Generally, epidemiology has shown that high vitamin C intakes may protect from all-cause mortality and cardiovascular disease. However, vitamin C is present in many foods that have other beneficial compounds (e.g. fruits and vegetables) and so it has been difficult for researchers to make conclusions from epidemiological studies. In addition, many intervention studies involving vitamin C supplements have not shown a protective effect. Vitamin C is an important water soluble antioxidant in human plasma which can protect tissues from damage by free radicals in vivo. This antioxidant action would suggest a role for vitamin C in the inhibition of inflammation. Evidence supports this anti-inflammatory role for vitamin C, with studies showing that vitamin C supplements decrease levels C-reactive protein, an important marker for chronic inflammation. An inverse association with fibrinogen also suggest an anticoagulative effect for vitamin C.
Research published in the American Journal of Nutrition in 20061 used a cross-sectional designed study of 3258 health men aged 60 to 79 to investigate the association between plasma vitamin C levels, fruits and vegetables, and markers of inflammation and cardiovascular disease. The researchers used food-frequency questionnaires to assess the fruit and vegetable and vitamin C intakes of the subjects, as well as blood samples to measure plasma vitamin C levels. The results showed that plasma vitamin C, fruit and vegetable and vitamin C intake were significantly inversely associated with mean concentrations of C-reactive protein and tissue plasminogen activator (t-PA) antigen, important markers for chronic inflammation and endothelial dysfunction, respectively. In addition, fruit and vegetable intakes were inversely correlated with t-PA antigen. Plasma vitamin C also showed and association with fibrinogen concentrations and blood viscosity.
This study suggest that vitamin C may be involved in protection from inflammation, although care should be taken in assigning cause and effect. The fact that vitamin C intake, vitamin C plasma levels and fruit and vegetable intakes were inversely associated with markers for endothelial dysfunction might suggest a protective role for vitamin C in the development of atherosclerosis. The results also support previous studies and suggest an anticoagulative blood thinning role for vitamin C in humans. Vitamin C levels have been shown to have an inverse association with abdominal obesity (here), and abdominal obesity is a known risk factor for cardiovascular disease. Obesity is also increasingly being thought of as a disease of chronic inflammation. Vitamin C is also known to increase levels of cellular glutathione (here), and high glutathione levels are associated with reduced mortality and improved health.
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