Muscle Pain
Vitamin D plays a role in muscle and nerve function. Low levels of vitamin D in your body can cause you to feel muscle pain. [23] This is true for both children and adults.
According to one study, 71 percent of people who had muscle pain were found to be deficient in vitamin D. [24] Another study involving rats found that vitamin D deficiency increased sensitivity and pain when the nociceptors in the muscles were stimulated. [25] The nociceptors are nerve cells that sense pain. These cells contain vitamin D receptors.
Some studies have shown that taking vitamin D supplements can reduce pain in people who are vitamin D deficient. [26]
Increased Susceptibility to Infections
Vitamin D interacts with immune cells and plays an essential role in keeping your immune system active. [27] Your immune system is what helps your body fight against infections and diseases. When the levels of vitamin D in your body are below normal, you may start to fall sick more often.
Studies [28] have linked [29] vitamin D deficiency to increased susceptibility to respiratory tract infections. Research has also shown that taking high doses of vitamin D supplements can reduce this risk. [30]