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Impact of Vitamin C on Endothelial Function and Exercise Capacity in Patients With a Fontan Circulation

Vitamin C is water-soluble, and probably the most famous of all the vitamins. Even before its discovery in 1932, physicians recognised that there must be a compound in citrus fruits preventing scurvy, a disease that killed as many as 2 million sailors between 1500 and 1800. Later researchers discovered that man, other primates and the guinea pig depend on external sources to cover their Vitamin C requirements. Most other animals are able to synthesise Vitamin C from glucose and galactose in their body. The most prominent role of Vitamin C is its immune stimulating effect, which is important for the defence against infections such as common colds. It also acts as an inhibitor of histamine, a compound that is released during allergic reactions. As a powerful antioxidant it can neutralise harmful free radicals and aids in neutralising pollutants and toxins.

Goldstein BH, Sandelin AM, Golbus JR, Warnke N, Gooding L, King KK, Donohue JE, Yu S, Gurney JG, Goldberg CS, Rocchini AP, Charpie JR. Impact of Vitamin C on endothelial function and exercise capacity in patients with a Fontan circulation. 1. Congenit heart Dis. 2012 May-Jun;7(3):226-34. doi: 10.1111/j.1747-0803.2011.00605.x. Epub 2011 Dec 18.

OBJECTIVE: ? To evaluate the impact of antioxidant therapy on functional health status in Fontan-palliated patients. Design.? Prospective, randomized, double-blind, placebo-controlled trial. PATIENTS: ? Fifty-three generally asymptomatic Fontan patients. INTERVENTIONS: ? Patients were randomized to receive either high-dose ascorbic acid (Vitamin C) or placebo for 4 weeks. OUTCOME MEASURES: ? Peripheral vascular function, as measured with endothelium-dependent digital pulse amplitude testing (EndoPAT), and exercise capacity were assessed before and after study drug treatment. Primary outcome measures included the EndoPAT index and peripheral arterial tonometry (PAT) ratio, both validated markers of vascular function. Secondary outcome measures included peak oxygen consumption and work. RESULTS: ? Twenty-three vitamin C- and 21 placebo-assigned subjects completed the protocol (83%). Median age and time from Fontan completion were 15 (interquartile range [IQR] 11.7-18.2) and 11.9 years (IQR 9.0-15.7), respectively. Right ventricular morphology was dominant in 30 (57%). Outcome measures were similar between groups at baseline. Among all subjects, Vitamin C therapy was not associated with a statistical improvement in either primary or secondary outcome measures. In subjects with abnormal vascular function at baseline, compared with placebo, Vitamin C therapy more frequently resulted in normalization of the EndoPAT index (45% vs. 17%) and PAT ratio (38% vs. 13%). CONCLUSIONS: ? Short-term therapy with Vitamin C does not alter endothelial function or exercise capacity in an asymptomatic Fontan population overall. Vitamin C may provide benefit to a subset of Fontan patients with abnormal vascular function.