Incorporation of apolar extracts of alfalfa into the diets of chickens
effected. significant reductions in hepatic 3-hydroxy-3-methylglutary
l coenzyme A reductase activity and serum concentrations of cholestero
l (total and LDL) and apolipoprotein B. One of several mevalonate-supp
ressive constituents of the extracts shared characteristics with beta-
ionone. Dietary beta-ionone, a potent inhibitor of hepatic 3-hydroxy-3
-methylglutaryl coenzyme A reductase activity, was most effective unde
r conditions favoring basal rather than induced reductase activity. Th
is inhibitory action is distinct from that of mevinolin, a competitive
inhibitor of reductase activity. The presence of beta-ionone in mills
was confirmed. This demonstration of the cholesterol-suppressive acti
on of a passive rather than a physiological constituent of milk may ex
plain the conflicting reports of the impact of dairy products on blood
cholesterol levels.