Decreased Vagal Influence on the Heart after 24-Week Carnitine Supplementation

Stanislaw Zajaczkowski1, Piotr Badtke1, Milosz A Zajaczkowski2, Robert A Olek3, Tomasz H. Wierzba4
1Department of Physiology, Medical University of Gdansk, 2Department of Clinical Anatomy, Medical University of Gdansk, 3Department of Bioenergetics and Nutrition, Gdansk University of Physical Education and Sport, 4Medical University of Gdansk


Introduction: Carnitine is a dietary supplement available freely on the market. Despite the large amount of research there is virtually no data on its effect on autonomic heart rhythm control. Aim: The study aimed to test the effect of 24-week carnitine supplementation on HRV in healthy people of advanced age. Methods: Volunteers aged 64-74 (n=13) participated in the study. The individuals were randomly divided into two groups: one supplemented with carnitine (2g/day) and their control group supplemented with a placebo for 24 weeks. High resolution ECG (4 kHz; PowerLab, AdInstruments, Australia) was recorded before and after the supplementation. Five-minute time-series of NN intervals were used for calculation of HRV parameters using Kubios Premium 3.1 software (Kuopio, Finland). Time- and frequency-domain (FFT method), Poincare plot and nonlinear parameters were assessed. Results: Supplementation with carnitine affected parasympathetic modulation of autonomic control of the heart. Surprisingly HRV parameters of vagal drive were decreased in carnitine group: rMSSD (from 23.87±8.84ms to 14.35±4.72ms; p=0.034), SD1 (from 16.91±6.26ms to 10.16±3.34ms, p=0.034) and HF (from 155.6±88.53ms2 to 79.38±52.66ms2, p=0.049). In contrast all indexes of long-term variability remained unchanged: SDNN 21.91±5.59 vs. 17.34±7.98ms, p=0.156; SD2 25.68±6.52 vs. 22.29±10.91ms, p=0.313; LF 202.3±127.6 vs. 183.7±171.9ms2, p=0.706. Interestingly, indexes of autonomic balance were almost unchanged: LF/HF 1.85±1.63 vs. 2.46±1.06, p=0.400 and SDNN/rMSSD 0.99±0.26 vs. 1.21±0.21, p=0.078. In placebo group all parameters remained unaltered. Additionally, nonlinear indexes such as: sample entropy, approximate entropy, detrended fluctuation analysis scaling exponent alfa1 and alfa2 and recurrence rate also remained unaffected in both groups. Summary: In people with advanced age carnitine supplementation suppressed vagal influence on the heart rhythm. Such profile of autonomic dysregulation is unbeneficial and may increase severe cardiac incidents.