Dietary Antioxidants May Reduce Parkinsonism Risk, Progression

Caroline Cassels

LOS ANGELES — Dietary antioxidants, including carotenoids, lutein, and vitamins E and C, have been strongly linked to a reduced risk for parkinsonism as well as progression of parkinsonian symptoms in older adults, new research shows.

Investigators at Rush University Medical Center in Chicago, Illinois, found adults with the largest intake of these nutrients from food had significantly lower rates of parkinsonism when compared with those in the lowest quintile.

"For total carotenoids those in the highest quintile of intake had a 30% reduced risk of developing parkinsonism while those in the highest quintile of lutein intake, a nutrient found in leafy green vegetables, such as kale, collard greens, and spinach, had a 44% reduced risk," study investigator Puja Agarwal, PhD, told Medical News.

In addition, the researchers, with principal investigator Martha C Morris, ScD, a nutritional epidemiologist, found that the highest dietary intake of carotenoids and lutein, as well as vitamins E and C, was significantly associated with a slower progression of parkinsonism with older age.

"So the higher the intake of these anti-oxidant nutrients, the slower is the progression of parkinsonism over time," said Agarwal.

The study was presented here at the American Academy of Neurology (AAN) 2018 Annual Meeting.

Growing Problem

During her presentation, Agarwal noted that parkinsonian signs are present in approximately 50% of individuals age 85 years and older and cause progressive disability and mortality. Because of the aging population, it is becoming a growing health problem. Identifying modifiable risk factors could help prevent the disorder, she added.

Previous research, conducted by Morris and colleagues and reported by Medical News,  has shown a healthy diet is associated with a lower risk for parkinsonism and a slower rate of progression, but no studies have examined the impact of specific nutrients.

Other studies by these investigators have also shown that lutein and vitamin E are important for brain health. Both nutrients have been strongly associated with slower decline in cognitive function likely by reducing oxidative stress and prevention of neuronal loss. These new findings suggest they may also have an impact on preserving motor function in old age, said Morris.

To examine the potential association between nutrient intake and parkinsonism, the investigators analyzed data on 706 participants from the Rush Memory and Aging Project, an ongoing longitudinal cohort study. The mean age of participants at study entry was about 80 years. Most subjects were white and had a relatively high level of education (mean, 15 years).

To assess incident parkinsonism, the researchers used the United Parkinson's Disease Rating Scale. Parkinsonism was present if there were two or more signs of the disorder. These included bradykinesia, tremors, rigidity, and gait. A continuous global parkinsonian scores summarized the overall severity of parkinsonism.

Individuals with baseline dementia, Parkinson's disease, or signs of parkinsonism were excluded.

Nutrient intake was assessed at study outset by using a 144-item validated food-frequency questionnaire. Participants were assessed annually for up to 12 years, with an average follow-up of 4.6 years. During the study, 287 (41%) of the participants developed parkinsonism.

Participants were divided into quintiles according to intakes of the different study nutrients. Parkinsonian risk and progression were compared between those in the highest quintile (n = 142) and those in the lowest (n = 141) for each nutrient.

Analyses adjusted for age, sex, and smoking showed that participants in the highest quintiles of lutein (hazard ratio [HR], 0.56; 95% CI, 0.39 - 0.81), total carotenoids (HR, 0.69; 95% CI, 0.48 - 1.00), and vitamin E (HR, 0.70; 95% CI, 0.50 - 1.00) intake had lower rates of parkinsonism when compared with those in the lowest quintile.

In the adjusted linear mixed models, nutrient intakes of β-carotene (P for trend = .01), lutein (P for trend = .009), total carotenoids (P for trend < .0001), vitamin E from foods (P for trend = .04), and vitamin C from foods (P for trend  = .007) were each associated with reduced progression of parkinsonian signs score.

On the basis of these findings, said Agarwal, clinicians should encourage their patients to "eat more bright color fruits and vegetables in their daily life and if possible also encourage the caregivers and/or families to equally support and participate in the healthy eating behavioral change."

She noted that a single daily serving of leafy green vegetables provides a good source of lutein; that vegetables such as carrots, sweet potatoes, squash, and tomatoes are excellent sources of β-carotene and vitamin C; that a single daily serving of berries or citrus fruits is a rich source of vitamin C; and that a daily serving of nuts is a good source of vitamin E.

Good for the Body, Good for the Brain

Commenting on the findings for Medical News, Natalia S Rost, MD, director of the Acute Stroke Service at Massachusetts General Hospital, associate professor of neurology at Harvard Medical School, Boston, and chair of the AAN scientific committee said the results underscore the importance of diet in brain health.

The study, she said, comes from a very reputable research group with a "robust" program that has previously demonstrated that the MIND diet, a hybrid diet that combines the Mediterranean-DASH (Dietary Approaches to Stop Hypertension) Intervention for Neurodegenerative Delay, has the potential to preserve cognition and reduce dementia risk.

These new findings further the field by shedding light on the exact nutrients that may be responsible for the preventive and potentially therapeutic effect in neurodegenerative disease.

However, Rost noted that although impressive, the 30% reduction in parkinsonism risk and the 40% reduction in parkinsonism progression shown in the study may not be generalizable to the general population but may reflect selection bias.

This elderly cohort was relatively healthy and well educated, so the findings need to be replicated or validated in different cohorts that are more representative of the general population.

The message from a growing body of evidence that diet is as important for the brain as for the body is beginning to reach grassroots clinicians, although it is still not part of standard counseling, said Rost.

"For stroke neurologists it is quite standard. We always talk to our patients about the importance of lifestyle and diet. For us it is a standard of care and something we have been trained to do in vascular neurology. But in the neurological subspecialties I don't think we're quite there yet. However, we are moving in a positive direction, and I believe that in the next decade or so we are going to have a much better appreciation that what's good for the body is good for the brain," she said.

Agarwal, Morris, and Rost have disclosed no relevant financial relationships.

American Academy of Neurology (AAN) 2018 Annual Meeting. Abstract S4.006. Presented April 22, 2018.

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