Influência da vitamina C na modulação autonômica cardíaca no repouso e durante o exercício isométrico em crianças obesas

Abstract

Objectives: To draw a comparison between obese and eutrophic children regarding cardiac autonomic modulation and to investigate the effect of vitamin C supplements on cardiac autonomic modulation in obese children, at rest and during isometric exercise. Methods: The study covered eight eutrophic (IMC= 18 ± 1Kg/cm 2) and 21 obese (IMC = 29 ± 1Kg/cm2) children aged between 8 and 11 years of both sexes, distributed into two groups: One receiving a 500 mg vitamin C supplement (n=11), and the other a placebo (n=10), for 45 days. Cardiac autonomic modulation was evaluated by way of spectral analysis of the variability of cardiac frequency at rest and during isometric exercise. Results: Obese children, at rest and during isometric exercise, presented a higher degree of sympathetic cardiac activation and less vagal activity. Comparison of the low- and high-frequency spectral components of the two groups revealed significant differences. After the use of vitamin C supplements, the spectral components were similar to those found in eutrophic children, both at rest and during isometric exercise. Conclusions: Obese children showed greater sympathetic activity and less vagal activity at rest and during isometric exercise compared to eutrophic children. The use of high doses of oral vitamin C supplements may correct the cardiac autonomic dysfunction in obese children.