October 2010 Issue

Prostate Protection — Diet May Play a Big Part in Lowering Men’s Disease Risk
By Maura Keller
Today’s Dietitian
Vol. 12 No. 10 P. 14

Consider this: According to the American Cancer Society, prostate cancer is the most common nonskin malignancy among men of all races. All men are at risk for developing prostate cancer—in fact, one in six men will be diagnosed with prostate cancer in his lifetime, but only one in 36 will die of this disease. And while there are key risk factors for developing prostate cancer, including age, race, and family history, diet can play a significant role in helping ward off this disease.

Standout Factors
As with most nutrition research, diet’s role in prostate cancer prevention has been difficult to pin down, but some factors stand out.

Fatty Foods
“Men who eat less fatty foods (from meats and dairy products) and more fruits and vegetables have a lower risk of developing prostate cancer,” says Robin McConnell, MS, RD, clinical nutrition coordinator at the John Theurer Cancer Center at Hackensack University Medical Center in New Jersey. “Grilled, charred meats produce a carcinogen that can concentrate in the prostate and potentially trigger DNA changes leading to prostate cancer.”

As Meagan Kennedy, RD, LD, of the oncology, cardiology, and inpatient rehab units at St. Francis Hospital in Greenville, S.C., explains, “Prostate cancer is much more common in countries where dairy and meat are dietary staples, such as the United States. Diet and lifestyle can help aid in prevention of prostate cancer, change the progress, and reduce risk of recurrence.”

It should come as no surprise that the American Cancer Society recommends a low-fat, increased-fiber, and nutrient-dense diet. “Eating a diet low in saturated fat can contribute to maintaining a healthy weight; obesity may affect the levels of hormones that affect prostate cancer incidence,” Kennedy says. “To reduce saturated fat in your daily diet, people should limit meat and dairy products, try soy-based products, choose low fat or fat free instead, and choose 1% or skim milk, light or fat-free yogurt, tofu, edamame, tempeh, [and] part-skim and white cheeses.”

Fruits and vegetables in their most colorful form have the highest nutritional bang for their buck. Hued foods are loaded with powerful plant compounds called phytochemicals, which can ward off cancer, heart disease, and stroke; help preserve eyesight; fight arthritis pain; and boost energy levels.

Cruciferous vegetables such as broccoli, cauliflower, Brussels sprouts, kale, and cabbage contain di-indolylmethane, which may offer some protection against prostate cancer.

“Lycopene, found in cooked and raw tomato products and watermelon, gained prestige after a Harvard study showed that men who ate more than 10 servings of tomato-based foods a day had a 35% lower risk of developing prostate cancer,” McConnell says.

Kennedy recommends that her oncology patients eat from the rainbow, including fruits and vegetables of all colors to ensure a nutrient-dense diet high in antioxidants and phytochemicals, which provide cancer cell-fighting properties.

“I also suggest incorporating more omega-3s, which can be found in foods such as salmon, mackerel, tuna, flaxseeds, walnuts, soybeans, navy beans, kidney beans, olive oil, [and] winter squash or can be supplemented in liquid or pill form,” Kennedy says. “You also can simply increase your daily fiber intake by making half your grains whole grains (whole-wheat bread or pasta, rye bread, bulgar wheat, oatmeal, brown rice, quinoa), and eating five or more servings per day of fresh fruits and vegetables (include skins).”

Obesity is a major risk factor for prostate cancer. As Jodi Newson, MS, RD, CSO, director of nutrition services at the Tower Hematology Oncology Medical Group and The Center for Radiation Therapy of Beverly Hills, explains, “Many published studies correlate obesity before age 30 with increased risk of developing not only prostate cancer but a recurrence of prostate cancer, more aggressive disease, and increased risk of dying from prostate cancer. A diet high in fat also increases risk. Simply put, if a man was obese prior to age 30, he has a much greater chance of dying from prostate cancer should he get diagnosed. Also, any obese man with prostate cancer has a greater chance of dying from it.”

Obesity at the time of prostate cancer diagnosis appears to have a negative effect on long-term survival. “A study conducted at Fred Hutchinson Cancer Research Center showed that men who were obese ([body mass index] greater than 30) at diagnosis had 2.6 times the risk of dying from the disease than men of normal weight,” McConnell says. “This was true regardless of the stage, grade, or treatment. The researchers attribute this to hormonal and inflammatory factors associated with obesity that may influence cancer growth.”

Newson points out that dietitians should clearly explain to their patients that lowering caloric intake does not necessarily mean eating less food. Plant foods are high in fiber, vitamins, and minerals and are low in calories.

But some patients may do well to reduce their overall food intake. “When adapting to consuming less food, they should try leaving a few bites of food on [the] plate at each meal to get used less volume,” she says. “If you need to see a plate full of food, at least one half of it should be filled with vegetables.”

Men should consume alcohol in moderation: two or fewer drinks per day. “Heavy drinking can increase the risk of aggressive prostate cancer,” Kennedy says.

It is almost impossible to separate exercise from diet when considering its role in weight control, building muscle and bone mass, modulating hormone levels, enhancing immune function, and reducing oxidative stress. “However, the specific role of exercise in cancer prevention remains elusive,” McConnell says. “Studies show a 10% to 30% risk reduction in the development of prostate cancer in people who exercise. Exercise may also have benefits during treatment in helping to reduce the fatigue associated with radiation therapy.”

As Newson explains, while many of the antioxidant supplement trials did not produce anything other than probable evidence, the antioxidants from food sources and those produced by the body from exercise do have an impact on prevention. “Vigorous exercise of five hours per week reduces prostate cancer death rates,” she says. “Studies are under way to formally connect exercise and prostate cancer prevention, but a sedentary lifestyle is a known risk factor for many diseases. We can safely assume a positive correlation between exercise and prevention based simply on both the antioxidant effects of regular exercise and the probability of a healthy weight and low body fat percentage associated with regular exercise and a healthful diet.”

— Maura Keller is a Minneapolis-based writer and editor.


Promising Nutrients
According to Robin McConnell, MS, RD, the following are several nutrients and factors that may prove promising in the fight against prostate cancer and warrant further research:

Omega-3 fatty acids (from fish and flaxseed): Due to anti-inflammatory properties, they may inhibit the growth of prostate cancer.

Soy and isoflavones: A higher intake of soy products may lower the risk of developing prostate cancer, but the effects are still being studied.

Vitamin D: This vitamin’s role in prostate cancer prevention requires further study. Reports have indicated that low serum levels of vitamin D may increase the risk of prostate cancer, but a detailed review by the Agency for Healthcare Research and Quality showed no link.

Green tea: A 2009 study published in Cancer Prevention Research found that Polyphenon E, a component of green tea, may have the potential to lower the incidence and slow the progression of prostate cancer. An epidemiologic study of Japanese men showed a 50% decrease in the risk of advanced prostate cancer with the consumption of 5 cups of green tea per day. The studies looking at green tea consumption and prostate cancer progression and risk are ongoing.

On the other hand, the following nutrients might not be beneficial and may be potentially harmful:

Calcium: Excessive calcium intake (more than 1,500 to 2,000 mg/day) may increase the risk of prostate cancer, but further studies are looking at parsing out the data to determine the difference between high calcium intake from supplemental calcium vs. calcium obtained from foods, specifically dairy.

Vitamin E and selenium: The Selenium and Vitamin E Cancer Prevention Trial showed that supplemental vitamin E and selenium, once thought to lower the risk of prostate cancer, were ineffective.

— MK