Carnauba et al. estimated dietary polyphenol intake in subjects aged ≥10 years and determined the major dietary contributors in the Brazilian population^{(Reference Carnauba, Hassimotto and Lajolo1)}. The median and 25–75th percentile of polyphenol intake were 364·3 and 200·9–1008 mg/d, and the median and 25–75th percentile of polyphenol intake were 204 and 111·4–542·1 mg/4184 kJ/d. Non-alcoholic beverages and fruits were the major polyphenol suppliers, and coffee and orange juice were the main individual food contributors to polyphenol intake. I have some concerns about their study.

First, Zamora-Ros et al. estimated dietary intakes of polyphenols and identified their main food sources in Mexican female teachers aged ≥25 years, including urban and rural areas^{(Reference Huang, Braffett and Simmens2)}. Median polyphenol intake was the highest in Baja California (750 mg/d) and the lowest in Yucatan (536 mg/d). Coffee and fruits were the most important food sources of phenolic acids and flavonoids, respectively. They pointed out that there was a large heterogeneity in intakes of individual polyphenols among Mexican women, which might be existed in other ethnic individuals. Sex, age and other socio-economic status should be specified for estimating dietary intakes of polyphenols.

Second, Huang et al. estimated dietary polyphenol intake among USA adults aged ≥20 years and also examined 10-year trends^{(Reference Zamora-Ros, Biessy and Rothwell3)}. The mean intake of dietary polyphenols was 884·1 mg/4184 kJ/d, and the mean daily polyphenol intake did not change significantly over time. Foods and beverages contributed 99·8% of polyphenol intake, with coffee (39·6%), beans (9·8%) and tea (7·6%). Miranda et al. estimated the intake of polyphenols and the major dietary contributors in adults and elderly adults of Sao Paulo^{(Reference Miranda, Steluti and Fisberg4)}. The mean intake of polyphenols was 377·5 mg/d, and intakes were relatively higher in the elderly adults, individuals with lower educational level and current smokers. The main dietary contributors for total polyphenols were coffee (70·5 %), citrus fruits (4·6 %) and tropical fruits (3·4 %), and coffee provided 266·2 mg/d of polyphenols. There is an ethnic difference in the amount of polyphenol intakes, and difference in the major dietary contributors of polyphenol should be considered for the estimation.

Finally, Knaze et al. presented food composition database for estimating polyphenol intakes in adults from 10 European countries^{(Reference Knaze, Rothwell and Zamora-Ros5)}. There is a variation for estimating polyphenol intakes, and an efficient procedure is indispensable for the estimation. Furthermore, food contributions to the different class of polyphenol intake have been reported^{(Reference Carnauba, Hassimotto and Lajolo1–Reference Miranda, Steluti and Fisberg4)}, which might contribute to the efficacy of disease prevention. Anyway, estimated dietary polyphenol intake can be used for the risk assessment of chronic diseases.