Vitamin C could reduce inflammation
By Stephen Daniells
08/03/2006 – A diet rich in sources of vitamin C could cut the level of markers for inflammation by 45 per cent, a result that needs verifying by supplementation studies, says a new study.
Consumers have a positive image of vitamin C, with public perception linking the vitamin to improved immune system health.
According to Frost and Sullivan, the US market generated $151.7m (€127.4m) in 2005. In Europe, revenue was calculated at $160.3m (€134.6m) for 2005, and is expected to grow to $192.5m (€161.6m) by 2011.
The new cross-sectional study, published in this month’s American Journal of Clinical Nutrition (Vol. 83, pp. 567-574), examined 3258 men aged between 60 and 69 with no history of diabetes or cardiovascular disease.
A food-frequency questionnaire was used to quantify vitamin C intake from dietary and supplemental sources, and related to blood levels of certain markers linked to inflammation: C-reactive protein (CRP) and tissue plasminogen activator (t-PA).
“Plasma vitamin C, fruit intake, and dietary vitamin C intake were significantly and inversely associated with mean concentrations of C-reactive protein, an acute phase reactant, and t-PA antigen, a marker of endothelial dysfunction,” wrote lead author Goya Wannamethee from the Royal Free and University College Medical School, London.
High blood levels of vitamin C were associated with a 45 per cent reduced risk of inflammation (with respect to CRP levels), and high fruit intake was related to a 25 per cent reduced risk of inflammation.
“Plasma (but not dietary) vitamin C also showed inverse associations with both fibrongen concentrations and blood viscosity,” reported Wannamethee.
In an accompanying editorial (Vol. 83, pp. 525-526), Ishwarlal Jialal and Uma Singh from the University of California Davis Medical Center, said: “It is important to emphasize that theirs was a cross-sectional study and not a randomized placebo-based clinical trial, and thus the authors conclusion is not firm and cannot be used for policy guidelines.”
The editorial also pointed out that the study was only focused on elderly white men and thus could not be generalized for other races, women, and age groups.
Jialal and Singh also questioned the use of t-PA as a measure of endothelial inflammation.
“It is not clear whether there is indeed a relation between vitamin C and biomarkers of endothelial function, because the authors did not show a correlation between vitamin C and von Willebrand factor, another biomarker.”
Both commentators stressed that previous clinical trials (with diabetics, smokers and healthy men) had not reported an anti-inflammatory effect from vitamin C supplementation.
In contrast, intravenous vitamin C trials did report an improvement in endothelial function.
“Much further research in a dose-response is required to ascertain whether oral vitamin C supplementation is anti-inflammatory and whether it improves endothelial dysfunction,” concluded Jialal and Singh.
The recommended daily intake of the vitamin in Europe is 60 mg. In the US, men are recommended to consume 90 mg per day, and women 75 mg per day.
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