It never ceases to amaze me just how confusing medical research can be. So often, the outpourings of the scientific community seem to be in conflict. The contradictory side of science was very much in evidence recently within the pages of a single edition of the British Medical Journal . While one study claimed to provide evidence to support the increasingly popular practice of using aspirin to ward off heart attacks and strokes, another was strongly critical of it. The author of the latter article, Professor John Cleland from the University of Hull, claimed that rather than actually preventing heart attacks and strokes, aspirin may merely mask their symptoms and make them harder to detect. The debate about the pros and cons of aspirin is likely to rage on for some time, but the evidence supporting its use as a disease-protector does seem to have been dealt a bit of a body blow.

While the doctors and scientists slug this one out, there is perhaps sense in seeking a viable aspirin alternative. For me, a serious contender has to be garlic. For thousands of years, this herb has been thought to promote the health of the heart and circulation, and garlic supplements enjoy a perennial popularity. There is also now a wealth of scientific evidence showing that garlic has a range of health-giving properties that might help keep heart attacks and strokes at bay.

The terms 'heart attack' and 'stroke' refer to death in part of the heart muscle and brain respectively. The majority of these events are related to the formation of small blood clots called thrombi, which can plug an artery and block vital blood flow. Thrombi are formed from clumps of tiny blood components called platelets. One of aspirin's effects in the body is to reduce the tendency of platelets to stick together, and it is this action which is believed to be behind its supposed ability to reduce the risk of heart attack and stroke.

But studies show that, just like aspirin, garlic reduces the tendency for platelets to gang up and form thrombi. Even a single dose of garlic appears to have blood-thinning potential. What's more, garlic has also been shown to have what is known as fibrinolytic activity, which means it helps to dissolve thrombi and other unwanted clots in the body. The ability to both prevent and dissolve artery-plugging thrombi suggests that garlic offers real potential to protect against heart attacks and strokes.

And the beneficial effects of garlic on the circulation do not end there. A review of several trials in the Journal of Hypertension concluded that garlic can bring about small but significant reductions in blood pressure. Another study found that long-term supplementation reduced the risk of unhealthy stiffening in the body's main artery (the aorta). Some research shows that garlic can also lower cholesterol levels. While not all the scientific evidence supports this, two meta-analyses (a meta-analysis combines the results of several studies) have found that garlic can reduce cholesterol by an impressive 10 per cent.

The vast majority of studies into the beneficial effects of garlic have used supplements, most of which were based on dried garlic powder. Suitable supplements (usually in tablet form) are widely available in health food stores and pharmacies. Garlic's effective dose appears to be around 800 mg per day (though larger doses appear to be necessary for cholesterol reduction). If you want to take a more natural route, then you'll need to consume the equivalent of one or two cloves of garlic a day. But be warned: many of garlic's therapeutic properties are believed to be lost during cooking, meaning that for maximum benefit, garlic needs to be taken raw.

Finally, a word of caution - while garlic does seem to have a myriad of desirable effects in the body, it does need to be handled with care. Because garlic thins the blood, it can increase bleeding tendency. For this reason, I don't recommend that it is mixed with blood-thinning drugs, such as warfarin (or aspirin for that matter). Also, anyone undergoing surgery should stop garlic 10 days before the operation, commencing again a week after the procedure. *

Dear John

I was interested to read your piece about brain function and how eating oily fish can help preserve this. However, I am a vegetarian. Is there something I could substitute for fish that might do the same job?
Mrs ME Cicolini, London

The two fats in oily fish that seem to help preserve brain function are eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), which are part of a class of fats known as the omega-3 fatty acids. EPA and DHA can be formed in the body from another omega-3 fat known as alpha-linolenic acid (ALA), which is found in foods such as flaxseeds (linseeds) and flaxseed oil, pumpkin seeds and walnuts.

However, it is known that the conversion of ALA into EPA and DHA can be somewhat sluggish, so consuming plenty of ALA may not provide all the benefits to be had from oily fish. For instance, fish oil supplementation has been shown to help in the treatment of rheumatoid arthritis and may reduce levels of unhealthy blood fats, while flaxseed oil has not been found to be of benefit here. Flaxseed oil, however, does appear to have desirable properties of its own, such as cholesterol and blood-pressure-reducing effects. Quite what the differences between eating ALA-rich foods versus oily fish mean in terms of long-term brain function is not known. However, the more ALA you consume, the greater the potential benefit to be had from both the ALA, and the EPA and DHA it may convert.

Nutrition news: Start as you mean to go on

We're always being told that breakfast is the most important meal of the day, but is it true and if so why? Well, one theory is that eating breakfast helps fuel the brain. It may only account for two or three per cent of our total body weight, but the brain soaks up a massive 20 per cent of our energy requirements. The theoretical benefits of eating breakfast do seem to translate into practise. For instance, there is evidence that those children who eat breakfast learn better than those who don't and they take less time off school. Plus, a recent study published in the American Journal of Clinical Nutrition found that getting fuel into the system first thing in the morning improved memory in older adults. So for adults and children alike, eating breakfast really does seem to be a smart move.