Vitamin C and plasma cholesterol

There has been a long-lasting controversy about whether vitamin C has any significant effect on plasma cholesterol levels in human beings. Some early Russian studies suggested that vitamin C may decrease elevated cholesterol levels, and so the vitamin was used to some extent in the treatment of hypercholesterolemia (for review see Reference 1). However, the studies were not well controlled, and duplications have yielded conflicting results. Nevertheless, animal studies have consistently found that vitamin C has substantial effects on cholesterol metabolism. The purpose of this review is to analyze the published intervention studies in order to identify the factors that may have resulted in the discordance in the results. Several of the studies have used subjects with initially low cholesterol levels. Such studies do not test the hypothesis that a low level of the vitamin may decrease the rate of cholesterol catabolism, and thereby enhance hypercholesterolemia in some people. Accordingly, studies with hypercholesterolemic subjects are more relevant for testing this hypothesis. Most of the studies in the latter group have reported a significant decrease in the cholesterol level with vitamin C supplementation. Furthermore, such results indicate that in certain people low vitamin C status may be one of the factors that lead to the elevation of cholesterol levels.