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J Epidemiol. 2018 Oct 5;28(10):428-436. doi: 10.2188/jea.JE20170063. Epub 2018 Jul 14.

The Validity and Reproducibility of Dietary Non-enzymatic Antioxidant Capacity Estimated by Self-administered Food Frequency Questionnaires.

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Department of Epidemiology and Prevention, Center for Clinical Sciences, National Center for Global Health and Medicine.
Functional Foods and Metabolic Stress Prevention Laboratory, Bioscience and Technology for Food, Agriculture and Environment, University of Teramo.
Department of Nutrition Management, Sagami Women's University.
Epidemiology and Prevention Division, Research Center for Cancer Prevention and Screening, National Cancer Center.
Department of Public Health, Juntendo University Graduate School of Medicine.
AXA Department of Health and Human Security, Graduate School of Medicine, the University of Tokyo.
Department of Nutritional Education, National Institute of Health and Nutrition.



High dietary non-enzymatic antioxidant capacity (NEAC) has been inversely related to the incidence of degenerative diseases. However, few studies have investigated the validity and reproducibility of dietary NEAC estimated from a food frequency questionnaire (FFQ). We assessed the validity and reproducibility of FFQ-based dietary NEAC against a dietary record (DR).


Participants were 244 men and 253 women who completed a 28-day DR and FFQs. NEAC for each food item was estimated according to available databases of antioxidant capacity, as measured by ferric reducing-antioxidant power (FRAP), oxygen radical absorbance capacity (ORAC), and total radical-trapping antioxidant parameter (TRAP). Using Spearman's rank correlation coefficients (CCs), we assessed the validity for dietary NEACs from a 28-day DR and a FFQ, and the reproducibility for them from two FFQs administered at a 1-year interval. Additionally, joint classification and the Bland-Altman method were applied to assess agreement between the two methods.


Regarding validation, deattenuated CCs for the energy-adjusted overall dietary NEACs between FFQ and DR for FRAP, ORAC, and TRAP were 0.52, 0.54, and 0.52, respectively, for all subjects. Extreme miscategorization rates by joint classification analysis were 2% for FRAP and ORAC and 1% for TRAP. Regarding reproducibility, CCs between the energy-adjusted dietary NEACs from two FFQs were 0.64 for FRAP and 0.65 for ORAC and TRAP.


The validity and reproducibility of dietary NEAC of total food from the FFQ were moderate. Estimations of dietary NEAC using FFQ would be useful in studying disease relationships by categorizing habitual dietary NEAC.


FRAP; ORAC; dietary assessment; human; non-enzymatic antioxidant capacity

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