Do Dairy Products Increase Risk of Parkinson Disease?

July 7, 2017

The largest study to date of a potential link between dairy intake and Parkinson disease found that risk varies depending on fat content and total intake. Details here.

The largest study to date of a potential link between dairy intake and Parkinson disease found that risk varies depending on fat content and total intake. Details here.

Is Dairy Linked to Parkinson Disease?
o Past prospective studies have suggested increased risk for PD with eating dairy[1-3]
o Unclear if certain dairy foods or specific nutrients within dairy contribute to the association
. Does nonfat, low fat, or whole fat dairy make a difference?
. What about dairy protein, calcium, vitamin D, lactose?

Largest Study of Link Between Dairy and PD to Date[4]
o Analysis of 2 prospective cohort studies:
   . Nurses’ Health Study: 80,736 female nurses, 26 years follow-up
   . Health Professionals Follow-up Study: 48,610 male health professionals, 24 years follow-up
   . Total: 1036 PD cases
o Diet assessed on validated food frequency questionnaires every 4 years
o PD incidence assessed with questionnaires every 2 years; confirmed with medical record review
o Compared levels of dairy intake in servings/day (<1, 1-<2, 2-<3, â¥3)
o Results pooled for women and men, adjusted for smoking, BMI, physical activity, coffee and alcohol intake, energy intake

Low-fat and Non-fat Dairy Linked to PD Risk
o Total Dairy: Increasing intake not significantly linked to PD (ptrend = 0.19)
   . 16% increased risk for highest intake level vs lowest (HR 1.16, 95% CI 0.92â1.48)
o Combined Low- and Non-fat Dairy: Increasing intake significantly linked to increased PD risk (ptrend <0.01)
   . 39% increased risk for highest intake level vs lowest (HR 1.39, 95% CI 1.12-1.73)
o High-fat Dairy: Increasing intake significantly linked to decreased PD risk (ptrend = 0.03)
   . 18% decreased risk for highest intake level vs lowest (HR 0.82, 95% CI 0.61â1.10)
o Similar results in women and men (pfor heterogeneity 0.05)
o Protein, calcium, vitamin D, and lactose not significantly linked to PD risk

Meta-Analysis: Total Dairy Intake Linked to Increased PD Risk
o Meta-analysis: Milk intake results pooled with 3 other studies, total dairy results pooled with 1 other study1-3
. Total of 1725 PD cases
o Total milk intake linked to increased PD risk, but results not significant:
. 56% increased risk for highest level of total milk intake vs lowest (pooled RR 1.56, 95% CI 1.30â1.88, p=0.495)
o Total dairy intake linked to significantly increased PD risk by 27% (pooled HR 1.27, 95% CI 1.04â1.55, p<0.00001)

Limitations
o Dairy intake self-reported
o PD diagnosis self-reported
o Early symptoms of PD could have affected dietary intake or questionnaire responses

Frequent Dairy Intake Linked to Modestly Increased PD Risk
o Frequently eating dairy products is associated with a modest increase in risk for PD, especially for low and non-fat dairy
o Possible mechanism:
. Dairy may decrease urate levels (some research suggests urate may protect against PD)
. Possible contaminants in dairy products, like pesticides
. General trend of increasing milk intake with increased PD risk across studies suggests general mechanism rather than specific contaminants

Take Home Points
o Results from Nurses’ Health Study and Health Professionals study suggests total dairy non-significantly linked to slight increased PD risk
o Low-fat and non-fat dairy significantly linked to increased PD risk
o Whole fat dairy significantly linked to decreased PD risk
o Pooled results from this study and others suggests total dairy intake linked to modestly increased PD risk
o Mechanism is unknown, more research is needed

References
1. Park M, Ross GW, Petrovitch H, et al. Consumption of milk and calcium in midlife and the future risk of Parkinson disease. Neurology. 2005;64:1047â1051.
2. Chen H, O’Reilly E, McCullough ML, et al. Consumption of dairy products and risk of Parkinson’s disease. Am J Epidemiol. 2007;165:998â1006.
3. Saaksjarvi K, Knekt P, Lundqvist A, et al. A cohort study on diet and the risk of Parkinson’s disease: the role of food groups and diet quality. Br J Nutr. 2013;109:329â337.
4. Hughes KC, Gao X, Kim IY, et al. Intake of dairy foods and risk of Parkinson disease. Neurology. 2017;Jun 8. pii: 10.1212/WNL.0000000000004057. doi: 10.1212/WNL.0000000000004057

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Do Dairy Products Increase Risk of Parkinson Disease?

Veronica Hackethal, MD