Cholesterol is a substance which has some important functions in our bodies. However, in excess it can build up in the artery walls and this can lead to risk of heart attack and stroke.
There are actually two types of cholesterol in our blood: LDL-cholesterol and HDL-cholesterol.
LDL-cholesterol is sometimes described as ‘bad’ cholesterol because it is the form that becomes deposited in arteries. HDL-cholesterol, on the other hand, is described as ‘good’ cholesterol because it is destined to be eliminated from the body. Although the total level of cholesterol in our blood is an indicator of our risk for heart disease, the ratio of LDL to HDL is also important. Ideally, we should keep our total levels of cholesterol low, but within this, the proportion of HDL should be high.
We eat very little cholesterol in our diet and it does not have a significant impact on our blood cholesterol levels. However, our blood cholesterol levels are influenced by the type of fat we eat, especially our consumption of saturated and unsaturated fats.
Monounsaturated fats lower total cholesterol and LDL-cholesterol, but have no effect on HDL-cholesterol. This is ideal, because not only do they lower blood cholesterol, but they also improve the ratio between LDL and HDL.
Polyunsaturated fats lower total cholesterol and lower LDL-cholesterol, but they also lower HDL-cholesterol, so their effects are only partly beneficial.
Saturated fats are well known to raise total cholesterol and LDL-cholesterol levels and are therefore harmful if eaten to excess.