Abstract
The authors prospectively investigated the association between intake of dairy products and risk of Parkinson's disease among 57,689 men and 73,175 women from the American Cancer Society's Cancer Prevention Study II Nutrition Cohort. A total of 250 men and 138 women with Parkinson's disease were identified during follow-up (1992-2001). Dairy product consumption was positively associated with risk of Parkinson's disease: Compared with the lowest intake quintile, the corresponding relative risks for quintiles 2-5 were 1.4, 1.4, 1.4, and 1.6 (95 percent confidence interval (CI): 1.1, 2.2; p for trend = 0.05). A higher risk among dairy product consumers was found in both men and women, although the association in women appeared nonlinear. Meta-analysis of all prospective studies confirmed a moderately elevated risk of Parkinson's disease among persons with high dairy product consumption: For extreme intake categories, relative risks were 1.6 (95 percent CI: 1.3, 2.0) for both sexes, 1.8 for men (95 percent CI: 1.4, 2.4), and 1.3 for women (95 percent CI: 0.8, 2.1). These data suggest that dairy consumption may increase the risk of Parkinson's disease, particularly in men. More studies are needed to further examine these findings and to explore underlying mechanisms.