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Do Dairy Products Increase Risk of Parkinson Disease?

Do Dairy Products Increase Risk of Parkinson Disease?

  • 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, ≥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 0.92–1.48)
    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 0.61–1.10)
    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 1.30–1.88, p=0.495)
    o Total dairy intake linked to significantly increased PD risk by 27% (pooled HR 1.27, 95% CI 1.04–1.55, 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;64:1047–1051.
    2. Chen H, O’Reilly E, McCullough ML, et al. Consumption of dairy products and risk of Parkinson’s disease. Am J Epidemiol. 2007;165:998–1006.
    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;109:329–337.
    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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