A systematic examination of the evidence on the relationship between serum
cholesterol and ischaemic
heart disease shows conclusively that serum
cholesterol reduction in populations with high rates of
heart disease is an effective and safe method of reducing ischaemic
heart disease rates. The relative protective effect is greater at younger ages (50% reduction at age 40 for a 0.6 mmol/l reduction in serum
cholesterol declining to about 20% at age 70 or more). The absolute protective effect is greater if the disease is common because the effect of a give serum
cholesterol reduction is proportional to the prevailing
heart disease rate. The full effect of a serum
cholesterol reduction is evident after about 5 years. The use of drugs of the '
statin' type can lower serum
cholesterol by about 1.8 mmol/l, yielding a reduction in risk of about 60% at age 60. A diet typical in Japan would lower serum
cholesterol by about 1.2 mmol/l and lead to a halving of the risk. Only modest serum
cholesterol reductions (about 0.3 mmol/l) are generally achievable by individuals altering their diet independently of others and this is expected to lead to a 15% reduction in the risk of ischaemic
heart disease at age 60. Larger reductions (about 0.6 mmol/l) require collective action over the supply and preparation of food which could reduce the risk by about 30%. Achieving the full impact of serum
cholesterol reduction in a population will require a national nutritional policy. It is not something that can be effectively left to individual action.