Flavonoid intake estimates

Chun OK, Chung SJ and Song WO. 2007. Estimated dietary flavonoid intake and major food sources of U.S. adults. J Nutt 37(5) 1244-1252. 

Estimation of Scottish Dietary Flavonoid Intake Using the New... 

Comparison with Other Estimates of Dietary Flavonoid Intake.245... 

An initial estimate of flavonoid intake of 1000 mg/day was calculated in the United States during the 1970s using semiquantitative food composition data (Table 4.13). " This estimate was not questioned until the 1990s with the calculation of dietary flavonol and flavone... 

Several dietary flavonoid intake studies have now been completed using the Dutch composition data often with additional estimates of flavonoid content of local food preferences such as berries (Table 4.14). Comparison of these intake studies indicates that quercetin is consistently the main contributor to flavonol and flavone intake. In the Netherlands, for example, quercetin accounts for 70% of the 23 mg/day total flavonol and flavone intake followed by kaempferol (17%), myricetin (6%), luteolin (4%), and apigenin (3%). ... 

Estimated Daily Dietary Flavonoid Intakes by Different Countries... 

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). 

Estimated Dietary Flavonoid Intake by UK (Scottish) Population (n = 81)... 

A comprehensive and critical review of food flavonoid literature has led to the development of a food composition database for flavonols, flavones, procyanidins, catechins, and flava-nones. This database can now be used and continuously updated to estimate flavonoid intake of populations, to identify dietary sources of flavonoids, and to assess associations between flavonoid intake and disease. However, there is a need for better food composition data for flavones, procyanidins, and flavanones as current literature is sparse particularly for citrus fruits, fruit juices, and herbs. In addition, anthocyanin food composition data are lacking although validated methods of determination are becoming available. 

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,... 

Further support for the cardioprotective effect of flavonoids has been obtained from a reexamination of food records from 16 cohorts within the Seven Countries Study [10]. During a 25-year follow-up period, an inverse association was observed between CHD mortality and flavonoid intake this explained a small but significant portion (8%) of the variance in CHD deaths, independently of intakes of alcohol and antioxidant vitamins. CHD mortality was observed to be lowest in Japan with an estimated average flavonoid intake of 61 mg/d, mainly derived from green tea. 

Earlier estimates of polyphenols consumption in the United States fixed at 1 g/day the intake of flavonoids, of which 115 mg/day were flavonols, flavones, and flava-nones." However, more recent data establish this intake in much lower amounts of these flavonoids ranging from 15 to 23 mg/day, plus 12 mg of anthocyanins and up to 70 mg of procyanidins per day in the United States (Table 3.4). Similarly, flavonols and flavone intake in other European countries and Japan show figures much lower that those initially estimated by Khiinau," as can be seen in Table 3.4." To these values, should be added the intake of flavonoids from nutraceuticals and functional foods enriched in these polyphenols, consumption of which has increased considerably in recent years. Therefore, it would be necessary to develop reliable databases of polyphenols/flavonoids in foods and nutraceuticals to obtain more updated estimates of flavonoids intakes. 

The estimated daily intake of flavonoids, including catechins and anthocyanins, is >50 mg for all the countries presented in Table 2, and realistically intake is probably higher than lOOmg/day if data on all flavonoid groups were available. If this intake is compare to daily intakes of other dietary antioxidants, such as vitamin C (80mg/day), vitamin E (8.5mg/day), and /3-carotene (1.9mg/day), it is clear that flavonoid intakes exceed or are at least comparable to those of other established... 

It is important to quantify the content of tea infusions when evaluating the intake of flavoiioids from consuming tea. However, the daily consumption of flavonoids from tea is difficult to estimate because values depend on accurate assessment of drinking habits and flavonoid content in teas. 

In Greece, a case-control study was conducted to investigate the incidence of liver cancer by estimating the consumption of six types of flavonoids with a semiquantitative questionnaire on the frequency of foods. The intake of flavones was inversely associated with hepatocellular carcinoma, irrespective of its etiology (viral or nonviral). With respect to cholangiocarcinoma, an inverse association with the consumption of flavan-3-ols, anthocyanidins, and total flavonoids studied was found. However, this last result should be viewed with caution because of the small sample size, due to the fact that this is a rare type of cancer (Lagiou and others 2008). 

In the study on laryngeal cancer (Table 20.3), significant inverse relations were found for flavan-3-ols (OR,0.64), flavanones (OR,0.60), flavonols (OR,0.32), and total flavonoids (OR,0.60), although the overall trends in risk were significant only for flavanones and flavonols [Garavello et al., 2007], The estimates persisted after controlling for vegetable, fruit, and vitamin C intake. 

In the study on colorectal cancer (Table 20.4), a reduced risk was found for increasing intake of anthocyanidins (OR, 0.67 for the highest versus the lowest quintile,p-trend, 0.001), flavonols (OR, 0.64,p-trend < 0.001), flavones (OR, 0.78, p-trend, 0.004), and isoflavones (OR, 0.76, p-trend, 0.001). [Rossi et al., 2006], The estimates did not substantially differ for colon and rectal cancers. After allowance for fruit and vegetable consumption, for dietary fiber, or for micronutrients previously associated to this tumor including vitamin C, the associations with flavonoids did not change by more than 10%. A recent case-control study of 1456 pairs of cases and controls conducted in Sweden confirmed a significant decrease in risk of colorectal cancer for intake of anthocyanidins and flavonols [Theodoratou et al., 2007], but there was no relation for isoflavones and flavones. However, the results on isoflavones and flavones are questionable due to the unusually and generally low intakes of the populations studied. In the Italian population, anthocyanidins were derived mainly from wine, red fruit, and onions, and flavonols from apples or pears, wine, and mixed salads. 

Among the major groups of flavonoids in the human diet are the flavonols, proanthocyanidins (which include the catechins), isoflavonoids, flavones, and flavanones. The closely related lignans (resorcyclic acid lactones) have similar properties as flavonoids, and are therefore included here for completeness. Quercetin, a flavonol, is the most predominant flavonoid in the human diet and estimates of human consumption are in the range of 4 to 68 mg/day. Among these studies, the Japanese population had the highest levels of flavonol intake, which was mainly attributed to their green tea consumption. 

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