Macronutrients intake and risk of Parkinson's disease: A meta-analysis

Aims: We carried out a meta-analysis to summarize the evidence from published studies on macronutrients intake and risk of Parkinson's disease (PD). Methods: Pertinent studies were identified by a search of PubMed and Embase. Study-specific effect was combined with the random-effect model. The dose-response relationship was assessed by the restricted cubic spline. Results: For highest versus lowest level of intake, the relative risk (RR) of PD was 1.13 (95% CI 0.88-1.44) for protein (7 articles including 1570 PD cases among 357 827 subjects), RR 1.24 (95% CI 1.05-1.48) for carbohydrate (8 articles including 1482 PD cases among 232 869 subjects), RR 0.88 (95% CI 0.74-1.06) for fat (12 articles including 2936 PD cases among 374 124 subjects), RR 0.97 (95% CI 0.75-1.26) for cholesterol (6 articles including 1713 PD cases among 170 058 subjects) and 1.39 (95% CI 1.01-1.92) for energy (8 articles including 1553 PD cases among 170 317 subjects), respectively. Among prospective studies adjusting for smoking and coffee/caffeine, no associations were found between PD risk and intake of protein (RR 1.02, 95% CI 0.80-1.30), carbohydrate (RR 1.11, 95% CI 0.86-1.43), fat (RR 0.90, 95% CI 0.70-1.16), cholesterol (RR 0.89, 95% CI 0.74-1.09) and energy (RR 0.97, 95% CI 0.93-1.02); however, polyunsaturated fatty acid (RR 0.78, 95% CI 0.64-0.96) was inversely associated with PD risk. Limited data showed a linear dose-response relationship between the aforementioned macronutrients and PD risk. Conclusions: Dietary intake of protein, carbohydrate, cholesterol and energy might be not independently associated with PD risk. Higher intake of polyunsaturated fatty acid might be inversely associated with PD risk. Confounding by smoking and coffee/caffeine should be considered regarding the association between fat intake and PD risk in further studies.