If you already have heart disease and you eat a Mediterranean diet, there's a good chance that your cholesterol level will fall. You are also likely to reduce your risk of having a heart attack or a stroke.

The Mediterranean diet is what people in countries like Greece and Italy traditionally eat. They use few saturated fats but use olive oil, which is a monounsaturated fat. If you don't like olive oil, you can try canola margarine. Canola is also a monounsaturated fat.

In one study that tested the benefits of a Mediterranean diet, patients were given canola margarine to use instead of butter.

If you want to follow a Mediterranean diet you should:

• Eat more bread
• Eat more root vegetables and green vegetables
• Eat more oily fish (such as mackerel, tuna, anchovies, and salmon)
• Eat less meat
• Eat some fruit every day<
• Replace all butter, cream, and other fats with olive oil (or canola margarine).

If you have heart disease and switch to a Mediterranean diet, you're 70 percent less likely to die from heart disease. But more research is needed.

The Mediterranean diet is rich in a type of fat called alpha-linolenic acid.

This fat is part of the family of polyunsaturated fatty acids known as omega-3 fatty acids. It's found in walnuts, walnut oil, pumpkin seeds, canola oil, linseed oil, salmon, mackerel, and a green vegetable called purslane.

In your body, alpha-linolenic acid is turned into the fats that are found in oily fish (called eicosapentaenoic acid and docosahexaenoic acid). These can protect you against heart disease. They do this by making your blood less sticky so that it is less likely to form blood clots that can block blood vessels and eventually lead to a heart attack or a stroke.

One study found a strong link between the level of these helpful lipids in the blood and the risk of having a heart attack. In this study the risk of having a heart attack fell by 70 percent among people who spent just over two years on the diet. During the same time, the levels of this helpful lipid rose by 68 percent.

The researchers who carried out the study pointed out that in Japan and Crete (part of Greece), people eat a lot of alpha-linolenic acid. And these two places have the lowest rate of deaths from heart disease in the world.

The researchers suggest that alpha-linolenic acid may help keep blood from clotting when you don't need it to. If blood clots form when a vessel isn't cut or damaged, the clots can block your blood vessels.

This makes it more likely that you will have a heart attack or a stroke. Alpha-linolenic acid may also stop the heart from beating irregularly (or developing what doctors call an arrhythmia). Irregular heartbeats can sometimes cause someone to die suddenly from a heart attack. This acid can also reduce blood pressure. Having high blood pressure increases your risk of heart disease.

To learn more about what causes strokes, see What is a stroke?

There is no evidence that eating a Mediterranean diet is harmful.