Information about cholesterol’s purpose, and the – not so proven – link with coronary heart disease.
Isolated cholesterol is a waxy substance, insoluble in water; and it is therefore classified as a lipid.
Contrary what you may hear in the media, cholesterol has several essential and positive functions in the body:
- Cholesterol is used in the structuring of cell membranes:
Cholesterol gets integrated into the cell membrane to make it stiffer when a diet high in unsaturated fats softens the membrane; - Cholesterol is a precursor for the making of steroid hormones:
The sex hormones estrogen, progesterone, and testosterone are synthesized from cholesterol; also the adrenal corticosteroid hormones (stress hormones); - Cholesterol is a starting substance for the making of vitamin D:
You also need the UV-B from sunshine (dietary vitamin D comes from animal sources also high in cholesterol); - Cholesterol is part of the bile production:
Bile acids are derived from cholesterol. The digestive purpose of bile is to emulgate fatty acids so they can be digested by enzymes. The body can get rid of excess cholesterol in the form of bile salts through the intestines, as long as the diet contains enough fibre and the bowel movement is regular enough, to avoid re-absorption in the intestines.
Cholesterol does not need to be ingested with food: the body produces its own cholesterol from the metabolic products of carbohydrates or fatty acids.
On average a person’s body has about 150 g of cholesterol stored in the cells and organs. Only about 7 g is circulated in the blood. The daily turnover in cholesterol is just over 1 g – depending on diet and body weight.
Plant food does not contain cholesterol. All cholesterol in the diet comes from animal sources. About half of the dietary cholesterol gets absorbed.
Even on a diet containing cholesterol, about two thirds of people can regulate their cholesterol levels automatically.
A diet high in carbohydrates, particular simple carbohydrates, and saturated fatty acids, can increase the amount of cholesterol in the blood. Alcohol and stress can have the same effect.
However, most people are able to regulate the amount of cholesterol in their blood naturally through dietary changes.
Why then is cholesterol considered bad?
Cholesterol has been linked with atherosclerosis and cardio vascular disease (CVD). In the search for the causes of heart disease, some studies found a correlation of higher levels of cholesterol in the blood and higher occurrence of heart disease (for example: Framingham Heart Study). Cholesterol was found in the plague layers that restrict arteries in people with atherosclerosis or CVD.
Later it was found that the total cholesterol is less important, and that the level of cholesterol carried in low density lipoproteins gives a better correlation with CVD.
(Cholesterol in the blood is transported in so called lipoproteins. Lipoproteins are combinations of fat and proteins that keep the insoluble cholesterol transportable in the blood stream.
Three types of lipoproteins are distinguished:
- HDL – high-density lipoprotein, containing little amounts of cholesterol, surrounded by proteins;
- LDL – low-density lipoprotein, containing high amounts of cholesterol, surrounded by proteins;
- VLDL – very low density lipoprotein, mostly containing triglycerides.)
Higher levels of HDL are considered rather protective, because HDL has the ability to take up cholesterol from the blood or from plaque.
Although other studies did not reproduce – or did even contradict – these findings, a whole industry was generated inventing cholesterol reducing pharmaceuticals, and advertising ‘cholesterol free’ foods, and food groups that claim to reduce cholesterol levels.
As the studies continue, more recently, newer findings make the levels of oxidised cholesterol or the level of triglycerides in the blood responsible for CVD.
Yet, there seems to be no direct causal link proven between cholesterol and CVD. Most studies, if at all, state that there is a higher risk of CVD in some people who also have higher levels of cholesterol. These people often have other risk factor, as stress, high blood pressure, smoking, obesity, sedentary lifestyle, and a high dietary intake of refined carbohydrates and saturated fats.
Just recently, a study contradicted the myth, that eggs and particularly egg yolks raise chlesterol levels. You might have heard the advertising slogan of the egg industry: “An egg per day is OK”.
Generally, dietary changes which lower cholesterol levels also lower the risk of CVD.
Eating more fruits and vegetables (i.e. fibre) in the diet, and less sugar and saturated fats, together with more exercise, is a healthy way to reduce cholesterol and the risk of CVD.
Foods that particularly good help to lower cholesterol include oats, walnuts, almonds, avocado, oily fish, fruit, vegetables, garlic, onions, blueberries, and other foods high in antioxidants.
bookmark this post
