Many studies have linked dairy consumption with an increased risk of prostate cancer. Two studies in a recent issue of the American Journal of Epidemiology looked at this connection in detail and reached the same surprising conclusion: it’s low-fat dairy that is problematic. Here are their abstracts:
High intakes of calcium and dairy products have been suggested to be related to prostate cancer risk. Such associations were examined in the Multiethnic Cohort Study (1993â€“2002) among 82,483 men who completed a detailed quantitative food frequency questionnaire. During a mean follow-up of 8 years, 4,404 total cases of prostate cancer were identified. In Cox proportional hazards models, no association was found between calcium and vitamin D intake and total, advanced, or high-grade prostate cancer risk, whether for total intake, intake from foods, or intake from supplements, among all male participants or among nonusers of supplemental calcium. No association of calcium or vitamin D intake was seen across racial/ethnic groups. In analyses of food groups, dairy product and total milk consumption were not associated with prostate cancer risk. However, low-/nonfat milk was related to an increased risk and whole milk to a decreased risk of total prostate cancer; after stratification, these effects were limited to localized or low-grade tumors. Although the findings from this study do not support an association between the intakes of calcium and vitamin D and prostate cancer risk, they do suggest that an association with milk consumption may vary by fat content, particularly for early forms of this cancer.
Calcium and dairy foods in relation to prostate cancer were examined in the National Institutes of Health (NIH)-AARP (formerly known as the American Association of Retired Persons) Diet and Health Study (1995/1996â€“2001). Diet was assessed with a food frequency questionnaire at baseline. Multivariate relative risks and 95% confidence intervals were estimated by Cox regression. During up to 6 years of follow-up (n = 293,888), the authors identified 10,180 total prostate cancer cases (8,754 nonadvanced, 1,426 advanced, and 178 fatal cases). Total and supplemental calcium were unrelated to total and nonadvanced prostate cancer. However, a statistically nonsignificant positive association with total calcium was observed for advanced (â‰¥2,000 vs. 500â€“<750 mg/day: relative risk (RR) = 1.25, 95% confidence interval (CI): 0.91, 1.71; ptrend = 0.06) and fatal (â‰¥1,000 vs. 500â€“<750 mg/day: RR = 1.39, 95% CI: 0.92, 2.09; ptrend = 0.10) prostate cancer. Skim milk, but not other dairy foods, was associated with increased risk of advanced prostate cancer (â‰¥2 vs. zero servings/day: RR = 1.23, 95% CI: 0.99, 1.54; ptrend = 0.01). In contrast, calcium from nondairy foods was associated with lower risk of nonadvanced prostate cancer (â‰¥600 vs. <250 mg/day: RR = 0.82, 95% CI: 0.68, 0.99; ptrend = 0.04). Although the authors cannot definitively rule out a weak association for aggressive prostate cancer, their findings do not provide strong support for the hypothesis that calcium and dairy foods increase prostate cancer risk.
Emphasis added. The differences between these two abstracts should interest people trying to learn how to write abstracts.