You can enhance your immune system by staying physically active, eating whole foods that provide a variety of nutrients, getting sufficient sleep, limiting alcohol consumption, and maintaining a healthy weight.
Taking certain supplements may also help strengthen your immunity. To find out whether vitamin D supplements can help in this department, we spoke with Matthew Badgett, MD, a primary care provider at Cleveland Clinic.
*This interview has been edited and condensed for length and clarity.
Q: How does vitamin D affect the immune system? Does it have a supportive role?
Badgett: Vitamin D is an immunomodulator hormone, meaning it helps activate immune cells. Immune cells can also convert vitamin D into its active form, enhancing the immune response. At the same time, vitamin D helps suppress excessive immune reactions, protecting against autoimmunity and excessive inflammation.
However, it also appears to help balance the immune system in ways that aid in fighting infections. People with higher vitamin D levels tend to fare better against infections, although this may be more correlational than causal.
Research is mixed—some studies show a benefit, while others show no benefit for taking vitamin D, and some show reduced infection risks. Although the effect is marginal, such as a 10% reduction in infections. The supplement would also need to be taken daily before you get sick, not once you get sick.
There are also trials showing a reduction in autoimmune diseases, as well as improved outcomes for patients with those autoimmune diseases who take it.
Are There Any Safety Concerns?
Watch your supplements and ensure you aren’t taking multiple supplements that contain vitamin D. Excessive vitamin D intake can cause problems. I see vitamin D toxicity affecting calcium levels quite often since people overdose on it.
I recommend daily supplements over weekly ones since they are more consistent, and the mega weekly doses have some trials showing harm in the elderly.
Check your levels before taking a supplement or upping your dosage, and note that levels drop in the winter since sunlight is what our body needs to make vitamin D. In theory, with enough sun, we don’t need vitamin D. Some people may take more in the winter and less in the summer to avoid overdosing, but this is a complicated strategy.
How Much Vitamin D Should You Take?
Trials vary, but typically range from 400 IU to 5,000 IU for several months to achieve higher serum levels. I usually recommend adults start at 1,000 to 2,000 IU.
The bottom line is that it’s difficult to say how vitamin D supplements will affect you or how they stack up to other supplements that support the immune system, such as vitamin C. Much of this depends on your individual body—what your vitamin D levels usually are to begin with—so it might be helpful to speak with a physician to see if vitamin D supplements are safe for you.
Your doctor can also help you decide which kind of vitamin D supplement—and what dosage—you should try. In the meantime, you can get vitamin D from the following food sources:
Fish liver oilsFatty fish (with the skin)Egg yolksBeef liverCheese
In America, many foods are fortified with vitamin D, such as milk and breakfast cereals, and adding these to your diet may also be helpful.
O’Neill is a reporter who covers new medical research and addiction. She previously worked at SELF magazine and Health.com, and she was a 2020 fellow at the Association of Health Care Journalists.
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