“It seems nearly all men will develop prostate cancer if they live long enough,” says Karen Collins, M.S., R.D., C.D.N., nutrition advisor for the American Institute for Cancer Research. Thus, scientists have been searching for lifestyle measures that can help stack the odds in your favor. Promising research reveals three important diet strategies that can help you mount a defense: A plant-based diet, moderate dairy consumption, and maintaining a healthy weight.
1. A plant-based diet to protect the prostate. Focusing on a predominantly plant-based diet, which includes a variety of fruits and vegetables, is key to prostate cancer protection, according to Collins. This style of eating means that you fill up at least three-fourths of your plate with whole plant foods, such as beans, lentils, whole grains, vegetables, fruits, nuts and seeds. Plant foods are rich in thousands of nutrients and compounds. “A variety of vegetable and fruit choices is especially encouraged, because some choices may provide unique protective effects,” says Collins. Here are a few plant foods recently being researched for their role in prostate cancer prevention.
• Tomatoes. Tomatoes and tomato products, such as canned tomatoes and pasta sauce, are rich in carotenoids that impart red, yellow and orange colors. The most abundant carotenoid is lycopene, which studies have linked with cancer protection. The lycopene from processed or cooked tomatoes is more bioavailable than that of fresh tomatoes. While lycopene is found in other fruits such as watermelon and guava, tomatoes account for 80 percent of our consumption.
There is a body of evidence to show that tomatoes are associated with lower incidence of prostate cancer. In a Summary of Research on Tomatoes/Lycopene and Disease Risk, 2011 update, Britt Burton-Freeman, Ph.D., director of the Center for Nutrition Research at Illinois Institute of Technology, reviewed 86 studies related to tomato and lycopene intake and prostate cancer and concluded that there is a protective relationship between tomato and tomato-based foods and prostate cancer.
“Lycopene does seem to offer benefit, both as antioxidant and through direct impact on cancer cell growth and development. However, an important distinction is that research provides greater support for consuming tomatoes as part of a healthy diet, but does not support the use of lycopene supplements to reduce risk of prostate cancer,” says Collins.
• Cruciferous vegetables, such as broccoli, cauliflower, Brussels sprouts, kale, cabbage, and bok choy, are another good vegetable choice to include regularly, although we need more research to confirm how much impact their glucosinolate compounds—naturally occurring compounds which appear to have anti-cancer effects—have on prostate cancer, reports Collins.
• Garlic. Some preliminary laboratory and animal studies suggest that the compounds in garlic, such as the organosulfur compounds, may help slow the development and reduce the risk of prostate cancer.
• Soy. While there is only limited scientific support for soy in prostate cancer prevention—laboratory studies suggest protection, but human studies have shown mixed results—soy clearly offers other health benefits, such as reduced heart disease risk and enhanced bone health. So, it may be a good idea to include more whole soyfoods, such as soymilk, tofu, soybeans, and edamame in your diet.
• Green tea. Polyphenols found in green tea arrest the growth of prostate cancer cells in laboratory studies, but more research is needed before recommendations can be made to drink green tea for prostate cancer protection. However, many other benefits, such as heart health and immune system support, are linked to this plant-based beverage.
• Pomegranate. One clinical trial showed that drinking pomegranate juice may slow the progression of prostate cancer but “other human studies are seriously lacking,” says Collins. “We just don’t have enough data on which to base any recommendations about pomegranate juice.”
2. Don’t overdo dairy. Some research indicates that excess consumption of dairy products may increase prostate cancer risk. The EPIC Study, published in the European Journal of Cancer in 2010, found that dairy consumption above 27 grams of dairy protein and 880 milligrams (mg) of dairy calcium per day (the amount found in more than three cups of milk) was linked to increased risk. However, those who consumed moderate amounts—equal to about 1 ½ to 2 ½ cups of milk—showed a non-significant increase in risk. Collins says, “The bottom line at this point is that men who want to consume dairy products need not be afraid that moderate consumption puts them at risk of prostate cancer. However, excess consumption should be avoided. Two or perhaps three standard servings per day appear safe. Men who consume dairy products should be cautious about foods that are highly fortified with calcium; and adding calcium supplements is not recommended, especially if it brings total calcium intake beyond the 1,200 mg/day that is the highest RDA for men, unless they are personally advised to consume more by their physician.” A standard dairy serving is one cup (8 ounces) of milk or yogurt, two cups cottage cheese, and 1 ½ ounces of hard cheese.
3. Healthy weight objective. One of the key strategies to lower cancer risk is to reach and maintain a healthy weight. “Obesity is only weakly linked to prostate cancer incidence, but obesity is linked to increased risk of dying from prostate cancer,” says Collins. The most effective way to achieve a healthy weight is to increase physical activity—which on its own is linked with a 10 percent lower risk of prostate cancer—and increase the nutrient quality of your food choices. That means fill your plate with nutrient-rich foods that provide fiber and bulk but few calories. This takes you right back to step one—eat more minimally processed plant foods, such as beans, lentils, whole grains, fruits and vegetables.
Supplement watch. Research has shown that supplements may not have a protective impact on prostate cancer—in fact, they may even have a negative impact. “At one time, there was big hope for vitamin E and selenium,” says Collins. And then came the Selenium and Vitamin E Cancer Prevention Trial, a large trial of vitamin E (400 International Units) and selenium (200 micrograms). The results, which were first published in 2008, showed an increased risk of prostate cancer with vitamin E alone, which continued even after supplements were discontinued, and the trial was halted early. Selenium supplements showed no decrease in prostate cancer risk, and a non-significant trend for increased risk of developing type 2 diabetes. “It’s not just that these supplements are no longer recommended, it’s that men (now) are discouraged from using them,” stresses Collins. It appears there are more benefits from eating nutrients found in real food, in which countless compounds and nutrients interact, than nutrients isolated in supplements.
—Sharon Palmer, R.D.