A ‘modest’ contributing factor?
Vikas Kotagal, MD, associate professor of neurology at the University of Michigan, Ann Arbor, offered a perspective on the study methodology, and suggested that a causal link between dairy intake and Parkinson’s disease, if present, is likely minimal.
Dr. Vikas Kotagal
“Limitations to the study include the fact that participants weren’t actually asked or tested for how much dairy they truly consumed,” Dr. Kotagal said*. “Their dairy intake was estimated based on their genetic background – there are certainly many assumptions baked into this analytic approach which may or may not be true. It is also worth noting the fact that this causal association was seen in men and not women, suggesting that even if dairy intake was truly causal, it is likely to be a modest contributing factor and not a significant cause of Parkinson’s disease in the broader population in general.”
Still, Dr. Kotagal agreed with Dr. Appel-Cresswell that underlying mechanisms need further investigation.
“The biggest takeaway here is to heighten the urgency for researchers and funders to explore whether factors that might cluster with dairy intake – including pesticide exposure in milk or even the make-up of bacterial populations in different peoples’ intestines – might deserve closer scrutiny as a missing link connecting dairy consumption to increased Parkinson’s disease risk,” Dr. Kotagal said.
Dietary advice
Considering all available evidence, Dr. Appel-Cresswell offered some dietary advice with benefits that may extend beyond prevention of Parkinson’s disease.
“From a clinical point of view, I suggest to limit dairy intake to a moderate amount,” she said. “Mediterranean diets so far have the best supporting evidence for a lower Parkinson’s disease risk, although data is lacking for benefits in established Parkinson’s disease. Given the low risk of the Mediterranean diet and the established benefits for a host of other medical conditions, this is generally a safe and delicious recommendation whether one is living with Parkinson’s or not.”
The study was supported by the European Union Joint Program for Neurodegenerative Disease Research, the National Centre of Excellence in Research on Parkinson’s Disease, the National Institutes of Health, and others. The investigators disclosed additional relationships with Astellas Pharma, Sanofi, Pfizer, and others. Dr. Kotagal and Dr. Appel-Cresswell reported no relevant conflicts of interest.
*Correction, 2/10/22: An earlier version of this article misstated Dr. Kotagal's name in certain instances, including a photo caption.