Dr Keith Souter writes: Last week I talked about adding prunes to the diet to help reduce the risk of osteoporosis. This was in addition to the usual advice we give about taking a calcium and vitamin D rich diet. This week I want to look at cholesterol and diet, focusing on the vegetable content of the diet rather than on just reducing animal fat, which of course is the main thing. It is well established that a high cholesterol level in the blood can increase the risk of heart disease and stroke. It is not just the level of cholesterol that matters, however, but the relative balance between good cholesterol and bad cholesterol. Cholesterol is carried around the bloodstream in packets called lipoproteins. There are two types of lipoprotein, which carry your cholesterol - low density lipoprotein or LDL, the bad cholesterol, and high density lipoprotein or HDL, or good cholesterol. The problem with too much bad cholesterol is that it tends to build up in your artery walls. Imagine that the lining of an artery is like a sponge with lots of small holes in it. Think of the LDL cholesterol as being like a small ball, about the size of the holes in the sponge. By contrast HDL cholesterol is like a much bigger ball, much larger than the holes. So, if you have blood carrying a mixture of both types of ball a large proportion of the small balls will lodge in the holes. The larger ones will just bounce off and carry on their way. If you have too much bad cholesterol then you will fill up all those holes and damage the arteries. Researchers from Canada examined 26 studies of cholesterol and dietary habits. In particular, they found that one daily helping of legumes, which is about three quarters of a cup, was linked to a reduction of bad cholesterol, by five per cent. That equates to a five per cent reduction in the risk of heart disease. Legumes include beans, peas, chickpeas and lentils. They suggest that a convenient way of adding them to the diet is by eating hummus, and adding beans to salads, pasta dishes and soups. Lentil soup is brilliant and easy to make, to the lentils just add stock, vegetables and herbs.