Flavonoid coronary heart disease protection

Because of human consumption of plant and plant products, there has been much interest on the impact of flavonoids on human health and this has been recently reviewed [149, 150 and ref therein]. Additionally, Passamonti et al. [151] have recently reviewed the issue of bioavailability of dietary flavonoids. Citrus flavonoids have been shown to have many beneficial effects on human health including anti-inflammatory activity, anticancer activity, antioxidant activity, and protection against coronary heart disease [reviewed in 152-154]. This has led to... 

A modest but not significant inverse correlation between the intake of flavonols and flavones and subsequent mortality rates was found in a prospective cohort study of US Health Professionals by Rimm et al [206]. The authors do not exclude that flavonoids have a protective effect in men with established coronary heart disease although strong evidence was missing. Also other studies failed to demonstrate a significant statistical association between the intake of polyphenols and CHD. In Great Britain for instance coronary and total mortality even rose with the intake of the major flavonol source, tea [207], The most likely explanation for the latter observation is that in this study tea consumption merely acted as a marker for a lifestyle that favours the development of cardiovascular disease. Indeed, men with the highest intake of tea and flavonols tended to be manual workers, and they smoked more and ate more fat [208],... 

ABSTRACT Several epidemiological studies have found an inverse correlation between the dietary flavonoid intake and a reduced mortality from coronary heart disease and the incidence of stroke. We will focus our review on several mechanisms which have been suggested to explain these protective effects. 

Hypertension is an important risk factor for coronary heart disease and stroke. Since ancient times, hypertensive patients have been treated orally with plant extracts based on folk medicine. However, and despite their in vitro vasodilator effects, little information about the protective effects of flavonoids on hypertension is available in the literature. Flavonoids have been considered as active principles of several antihypertensive plant extracts (e.g. rhamnoglycoside of limocitrin isolated from Citrus limonum, kaempferol 4 -0-glucose and hyperin from Euphorbia maddeni, moracenins from Morus alba, procyanidin glycoside from Rhamnus lycioides) [150,151]. In all cases, only the acute antihypertensive effects after i.v. administration in anaesthetised normotensive and/or hypertensive animals have been described. In addition to the direct vasodilator effects discussed above, the inhibition of angiotensin-converting enzyme reported... 

HOLLMAN, P.C.H., HERTOG, M.G.L., KATAN, M.B., Role of dietary flavonoids in protection against cancer and coronary heart disease, Biochem. Soc. Trans., 1996,24, 785-789. 

Several cohort studies have been performed in which the relationships between flavonoid intake and the risk of coronary heart disease have been investigated. The studies have shown that the mortality from coronary heart diseases (CHD) is inversely correlated with the intake of flavonoids in the diet. Hollman and Katan (1998) summarize that in three out of five cohort studies, in addition to one cross-cultural study, flavonoids from the flavonol and flavone subgroups demonstrated a protective role toward cardiovascular disease. The protective effect of the flavonoids is partly explained by the inhibition of LDL oxidation and by reduced platelet aggregability. As reviewed by Cook and Samman (1996), there are several possible routes as to how LDL is oxidized by free radicals generated in the cells and how the oxidized LDL initiates and promotes atherosclerosis in the human body. 

To summarise, from the available epidemiological studies, 3 out of 5 indicate the protective role of flavonoids, one shows that there is no association, and one indicates a positive association of flavonoid intake with the development of coronary heart disease. These results show that the evidence obtained is not conclusive and that more studies need to be carried out. 

Flavonoids are one of the largest groups of phenolic natural compounds. They often occur in plants as O-glycosides. Epidemiological studies indicate that daily flavonoid intake in vegetables and fruits has a protective effect against cancer and coronary heart disease. 

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