Effect of carbohydrate and vitamin B-6 on QTc intervals in women during exercise
1987
Manore, M.M. | Leklem, J.E. | Maksud, M.G. | Carroll, S.S.
Extract: Vitamin B-6 (B6), as pyridoxal 5'phosphate, is essential for glycogenolysis and gluconeogenesis. Changes in B6 status may alter fuels available for the heart and muscles during exercise (EX). We investigated whether dietary carbohydrate (CHO) and B6 could alter QT intervals in 5 young/trained, 5 young/untrained and 5 postmenopausal/untrained women fed a moderate CHO diet for 2 wk, a high CHO diet for 1 wk, a moderate CHO+B6 diet for 2wk and a high CHO+B6 diet for 2 wk and a high CHO+B6 diet for 1 wk. EX testing included 20 min on a cycle ergometer at 80% VO2max at the end of each dietary treatment. ECG tracings were monitored and QT corrected (QTc) was measured at rest and 80% maximal heart rate (MHR). There were significantly longer QTc intervals when the moderate CHO diet was fed as compared to when the other diets were fed. For all diets, QTc increased from rest to 80% MHR in all but the young/untrained group. The magnitude of change in QTc intervals from rest to 80% MHR was significantly different between the groups. QTc intervals measured occurred while subjects were in adequate B6 metabolism as indicated by plasma pyridoxal 5'-phosphate concentrations within normal range. This research supports the finding that diet (B6 and/or CHO) can alter QT intervals in women during exercise. (author)
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