Eating Low-Fat Dairy Linked to Higher Parkinson's Risk

What a new study does and doesn't say.
June 9, 2017, 5:11pm
Marko Milanovic

We recently explained that full-fat dairy is good for you, as it's nutrient-dense in critical calcium and vitamin D. The caveat there, of course, was that consuming too much saturated fat has been associated with weight gain and, subsequently, a higher risk of heart disease. For those most concerned about losing or maintaining weight, low-fat dairy might be a better option: You'd get the same vitamins while keeping your saturated fat intake in check.

It was almost inevitable, then, that research would link low-fat dairy to something bad. We know, it's frustrating, and confusing, and findings keep flip-flopping. But as we said before: "nutrition studies are really hard to do."

This time, a new study from the Harvard TH Chan School of Public Health finds that people who consumed at least three servings of low-fat dairy a day had a 34 percent greater risk of developing Parkinson's disease compared to those who had less than one serving a day. On top of that, people who drank more than serving of low-fat or skim milk a day specifically showed a 39 percent greater risk than people who had less than one serving per week. There was a modest increase in risk for people who ate sherbet or yogurt; meanwhile, researchers found no association between full-fat dairy and Parkinson's.

Obviously, this doesn't mean that low-fat dairy causes Parkinson's, a very rare central nervous system disorder that affects movement and causes telltale tremors. And increases in risk of more than 33 percent sound high, but the number of people who developed Parkinson's is small so the overall risk is very low. The study relies on 25 years of data on more than 80,000 women and 48,000 men; subjects submitted questionnaires about their health every two years, and questionnaires about their diet every four years. Over the study period, 1,036 people developed Parkinson's. Of the people who'd consumed at least three servings of low-fat dairy per day, only 1 percent developed the disease, and only 0.6 percent of people who had less than one serving a day did.

The authors describe their study as the largest analysis of dairy and Parkinson's, but it's still observational, meaning we can't yet tease apart cause and effect. It's not like they randomly assigned people to eat different amounts of low- and full-fat dairy and then followed them for 25 years. Plus, the disease itself may be affecting results, if early symptoms change dietary behaviors or how participants answered their questionnaires.

More study will be needed to establish a causal connection, if there is one. "Previous research has suggested that traces of pesticides in dairy products might be involved, and more recently there have been a number of studies suggesting that bacteria living in the gut may play a role, but there is much more research needed in this area," Claire Bale, head of research at Parkinson's UK, told Medical News Today. In other words, no need to throw out all your skim milk and fat-free yogurt just yet. But, hey, the full-fat stuff is more delicious and filling, anyway.

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