by lisa A. Beach

Vitamin D plays a vital role in your health. It aids in calcium absorption (which helps build strong bones) and assists with proper muscle and nerve function. But did you know it also helps the immune system fight off bacteria and viruses? Whether it’s during flu season or a pandemic, it’s more important than ever to ensure you’re getting enough vitamin D.

As both a nutrient and a hormone, vitamin D helps to reduce inflammation as well as control processes such as immune function and cell growth, including antigen-presenting cells and regulatory T cells. Research shows that vitamin D plays a variety of roles in immune system functioning, which may improve the body’s first line of defense against foreign invaders and deter the development of autoimmunity (when the body’s immune system attacks its own healthy cells and tissues).

In fact, researchers have been studying the immunity-building benefits of vitamin D as they relate to respiratory infections. Recent studies (see “COVID-19 and D”) found that using vitamin D supplements showed promise in both preventing and treating respiratory infections.

While the amount of vitamin D needed daily varies by age, most adults need 15 to 20 micrograms (mcg), about 600 to 800 IUs. However, research shows that many people aren’t getting enough. The National Institutes of Health found that about one in four people have inadequate vitamin D blood levels, and a June 2020 article in Nutrients, a peer-reviewed scientific journal, says 95% of Americans don’t get enough vitamin D in their diet.

“Some people don’t consume fish, eggs, milk or milk alternatives, or other vitamin-fortified foods,” says Mira Ilic, a registered dietitian with Cleveland Clinic.

Get outside. Spending time in the sun can pose challenges, since dermatologists recommend using sunscreen to protect against skin cancer. “Sunscreen with SPF 15 or higher blocks the UVB rays that are responsible for making vitamin D in the skin,” explains Ilic. The time of day, geographical latitude, seasons and amount of exposed skin all affect how much vitamin D the body can make from the sun.

Stefanski advises going outdoors without sunscreen for just 20 minutes, three to four times a week. Besides boosting your vitamin D, being outside in the fresh air and sunshine elevates your mood and provides opportunities for physical activity. “Sun makes us feel good—an important part of human health,” says Stefanski.

Take a supplement. “Your doctor can order a blood test and, based on the results, let you know if you need to supplement and in what amount,” says Ilic. “Too much vitamin D can cause the body to absorb too much calcium, which can lead to kidney stones or damage.”

And Stefanski points out that, when taking a supplement, you should choose vitamin D3: “Sometimes food can be fortified with vitamin D2, but it’s not as well absorbed by the body.”