Viral infections occur in a predictable seasonal pattern increasing in prevalence during the colder months of the year. In fact, a low-grade viral infection is commonly referred to as a “cold” because of when it occurs.
What environmental factor varies with the seasons and affects our biology to such an extent that it influences our susceptibility to viral infection? The answer is sunshine, or more accurately, the predictable seasonal peaks and troughs of skin-produced, solar-generated vitamin D.
Well known for its role in building and maintaining strong bones, vitamin D is also essential to the proper functioning of the immune system. Our immune system is tasked with identifying and eliminating cells invading the body that can make us sick. Without adequate levels of vitamin D, the immune system can’t differentiate disease-causing cells from healthy cells. The result is a dysfunctional immune system; invading cells that cause sickness go undetected and healthy cells can be mistakenly attacked.
Most Americans Are Vitamin D Deficient
The amount of vitamin D the government recommends to maintain bone health is 800 IU per day. This amount will help ensure that your bones won’t crumble but it is vastly less than what our bodies need on a daily basis, and many orders of magnitude below what the immune system needs to function optimally.
The average adult uses about 4000 IU of vitamin D per day, if 800 IU is the recommended amount to take in, where does the extra 3200 IU needed come from?
A normal diet contributes next to nothing. The answer is the sun during summer months and stored excess summer-made, fat-stored vitamin D during the colder months. There is virtually no solar-generated vitamin D in skin from the sun in the vast majority of the United States (>37 degrees latitude) from November to March due to the oblique angle of the earth relative to the sun resulting in the ozone layer absorbing more ultraviolet-B (UVB) photons. Due to the use of sunscreens and an indoor lifestyle, most Americans don’t generate much vitamin D from their skin during the summer months either, so they are severely depleted by the time winter rolls around.
Chronic Inflammation, Autoimmune Disease, and Vitamin D
Without adequate vitamin D, a dysfunctional immune system attacks healthy tissue causing chronic inflammation. Diseases linked to chronic inflammation are familiar and prevalent, and as a group are called autoimmune diseases: arthritis, atherosclerosis, Type 1 diabetes, multiple sclerosis, psoriasis, Crohn’s disease, ulcerative colitis among others.
Other factors can contribute to the onset of these diseases beyond vitamin D deficiency.
But people deficient in vitamin D are also more likely to develop cardiovascular disease and cancers of epithelial origin (breast, prostate, colon, lung, for example). Many studies have confirmed that living in a northern climate—and its lack of vitamin D—is a risk factor for developing these maladies. Being chronically vitamin D deficient causes immune dysfunction resulting in chronic inflammation, and is a recipe for poor health going forward.
COVID-19, Pre-existing Disease, Race, and Vitamin D
The current wave of COVID-19 hits those with the diseases listed above, plus the elderly and African Americans, the hardest. The elderly are typically severely vitamin D deficient because older skin is much less efficient at producing sunlight-generated vitamin D compared to younger skin.
Likewise, darker skin (due to increased UVB absorbing melanin content) produces less vitamin D as well, leading to greater vitamin D deficiency among African Americans. Since vitamin D deficiency is related to the incidence of these diseases, it is no wonder that older people and African Americans with any of these conditions didn’t do well when infected with COVID-19.
To make matters even worse for these groups of people, they are also more likely to be taking therapeutic drugs that specifically suppress a component of their immune response in an effort to treat the symptoms of their specific disease. An elderly African American man taking an immunosuppressant biologic drug to treat a condition like psoriasis has less chance to defend himself against COVID-19.
Treatment of many autoimmune diseases involves further disruption of the immune system through the use of drugs that suppress segments of the immune response. Then, along comes COVID-19 to exploit this immune system flaw.
The immune storm that does the killing with COVID-19 reflects an immune system gone haywire. Proinflammatory cytokines—substances like interferons and interleukins secreted by immune cells—are released inappropriately and destructively causing fluid in the lungs to build up, essentially drowning the victim. COVID-19 hijacks the immune system, and if that immune system is impaired or dysfunctional due to chronic vitamin D deficiency, the outcome isn’t good.
Preventing or Reducing Impact of Next Wave of COVID-19
Using the Spanish flu pandemic as a model, in 1918, the second wave of the flu was five times deadlier than the first wave. In real numbers, according to CDC figures, the peak death rate in late June 1918 was around 5 per 1000 persons. In early November 1918, it was 25 per 1000.
That’s the bad news. The good news is that there is something we can all do to help protect ourselves from the coming scourge. It’s easy, it’s cheap, and it’s safe. Around 5,000 to 8,000 IU vitamin D3 daily will get most people’s blood levels into the range to optimize immune system function. While it is no guarantee that if you fix the underlying vitamin D deficiency your body will defeat the virus, it could be a factor. And it is easy to get your daily dose. Skin generates 10,000 IU of vitamin D when exposed to summer sunlight for 15 minutes.
Our bodies are designed to be vitamin D rich. Our inability to appreciate the importance of the sun and its vitamin D in biological function is undermining our immunity.
What to do? Consult with your doctor. Get your vitamin D levels tested, 50–100 ng/ml is optimal. If you are vitamin D deficient, and getting sunlight is a problem, supplement with vitamin D3 (cholecalciferol) the most bioavailable form of vitamin D. Start to build up your blood levels of vitamin D now, and keep them there from now on.
[Editor’s note: For links to sources of facts claimed in the article, please find the online version with the sources hyperlinked.]
William F. Supple Jr., Ph.D. He received his doctorate in Neuroscience from Dartmouth College in 1986. He is one of the founders of StarPower LifeSciences, a research and educational foundation in South Burlington, Vt., that serves to inform regarding the power and benefits of vitamin D in health, disease, and longevity. Learn more about the health benefits of vitamin D at StarPowerLifeSciences.org