Shining Light on Dysautonomia: The Role of Vitamin D in Cardiac Autonomic Regulation.

PURPOSE OF REVIEW: Traditionally recognized for its role in calcium homeostasis and bone metabolism, vitamin D is increasingly acknowledged for its broader physiological effects, particularly in cardiovascular health. One area of growing interest is its influence on cardiac autonomic function. Cardiac autonomic dysfunction, characterized by an imbalance between sympathetic and parasympathetic activity, is a well-established predictor of adverse cardiovascular outcomes. This narrative review aims to synthesize the current literature on the association between vitamin D status and cardiac autonomic function.

RECENT FINDINGS: Accumulating observational data indicate that individuals with vitamin D deficiency exhibit poorer cardiac autonomic function, reflected by reduced heart rate variability indices, compared to vitamin D-sufficient individuals. Interventional trials, though limited, suggest that vitamin D supplementation may improve autonomic balance, especially in those with baseline deficiency. The relationship appears to be affected by factors such as glycemic control, disease state, and vitamin D binding protein levels. Vitamin D may modulate autonomic regulation largely via the vitamin D receptor, which activation influences multiple downstream pathways, including central nervous system effects, neurotrophic properties, regulation of the renin-angiotensin-aldosterone system, calcium-parathyroid hormone axis, and immune modulation. However, inconsistencies in study design, population characteristics, and assessment methods limit the strength of current evidence. Further longitudinal and interventional studies are warranted to establish causality and determine whether vitamin D repletion can reduce cardiovascular risk by restoring autonomic balance.