Insulin resistance, hyperinsulinemia, and cardiovascular disease. The need for novel dietary prevention strategies.

Insulin resistance associated with hyperinsulinemia (metabolic syndrome) emerged in recent years as an important health risk which is present in approximately 25% of the normal population in western industrialized societies. Insulin resistance as assessed for the whole body arises from a reduced glucose utilization of skeletal muscle. If the metabolic syndrome persists over a prolonged period of time, detrimental influences on the cardiovascular system become apparent involving diabetes mellitus, hypertension, and arteriosclerosis. Of particular pathogenic relevance is an unbalanced influence of insulin arising either from a diminished or enhanced insulin action depending on whether the various tissues of the body exhibit a reduced or unchanged insulin sensitivity. Since insulin resistance and hyperinsulinemia appear to be affected by various lifestyle factors, the unique opportunity exists of reducing cardiovascular mortality by correcting this syndrome at a time when degenerative changes have not occurred in the cardiovascular system. Of great importance is the finding that dietary factors can have a modulatory action on insulin sensitivity. In animal experiments, an increased intake of (saturated) fat and refined carbohydrates increased insulin resistance. Since psychosocial distress is expected to be associated with a sustained activation of the sympathoadrenal axis, it is likely also to aggravate the metabolic syndrome. A factor with a beneficial action appears to be physical exercise. In view of the high incidence of cardiovascular diseases, further research on lifestyle factors with an insulin-sensitizing or insulin-desensitizing action is required. Of prime importance is the reevaluation of established dietary recommendations and diets should be designed which take into account the individual cardiovascular risk factor profile.