Our bodies need cholesterol- Cholesterol is present in the cell membrane and acts as insulation, protecting against cell damage. Cholesterol is also an essential component of hormones such as sex hormones, the brain and the nervous system. It is a form of fat that is synthesised by all cells within the body, a component which is required for normal physiological function.
But too much can be a health risk- The human body produces sufficient concentrations of cholesterol for its needs and does not require exogenous cholesterol through our diet. In fact a high level of blood cholesterol is a risk factor for the development of heart attack and stroke.
‘Good’ and ‘Bad’ Cholesterol - High density lipoprotein (HDL) also called “Good” cholesterol protects arteries from clogging. Low density lipoprotein (LDL) also known as “Bad” cholesterol occludes the arteries.
HDL carries cholesterol away from the tissues and organs and back to the liver for excretion to the bile and decreases the risk of heart attack. In contrast LDL carries cholesterol to the tissues and organs and is associated with increases in the risk of cardiovascular diseases such as heart attack. Therefore the most effective way of reducing cholesterol in the blood is to avoid food with high LDL levels.
Forms of fatty acid which tend to increase ‘bad’ cholesterol, and should therefore be avoided where possible are:
Saturated fatty acids, which are predominantly animal fats (red meat and its products such as sausages, meat pies, etc, and dairy products) with the exception of coconut and palm oils. These tend to increase LDL (bad cholesterol), so should be eaten in moderation.
Transfatty acids are present naturally in meat and dairy products. They are also generated during the process of hydrogenations when liquid oil is converted to semi-solid fat. Transfatty acids are found in abundance in biscuits, cakes, pastries, meat pies, sausages and take away foods. In the body transfatty acids act as saturated fat. These should be avoided as far as possible.
Trigycerides are fatty acid substances that are absorbed from the diet and excess calories. High level of triglycerides is considered a risk factor for cardiovascular diseases, so should also be avoided.
Forms of fatty acid which tend to lower ‘bad’ cholesterol, and should therefore be consumed where possible are:
Monounsaturated fatty acids present in plant oils (olive, rapeseed, sesame which are best for cooking), avocados and nuts. These help to lower LDL and triglyceride in the blood with no effects on HDL, so are beneficial for our health.
Polyunsaturated fatty acids, which consist of two groups of linoleic fatty acids, Omega 3 – (oily fish including tuna, sardines, herring, salmon and walnuts), and are shown to reduce the risk of cardiovascular diseases such as heart attack; and Omega-6 fatty acids present in sunflower seeds. Both are beneficial.
Putting all this information together suggests we should eat food which reduces the risk of cardiovascular disease: Almonds, walnuts, linseeds, soya beans, garlic and artichoke are all rich sources of linoleic acids that lower total blood cholesterol levels and they are also rich with vitamin E. Citrus fruit, pulses, oats, whole grains and leafy green vegetables which are high in fibre lower LDL cholesterol and blood pressure.
20 minutes of vigorous exercise is most effective in lowering LDL cholesterol when it is combined with diets which avoid saturated fatty acids (animal fat) such as cream, hard cheese, eggs and red meat.
Published 30/03/2011, Review date May 2015