Flavonoid dietary sources

Main Dietary Sources of Flavonoids from UK (Scottish) Diet ... 

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. 

Cook, N.C. and Samman, S., Flavonoids — chemistry, metabolism, cardioprotective effects, and dietary sources, J. Nutr. Biochem., 7, 66, 1996. 

Tea is another important dietary source for flavonoids, In fact, about half of the flavonoid intake in western populations is derived from black tea. Tea was the major source of flavonoids in the Dutch [6,13] and Welsh studies [17]. Only a small number of studies investigated the association between tea consumption and cardiovascular disease risk. No association between tea consumption and cardiovascular disease risk were reported in Scottish men and women [28] and in U.S. men in the Health Professionals follow-up study [29]. However, in a Norwegian population an inverse association was reported between tea intake, serum cholesterol, and mortality from coronary heart disease [30]. Several studies reported that tea consumption did not affect plasma antioxidant activity [31] and hemostatic factors [32]. However, a recent prospective study (the Rotterdam study) of 3,454 men and women 55 years and older followed for 2 to 3 years, showed a significant, inverse association of tea intake with severe (> 5 cm the length of the calcified area) aortic atherosclerosis. Odds ratios decreased approximately 70 % for drinking more than 500 mL/day (4 cups per day). The associations were stronger in women than in men. However, the risk reductions for moderate and mild atherosclerosis were only weak or absent [33]. 

Flavonoids represent one class of bioactive compounds that may have multiple beneficial effects on several chronic diseases [3-4]. Cocoa represents an example of a potentially rich dietary source of flavonoids. High concentrations of flavonoids are present in certain cocoas, predominately as the flavanol monomers (-)-epicatechin (epicatechin) and (+)-catechin (catechin), and as oligomers of these monomeric base units which are known as the procyanidins (Figure 1) [5]. Other potential rich dietary sources of flavonoids include tea, wine, grape juice, apples, onions and certain nuts. 

The flavonoids are a group of secondary metabolites widely distributed in the plant kingdom [63]. In 1984, more than 4000 flavonoids were identified in plants [64]. The major dietary sources of flavones are spices and pot herbs, such as parsley, rosemary, and thyme [65], whereas flavonols are predominantly found in onions, kale, broccoli, apples, berries and cherries, and in tea and red wine [66]. The flavanones are mainly restricted to citrus fruits [67], and flavanols are found in considerable amounts in tea, apricots, apples, and cherries [66]. 

Cook NC, Samman S. Flavonoids—chemistry, metabolism, cardioprotective effects and dietary sources. Nutr Biochem i996 7 66-76. 

Over the last 100 years, the grapevine Vitis vinifera L. (Vitaceae), the primary source of wine, has been the subject of numerous chemical studies. While stilbenoids are found in a number of plant species [19], grapes and related products are the most significant dietary source of these substances [20]. Stilbenoids are non-flavonoid polyphenols with an essential structural skeleton of two aromatic rings joined by an ethylene bridge (C6-C2-C6). Over 1,000 stilbenoids have been... 

It has been showed that chocolate is one of the most polyphenol-rich foods. According to Lee et al. [9], cocoa contains a higher content of flavonoids per serving than teas or red wine. Moreover cocoa powder is one of the richest dietary sources of flavanols (on a weight basis) identified so far, exceeded only by a few food ingredients such as buckwheat huUs, sorghum, cinnamon, and some superfruit [10]. Cocoa is also one of the richest dietary sources of polyphenols fisted in the Phenol-Explorer database [11] and one of the richest sources of procyanidins in the USDA Database for the Proanthocyanidin Content of Selected Foods [12] (Fig. 74.1). 

Procyanidins have been considered antinutritional compounds because they can interact with proteins, starch, essential amino acids, and carbohydrates and inhibit certain enzymes [121-123]. This binding depends on the degree of polymerization the larger molecules tend to bind more efficiently [7]. However, at the dose present in cocoa no adverse effect has been observed [124, 125]. In addition, the level of flavonoids required to induce mutations and cytotoxicity may not be physiologically achievable through dietary sources however the use of flavonoid supplements could result in... 

Table 1 The Neuroprotective Actions of Flavonoid-Rich Extracts Found in Dietary Sources... 

Pencer, J.P.E. 2006. Classification, dietary sources, ahsorption, hioavailability, and metabolism of flavonoids. Nutrition and Cancer Prevention, 273-294. 

Erlund, I. 2004. Review of the flavonoids quercetin, hesperetin, and naringenin Dietary sources, bioactivities, bioavailability, and epidemiology. Nutr. Res. 24 851-874. 

Cranberries (Vaccinium macrocarpon) are potentially an excellent dietary source of phenolic confounds such as flavonoids, anthocyanins and caffeic acid derivatives which are potent antioxidants. Studies also link a lowered incidence of breast cancer to cranberry juice consumption. In this study, cranberry fruits were fractionated by several methods and tested for radical-scavenging activity in an effort to begin establishing a link between chemical composition and antioxidant activity. The strongest activity was observed in flavonoid-rich extracts. Cytotoxicity assays in several tumor cell lines showed some specificity for HT-29 tumor cells and K562 cells from a methanolic cranberry extract containing several phenolic compounds. 

---