Most people tend to blame high cholesterol levels on diet. However, some cultural groups have a relatively high dietary intake of cholesterol yet have a surprisingly low incidence of heart disease. The French are a good example. They have a high intake of cholesterol in their normal diet and a low heart disease rate. This has been termed the French paradox and suggests that there are other factors involved. Some researchers believe that the French paradox is due to the high levels of antioxidants normally found in the French diet. This is supported by a study in the United States that demonstrated that the consumption of 100mg per day of vitamin E reduced the risk of heart attack by approximately 50%.
In countries such as Australia, a diet that is high in cholesterol usually contains lots of processed foods, fatty meats and dairy food and relatively low amounts of fresh fruit and vegetables. This is significant because this type of diet is usually low in antioxidants, vitamin C and dietary fibre.
Cholesterol that is damaged by free radicals (oxidised) is more likely to form plaques on the artery walls. Cholesterol can be oxidised prior to consumption in the cooking process, or if the body's antioxidant protection is low in the blood itself.
The body's own production of LDL is increased with vitamin C deficiency. This happens because vitamin C is required to produce strong artery walls. Deficiency leads to damage to the walls and the cholesterol plaque act a little bit like a bandaid, stopping blood leaking into surrounding tissues. If the vitamin C deficiency is prolonged, significant blockage of the arteries can develop. Dietary fibre protects against high cholesterol by increasing its removal from the body. The cholesterol binds to the fibre in the gut and is excreted in the stool.
Dietary fibre is also fermented in the large intestine and one of the products produced inhibits the production of cholesterol in the liver. Lifestyle choices such as smoking and inactivity can also contribute to high cholesterol levels.