Is There a Link Between Macronutrient Intake and Prostate Cancer?

Michael F Leitzmann

Disclosures

Nat Clin Pract Oncol. 2005;2(4):184-185. 

In This Article

Commentary

Despite considerable research on diet and prostate cancer, overall findings from previous investigations have proven inconclusive. The large, hospital-based, case-control study from Italy by Bidoli et al . helps to address this issue by examining macronutrients, sources and types of dietary fat, and specific fatty acids in relation to prostate cancer risk.

The main result was that dietary starch intake was associated with an increased risk of prostate cancer. Although dietary glycemic load was not evaluated, this finding, if confirmed in prospective studies, has potentially significant public health implications. It suggests that high intake of carbohydrate-rich foods, such as pasta, potatoes, rice, and bread, may increase prostate cancer risk. Possible biological mechanisms linking high intake of rapidly absorbed carbohydrates to increased risk of prostate cancer include hyperinsulinemia[1] and chronic inflammation.[2]

A modest increase in prostate cancer risk was also observed with increased monounsaturated fatty acid intake, which is puzzling because olive oil is the major source of monounsaturated fat in Mediterranean diets, and prostate cancer mortality rates have traditionally been low in areas with high olive oil consumption. However, animal products such as meat and dairy foods do contribute to the total monounsaturated fatty acid intake in Italian diets. A presentation of the separate contributions of monounsaturated fat from animal and vegetable sources may have indicated whether animal-derived monounsaturated fat intake masked a potentially protective effect of olive oil-derived monounsaturated fat intake in the present study. In addition, the monounsaturated fatty acid result in the fully partitioned statistical model may have been confounded by total energy intake.

High polyunsaturated fatty acid intake was associated with decreased prostate cancer risk, which was primarily due to linoleic acid and alpha-linolenic acid, the two principal fatty acids in this group. Most previous epidemiologic studies that have examined linoleic acid indicate no association with prostate cancer.[3] In contrast, numerous previous investigations have reported an increased prostate cancer risk with high alpha-linolenic acid intake.[4] The inverse relationships of both linoleic and alpha-linolenic acid with prostate cancer in the present study may have been partly attributable to favorable dietary components associated with vegetable oil use, such as vitamin E and lycopene, which were unaccounted for in the analysis. Rather surprisingly, intakes of polyunsaturated fatty acids other than linoleic and alpha-linolenic acid (presumably the combination of eicosapentaenoic and docosahexaenoic acid) were related to increased risk of prostate cancer. Whether this indicates an adverse effect of fish intake on prostate cancer risk, as has been suggested by a recent prospective study from Japan,[5] or is due to biased recall of past fish intake among prostate cancer cases remains speculative.

The major implication of the present report is that a carbohydrate-based diet may adversely affect prostate cancer risk. Prospective observational and directed studies are needed to confirm this finding and to uncover the biological mechanisms involved. Additional work is required to examine the associations with animal versus vegetable sources of monounsaturated fat and to further clarify the relations of individual polyunsaturated fatty acids to prostate cancer risk, in particular to advanced prostate cancer risk.

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