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How it works: possible mechanisms underlying the beneficial effects of alcohol

In the other articles here, we’ve seen that alcohol has a number of beneficial effects on health. Most importantly, drinking decreases the risk of cardiovascular disease (in particular coronary heart disease). How does it have this effect? This is one of the key unanswered questions in research on the health effects of alcohol, and is currently a key area of research. There are no clear-cut answers yet, but there are three potential mechanisms that have been identified.

Time for some biochemistry. There are some bad molecules circulating in the body called free radicals. These cause oxidative damage to the sort of cholesterol known as low density lipoproteins (LDLs), making them more likely to damage the walls of arteries -- and it is this atherosclerotic damage that increases the probability of heart attacks. Red wine contains compounds called polyphenols, which have antioxidant activity. That is, when you put them in a test-tube (in vitro), they have antioxidant activity: as yet, no one has been able to show that the antioxidants in red wines work in the body (in vivo), despite many attempts. But the antioxidant hypothesis is immensely attractive and intuitive, and has received a lot of publicity because of this. It is quite possible that the dominant pro-oxidant effect of alcohol itself may outweigh the potential benefits of any antioxidants that wine contains. In addition, several studies comparing the health effects of different alcoholic drinks have shown that beer and white wine, which lack the antioxidants that red wines possess, have the same beneficial effects.

Blood lipid fractions
This is currently the most likely looking mechanism for the alcohol's positive effect on cardiovascular disease. It's a story of two different sorts of cholesterol, low density lipoprotein (LDL) and high density lipoprotein (LDL). LDL is the bad guy: it's the lipid that, when oxidised, plays a potent role in atherosclerosis, which leads to heart disease. Alcohol itself, rather than any particular component of it has been shown to cause elevated levels of the good cholesterol, HDL, compared with LDL. Exactly how alcohol has this effect is not known, but it seems to be quite a robust finding.

Platelets are small cells that circulate in the bloodstream that play a vital role in initiating the process of blood clotting. The control of blood clotting is crucial, and our bodies have to maintain a delicate balance. If you cut yourself, clotting must take place rapidly, or you will lose a lot of blood from the damaged vessels. However, if the clotting process is initiated inappropriately, the consequences can be equally disastrous. Some studies have suggested that alcohol has the effect of increasing bleeding time and reducing clotting, possibly by reducing the stickiness of platelets. The jury is still out on this one.

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