Dr Linus Pauling suggested that high intakes of ascorbate were protective of cardiovascular disease because the vitamin was able to reduce levels of a sub-type of low density lipoprotein particle [lipoprotein (a)] that may play a role in the pathology of atherosclerosis. That vitamin C is protective of the vasculature is know from the deficiency disease scurvy, which results in a breakdown of the vasculature of the body. A diet high in vitamin C should provide roughly 300mg of vitamin C per day, but supplementation can significantly increase intakes and with them plasma levels of ascorbate. Obese individuals have lower levels of plasma ascorbate than lean counterparts, and obesity is known to increase the risk of developing cardiovascular disease. Some research suggests that vitamin C may be protective of cardiovascular disease because it can raise levels of high density lipoprotein (HDL) in the plasma.
For example, researchers1 determined the plasma lipid and vitamin C levels in 316 women and 511 men aged 19 to 95 years between 1987 and 1990. Adjustments were made age, sex, obesity, and smoking, because they are known risk factors for cardiovascular disease. The results showed that plasma vitamin C was associated with HDL and HDL2 cholesterol. This association persisted even when subject with diseases that might affect blood lipid levels were excluded. The association between plasma vitamin C and HDL and HDL2 were highest in men. Analysis of diet record taken over 7 days showed that the mean vitamin C intakes were well above the recommended dietary allowances in a sub-set of the subject population. Of the subjects tested, 30% of men and 43% of women were taking vitamin C supplements.
The association between plasma vitamin C and HDL do not show the cause and effect and so care must be taken in interpretation of these results. The subjects were healthy and had intakes of vitamin C above the recommended level, yet there still persisted an association between vitamin C and plasma levels of HDL. This suggests that the recommended levels of vitamin C, while high enough to prevent the deficiency disease scurvy, are not high enough to prevent changes to the blood lipid levels of subjects. Lipoprotein(a) is an extremely atherogenic particle that has been suggested to act as a surrogate for vitamin C in the vasculature during times of vitamin C insufficiency. When vitamin C intakes are low, lipoprotein(a) may stabilise the endothelial lining of major blood vessels and prevents bleeding at the expense of atherosclerotic growth, but it is not known how this may relate to HDL.
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