and diets high in processed foods and low in fiber have been associated with increased prostate cancer risk.

On the other hand, evidence is accumulating that a low–fat, vegetarian diet may be helpful for the prevention and possibly for the treatment of prostate cancer. In research studies, the following nutritional steps are associated with a reduced risk of prostate cancer:

• Limited dairy consumption: Consumption of dairy products has been shown to increase the risk of prostate cancer. Several studies, including two large Harvard University studies, have shown significant increases in prostate cancer risk among men who consume the most dairy.
  
  This may be explained by the fact that milk consumption increases the blood levels of IGF–1, which may promote cancerous growth.
  
  Another explanation is that excess calcium intake may predispose one to cancer. Compared with men who have the lowest calcium intake, those with the highest intakes appear to have nearly double the risk for developing prostate cancer. This may be related to calcium’s tendency to decrease the activation of vitamin D in the body.
• Limited consumption of processed foods, including processed meat, refined grains, packaged foods, and soft drinks
• High fiber intake: High–fat, low–fiber diets are associated with elevated blood testosterone concentrations, which has been shown to increase the risk of prostate cancer in several studies.
• A low–fat, vegetarian diet: Studies have shown that prostate cancer risk increases with animal fat consumption, and certain foods containing animal fat (red meat and dairy products) appear to double the risk for advanced, metastatic prostate cancer.
  
  Another reason meat should be avoided is carcinogenic compounds called heterocyclic amines. These tend to form when meat is cooked at high temperatures and have been associated with an increased risk of prostate cancer and other cancers.
• A diet rich in fruits, vegetables, and whole grains: Fruits and vegetables have numerous nutrients that may prevent prostate cancer and promote overall good health.
  
  Lycopene is a nutrient that has been associated with a decreased risk of prostate cancer. It is an antioxidant that is responsible for the bright red color of tomatoes, watermelon, and pink grapefruit. Lycopene may interfere with IGF–I and other dangerous chemicals. However, it is not yet clear whether it is lycopene itself or other nutrients or groups of nutrients contained in fruits and vegetables that decreases the risk of prostate cancer.
   
  Cruciferous vegetables (e.g., broccoli, cabbage, cauliflower, and Brussels sprouts) and the antioxidant selenium are other noted nutrients that are associated with reduced risk for prostate cancer.
  
• Maintenance of a healthy body weight: Some studies suggest that obesity and obesity–related disease (e.g., diabetes) may increase the risk for development of prostate cancer, especially in younger men. There is also growing evidence that men who are obese have a more aggressive form of the disease and are at greater risk of cancer recurrence after treatment.
  
• Limited alcohol consumption: A large study found that men who drank at least eight to nine drinks per week had the highest prostate cancer risk. However, it is unclear whether the type of alcoholic beverage affects the risk of prostate cancer. Some evidence suggests that liquor consumption increases risk more than beer or wine, but other studies indicate that risk increases dramatically with any type of alcohol.

Diet and Prognosis

A limited number of studies have addressed how dietary changes influence survival in patients already diagnosed with prostate cancer. Overall, the evidence suggests that low–fat, plant–based diets may be helpful.

• In addition to increasing the risk of cancer, diets high in saturated fat from meat and dairy products may also decrease survival after the diagnosis of prostate cancer.
  
• In addition to decreasing the risk of prostate cancer, diets high in vegetables and whole grains may improve survival in patients who already have the disease. In particular, a randomized clinical trial using a vegan diet and stress reduction in newly diagnosed prostate cancer patients showed a significant reduction in PSA levels and the need for medical treatment.
  
• In men 65 years or older, those who were most active had a 70 percent lower risk of advanced, fatal disease.
  
• The benefits of healthy eating and exercise are especially important because many patients with prostate cancer ultimately die from cardiovascular disease, rather than prostate cancer itself.