Researchers have identified a link between higher intake of low-fat dairy and the risk of Parkinson's.
Researchers found that the risk of Parkinson's disease was greater for adults who consumed at least three servings of low-fat dairy products every day, compared with those who consumed just one serving.
Study co-author Katherine C. Hughes, of the Harvard T.H. Chan School of Public Health in Boston, MA, and colleagues recently reported their findings in the journal Neurology.
Parkinson's disease is a neurological disorder characterized by tremors, problems with movement, impaired balance or coordination, and muscle rigidity.
According to the Parkinson's Disease Foundation, up to 1 million people in the United States are living with Parkinson's disease, and around 60,000 U.S. adults are diagnosed with the condition annually.
Previous studies have suggested that there may be a link between the consumption of dairy products, particularly milk, and increased risk of Parkinson's disease.
Hughes and colleagues set out to investigate this association further with their new study, which involved an analysis of around 25 years worth of data from more than 120,000 men and women.
Skim, low-fat milk linked to higher Parkinson's risk
The study included a total of 80,736 women who were a part of the Nurses' Health Study, as well as 48,610 men who were enrolled in the Health Professionals' Follow-up Study.
Every 2 years, study participants completed a health questionnaire, while a dietary questionnaire was completed every 4 years. The researchers used the latter to assess what types of low-fat and full-fat dairy products subjects consumed - including milk, cream, cheese, butter, ice cream, and sherbet - as well as the frequency of dairy intake.
Over 25 years of study, a total of 1,036 participants developed Parkinson's disease.
Compared with participants who consumed less than one serving of dairy every day, subjects who consumed at least three servings daily were found have a 34 percent greater risk of developing Parkinson's disease.
What is more, the team found that the risk of Parkinson's could be linked specifically to milk intake; subjects who consumed at least one serving of skim milk or low-fat milk every day had a 39 percent increased risk of Parkinson's, compared with those who drank less than one serving per week.
Consumption of sherbet and frozen yogurt was also associated with a modest increased risk of Parkinson's disease, the researchers report.
No link was identified between consumption of full-fat dairy and Parkinson's disease.
"The results provide evidence of a modest increased risk of Parkinson's with greater consumption of low-fat dairy products. Such dairy products, which are widely consumed, could potentially be a modifiable risk factor for the disease."
Katherine C. Hughes
'No reason to change diet based on this research'
Based on their findings, Hughes and colleagues conclude that greater intake of low-fat dairy products, especially milk, may be associated with a greater risk of Parkinson's disease.
However, they point out that their study is purely observational, so it is unable to prove cause and effect.
Commenting on the results, Claire Bale, head of research as Parkinson's UK, notes that while the study is interesting, individuals should not alter their diets based on the results.
"It's really important to point out that the risk of developing Parkinson's was still very low (around 1 in 100), even in those who consumed lots of dairy, so there is no reason for people to make changes to their diet based on this research," she says.
Bale adds that the study was also unable to determine what might explain the link between low-fat dairy intake and Parkinson's disease.
"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," she notes.
"If we can understand more about how and why dietary factors influence Parkinson's, it could reveal exciting opportunities for developing urgently needed treatments that can slow, stop, or even prevent the condition."