SAN DIEGO—Patients with Parkinson’s disease were less likely to adhere to a Mediterranean-type diet, compared with people without Parkinson’s disease, according to research presented at the 136th Annual Meeting of the American Neurological Association.
The Mediterranean diet—characterized by a high intake of fruits, vegetables, legumes, and olive oil and a low intake of saturated fatty acids—has been linked to a lower risk for other diseases as well. In 2009, Nikolaos Scarmeas, MD, lead investigator of the current study, published research demonstrating that higher adherence to the Mediterranean diet, along with more frequent physical activity, were independently associated with a reduced risk for Alzheimer’s disease.
In the current study, Dr. Scarmeas and a team of investigators led by Roy N. Alcalay, MD, Assistant Professor of Neurology at the Movement Disorders Division of the Department of Neurology at Columbia University Medical Center in New York City, also found that poorer adherence to the diet was associated with a younger age of Parkinson’s disease onset.
“The interesting question of whether adherence to a Mediterranean-type diet may reduce one’s risk for Parkinson’s disease is unknown,” Dr. Alcalay told Neurology Reviews. “There are many ongoing studies that approach populations at risk for Parkinson’s disease. Considering whether Mediterranean diet adherence reduces their risk for Parkinson’s disease can be very helpful.”
Comparing Patients and Healthy Controls
Dr. Alcalay and colleagues recruited 257 patients (115 women) with Parkinson’s disease and 198 healthy controls (96 women) from three Columbia University and community-based study populations for their case–control study. “Parkinson’s disease participants were younger (68 vs 72) and more educated (14 years vs 12 years) than controls,” the researchers noted.
All participants completed the Willett semiquantitative food frequency questionnaire. A Mediterranean-type diet adherence score was calculated using a 9-point scale, with higher scores representing stricter adherence to the diet.
“The Mediterranean diet is characterized by a high intake of vegetables, legumes, fruits, and cereal; a high intake of unsaturated fatty acids (mostly in the form of olive oil) compared with saturated fatty acids; a moderately high intake of fish; a low-to-moderate intake of dairy products, meat, and poultry; and a regular but moderate amount of ethanol, primarily in the form of wine and generally consumed during meals,” Dr. Alcalay noted. Total daily caloric intake for patients with Parkinson’s disease was slightly higher than for controls, and patients’ mean Mediterranean diet score was lower (4.3 vs 4.7).
Mediterranean Diet Adherence and Parkinson’s Disease Status
When they compared the demographics and clinical and dietary characteristics of controls and patients, the researchers determined that lower Mediterranean-type diet adherence was associated with higher odds for Parkinson’s disease (odds ratio per Mediterranean-type diet point, 0.86) after adjusting for age, education, race, gender, and total daily caloric intake.
“Lower Mediterranean-type diet score was associated with earlier Parkinson’s disease age at onset,” Dr. Alcalay and his colleagues stated.
The researchers then categorized the study participants into three groups according to Mediterranean-type diet scores. A majority of the study participants (206) were in the middle tertile, 125 were in the low tertile, and 124 were in the high tertile. “We observed that people with Parkinson’s disease were more likely to belong to the lower tertile of Mediterranean diet adherence than people without Parkinson’s disease,” Dr. Alcalay stated. When the researchers compared clinical and demographic characteristics of these groups, they found that the adjusted odds ratio was 0.64 for the middle versus low tertile comparison group, and 0.48 for the higher vs lower tertile comparison group.
Possible Mechanisms of the Mediterranean Diet’s Protective Function
The Mediterranean diet has been associated with a lower risk for Alzheimer’s disease, cardiovascular disease, several forms of cancer, and overall mortality, the researchers noted. Although the role of environmental exposures in the pathogenesis of Parkinson’s disease is well established, most studies that have investigated associations between Parkinson’s disease risk and intake of individual foods and nutrients reported inconsistent results, according to the investigators.
“Mediterranean diet adherence may be protective because of lower consumption of compounds that are associated with higher Parkinson’s disease risk,” Dr. Alcalay theorized. “Previous studies have shown an association between animal fat consumption and Parkinson’s disease, and the association between higher dairy intake and Parkinson’s disease was previously reported.”
Prior studies that have linked the Mediterranean diet with a lower Alzheimer’s disease risk have attributed the mediating effects of the diet on oxidative stress and inflammation as possible mechanisms for the perceived effects on decreased disease risk.
“Both oxidative stress and inflammation have been frequently implicated in the pathogenesis of Parkinson’s disease,” Dr. Alcalay stated. “The mechanism by which the Mediterranean diet may be protective from neurodegenerative disorders is largely unknown.”