Preventing prostate cancer and diet

Excerpted from Prostate Disease: Finding the Cause and Cure, a Harvard Health Publications Special Health report (2003)

Preventing prostate cancer

The cause of prostate cancer is unknown, which means it’s hard to suggest preventive strategies. Researchers have not found a powerful association with lifestyle, although there is some evidence that diet may play a role.

Diet

The science of food and cancer prevention is a moving target that, so far, hasn’t produced clear-cut advice for prostate cancer prevention. But some interesting trends are emerging.

For example, increasing though still inconclusive evidence links the consumption of fatty foods, particularly dairy products and red meat, to prostate cancer. In 1993, researchers at the Harvard School of Public Health published a survey of more than 51,000 American men (ages 40–75), showing that men who ate the most fat (89 grams daily) had nearly twice the risk for advanced prostate disease as those who consumed the least (53 grams daily). Red meat appeared to be a greater risk factor than other high-fat foods.

A diet high in dairy products has also been implicated as a risk factor for prostate cancer, and this relationship may have little to do with fat. In nine separate studies, the strongest and most consistent dietary factor linked with prostate cancer was high consumption of milk or dairy products. In the largest of these, the Health Professionals Follow-Up Study, men who drank two or more glasses of milk a day were almost twice as likely to develop advanced or metastatic (spreading) prostate cancer as those who didn’t drink milk at all.

At first, researchers thought the connection was due to the saturated fat in dairy products. But results from the study, as well as more careful analyses of other data, suggest calcium might be the culprit. The men who took more than 2,000 mg of calcium a day were almost three times as likely to develop metastatic prostate cancer as men who got less than 500 mg per day.

In contrast, there is evidence that a diet rich in fruits and vegetables may reduce your risk for prostate cancer. In 1995, a large epidemiological study by Harvard researchers found that men who ate at least 10 servings a week of tomato-based foods reduced their risk for the disease by 45%, while those who had 4–7 servings lowered their risk by 20%. Researchers suspect the protective agent is lycopene, a carotenoid and antioxidant found mostly in tomatoes and tomato products.

Because lycopene is tightly bound inside cell walls, your body has a hard time extracting it from raw tomatoes. Cooking breaks down these walls. Cooking oil dissolves it and helps shuttle it into the bloodstream. Quercetin, a flavonoid most abundant in apples, onions, black and green teas, and red wine, is also showing promise as a source of protective benefits.

Vitamins and minerals.

Another potentially protective substance is vitamin E. A large Finnish study found that male smokers who took 50 IU (international units) of vitamin E daily were 32% less likely to develop prostate cancer and 41% less likely to die from it than those who didn’t take vitamin E supplements. But be aware that antioxidant vitamins, including vitamin E, may interfere with the benefits of the cholesterol-lowering drugs taken by people at risk for heart disease. On the other hand, a multivitamin containing the usual recommended daily amount of vitamin E is considered safe.

Selenium, found in certain plant foods, may also help prevent several types of cancer, including prostate cancer. The amount of selenium in the soil, which varies by region, determines the amount found in the plant. But your selenium intake isn’t wholly dependent on the amount of fruit and vegetables in your diet; animals that eat plants grown in selenium-rich regions also have higher levels. In the United States, the highest soil concentrations are found in the high plains of northern Nebraska and the Dakotas.

A study of 1,312 men at the Arizona Cancer Center showed that those who took 200 micrograms (mcg) of selenium per day were 63% less likely to get cancer of any kind and, in particular, reduced their risk for lung, colorectal, and prostate cancers. Even larger trials are under way, including the Selenium and Vitamin E Cancer Trial (SELECT), which involves some 32,000 participants.

All in all, the evidence that any food or nutrient plays a role in preventing cancer of the prostate remains sketchy. To reach any firm conclusions, further study is clearly needed.