Everyone often talks about the need for calcium and vitamin D supplements, but what exactly does vitamin D do? Its physiological functions mainly involve two aspects:
1. Maintaining Calcium and Phosphorus Balance
Vitamin D primarily functions in its form as 1,25-dihydroxyvitamin D in target organs such as the small intestine, bones, and kidneys. It maintains intracellular and extracellular calcium concentrations and regulates calcium and phosphorus metabolism. Working alongside parathyroid hormone, it promotes the reabsorption of calcium and phosphorus in the intestines and the reabsorption of calcium in the renal tubules.
1,25-dihydroxyvitamin D also directly acts on osteoblasts and indirectly affects osteoclasts through osteoblasts, thus influencing bone formation and resorption. This maintains the balance of calcium and phosphorus between bone tissue and blood circulation.
2. Participating in Immune Regulation
1,25-dihydroxyvitamin D induces the differentiation of macrophages, regulates T cell functions, and the secretion of cytokines, playing a crucial role in the body's immune regulation.
Recent studies have also found that vitamin D levels are inversely related to the risk of various diseases, including cardiovascular diseases, type 2 diabetes, and tuberculosis. Therefore, vitamin D is an essential fat-soluble vitamin for humans.