Vitamin C (ascorbic acid) supplements improve the response of the sympathetic nervous system during exercise in patients who have had a heart attack (myocardial infarction), according to a report in the International Journal of Cardiology.

The sympathetic nervous system is a part of the nervous system that controls heart rate and other involuntary body responses. Patients with heart disease sometimes have poor sympathetic function, the authors explain, but whether or not antioxidants can improve this complication remains unclear.

Dr. Kazuyo Kato and colleagues from Nippon Medical School, Tokyo, investigated whether ascorbic acid influenced the sympathetic response to exercise in 21 men who were studied at least one month after a myocardial infarction. The participants underwent symptom-limited exercise testing twice, once 2 hours after oral administration of 2 grams of ascorbic acid and once without the supplement.

Although resting blood pressure and heart rate did not differ with or without ascorbic acid, the authors report, the heart rate response to peak exercise was significantly higher, an indication of better heart function, after ascorbic acid than without ascorbic acid.

Ascorbic acid administration also improved heart rate increases from rest to peak exercise, as well as the peak oxygen consumption, the results indicate.

“These data suggest that an antioxidant vitamin such as ascorbic acid can effect a recovery of the sympathetic dysfunction caused by injury through excessive oxidative stress and improve exercise intolerance,” Dr. Kato and colleagues conclude.

“Further studies are needed to determine whether long-term ascorbic acid administration will improve sympathetic nerve dysfunction in patients and whether other antioxidants would have the same effects as ascorbic acid,” the investigators add.

SOURCE: International Journal of Cardiology, August 2006.