The idea that moderate consumption of alcohol (say, one to three glasses a day) helps protect us from heart disease isn't exactly new. Far more surprising is the claim that red wine in particular offers additional protection. Recent research goes one stage further, focusing on precisely which types of red wine to drink for maximum benefit to health. The results are published in The Save Your Heart Wine Guide (Headline pounds 6.99) whose author, Welsh-Canadian journalist Frank Jones, concludes that Pinot Noir is best, or failing that Merlot, Gamay, Shiraz, Syrah, Zinfandel or Pinotage. So much the better if the wine is fairly young, grown in a cool climate, with not too much wood ageing.
Most scientists in the field would probably accuse Jones of jumping the gun. His league table for heart-friendly wines is based on varying levels in red wines of one natural constituent, resveratrol - a phenolic compound often found in grape skins. Medical researchers are currently divided over the relative importance of this and another phenolic compound, quercetin, and a few other compounds are also under the microscope.
Some epidemiologists remain sceptical about the entire red-wine-is-best theory. Most of the earlier work done on alcohol and the heart did not differentiate between wine and other drinks, never mind colours of wine, and failed to take into account other dietary factors. But according to Dr Serge Renaud, "The two main papers on the separate effects of wine compared with beer or spirits both show wine to be superior. We need just one or two more papers to convince the world."
One of those will be his own, due out shortly. His team in Bordeaux studied 37,000 Frenchmen over a 12-year period. "This study convinced me," he says, "that red wine is more effective in protecting against heart disease than any other beverage."
What exactly is it in red wine that performs this feat, and how? Attention closed in some time ago on the phenolics, a group of 50 or so compounds in wine, including the tannin and red colouring matter. Red wines contain these at uniquely high levels compared with other foods and drinks, and the fact that they are dissolved in the wine's alcohol probably makes them more easily absorbable. They are far more prolific in red wines than in whites, because the phenolic-rich skins and pips have been left in the juice to release colour and tannin. Theories about their effect on the blood have been proved on animals, on human blood in test tubes, and on small groups of human guinea-pigs.
Research has tended to concentrate on resveratrol because it had an ancient track record. In China, Japan and Korea, it has been prescribed for centuries, extracted from Japanese knot weed and certain lilies. Here, other than in red wine, it is found in almost nothing else we eat or drink, except peanuts. Resveratrol is a natural fungicide, produced automatically by grape vines when they feel threatened by mould. Since the grape skins are the front line of attack for vineyard moulds, that's where the compound concentrates. So it makes sense that resveratrol should be found in red wines, made red by maceration of their skins in the fermenting juice, but very little in whites, generally made from juice pressed quickly out of the bitter skins.
Resveratrol appears to act in the blood and arteries in the same two ways as alcohol, with an added bonus. Half alcohol's (and part of resveratrol's) benefit to the circulatory system comes from its ability to rid the blood of unwanted cholesterol. Cholesterol is not all bad. It's a soft, fatty substance that forms part of our cells and to a certain extent is necessary for life. Because it's fatty, it can't dissolve in blood and needs to be carried around by something else. Lipoproteins are its means of transport. Low-density lipoproteins (LDLs) deliver cholesterol to the cells, and high-density lipoproteins (HDLs) carry any excess back to the liver for safe disposal. If, however, there are too many LDLs and too few HDLs, surplus cholesterol gets deposited on or in the artery walls. The walls become pitted, and the blood channel narrows. What moderate alcohol consumption does is to boost HDL levels by about 15 per cent, so helping to keep the artery walls clear. Resveratrol appears to do the same, adding its own (as yet uncalculated) percentage of extra HDL to that already provided by the alcohol in red wine.
The other trick performed by alcohol (and resveratrol) is to make the blood less likely to form dangerous, heart-stopping clots. Both alcohol and resveratrol affect the platelets, tiny discs in the blood that staunch the flow when we cut ourselves. Normally, when LDLs cause serious damage in a particular spot on an artery wall, the platelets link together to form a protective net around the wound, oozing a clotting agent. If the clot bungs up narrowed arteries, enter heart attack. Regular, moderate amounts of alcohol, however, make the platelets less "sticky", so less able to form a clot. (Aspirin and moderate amounts of alcohol work together to give even more protection.)
But binge drinkers beware: about 18 hours after a heavy drinking session, the stickiness of the platelets actually increases, which means increased risk of thrombosis or stroke. But even for Saturday-night drinkers, red wine is still a shining knight, according to Serge Renaud, who published his work on "alcohol withdrawal rebound effect" after Jones's book came out. Renaud's experiments on rats showed that, while those that had been fed a pure alcohol solution suffered a surge in platelet aggregation 18 hours after drinking, rats that drank red wine showed no increase. Those that drank white wine fell in between.
