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Wine, acting as an antioxidant, may have health benefits
Heart attacks are a real risk to persons living a westernised lifestyle and remain poorly predictable for an individual despite clear links to several risk factors. These risk factors include age, male gender, smoking, blood pressure, diabetes and cholesterol. Cholesterol, an essential component of all cells in the body, can be made in the body or assimilated from the diet. Cholesterol is nowadays divided mainly into LDL (low density lipoprotein) and HDL (high density lipoprotein). The former is predictive of atherosclerosis and the latter is protective. Inherited disorders usually give rise to blood cholesterol concentrations of greater than 7,5 mmol/l and are associated with such a high risk of heart disease that there is no debate about the need for treatment. In most other contexts, the risk factors outlined above have to be combined to express the risk of heart disease for an individual as a percentage of similar people who will have a heart attack over 10 years. In Europe and South Africa, a risk of more than 20% is taken as adequately high for the instigation of specific action. There is now clear evidence that the occurrence and recurrence of heart attacks can be reduced by both a healthy lifestyle and medication. Since medication to treat and to prevent heart disease is expensive, every person should consider taking preventive action against heart disease by adopting a healthy lifestyle as early as possible. In this context, the role that wine can play needs further exploration. Let us first examine the newer findings about fats and heart disease before looking at the evidence that alcoholic beverages can reduce heart disease and how this protective effect may be explained and possibly be exploited.
A fat or lipid is a substance that does not dissolve in water, whether it be in the body or in foods. Two simple classes of lipids are important for the function of the body: cholesterol and fatty acids. Most people would have been exposed to the importance of cholesterol in the blood and will appreciate that the blood cholesterol is related to inherited factors and dietary intake of cholesterol. Blood cholesterol concentrations between 5 and 7,5 mmol/l pose an increasing risk of heart disease and concentrations that are higher than 7,5 mmol/l are indicative of high risk.
Fatty acids are the building blocks for triglycerides (3 fatty acids added to a glycerol molecule) and phospholipids (2 fatty acids added to a glycerol molecule together with a phosphorus atom and another extension). Triglycerides represent a way of storing energy and form the bulk of the visible lipids in food, being either solid (e g beef tallow) or liquid (e g sunflower oil) and phospholipids are integral components of cell membranes. Saturated fatty acids, found mainly in mammals, have single chemical bonds between all of their carbon atoms (usually 14 to 18) while unsaturated fatty acids will have at least one double chemical bond. Unsaturated fatty acids are classified into mono-unsaturated (1 double bond) or poly-unsaturated (2 or more double bonds). The unsaturated fatty acids are found mainly in plants, fish and birds. Some of the poly-unsaturated fatty acids are termed essential fatty acids as they cannot be synthesised in mammals. Unsaturated fatty acids can be damaged in reactions involving oxyen, especially if they are poly-unsaturated, in a process which is termed lipid peroxidation. The complex chemistry can be summarised as progressing from the native unsaturated fatty acid through a conjugated diene, a lipid hydroperoxide and then a fragmentation of the fatty acid into reactive aldehydes. Lipid peroxidation can be reduced by antioxidants and can be accelerated by heat and metals. The blood levels of triglycerides are measured in clinical practice but phospholipids, being mostly in cells, are usually not measured in the blood. The lipid peroxides, though present in the blood at very low levels, are not routinely measured and are probably more important in the tissues. Some of the lipid peroxidation products have been linked with atherosclerosis.
The enthusiasm for a reduction in heart disease was rekindled in 1992 when Renaud found that, when comparing death rates from heart disease between different populations, the French had a lower than expected rate compared with other European countries for the same blood cholesterol. Although it was known that alcohol could increase the protective HDL cholesterol, this appeared not to be the case in Renaud’s study. It was speculated that the benefit might have come from a reduced tendency for platelets to clot, or from a protection against oxidation of lipids. Gaziano reported in a smaller and later in a larger study that regular modest consumption of alcoholic beverages was associated with a lower risk of heart disease in the USA but an association is not proof of a benefit, especially if the potential mechanism(s) by which such a benefit could accrue was not understood. Subsequent to the French Paradox of Renaud, it became clear that the difference in heart disease in Europe was related to differences in definition of heart disease. Research into potential beneficial effects of alcoholic beverages had however started and showed some interesting observations.
Wine contains "phenols" that have antioxidant properties by acting as chelators of metals and more directly as antioxidants. Red wines contain about 1 mg/ml, about 20-fold more than white wines. Broadly, these phenols can be divided into non-flavonoids and flavonoids. Flavonoids come from grape skins, seeds and stems and include flavonols, anthocyanins, catechins and tannins. In animals, it has been established that procyanidins are present in the circulation after feeding alcoholic beverages and that these substances can reduce the oxidation in LDL when added to plasma.
Although there appears to be an association of improved health with moderate wine consumption, much more research still has to be done to investigate the mechanisms by which wine may influence health.
References
Soleas G J, Diamandis E P, Goldberg D M. J Clin Lab Anal 1997;11:287-313. Wine as a biological fluid: history, production, and role in disease prevention.
Baraona E, Lieber C S. Alcohol. Chapter 58, 1011-1036. Lipoproteins in Health and Disease. Betteridge D J, Illingworth R I, Shepherd J. 1999. Arnold Press.
Renaud S, De Lorgeril M. Lancet 1992;339:1523-1526. Wine, alcohol, platelets and the French Paradox for coronary heart disease.
Gaziano J M, et al. N Engl J Med 1993;329:1829-1834. Moderate alcohol intake, increased levels of HDL and its subfractions, and decreased risk of myocardial infarction.
Gaziano J M, et al. J Am Coll Cardiol 2000;35:96-105. Light to moderate alcohol consumption and mortality in the Physicians Health Study Enrollment Cohort.
Miyagi Y, Miwa K. Am J Cardiol 1997;80: 1627-1631. Inhibition of human LDL oxidation by flavonoids in red wine and grape juice.
Yamakoshi J, et al. Atherosclerosis 1999;139-149. Pro-anthocyanidin-rich extract from grape seeds attenuates the development of aortic atherosclerosis in cholesterol-fed rabbits.
Yamakoshi J, et al. Atherosclerosis 1999;142:139-149.
Mazur A, et al. Atherosclerosis 1999;145;421-422.
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Right: Dee Blackhurst and David Marais from the University of Cape Town Medical School, examining an oil due to be heated with red wine. The research project is funded by Winetech.
Right: The thiobarbituric acid reactive substances (TBARS) assay that is used to demonstrate reactive aldehydes from heated oil (red colour on the right).
Right: Antioxidant effect of red wine on heated sunflower oil.
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