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Q J Med 2001; 94: 174-175
© 2001 Association of Physicians
Correspondence |
The Mediterranean diet revisited
The George Washington University, Washington, DC, USA
Sir,
Despite a high level of risk factors such as elevated serum cholesterol level, diabetes, hypertension and a high intake of saturated fat, French males display the lowest mortality rate from coronary heart disease and cardiovascular diseases in Western industrialized nations (36% lower than the USA and 39% lower than the UK).1 It has been suggested that regular consumption of red wine may explain this phenomenon, which has been dubbed the ‘French paradox’,2 i.e. the coexistence of a high-fat diet and a low incidence of coronary artery disease. Of course, as was pointed out by Yarnell and Evans in their recent editorial,3 France is not alone and other southern European countries show this ‘paradox’ too.
Although the cardioprotective effects of most alcoholic beverages are probably due to an elevation of high-density lipoprotein as well as the ability of alcohol to prevent platelet aggregation and increased fibrinolysis, there is an increased favourable effect of red wine.4 The unique cardioprotective properties of red wine reside in the action of flavonoids, which are absent in white wine (with the exception of champagne) and sparse in beer (with the exception of dark beers).4,5 Tea, especially Chinese green tea, is also rich in flavonoids and thus cardioprotective.6–8 The best research flavonoids are resveratrol and quercetin, which confer antioxidant properties more potent than alpha-tocopherol.4
Resveratrol (3,4',5 trihydroxystilbene) is a naturally occurring phytoalexin produced by some spermatophytes, such as grapevines, in response to injury.9 Given that it is present in grape berry skin but not in flesh,9,10 white wine contains very small amounts of resveratrol, compared to red wine. As phenolic compound, resveratrol contributes to the antioxidant potential of red wine, and thereby may play a role in the prevention of cardiovascular diseases. Moreover, as a phytoestrogen, resveratrol may provide additional cardiovascular protection.
Recent studies suggest that high plasma homocysteine concentrations are an independent risk factor for coronary artery disease.11–17 One of several routes for metabolism of homocysteine involves methylation using betaine as the methyl donor. Betaine is often added to less expensive wine when beet sugar is used to increase alcohol content.18 Many commercial wines contain betaine; an average glass of wine contains approximately 3 mg betaine.18 This small amount is less than the dose used to lower homocysteine in patients with genetic forms of hyperhomocysteinemia, but it is possible that humans with modest elevations of homocysteine would be influenced by this dose.18
Finally, Blanco-Colio et al.19 came up with another new potential mechanism to explain the beneficial effects of red wine in the reduction of cardiovascular mortality. They found that red wine intake, but not another form of alcohol beverage intake (vodka), prevented NF-
B activation in peripheral blood mononuclear cells elicited in healthy volunteers by postprandial lipidaemia. Because NF-B activation is involved in the pathogenesis of atherosclerotic lesions, the inhibitory effect of red wine on NF-B activation provides a further explanation of the beneficial effects of red wine intake in cardiovascular disease.
References
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3.
Yarnell JWG, Evans AE. The Mediterranean diet revisited—towards resolving the (French) paradox. Q J Med2000; 93:783–5.
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6.
Cheng TO. Antioxidants in Chinese green tea. J Am Coll Cardiol1998; 31:1214.
7. Cheng TO. Antioxidants in wine and tea. J Roy Soc Med1999; 92:157.
8. Cheng TO. Tea is good for the heart. Arch Intern Med2001; 160:2397.
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11.
Cheng TO. Hyperhomocysteinaemia. Postgrad Med J1997; 73:606–7.
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14.
Cheng TO. Hyperhomocysteinaemia and the heart. Q J Med1996; 89:877–8.
15. Cheng TO. Homocysteinaemia and coronary atherosclerosis. Heart1997; 77:390–1.
16. Cheng TO. Another cause of hyperhomocysteinemia. Hosp Pract1997; 32:44.
17. Cheng TO. Hyperhomocysteinemia is a risk factor for coronary artery disease even in the presence of elevated high-density lipoprotein cholesterol. Am J Cardiol1997; 80:683.
18. Mar MH, Zeisel SH. Betaine in wine: answer to the French paradox? Med Hypotheses1999; 53:383–5.[Web of Science][Medline]
19.
Blanco-Colio LM, Valderrama M, Alvarez-Sala LA, Bustos C, Ortego M, Hernández-Presa MA, Cancelas P, Gómez-Gerique J, Millán J, Egido J. Red wine intake prevents nuclear factor-B activation in peripheral blood mononuclear cells of healthy volunteers during postprandial lipemia. Circulation2000; 102:1020–6.
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