The efficacy of vitamin C supplementation on reducing total serum cholesterol in human subjects: a review and analysis of 51 experimental trials

ObjectiveObservational studies in humans have shown an inverse relationship between plasma vitamin C concentration and total serum cholesterol. However, experimental studies have shown inconsistent results regarding the ability of vitamin C to reduce total serum cholesterol.MethodsPublished reports of trials studying the effects of vitamin C on serum lipids were identified by a search of Medline from 1966 to 2004. Data from 51 experimental studies comprising of 1666 pooled subjects were selected for analysis.ResultsA very strong negative association was observed between baseline total serum cholesterol and the percent change in cholesterol (r = −0.585, p<0.001). When subjects were divided into 4 groups based on their baseline total serum cholesterol levels, the following weighted mean percent changes in cholesterol from baseline were observed: normal cholesterol (<199mg/dl): 0.91±6.8% (n=508); borderline high cholesterol (200–239mg/dl): 3.90±5.78% (n=605); high cholesterol (240–279mg/dl): 11.40±7.96% (n=300); severe cholesterol (>280mg/dl): 14.30±8.36% (n=253). A significant inverse relationship was found between the baseline plasma vitamin C concentrations and mean percent change in total cholesterol from baseline (r = −0.500, p<0.005). It was also observed that the high and severe baseline cholesterol groups possessed lower baseline plasma vitamin C concentrations than those in the normal cholesterol groups (0.79 and 0.55 versus 1.24 mg/dl respectively).ConclusionThis finding strengthens the hypothesis that the cholesterol lowering and cardio-protective benefit of vitamin C supplementation may be in its ability to elevate plasma vitamin C concentrations in those patients who initially possess lower than normal vitamin C plasma concentrations.