Adhering to a healthy diet was associated with a lower risk for co-occurring prodromal features of Parkinson’s disease, according to research published in Neurology, the medical journal of the American Academy of Neurology.

“While symptoms such as constipation commonly occur in the population, it is relatively uncommon for individuals to develop multiple of the features we investigated independently,” Samantha Molsberry, PhD, a postdoctoral research fellow in the department of nutrition at Harvard T.H. Chan School of Public Health, told Healio Primary Care. “Instead, the co-occurrence of multiple features may suggest that there is an underlying disease process causing all of them, such as the early stages of Parkinson’s disease.”

To assess how diet relates to prodromal Parkinson’s disease, Molsberry said it was important to investigate the relationship between diet and each symptom individually as well as how it relates to multiple prodromal features, “as these are the individuals most likely to be in the prodromal phase of [Parkinson’s].”

Molsberry and colleagues conducted analyses of participants from the Nurses’ Health Study and the Health Professionals Follow-Up Study, which collected dietary information from participants every 4 years starting in 1986. Within these cohorts, researchers calculated scores for adherence to multiple dietary patterns, including the alternate Mediterranean diet and the Alternative Healthy Eating Index.

Prodromal features of Parkinson’s disease that were assessed in the study included body pain, constipation, probable REM sleep behavior disorder, excessive daytime sleepiness, impaired color vision, hyposmia and depressive symptoms.

A total of 47,679 participants were analyzed in the study. Of those, 17,400 were included in a subset of patients who responded to a 2012 questionnaire on REM sleep and constipation and had five additional prodromal features evaluated in 2014-2015.

Compared with those with the lowest adherence to an alternate Mediterranean diet, Molsberry and colleagues determined that the odds ratio for experiencing three or more features was 0.82 (95% CI, 0.68-1.0) at baseline and 0.67 (95% CI, 0.54-0.83) with long-term diet adherence.

They found that the results were similar for the association with adherence to the Alternative Healthy Eating Index. Researchers also observed a similar pattern when comparing the occurrence of two and one prodromal features with zero prodromal features, but the pattern attenuated as features decreased.

When examining specific prodromal features and dietary pattern, Molsberry and colleagues found that long-term adherence to an alternate Mediterranean diet was associated with lower risks for constipation, excessive daytime sleepiness and depressive symptoms. These results were similar with the Alternative Healthy Eating Index, but the association between long-term adherence to the diet and lower risk for depressive symptoms was marginally significant.

When examining specific components of the alternate Mediterranean diet, they found that eating more vegetables, nuts, legumes and moderate alcohol consumption was associated with a lowered risk for three or more prodromal symptoms.

“It is important to note that our study does not establish a causal role between following a healthy diet pattern and risk of prodromal Parkinson’s disease features nor does it explore whether adhering to a healthy diet pattern can slow or prevent the develop of clinically manifest Parkinson’s disease among those with prodromal features of Parkinson’s disease,” Molsberry stressed. “That being said, our investigation adds to a previous body of literature suggesting that adherence to a healthy diet pattern may reduce [the] risk of Parkinson’s disease and prodromal features of Parkinson’s disease.”

In clinical practice, she added, the findings suggest that physicians should consider encouraging patients to follow a healthy diet, “which, based on our findings, need not necessarily be a specific diet pattern like the Mediterranean diet so long as it is a healthy diet pattern rich in foods like fruits, vegetables, nuts and legumes, and only low to moderate intake of red meat and processed foods.”