At the start of the coronavirus crisis, a lifestyle with relatively high levels of physical activity reduced the risk of hospitalization and death from COVID-19 by 36 and 45 percent, respectively. [Sports Med. 2021 Aug;51(8):1673-86.] Exercise apparently protects against viruses. A human study from the 1980s likely explains how.

Study
In 1989, Danish virologists from Rigshospitalet, the university hospital in Copenhagen, published a study involving 27 young cyclists and 15 untrained young men. The researchers took blood samples from the men, extracted the CD16+ natural killer cells, and added them to K562 cancer cells. They then determined what percentage of the cancer cells the CD16+ natural killer cells could eliminate.

Most CD16+ natural killer cells are CD16+ and CD56+ natural killer cells. Below, we summarize the key characteristics of this cell type. Essentially, these cells become active in the initial stages of a viral infection or the development of cancer. These natural killer cells kill off defective or infected cells.

Click on the table for a larger version.

Results
The cyclists' natural killer (NK) cells were 30 percent more active than those of inactive men. A lifestyle with a lot of intense physical activity apparently makes this type of immune cell more active.

But that's not all. An active lifestyle also increases the number of NK cells. In this study, this lifestyle also increased the number of CD16+CD56+ NK cells.

Conclusion
A few days ago, we wrote about another lifestyle factor that increases NK cell activity. Sleep.

More coming soon.