Vitamin D and Exercise Boost Natural Killer (NK) Cells, Important for Immune Health

by Mike Mutzel




We share a fascinating study that found correlations between NK cell activity, vitamin D status and exercise habits. Since NK cells are a vitally important first-line defense against pathogens, these findings have timely, real-world implications.

We also review a recent study which found a correlation between belly fat and viral load in hundreds of subjects.


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Key Time Stamps:

01:15 Your adaptive immune system includes antibodies and T-cell immunity. It provides immunologic memory, providing groundwork for the next exposure.

01:40 Natural killer cells are part of your innate immune system, which has no memory and provides an all or nothing response.

01:50 Increased expression of innate immune system activation is found with obesity, insulin resistance, hypertension, and other chronic inflammatory diseases. This seems to distract the natural killer cells from a robust initial response.

02:55 Overweight individuals tend to have a higher viral load.

03:10 Natural killer cells deal with pathogens, bacteria, and viruses. The cytokines released by natural killer cells, help to signal your adaptive immune system.

04:00 Natural killer cells are important in preventing cancer. They seek and destroy neoplastic cells, malignant cells and cells infected with viruses and other pathogens.

04:15 Vitamin D and exercise are major determinants of natural killer cell activity.

04:40 Age, gender, vitamin D and exercise are associated with immune function determined by natural killer cell activity.

04:45 Age was a determining factor for low natural killer cell activity in men, but not women.

05:10 Sufficient levels of vitamin D reduced risk of low natural killer cell activity in men.

05:30 Exercise reduced risk of low natural killer cells in women. Exercise reduced the probability of risk of very low natural killer cells in both men and women over the age of 60.

05:45 A natural killer cell assay measures the amount of interferon gamma released by natural killer cells. This test is not commercially available here in the US.

 07:30 Decreased natural killer cell function in immunologically normal elderly is associated with increased risk for severe infections and mortality in general.

07:40 Natural killer cells may play a critical role in the early immune response, which can be determined by the overall outcome for COVID 19.

08:20 An exhausted innate immune system can become depleted with a severe infection. Natural killer cells, which mediate cyto-toxicity, were depleted in ventilator dependent COVID patients.

09:35 Men with vitamin D levels 30 to 39 nanograms/ml had decreased risk for very low natural killer cell activity.

10:20 Medium to high intensity exercise decreased the risk for very low natural killer cell activity in women.

11:50 The vitamin D level sweet spot appears to be between 40 and 60 nanograms/ml.

13:25 Low natural killer cell activity in women did not seem be impacted by age as much as with men.

13:55 The size of your thymus gland and the amount of T cells that you produce decline (immunosenescence) as you age. Natural killer cells may compensate for this.

14:40 Over-exercise is associated with greater odds of low natural killer cell activity.

15:30 Vitamin D deficiency and insufficiency were associated with increased susceptibility to COVID 19.

17:00 Immune system assays are expensive. Triangulate looking at things like white blood cell count, C-reactive protein.

20:45 Each 1 unit increase in BMI, reflected a 12% increase in the risk for severe COVID 19. Viral loads are increased in individuals who are obese.



Oh, S., Chun, S., Hwang, S., Kim, J., Cho, Y., Lee, J., et al. (2021). Vitamin D and Exercise Are Major Determinants of Natural Killer Cell Activity, Which Is Age- and Gender-Specific, 1–12.

O’Shea, D., & Hogan, A. E. (2019). Dysregulation of Natural Killer Cells in Obesity. Cancers, 11(4), 573.

Clinical, immunological and virological SARS-CoV-2 phenotypes in obese and non-obese military health system beneficiaries. (2021). Clinical, immunological and virological SARS-CoV-2 phenotypes in obese and non-obese military health system beneficiaries, 1–34.

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