ApoA-I/ApoA-II ratios in plasmas of vegetarians.
Diets low in fat and cholesterol and high in P/S ratio are accompanied by low HDL-cholesterol levels. Short-term experimental feeding of such diets demonstrates that the HDL2 fraction is reduced preferentially. In order to ascertain whether the HDL2 lowering effects persist over the long-term, apolipoprotein A-I/A-II ratios, which are indices of the HDL2 relative to HDL3 in plasma, were measured in three groups of vegetarians (n = 35) who had been eating vegetarian diets for 1 to more than 5 years varying in cholesterol contents from less than 10 to 300 mg/d, fat between 30% to 50% of calories, and P/S ratio between 0.7-2.5. Concentrations of apoA-I were lower in those eating the least cholesterol and the highest P/S ratio, ie, apoA-I correlated positively with dietary cholesterol (r = 0.38, P less than 0.05), and both apoA-I and the A-I and the A-I/A-II ratio correlated negatively with the ratio of polyunsaturated-to-saturated (P/S) fatty acids (r = -0.39, P less than 0.05, and r = -0.41, P less than 0.02, respectively). There was no significant correlation between apoA-I, apoA-II, the A-I/A-II ratio or the high-density lipoprotein cholesterol/apoA-I ratio and consumption of total calories, fat, protein, or carbohydrate. Since the A-I/A-II ratio is much higher in HDL2 than in HDL3, these data suggest that cholesterol intake and the P/S ratio are important long-term dietary determinants of plasma HDL2 levels. Thus, in vegetarians, despite a reduced risk of coronary heart disease, the high-density lipoprotein cholesterol (HDL-C) and especially HDL2 concentrations were low. More work is needed to elucidate this interesting paradox.