“…Vitamin D (VD) is a fat-soluble steroid that is a key regulator of calcium and phosphorus metabolism ( Holick, 2007 ), which mainly circulates to form 25-hydroxyvitamin D3 [25 (OH)D3]. Recently, studies have found that VD plays a vital role in development of depression ( Kaviani et al, 2020 ), irritable bowel syndrome (IBS) ( Alvi et al, 2022 ), type 1 diabetes mellitus ( Liu et al, 2015 ), and obesity ( Yu et al, 2023 ; He et al, 2023 ; Li et al, 2023 ). Current research suggests that VD can interfere with a plethora of cellular mechanisms and directly or indirectly modulate the microbiota ( Tangestani et al, 2021 ), release antimicrobial peptides, and modulate the immune system and inflammatory processes ( Song et al, 2023 ) this, in turn, can actively interfere with changes in gut function.…”