Plasma and erythrocyte fatty acids: a methodology for evaluation of hypocholesterolemic dietary interventions.

A major source of concern in the management of hypercholesterolemia is the careful evaluation of adherence to dietary prescriptions. Routine analysis of plasma fatty acids to monitor adherence of hyperlipidemic outpatients to diets varied in lipid composition is a major task of our research group. Plasma fatty acid patterns are determined by gas-liquid chromatography 60 days after starting an experimental normocaloric diet with 37% fat calories and a polyunsaturated/saturated (P/S) ratio of 3.4. Where poor adherence is observed, the dietary message is administered more incisively or changed accordingly. It is also possible to identify with certainty diet-resistant hypercholesterolemic individuals, i.e., the true nonresponders, who represent only a minority. The determination of erythrocyte fatty acid patterns represents a useful index of adherence in long-term feeding studies and has been extensively carried out in subsamples of persons examined at the fourth rescreening of a controlled trial of primary prevention of coronary heart disease. Increases in mean erythrocyte linoleic/oleic (L/O) and P/S ratios were observed in persons undergoing collective or individual hypocholesterolemic treatment, mean changes being proportional to the different type of nutritional approach. In our opinion, this methodology is the most reliable technique not only for the identification of the different responses to hypocholesterolemic dietary recommendations but also to monitor fat consumption in population samples.