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Can Vitamin D3 Help Prevent Infections?

Written by Joe Cohen, BS | Last updated:
Puya Yazdi
Medically reviewed by
Puya Yazdi, MD | Written by Joe Cohen, BS | Last updated:

Vitamin D, the “sunshine vitamin,” works to maintain healthy immune function and general well-being. Research reveals it may also help prevent infections, especially in people who are deficient. Read on to find out what the latest science has to say about its potential to strengthen the immune response.

Vitamin D & Immunity Snapshot

  • Vitamin D maintains immune balance
  • Deficiency increases the risk of bacterial and respiratory infections
  • Supplementation may strengthen the immune response in people who are deficient
  • Limited evidence suggests supplementation may improve immunity in people with HIV

The body naturally makes vitamin D when exposed to sunlight. Getting regular, moderate sun exposure is a safe way to maintain normal vitamin D levels during the summer months.

Vitamin D is also found in certain foods, such as fatty fish like salmon and sardines. Additionally, many vitamin D supplements are available on the market.

Taken at the recommended doses, vitamin D supplements are considered safe. However, taking too much can be harmful. Vitamin D supplements may also interact with prescription medications. Remember to talk to your doctor before supplementing.

Vitamin D helps maintain immune balance. People who don’t get enough of this vitamin through sunlight and food are at risk of deficiency, which can make the m prone to infections.

Does Vitamin D Reduce the Risk of Tuberculosis?

There is insufficient evidence to determine if vitamin D supplementation is effective and safe and safe in people with tuberculosis.

Patients with low vitamin D levels have a higher risk of active tuberculosis [1, 2, 3].

Extreme vitamin D deficiency is associated with a 5-fold increased risk for progression to tuberculosis among healthy individuals who come in contact with tuberculosis [4, 5].

Blood levels of this vitamin are lower in tuberculosis patients comparing to healthy individuals [6].

Vitamin D supplementation may prevent tuberculosis, reduce infectivity and shorten the duration of disease and treatment [3, 7].

Vitamin D supplementation enhances immunity to mycobacteria [8, 9].

Scientists discovered that people deficient in vitamin D are more likely to get tuberculosis. Limited research suggests supplementation may prevent tuberculosis or shorten the disease duration by strengthening the immune response, the evidence is insufficient.

Vitamin D May Reduce the Risk of Respiratory Infections

Some clinical evidence suggests that vitamin D help prevent respiratory infections.

Lower levels of vitamin D are related to increased risk of respiratory infections [10].

Studies showed a decrease in respiratory tract infections in children taking 600 to 700 IU/d vitamin D supplementation [11].

Supplementation with 1,200 IU/day prevents against the flu (influenza A) in schoolchildren between December and March [12].

Supplementation with this vitamin (at 300 IU daily) significantly reduced the risk of acute respiratory infections by 50% among Mongolian children with vitamin D deficiency in winter [13].

However, a monthly dose of 100,000 IU of vitamin D in healthy adults did not significantly reduce the incidence or severity of upper respiratory tract infections [14].

Watch SelfDecode founder & CEO Joe Cohen and Dr. Mercola discuss vitamin D:

Several studies revealed that vitamin D supplementation, especially over the winter months, may protect children against the flu and respiratory infections. Stronger evidence for supplementation in adults is needed.

Is Vitamin D Beneficial for People with HIV?

Vitamin D deficiency is common among people infected with human immunodeficiency virus (HIV).

It is associated with an increased risk of HIV disease severity and death [15, 16, 17].

HIV-infected patients with abnormally low vitamin D levels had shorter survival than other HIV-infected subjects [18].

100,000 IU of vitamin D supplementation every 2 months is safe and improves vitamin D status [16, 19].

This vitamin improves HIV-associated immunity.

High doses of vitamin D supplementation decreases virus production and increases white blood cells [20].

People with HIV are often deficient in vitamin D, which can further weaken their immune response. Some evidence suggests supplementation can safely improve their immunity and vitamin D status.


Vitamin D is also known as the “sunshine vitamin” because it’s produced when the skin is exposed to sunlight.

Its role in maintaining healthy immune function is backed up by some research. New findings suggest that vitamin D may help help prevent respiratory, seasonal infections.

Clinical studies revealed that people deficient in vitamin D are more likely to get tuberculosis or catch the flu, but there’s not enough evidence to determine the benefits of supplementing in people with tuberculosis.

Limited research also suggests that supplementation helps strengthen the immune response in people with HIV who tend to be deficient, but further work is needed.

All in all, supplementation may be a good idea for children and adults who can’t get enough of this vitamin from sun exposure and food.

Remember to talk to your doctor first, though, since vitamin D supplements can interact with medications.

Further Reading

About the Author

Joe Cohen, BS

Joe Cohen, BS

Joe Cohen flipped the script on conventional and alternative medicine… and it worked. Growing up, he suffered from inflammation, brain fog, fatigue, digestive problems, insomnia, anxiety, and other issues that were poorly understood in traditional healthcare. Frustrated by the lack of good information and tools, Joe decided to embark on a learning journey to decode his DNA and track his biomarkers in search of better health. Through this personalized approach, he discovered his genetic weaknesses and was able to optimize his health 10X better than he ever thought was possible. Based on his own health success, he went on to found SelfDecode, the world’s first direct-to-consumer DNA analyzer & precision health tool that utilizes AI-driven polygenic risk scoring to produce accurate insights and health recommendations. Today, SelfDecode has helped over 100,000 people understand how to get healthier using their DNA and labs.
Joe is a thriving entrepreneur, with a mission is to empower people to take advantage of the precision health revolution and uncover insights from their DNA and biomarkers so that we can all feel great all of the time. 


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