Bottom Line:
- Dairy intake (specifically low fat or skim milk) may be associated with a small increase in risk for Parkinson disease.
Why this matters:
Dairy products are widely consumed. In 2016, 212.4 billion lbs of milk were produced in the United States. Previous studies have suggested a possible link between dairy intake and Parkinson disease.
Study Design:
- 2 prospective cohort studies
- Nurses Health Study (n=80,736) w/ 26 yr follow-up
- Health Professionals Follow-up study (n=48,610) with 24 years of follow-up
- Meta-analysis of current study plus 4 previously published studies
Key Findings:
- Main analysis: association between total dairy and Parkinson disease not significant
- But, looking at low-fat dairy foods, >3 servings per day vs < 1 were associated with 34% (HR 1.34, 95% CI 1.01-1.79, p = 0.04) higher risk of Parkinson disease.
- Drinking one serving per day of skim or low-fat milk had a 39% higher risk of Parkinson disease versus less than 1 serving per week.
- Interestingly, there was a significant linear trend for decreased risk of Parkinson disease with increased intake of high-fat dairy.
- The meta-analysis of pooling the results for total milk intake in the current study with 3 previous studies showed 56% increased risk for Parkinson Disease. Also, pooling the results for total dairy intake with 1 previously published study showed 27% higher risk for Parkinson disease.
- NOTE: overall risk of Parkinson disease was very low.
- Of the 5,830 people who consumed 3 or more servings daily of low-fat dairy at the start of the study, only 60 people (1%), developed the disease over the study period.
- Of the 77,864 people who consumed less than one serving per day of low-fat dairy, 483 people (0.6%), developed Parkinson disease.
Limitations:
- It is important to understand this is a correlation study and not causation study. The data on dairy intake is collected via surveys and there can be recall bias and respondent bias.
References:
- http://www.americasdairyland.com/economicimpact/statistics/dairystatistics
- Katherine C. Hughes, Xiang Gao, Iris Y. Kim, Molin Wang, Marc G. Weisskopf, Michael A. Schwarzschild, Alberto Ascherio. Intake of dairy foods and risk of Parkinson disease. Neurology, 2017; DOI: 10.1212/WNL.0000000000004057
