Frequent illness or infections

One of vitamin D's most important functions is to support immune health, which helps you fight off viruses and bacteria that cause illness. Vitamin D interacts directly with the cells responsible for fighting infections. If you get sick frequently, especially with colds or the flu, low vitamin D levels may be a factor. A deficiency has been linked to respiratory tract infections such as colds, bronchitis, and pneumonia in several large observational studies.

A number of studies have found that taking up to 4,000 IU of vitamin D daily may reduce the risk of respiratory tract infections. Recently, vitamin D deficiency has been linked to an increased risk of COVID-19, as well as an increased risk of experiencing severe effects from the condition. However, it is important to note that taking vitamin D supplements at any dosage will not prevent COVID-19.