WHAT WE KNOW ABOUT CHOLESTEROL

Cholesterol in blood must be distinguished from cholesterol in food. There is no definite cut-off point below which no coronary heart disease occurs, but it is extremely uncommon below a blood cholesterol concentration of 4.5 millimole per litre. In Australia, it is recommended that total cholesterol in blood be below 5.5, in the USA below 5.2 and in Japan below 5.0 millimole per litre. Sometimes if the blood cholesterol level is above 5.5, it is because of an increase in 'HDL' or high density lipoprotein cholesterol, which is usually a good thing. Most of the blood cholesterol is 'LDL' or low density cholesterol, too much of which tends to deposit in tissues like the arteries.

Food factors which can increase the level of cholesterol in blood (or plasma or serum) include:

• cholesterol (which comes from animal-derived rather than plant-derived food);
• saturated fat (which comes mainly from animal sources);
• something in coffee (not caffeine) which is more evident in boiled than brewed coffee.

Food factors which can decrease the level of cholesterol in blood (or plasma or serum) include:

• polyunsaturated fats of the 'omega-6' kind (which come mainly from plant sources e.g., margarine made from safflower seeds);
• polyunsaturated fats of the 'omega-3' kind (which often have effects on different forms of cholesterol in blood, so-called 'risky' LDL or low density lipoprotein, and 'protective' HDL or high density lipoprotein, cholesterol, and which come mainly from fatty fish, but are also present in lean meat);
• monounsaturated fats (especially from olive oil and canola oil), which improve the HDL cholesterol in relation to the LDL cholesterol;
• some dietary fibre types (in oats and legumes) of the soluble kind lower risky LDL cholesterol;
• saponins (found in chick peas, alfalfa sprouts and other foods);
• allicin (in garlic).

Some foods can protect against coronary heart disease other than through their effect on blood cholesterol. For example:

• fish oil

(a) reduces the stickiness of blood due to cells known as platelets, allowing it to flow freely,
(b) reduces blood pressure,
(c) decreases likelihood of heart to develop abnormal rhythms;

• fruits and vegetables - the protective mechanisms are, however, poorly understood;
• wholegrain wheat cereals;
• a low sodium/potassium ratio (i.e., little sodium and more potassium) in the diet is likely to keep blood pressure lower;
• minimising alcohol intake can lower blood pressure and reduce risk of heart muscle damage;
• polyunsaturated fat from plant sources (such as safflower, sunflower) alters the composition of body fat stores and cell membranes and, independently of serum cholesterol, reduces risk of coronary heart diseases;
• monounsaturated fat, like that from olive oil or rapeseed (canola), is apparently protective against coronary heart disease by reducing the ratio of 'risky' LDL to 'protective' HDL cholesterol in blood. There may be little change in total blood cholesterol which includes LDL and HDL cholesterol.