Risk Factors for Prostate Cancer Development
The explanation for this possible association between prostate cancer and dietary fat is unknown. Several hypotheses have been advanced, including:
- Dietary fat may increase serum androgen levels, thereby increasing prostate cancer risk. This hypothesis is supported by observations from South Africa and the United States that changes in dietary fat intake change urinary and serum levels of androgens.[37,38]
- Certain types of fatty acids or their metabolites may initiate or promote prostate carcinoma development. The evidence for this hypothesis is conflicting, but one study suggests that linoleic acid (omega-6 polyunsaturated fatty acid) may stimulate prostate cancer cells, while omega-3 fatty acids inhibit cell growth.
- An observation made in an animal model is that male offspring of pregnant rats who are fed a high-fat diet will develop prostate cancer at a higher rate than animals who are fed a low-fat diet. This observation may explain some of the variations in prostate cancer incidence and mortality among ethnic groups; an observation has been made that first trimester androgen levels in pregnant blacks are higher than those in whites.
Dairy and Calcium Intake
In a meta-analysis of ten cohort studies (eight from the United States and two from Europe), it was concluded that men with the highest intake of dairy products (relative risk [RR] = 1.11; 95% confidence interval [CI], 1.00-1.22; P = .04) and calcium (RR = 1.39; 95% CI, 1.09-1.77; P = .18) were more likely to develop prostate cancer than men with the lowest intake. The pooled RRs of advanced prostate cancer were 1.33 (95% CI, 1.00-1.78; P = .055) for the highest versus lowest intake categories of dairy products and 1.46 (95% CI, 0.65-3.25; P > .2) for the highest versus lowest intake categories of calcium. High intake of dairy products and calcium may be associated with an increased risk of prostate cancer although the increase may be small.
Regular multivitamin use has not been associated with the risk of early or localized prostate cancer.
The Aspirin/Folate Polyp Prevention Study, a placebo-controlled randomized trial of aspirin and folic acid supplementation for the chemoprevention of colorectal adenomas, was conducted between July 6, 1994, and December 31, 2006. In a secondary analysis, the authors addressed the effect of folic acid supplementation on the risk of prostate cancer. Participants were followed for up to 10.8 (median = 7.0, interquartile range = 6.0-7.8) years and asked periodically to report all illnesses and hospitalizations. Supplementation with 1 mg of folic acid was associated with an increased risk of prostate cancer. However, dietary and plasma levels among nonmultivitamin users were inversely associated with risk. These findings highlight the potentially complex role of folate in prostate carcinogenesis.[44,45]