Coronary Heart Disease, A Self Inflicted Condition ?

Cigarette smoke is a major factor in many cases of CHD. Smoking increases risk in two ways.

- Carbon monoxide absorbed through the lungs reduces the amount of oxygen the blood can carry. By binding with the haemoglobin in red blood cells a given volume in blood is able to carry less oxygen. Therefore more blood is required to supply the heart which clogged arteries may not be able to provide.

- Carbon monoxide makes the blood sticky and more likely to clot causing heart attack. Again diseased arteries are narrowed and more susceptible to blocking by blood clots.

Although addictive, smoking is best classified as a self inflicted risk.

Diet is another important factor in CHD. Places such as Italy or Spain have a low rate of CHD attributed to a diet low in saturated fats, whilst other countries that eat a diet high in animal fats generally have a high rate of CHD. The type of fat is important. Unsaturated fats such as Olive Oil are thought to pose a lower risk of CHD than saturated/animal fats such as lard or dairy produce.

The problem with saturated fat is that it is used by the body to make cholesterol. This is the source of most cholesterol in the body - only a small percentage is eaten directly through the diet. Therefore it is not cholesterol in food but saturated fats that are implicated in CHD.

Bad cholesterol is Low Density Lipoprotein Cholesterol (LDL) which lays down fat in the tissues - including the coronary arteries. High Density Lipoprotein Cholesterol moves cholesterol out of the body and is considered good cholesterol. A high LDL level is a risk factor in CHD - a high HDL level is inversely correlated to CHD. Choleseterol lowering drugs are most useful when they target LDL - modern drugs such as Statins do this. However our levels of HDL and LDL are not entirely due to diet. Research suggests that we have differing genetic propensities to produce both HDL and LDL. There is a recognized medical condition called hypercholesterolemia whereby suffers produce too much LDL cholesterol. Therefore high cholesterol is not entirely due to behavioural choices and so is not entirely a self inflicted risk.

Other lipids - triglycerides - are another risk factor in CHD. Triglycerides are also linked to a high fat diet. Again they are linked primarily to a diet high in saturated fats.

Research suggests that some foods are protective. Red wine, fruit, vegetables, high fibre, oats and other foodstuffs are considered to be functional foods. Research is ongoing as to how these foods protect against CHD. Currently the evidence is largely epidemiological - a correlation has been found but there is no absolutely accepted explanation as to what mechanism is at work.

Other relevant factors are diabetes and high blood pressure. Both of these can be due to genetic susceptibility - but can also be due to lifestyle. It depends on the individual case whether these factors are self inflicted or not. High blood pressure causes the arteries to thicken narrowing the lumen and restricting blood flow.

Gender is important. Pre menopausal women are protected by oestrogen - after the menopause their risk of CHD is equivalent to that of men. HRT is one way of maintaining this protective effect. You can speculate on the effect of feeding men oestrogen, perhaps it would offer a similar effect, though as a female hormone it might have unwanted side effects.

Overall then CHD is sometimes self inflicted by lifestyle choices, and sometimes inherited through genetic susceptibility. It is generally going to be impossible to say it is entirely one or the other. In all cases it makes sense to make good lifestyle choices. Tests for those at particular risk would allow people that are to make more extreme lifestyle choices in order to protect themselves. It would also allow protective medical intervention at an early stage.

Bibliography

* British Heart Foundation, URL http://www.bhf.org.uk/hearthealth/index.asp, accessed March 25th 2003.

* British Heart Foundation (January 2002) Coronary Heart Disease Statistics:British Heart Foundation Statistics Database 2002, URL http://www.dphpc.ox.ac.uk/bhfhprg/stats/2000/2002/keyfacts/index.html accessed 28th January 2003.

* Inge, Further studies in Human Biology

* Biological Sciences, Nov, 2000