DIETARY AND LIFESTYLE FACTORS
The incidence of prostate cancer is increasing in other countries where Western diets and lifestyles have been adopted,59,60 suggesting that nutritional factors may also contribute partly to prostate carcinogenesis. Culture- and race-specific differences in diet may play an important role in prostate cancer risk in certain racial minorities. Many aspects of diet and nutrition have been studied for their impact on prostate cancer.
Dietary risk factors
Too much red meat and processed meat? Although some have suggested that diets high in red and processed meats may lead to a higher risk of prostate cancer, a meta-analysis showed no association.61,62
Too much calcium? The European Prospective Investigation Into Cancer and Nutrition study found that high dietary intake of dairy protein and calcium from dairy products was associated with a higher risk of prostate cancer.63 A cohort study in the United States had similar findings with regard to calcium.64 However, the higher risk of prostate cancer was associated with consumption of 2,000 mg or more of calcium per day, which was consumed by only 2% of the study’s cohort and, as the study’s authors reported, fewer than 1% of US men. As such, only a small population of American men seem to be exposing themselves to a higher risk of prostate cancer by high calcium consumption.
High fat intake? Certain fatty acids have been implicated in general tumor genesis, and that risk has been extrapolated to prostate cancer.65 For example, high fat intake and obesity are associated with increased levels of insulin-like growth factor 1, which in turn has been shown to correlate with a significantly elevated risk of prostate cancer.63,65
Obesity has been shown to increase the risk of more-aggressive prostate cancer, but not of less-aggressive tumors.66 Moreover, men who lost weight had a lower risk of prostate cancer than those who maintained their weight over 10 years.66 Obesity may be particularly risky for African American men, in whom it was found to be associated with shorter biochemical relapse-free survival, whereas it was not an independent risk factor in white men.67
Preventive dietary agents have been elusive
Unfortunately, despite attempts to identify preventive dietary agents, none has yet been confirmed.
No benefit from selenium or vitamin E. The Selenium and Vitamin E Cancer Prevention Trial was discontinued, as there was no evidence that either agent prevented prostate cancer in relatively healthy men.68
Vitamin D? It has been suggested that lower levels of vitamin D could contribute to the higher rates of prostate cancer in African Americans, as vitamin D deficiency is more common in African Americans.69 However, several meta-analyses have shown no association between vitamin D and prostate cancer.70–72
Soy? Attempts at correlating the relatively low incidence of prostate cancer in Asians have revealed that high soy intake may be protective. Asians consume more soy than Americans do (100 vs 3 mg/day), and soy isoflavones such as genistein, glycitein, and daidzein lower the incidence of prostate cancer in laboratory mice.73
Other lifestyle factors
Other lifestyle factors have also been analyzed to see if they contribute to prostate cancer.
Pollution. Some studies have suggested that the etiology of prostate cancer may lie in environmental exposures to pesticides,74 metal industrial facilities,75 and urban living.76
Smoking. Watters et al77 found that current and former cigarette smokers were actually at a lower risk of being diagnosed with non-advanced prostate cancer, but current smokers were at higher risk of dying from prostate cancer.
Physical activity. A prospective study of lifetime physical activity of more than 45,000 men found that men who were not sedentary during work and who walked or bicycled more than 30 minutes per day during adult life had an approximately 20% lower incidence of prostate cancer.78
In sum, primary care providers who are generally promoting healthy lifestyles can point to a reduction in risk for prostate cancer as yet another benefit to a low-fat diet, a healthy body mass index, and daily exercise.
HOW PRIMARY CARE PHYSICIANS CAN HELP CLOSE THE GAP
Primary care physicians serve as the first point of health access for many in the United States today.
The diagnosis of prostate cancer is made more frequently in African American men than in other American men, often at a higher pathological grade, and with a worse mortality rate. Primary care physicians can help improve these statistics. Interventions targeting overall health, such as promotion of a healthy diet, could be established at primary care visits and could also reduce the incidence of prostate cancer in African American men. Patient education regarding prostate cancer screening, the impact of family history, and the rate of PSA screening could be improved.
Primary care physicians serve a vital role in health education and prostate cancer screening, and therefore they begin the process in potentially reducing the impact of prostate cancer in African American men. The racial disparity seen in prostate cancer may begin to be minimized with primary care physicians and specialists working together to ensure that all men receive appropriate treatment.