Diet and Prostate Cancer
A fat-laden diet and high calcium consumption are both well-known suspected risk factors for prostate cancer. However, new findings from the Fred Hutchinson Cancer Research Center suggest that fat and calcium themselves may not cause prostate cancer, as previously thought, but instead may fuel its progression from localized to advanced disease.
Kristal and colleagues found that men who ate lower-fat diets, with fat accounting for no more than 30 percent of their daily calorie intake, had half the risk of late-stage cancer than men who consumed more fat. However, there were no associations of fat intake with early-stage disease.
Saturated fats (found in meat and dairy fat) and monounsaturated fats (found in certain oils, such as olive and peanut) were associated with an increased risk of advanced prostate cancer. Polyunsaturated fats (found in certain oils, such as safflower and canola) were not. Consumption of omega-3 fatty acids (found in fatty fish such as salmon and mackerel) also did not have an impact on overall prostate-cancer risk, contrary to experimental studies in cell cultures that have suggested there may be a protective effect.
The U.S. Department of Agriculture’s Dietary Guidelines for Americans recommends no more than 30 percent of total daily calories from fat. For example, a person who needs 2,000 calories a day based on their height, weight and activity level would want to aim for no more than 600 calories from fat, or 65 grams (1 gram of fat has 9 calories, compared to only 4 calories in a gram of carbohydrate or protein).
One reason that low-fat diets could reduce the risk of prostate cancer is because they reduce blood levels of circulating male hormones such as testosterone. Growth of the prostate, and perhaps growth of prostate cancer, is fueled by male hormones.
The only dietary risk factor that appeared to carry equal weight among men with both early and advanced prostate cancer was the amount of total calories consumed, regardless of fat. “Total energy intake was significantly associated with risk for both localized and advanced disease,” Kristal said. Men who ingested the most calories each day more than doubled their risk of localized prostate cancer (a 115 percent increased risk) and nearly doubled their risk of advanced prostate cancer (a 96 percent increased risk) compared to men who ate the fewest.
“While there is an increasingly popular message that fat intake is not important for health,” Kristal said, “there is no doubt that high-fat diets are associated with high calorie intake and obesity. A low-fat diet may well be important for the thousands of men who are diagnosed each year with early-stage prostate cancer.”