527 THE EFFECTS OF HUMAN MILK AND INFANT FORMULAS ON CIRCULATING HIGH DENSITY LIPOPROTEIN

Abstract

Infant formulas, in contrast to human milk, contain up to 3 times as much polyunsaturated fat (PUFA) and about 10% as much cholesterol. Such formulas are known to reduce plasma cholesterol in comparison to human milk, but the reduction has been difficult to attribute specifically either to reduced dietary cholesterol or increased PUFA. Circulating lipoproteins were studied in infants (4-6 mos.) fed at least 90% of energy from human milk (12-15% PUFA), SMA (15% PUFA) or Enfamil (52% PUFA). Apoproteins A-I. and A-II, the major proteins of high density lipoprotein (HDL), were quantitated by radialimmunodiffusion against rabbit antihuman serum. HDL and plasma cholesterol were analyzed by gas-liquid chromatography and LDL cholesterol was assumed to account for the remaining circulating cholesterol. Breast-fed and SMA-fed infants had identical amounts of both circulating HDL apoproteins and cholesterol, but LDL cholesterol was significantly lower in SMA-fed infants. Apoproteins A-I and A-II were lower in Enfamil- vs. SMA-fed infants by 25 and 20%, and HDL and LDL cholesterol by 35 and 18%, respectively. The data suggest that dietary cholesterol increases LDL cholesterol but not HDL cholesterol, and that PUFA most significantly decreases circulating HDL, although the reduction in total plasma cholesterol with Enfamil vs. SMA feeding was attributed equally to changes in HDL and LDL cholesterol concentration.