Flavonoids dietary intake

The amount consumed could be considerably higher in the Mediterranean diet, which is rich in olive oil, citrus fruits, and greens. These quantities could provide pharmacologically significant concentrations in body fluids and tissues. Nevertheless, flavonoid dietary intake far exceeds that of vitamin E, a monophenolic antioxidant, and that of P-carotene on a milligram per day basis. From this we can conclude that... 

Small-molecule antioxidants include glutathione, ascorbic acid (vitamin C), vitamin E and a number of dietary flavonoids. Because humans, in contrast to most other animals, are unable to synthesize vitamin C, this important antioxidant must be supplied entirely from dietary intake. Other proteins, such as thioredoxin and metallothionein, may also contribute to some extent to the cellular antioxidant pool. 

The flavonoid database described in this chapter was applied to 4-day weighed food records obtained from healthy Scottish men n = 41) and women ( = 52) to provide a provisional estimate of flavonoid intake in Scotland. All subjects consumed foods containing flavonols, procyanidins, and catechins, dietary intakes of which are given in Table 4.15. The main flavonol consumed was quercetin, accounting for 66 and 63% of the total flavonol intake of 18.8 mg/day. Primary sources of flavonols were from black tea (42.7%), onions (14.3%), apples (10.2%i), and lager (7.2%i) (Table 4.16). 

The same authors [204] confirmed these results in the Seven Country Study. The contribution of flavonols and flavones in explaining the variance in coronary heart disease mortality rates across 16 cohorts from seven countries was studied. Flavonol and flavone intake was inversely correlated with mortality from coronary heart disease. These finding are in line with the results of a cohort study in Finnland [205], where a significant inverse gradient was observed between dietary intake of flavonoids and total and coronary mortality. 

In the Finnish Mobile Clinic examination there was an inverse relation between the dietary intake of some flavonoids and the incidence of several chronic diseases, The positive outcome was related to the consumption of apples, The authors concluded, although our finding was independent of the intake of antioxidant vitamins, the potential... 

The yield of flavonoids in the urine is dramatically dependent on the flavonoid under examination. For quercetin and anthocyanins, it is less than 1.5%, for isofla-vones it is 2 to 20% and for catechins it is -5% (reviewed in Scalbert and Williamson ). Flavonoids are found in urine as conjugated forms for example, rat urinary catechins are (+)-catechin-5-0-P-glucuronide and (-)-epicatechin-5-0-P-glucuronide. Generally, renal excretion is not a major pathway for intact flavonoids and the urinary content of flavonoids cannot be used as a biomarker of bioavailability or dietary intake. 

Not all the effects of dietary intake of flavonoids are positive. The excessive consumption of soybean and its products has been considered goitrogenic in humans and animals. Several researchers have reported induction of goitre in iodine-deficient rats maintained on a soybean diet [125, 126, 127], In some cases, the extreme intake of soybean has been correlated with cancer. Thus, Kimura et al reported the induction of thyroid carcinoma in rats fed on defatted soybean deficient in iodine by up to 40% [128],... 

In contrast to epidemiological studies of these diseases, there has been just one study that compared flavonoid intake and cataract [44]. In this Finnish study the dietary intakes of over 10,000 men and women were estimated for the year preceding baseline health examination. Health outcomes were determined 28-30 years later using Finnish government health statistics and compared with the highest and lowest intakes. Neither higher total flavonoid intake nor higher intakes of quercetin, kaempferol, myricetin,... 

In the Zutphen Elderly Study (in Holland) carried out on 805 men aged 65-84 years, dietary intake of flavonoids was calculated during a five-year period. The study indicates that the intake of flavonoids is inversely associated with mortality from coronary heart disease and, to a lesser extent, myocardial infarct. The main source of flavonoids in the men s diets were tea, onions and apples. These flavonoids include quercetin, kaempferol and myricitin as well as the catechin-type condensed tannins found in black tea (Hertog et al. 1993). 

Weame S. Estimating dietary intakes of flavonoids. In Rice-Evans C, ed. Wake Up to Flavonoids. London Royal Society of Medicine Press, 2000 35-43. 

Flavonoids are part of the hiunan diet, and high levels occm in fruits, vegetables, wine, tea, and cocoa. It is suggested that dietary intake of flavonoids has beneficial health effects due to their antioxidant and radical-scavenging properties... 

Estimation of the daily intake of flavonoids is not a straightforward matter because of the mentioned variation in the content and composition of flavonoids in foods. Moreover, the variability and the lack of standardized analytical methods for their estimation further hinder the creation of compositional databases necessary to calculate flavonoids consumption. Intakes wUl also be affected by seasonal and regional availability of plant foods, as weU as by dietary habits dependant of cultural traditions and individual preferences. 

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