Dietary Antioxidants and the Risk of Parkinson Disease: The Swedish National March Cohort
Authors: Hans-Olov Adami
Stephanie Bonn
Mauro Serafini
Weimin Ye
Rino Bellocco
Essi Hantikainen
Ylva Trolle Lagerros
Journal: Neurology (2021)
Discipline: NEUROSCIENCE & BEHAVIOR
Keywords: dietary antioxidants; nonenzymatic antioxidant capacity; Parkinson disease; vitamin E; vitamin C
Affiliations: From the Department of Statistics and Quantitative Methods (E.H., R.B.), University of Milano-Bicocca, Milan; Institute for Biomedicine, Eurac Research (E.H.), Affiliated Institute of the University of Lübeck, Bolzano, Italy; Clinical Epidemiology Division, Department of Medicine (Solna) (Y.T.L., S.B.), and Department of Medical Epidemiology and Biostatistics (W.Y., H.-O.A., R.B.), Karolinska Institutet, Stockholm; Obesity Center, Academic Specialist Center (Y.T.L.), Stockholm Health Services, Sweden; Functional Food and Metabolic Stress Prevention Laboratory, Faculty of BioSciences and Technology for Food, Agriculture and Environment (M.S.), University of Teramo, Italy; and Clinical Effectiveness Research Group, Institute of Health (H.-O.A.), University of Oslo, Norway. ., From the Department of Statistics and Quantitative Methods (E.H., R.B.), University of Milano-Bicocca, Milan; Institute for Biomedicine, Eurac Research (E.H.), Affiliated Institute of the University of Lübeck, Bolzano, Italy; Clinical Epidemiology Division, Department of Medicine (Solna) (Y.T.L., S.B.), and Department of Medical Epidemiology and Biostatistics (W.Y., H.-O.A., R.B.), Karolinska Institutet, Stockholm; Obesity Center, Academic Specialist Center (Y.T.L.), Stockholm Health Services, Sweden; Functional Food and Metabolic Stress Prevention Laboratory, Faculty of BioSciences and Technology for Food, Agriculture and Environment (M.S.), University of Teramo, Italy; and Clinical Effectiveness Research Group, Institute of Health (H.-O.A.), University of Oslo, Norway.

Abstract:  Objective: To determine whether high baseline dietary antioxidants and total nonenzymatic antioxidant capacity (NEAC) is associated with a lower risk of Parkinson disease (PD) in men and women, we prospectively studied 43,865 men and women from a large Swedish cohort. Methods: In the Swedish National March Cohort, 43,865 men and women aged 18-94 years were followed through record linkages to National Health Registries from 1997 until 2016. Baseline dietary vitamin E, vitamin C, and beta-carotene intake, as well as NEAC, were assessed by a validated food frequency questionnaire collected at baseline. All exposure variables were adjusted for energy intake and categorized into tertiles. Multivariable Cox proportional hazard regression models were fitted to estimate hazard ratios (HRs) with 95% confidence intervals (CIs) for PD. Results: After a mean follow-up time of 17.6 years, we detected 465 incidence cases of PD. In the multivariable adjusted model, dietary vitamin E (HR 0.68, 95% CI 0.52-0.90; p for trend 0.005) and vitamin C (HR 0.68, 95% CI 0.52-0.89; p for trend 0.004) were inversely associated with the risk of PD when comparing participants in the highest vs the lowest tertiles of exposure. No association was found with estimated intake of dietary beta-carotene or NEAC. Conclusion: Our findings suggest that dietary vitamin E and C intake might be inversely associated with the risk of PD. No association was found with dietary beta-carotene or NEAC. Classification of evidence: This study provides Class III evidence that dietary vitamin E and C intake are inversely associated with the risk of PD. 

Retracted: No

PubPeer comments:
 This article was reviewed on the error bar podcast episode 1: https: theerrorbar.com ?e=1. The review was done in the light of newspaper headlines about the article. The slightly-edited transcript is copied here: headline: VEGETABLES FOR BRAIN HEALTH tweet: eating a mediterranean diet may only slow cognitive decline if you don t also eat lots of western food (spoiler: not really) description: a paper claims that brain degeneration can be prevented by the foods we eat. this paper looks at the historical food reports of 10000 people in the USA, along with how they performed on follow-up cognitive tests every three years. only half of the 10000 volunteers data were used - some had died, and others hadn t filled in the food questionnaires correctly. somewhat suspiciously, people who reported eating too little or too much food, or had poor mental state scores, were removed from the analysis. the headline-grabbing claim is that a mediterranean-style diet with lots of fruit and vegetables is only good for your brain if you also don t eat lots of western food on the side evaluation: the claim is that mediterranean food is only good for you if you don t also eat lots of western food. but that s not actually what the study found. it s more subtle and contextual than that. as is common in studies like this, there are lots of possible variables to take into account - the age, sex, ethnic group, and pre-existing health conditions. for example, people with a high western style diet were more male, and those with a high mediterranean diet also took more exercise. but let s just examine the central claim. if you eat lots of mediterranean food, that is always a good thing - cognitive test scores were higher and declined less slowly. and if you eat lots of western food, then you were a little worse off overall. but these two trends were totally unrelated to each other - not what the headline claims. the researchers then divided the western diets into a high and a low diet and did analyses on each part separately. this median split is a common tactic - divide the data into slices and look at each slice separately. in the low-western slice they found slightly stronger relationships than in the high western slice. but the direction and size of these relationships was quite comparable. so, while the conclusions were that a mediterranean diet is only good for you if you don t also eat lots of western food, actually, the benefit of eating lots of mediterranean foods was always about 6 years additional brain health, for both high and low western diets conclusion: eat a balanced diet, lots of fresh fruit and vegetables, exercise lots, stay mentally active; don t believe everything you read in retrospective food questionnaire studies ,