A daily vitamin D dose of 5,000 IU for 28 days was associated with maintenance of the so-called sympatho-vagal balance, or the interaction between the sympathetic nervous system and the vagus nerve, according to findings published in the International Journal of Cardiology .
Pre-supplementation, an acute stressor was associated with an unfavorable shift in this sympatho-vagal balance, said the researchers.
The data also indicated improvements in cardiac autonomic tone, which refers to the the heart’s ability to respond to a stressor and return to normal, said researchers from the University of Calgary, the Libin Cardiovascular Institute of Alberta, and the Alberta Kidney Disease Network.
“To our knowledge, this is the first study investigating the association of vitamin D3 supplementation on cardiac autonomic tone, a potentially modifiable target for risk of sudden arrhythmic death, in humans,” they wrote.
“Pre-vitamin D3 supplementation, subjects demonstrated an unfavorable increase in sympatho-vagal balance in response to an acute physiological stressor, whereas post-vitamin D3 supplementation, cardiac autonomic tone was maintained in response to the same stressor, largely driven by restoration of cardioprotective vagal input.
“These novel findings suggest a mechanism by which vitamin D3 supplementation may improve cardiac autonomic function and potentially decrease cardiovascular and risk of sudden arrhythmic death in [high risk] populations.”
The Alberta-based researchers recruited 13 healthy men and women with vitamin D insufficiency to participate in their study. All participants received the vitamin D supplements for 28 days, and results showed that blood levels of vitamin D increased to sufficient levels.
Vitamin D refers to two biologically inactive precursors - D3, also known as cholecalciferol, and D2, also known as ergocalciferol.
Both D3 and D2 precursors are transformed in the liver and kidneys into 25- hydroxyvitamin D (25(OH)D), the non-active 'storage' form, and 1,25-dihydroxyvitamin D (1,25(OH)2D), the biologically active form that is tightly controlled by the body.
Vitamin D deficiency (less than 20 ng/mL) can cause a number of health issues, including rickets and other musculoskeletal diseases.
Data obtained pre-supplementation showed that the subjects responded unfavorably to a stressor, obtained by measuring variability in heart rate.
“The assessment of heart rate variability (HRV), particularly its vagal component, is strongly linked to the development of serious cardiovascular events, including sudden death,” they said.
“In summary, our results suggest that vitamin D3 supplementation improves cardiac autonomic tone in response to an acute stressor in healthy humans. While larger, prospective studies are required to determine the effect of vitamin D3 supplementation on clinical outcomes, optimizing vitamin D levels remains an exciting potential therapeutic target for those populations at high risk of cardiovascular mortality.”
Source: International Journal of Cardiology
Volume 172, Issue 2, Pages 506-508
“Vitamin D supplementation is associated with improved modulation of cardiac autonomic tone in healthy humans”
Authors: M.C. Mann, D.V. Exner, B.R. Hemmelgarn, T.C. Turin, D.Y. Sola, L. Ellis, S.B. Ahmed