Validation of a food frequency questionnaire assessing dietary polyphenol exposure using the method of triads

[Design and validation of a self-reported dietary polyphenol intake frequency questionnaire.]

Introduction

Introduction: although there is evidence linking polyphenol consumption with better health outcomes, information on consumption patterns, particularly in Latin American countries, is scarce. Objective: to design and evaluate the validity of an online self-reported food frequency questionnaire to measure dietary total polyphenol intake in the Chilean adult population. Methods: the designed questionnaire (FFQ-P) was submitted to expert opinion for content validity coefficient estimation; then a pilot study was conducted in 47 adults who completed FFQ-P, in addition to a six-day food record as a reference method. Wilcoxon was applied in related samples, Spearman's correlation to determine the strength of association and Bland-Altman diagrams to examine the difference between methods. Results: content validity reflected concordant values for adequacy (0.94 ± 0.04) and relevance (0.93 ± 0.05). The percentage difference between both methods was 1.2 %, with greater variability observed in fruits (9 %) and alcoholic beverages (4 %). The Wilcoxon test showed no significant differences between food groups. Medium reliability was observed for vegetables, fruits, tea, and coffee (0.26 to 0.5) and moderate reliability for alcoholic beverages (0.5 to 0.75). The mean value of the difference was 9.8, being within a short distance of zero. Conclusion: FFQ-P is reliable for estimating polyphenol intake from fruits, vegetables, alcoholic beverages, tea, and coffee; however, the intake of non-alcoholic beverages, nuts and olives should be interpreted with reservation.

Ex Vivo Antioxidant Capacities of Fruit and Vegetable Juices. Potential In Vivo Extrapolation

BACKGROUND

In support of claims that their products have antioxidant properties, the food industry and dietary supplement manufacturers rely solely on the in vitro determination of the ORAC (oxygen radical antioxidant capacity) value, despite its acknowledged lack of any in vivo relevance. It thus appears necessary to use tests exploiting biological materials (blood, white blood cells) capable of producing physiological free radicals, in order to evaluate more adequately the antioxidant capacities of foods such as fruit and vegetable juices.

MATERIALS

Two approaches to assessing the antioxidant capacities of 21 commercial fruit and vegetable juices were compared: the ORAC assay and the "PMA-whole blood assay," which uses whole blood stimulated by phorbol myristate acetate to produce the superoxide anion. We described in another paper the total polyphenol contents (TPCs) and individual phenolic compound contents of all the juices were investigated.

RESULTS

Ranking of the juices from highest to lowest antioxidant capacity differed considerably according to the test used, so there was no correlation (r = 0.33, p = 0.13) between the two assays when considering all juices. Although the results of the ORAC assay correlated positively with TPC (r = 0.50, p = 0.02), a much stronger correlation (r = 0.70, p = 0.004) emerged between TPC and % superoxide anion inhibition. In the PMA-whole blood assay, peonidin-3-O-glucoside, epigallocatechin gallate, catechin, and quercetin present in juices were found to inhibit superoxide anion production at concentrations below 1 µM, with a strong positive correlation.

CONCLUSIONS

Associated with the determination of total and individual phenolic compounds contained in fruit and vegetable juices, the PMA-whole blood assay appears better than the ORAC assay for evaluating juice antioxidant capacity.

Validity of a food frequency questionnaire for the estimation of total polyphenol intake estimates and its major food sources in the Japanese population: the JPHC FFQ Validation Study

We examine the validity and reproducibility of a food frequency questionnaire (FFQ) in a subsample of participants in the Japan Public Health Center-based Prospective Cohort Study using a database of polyphenol-containing foods commonly consumed in the Japanese population. Participants of the validation study were recruited from two different cohorts. In Cohort I, 215 participants completed a 28-d dietary record (DR) and the FFQ, and in Cohort II, 350 participants completed DRs and the FFQ. The total polyphenol intake estimated from the 28-d DR and FFQ were log-transformed and adjusted for energy intake by the residual method. Spearman correlation coefficients (CCs) between estimates from the FFQ and 28-d DR as well as two FFQs administered at a 1-year interval were computed. Median intakes of dietary polyphenols calculated from the DRs were 1172 mg/d for men and 1024 mg/d for women in Cohort I, and 1061 mg/d for men and 942 mg/d for women in Cohort II. The de-attenuated CCs for polyphenol intake between the DR and FFQ were 0⋅47 for men and 0⋅37 for women in Cohort I and 0⋅44 for men and 0⋅50 for women in Cohort II. Non-alcoholic beverages were the main contributor to total polyphenol intake in both men and women, accounting for 50 % of total polyphenol intake regardless of cohort and gender, followed by alcoholic beverages and seasoning and spices in men, and seasoning and spices, fruits and other vegetables in women. The present study showed that this FFQ had moderate validity and reproducibility and is suitable for use in future epidemiological studies.

Dietary Assessment Methods to Estimate (Poly)phenol Intake in Epidemiological Studies: A Systematic Review

Nutritional epidemiological studies have frequently reported associations between higher (poly)phenol intake and a decrease in the risk or incidence of noncommunicable diseases. However, the assessment methods that have been used to quantify the intakes of these compounds in large-population samples are highly variable. This systematic review aims to characterize the methods used to assess dietary (poly)phenol intake in observational studies, report the validation status of the methods, and give recommendations on method selection and data reporting. Three databases were searched for publications that have used dietary assessment methods to measure (poly)phenol intake and 549 eligible full texts were identified. Food-frequency questionnaires were found to be the most commonly used tool to assess dietary (poly)phenol intake (73%). Published data from peer-reviewed journals were the major source of (poly)phenol content data (25%). An increasing number of studies used open-access databases such as Phenol-Explorer and USDA databases on flavonoid content since their inception, which accounted for 11% and 23% of the data sources, respectively. Only 16% of the studies reported a method that had been validated for measuring the target (poly)phenols. For future research we recommend: 1) selecting a validated dietary assessment tool according to the target compounds and target period of measurement; 2) applying and combining comprehensive (poly)phenol content databases such as USDA and Phenol-Explorer; 3) detailing the methods used to assess (poly)phenol intake, including dietary assessment method, (poly)phenol content data source; 4) follow the Strengthening the Reporting of Observational Studies in Epidemiology-Nutritional Epidemiology (STROBE-nut) framework; and 5) complementing dietary intake assessment based on questionnaires with measurement of (poly)phenols in biofluids using appropriate and validated analytical methods.

Electrochemical Methodology for Evaluating Skin Oxidative Stress Status (SOSS)

For the purpose of human disease prevention, several methods have been developed, and are still developing, to assess the oxidative stress status (OSS) of individuals. In the present paper, we describe an approach based on electrochemical detection able to evaluate skin oxidative stress status (SOSS) as a PAOT (Pouvoir AntiOxydant Total)-Skin Score^®. Normal reference values for the PAOT-Skin Score^® were: 0-62.94 (n = 263). Intra- and inter-assay coefficients of variation were, respectively, 12.47 ± 4.29% and 7.0 ± 2.5%. Our technology showed increased skin antioxidant activity following topical application of reduced coeznyme Q₁₀ cream or vitamin C intake as orange juice or supplements. Moreover, we found significant correlations between some blood oxidative stress biomarkers and the PAOT-Skin Score ^® (-tocopherol/α-tocopherol ratio (r = 0.43, p = 0.020); copper (r = -0.42, p = 0.022); copper/zinc ratio (r = -0.49, p = 0.006), and lipid peroxides (r = -0.43, p = 0.002)). In addition to being non-invasive, the present electrochemical methodology is also not expensive, fast, and easy to use.