According to a British observational study1 posted July 6, 2020, on the preprint server medRxiv, ultraviolet (UV) radiation exposure appears to lower COVID-19 mortality rates.
As reported by News Medical Life Sciences,2 environmental factors such as temperature, humidity and UV irradiation are known to play a role in other infectious diseases, including seasonal influenza, so it shouldn’t come as a surprise that SARS-CoV-2 — the virus responsible for COVID-19 — can be affected in a similar manner.
UV Radiation Lowers COVID-19 Mortality
I’ve written extensively about the importance of vitamin D and its influence on COVID-19 specifically, but this research suggests there are other benefits to sun exposure besides vitamin D production.
The researchers looked at UVA measures and COVID-19 death statistics in 2,474 U.S. counties, 6,755 Italian municipalities and 6,274 areas in England between the months of January and April 2020, which is when vitamin D production due to low sun exposure tend to be minimal. According to the authors:3
“Our fully adjusted model showed an inverse correlation between UVA and COVID-19 mortality with a Mortality Risk Ratio (MRR) of 0.73 … per 100KJ/m2 increase UVA in the USA, 0.81 … in Italy and 0.51 … in England. Pooled MRR was 0.68 …
This represents a halving of the average risk of death across the lower and narrower range of UVA experienced across England and across the higher and wider range across Italy and the USA …
Our analysis suggests that higher ambient UVA exposure is associated with lower COVID-19 specific mortality. This effect was independent of temperature and UV within the vitamin D action spectrum.
Relatively higher UVA, across a country experiencing lower average levels of UVA during and immediately preceding the pandemic (England), is associated with greater falls in mortality risk compared to countries (Italy and the USA) with a higher average level suggesting an exposure tolerance effect …
We have been able to show a possible benefit from UV at wavelengths that do not cause synthesis of vitamin D. this suggests that explanations for seasonal and geographic variations in COVID-19 prevalence need to consider mechanisms other than just vitamin D.”
Mechanisms of Action
The researchers hypothesize UV exposure “may have a direct effect on the viability of SARS-CoV-2 virus in airborne droplets,” as well as the virus’ ability to stay viable on various surfaces, thus reducing overall infection rates and lowering the initial inoculation load in those infected, which in turn might reduce the risk of severe illness.
Another mechanism of action may involve nitric oxide. UVA radiation triggers the release of nitric oxide in your skin, mobilizing it into your circulation. This lowers blood pressure by causing your blood vessels to expand. This, the researchers say, is one important metabolic benefit of UV exposure that does not involve vitamin D.
“As cardio-metabolic disease and possibly hypertension increase the risk of death from COVID-19, any UV driven improvements in these risk factors would be expected to reduce mortality,” the researchers note.
What’s more, nitric oxide may help mitigate the endothelial damage seen in severe COVID-19 infection that leads to organ failure. While not mentioned in this study, nitric oxide also improves your immune function, thins your blood and decreases blood viscosity, which in turn decreases platelet aggregation. As such, nitric oxide helps reduce your risk of developing a life-threatening blood clot.
Previous research has also found nitric oxide inhibits replication of the SARS virus (SARS-CoV), and the researchers hypothesize that, since the spike proteins of the two viruses are similar, nitric oxide may have a similar effect on SARS-CoV-2. If correct, this could be yet another mechanism of action by which nitric oxide helps reduce disease transmission and severity.
So, to summarize, not only does exposure to sunlight lower COVID-19 mortality, but just about any strategy that boosts nitric oxide production may also have a similar effect. Examples of such strategies include the Nitric Oxide Dump workoutand consuming nitrate-rich foods such as beetroot juice, arugula and cilantro.