Resveratrol also has a third property - it works as an antioxidant. Medical science is becoming increasingly excited about the use of antioxidants to mop up "free radicals". These are highly unstable and damaging atoms and chemical groups that can oxidise our body tissues, sometimes causing cancer, or damaging the arteries. Our bodies produce free radicals in reaction to various things, including radiation, smoke or exhaust fumes, poison or disease, metals, or lack of oxygen.
LDL is one of the free radicals' targets. "On their own, LDL particles are fairly benign," says Jones. "It's only after being attacked by free radicals that they turn into dangerous and aggressive cells, capable of penetrating and injuring the smooth walls of arteries. Oxidised LDL is taken up by the cells at 20 times the rate of ordinary LDL. Fatty streaks form within the walls, calcium accumulates (hence the 'hardening' of the arteries), inflammation occurs and scar tissue forms."
Our bodies contain their own natural antioxidants, but these don't always suffice, and there is now much evidence that antioxidants in our diet, or in pill form, can protect us from disease. Tea, onions, leeks, garlic and apples have been shown to be particularly good news. Vitamins C and E and beta-carotene are prescribed as antioxidant supplements. But according to researchers at the University of California at Davis, the antioxidants in red wine are 10-20 per cent more effective than vitamin E. Two glasses of red wine a day, says Jones, will enhance the antioxidant content of the average diet by 40 per cent. Binge drinkers beware again, however. According to Bruce German, associate professor of food sciences at Davis, "if you do all your drinking on Saturday night instead of spreading it over the week, it probably means you are without the antioxidant protection 80 per cent of the time."
Resveratrol is quite good as an antioxidant, but some other phenols found in red wine, quercetin, catechins and and epicatechins, appear to be more interesting in this respect. Since resveratrol is formed as a response to mould, its levels tend to be higher in grapes from cooler, damper places. Claret contains far more, for example, than California Cabernet. Quercetin (also abundant in garlic, onions and leeks) is a sun-lover, found in significant quantities in grape skins of any variety from all sunny vineyards. Like resveratrol, it can reduce blood clotting, though not as effectively. But it is a far more powerful antioxidant than resveratrol. It may be more effective in wine than in vegetables, as the alcohol may facilitate its absorption by the blood. Unlike resveratrol, it does not disappear as wine ages. A few other phenolic compounds are being investigated, though they are probably less important. Most of the available analyses relate to resveratrol, however, and according to Jones, wines with lots of resveratrol also tend to have high levels of quercetin and catechins.
Wine buffs will notice that Jones is not one. He occasionally gets his wine facts wrong, or fails to draw obvious conclusions. His country-by- country resveratrol trawl is fascinating, nevertheless. Red Burgundy, he says, is "unbeatable". It is made with Pinot Noir, best-scoring grape for resveratrol, in a damp, mould-prone climate. Interestingly, it's the cheaper, simple Bourgognes rouges that score best. Some resveratrol is lost during barrel- ageing, and some more during long bottle-ageing. Fine Burgundy will be both barrel- and bottle- aged. Burgundy is not unbeatable, though. Jones later quotes higher resveratrol figures for Swiss Pinot Noir, and reds from Alsace and Sancerre (both made from Pinot Noir in cooler climates than Burgundy). Pinot Noirs from Germany and New Zealand must logically be high in resveratrol, too, though not analysed in the book.
Beaujolais (made from Gamay) has a lot, though not the quickly fermented Beaujolais Nouveau, says Jones. He recommends regular Beaujolais or Beaujolais Superieur because the skins stay in longer during fermentation; he might also have mentioned the Beaujolais crus (Fleurie, Morgon and the like), probably even better for the same reason. Bordeaux clarets all have high levels, and Rhones score nearly as well. Few data exist for Spain, Italy and Portugal. You may be better off in these countries, he says, with wines made from the Merlot grape (high in resveratrol), and Chianti may be better than Barolo or Valpolicella. He wrote before the l995 vintage - Italy's coolest, wettest and mouldiest for decades. And in any vintage it would be interesting to analyse reds from the cool areas of northern Italy - the Alto Adige/Sudtirol or Trentino. Outside Europe, cool New Zealand did well with all its reds, and Pinot Noir from Oregon in the cool North-West of the USA had levels approaching those of Burgundy, as well as very high levels of all the other useful phenols. Hotter places tended to score badly. Everywhere, however, resveratrol values vary from one vineyard or vintage to the next, so the best policy, says Jones, is to drink a variety - from the point of view of pleasure, as well as maintenance of the heart.
Jones quotes various medical researchers who insist that red wine is not a substitute for a good diet and exercise. You need those as well, and if you smoke, there is nothing you can do to get the risk down to that of a non-smoker. But those of us who are most at risk of heart disease - men from the age of around 30, women from menopause onwards - might do well to invest in a copy of this book and reach for our corkscrews. !Reuse content