As millions of Americans are currently practicing social distancing and working and studying from home, the idea of proactively strengthening your immune system often gets lost in the noise.

What recent studies have shown is that we should be focusing on consuming more vitamin D, a key nutrient for building up your immune system. Vitamin D might be best known for strengthening bones, but it can also help prevent respiratory infections or reduce the severity of them, which can be considered heartening news for people who are worried about being infected by COVID-19.

There is widespread consensus in the medical community that COVID-19 is most dangerous for elderly patients and those with preexisting health conditions. In order to stay out of that vulnerable group, your vitamin D-boosted immune system needs to be ready to fight should an infection occur.

One of the chief functions of vitamin D is to help activate T cells in the body. T cells are there to detect and destroy foreign pathogens like viruses, keeping your body in tip-top shape by maintaining a robust immune system.

The recommended amount of vitamin D for adults is between 600 and 800 IU, although this can vary, and you can get it through supplements, food and direct sun exposure. Even so, medical experts have said that about 1 billion people worldwide have insufficient levels of vitamin D, which have been linked to osteoporosis, muscle weakness, cancer and depression.

Some major food sources with high levels of vitamin D are egg yolks, cheese, beef liver and fatty fish. Keep in mind that cereals and dairy and plant milks have vitamin D added to them. Despite all of these choices, experts say it is still difficult to get your recommended daily allowance of vitamin D only through food.

One way to supplement the shortfall is to get outside and receive direct sun exposure. Many experts say getting about 15 minutes of sun per day is sufficient for your body to make its own vitamin D. This is accomplished when the sun's ultraviolet rays hit cholesterol in skin cells, which provide the required energy for vitamin D synthesis to occur.

In an article published in the Irish Medical Journal​, one research team revealed that 47 percent of all adults over 85 are deficient in vitamin D in the winter, putting this group at extremely high risk of mortality if they are infected by COVID-19. The report also found that only 4 percent of men and 15 percent of women take a vitamin D supplement.

Ethen Kim Lieser is a Tech Editor who has held posts at Google, The Korea Herald, Lincoln Journal Star, AsianWeek and Arirang TV.

Image: Reuters.