Decomposition of anticarcinogen factors of the beetroot during juice and nectar production

Quercetin and related flavonoids are anticarcinogenic in rats, but little is known about human intakes. The intake of five major flavonols and flavones was calculated using 1-day dietary records of 17 volunteers from 14 countries, and using both 3-day records and a food frequency questionnaire of eight Dutch adults. Total consumption (±SD) was 27.6 ± 19.5 mg/day in the international subjects, 34.1 ± 31.2 mg/day in the Dutch adults according to 3-day records, and 41.9 ± 23.7 mg/day according to questionnaires. Quercetin contributed 68–73%, and kaempferol 22–29%, the major sources being tea and onions. A brief food frequency questionnaire may be a suitable method for ranking individuals by flavonol intake.