Vitamin D Deficiency and COVID-19

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Lately, we’ve been reviewing the potential for vitamin deficiencies to play a significant role in disease in people who, you’d think, would be otherwise healthy. This article is about vitamin D.


Vitamin D is an essential nutrient your body needs to maintain good health. It is produced in your skin when exposed to sunlight. It helps your body absorb and maintain adequate levels of calcium and phosphate that are important for strong bones. In the past, deficiency of vitamin D was considered to be a cause for “rickets”, a condition which caused weak, deformed bones in children. Recently, more benefits of adequate blood levels of vitamin D have been found. It is even thought to decrease the risk of severe cases of respiratory infections, including COVID-19.


It has been suggested by some vitamin D researchers that approximately 10–20 minutes of midday sun at least twice a week to the face, arms, legs, or back without sunscreen may be enough to produce the vitamin D needed by the average person .

Despite this, deficiency of vitamin D in the U.S. is seen in 42 percent of the total population, with different demographics having more risk than others. It seems to be more common in people who are:

  • Over age 65
  • African-Americans
  • Hispanics
  • Caucasians who avoid sun exposure
  • Premenopausal females
  • Nutritionally deficient
  • Take certain meds for GI problems like heartburn, constipation, and others
  • Obese
  • People who have chronic kidney or liver disease

Other factors like weather, pollution, and the amount of time indoors also come into play. Complete cloud cover drops ultraviolet (UV) energy from the sun by half, shaded areas by more. This includes “shade” provided by air pollution.  As UVB radiation doesn’t go through glass, sunshine radiating indoors through windows doesn’t help produce enough vitamin D. SPF 8 or greater sunscreens potentially block these same rays (although people don’t put enough on).

Putting together all these risk factors includes a pretty big chunk of the general population. I was initially surprised that darker-skinned people have more of a chance (up to 80%) of being vitamin D deficient. Most of us know that dark colors absorb light and light colors reflect it. In humans, however, it turns out that the more melanin pigment in your skin, the less vitamin D gets produced by exposure to sun. The percentage of African-Americans with vitamin D deficiency may be up to 80 percent, with Hispanics at about 70 percent. This percentage seems to be less in Africa and South America, where people spend more time outside and are exposed to more direct sunlight.


Even in those on an average diet, vitamin D is naturally present in just a few foods. This is why some food items, like milk and orange juice, are “vitamin D-enriched”. Infant formula is required to have vitamin D added in both the United States and Canada.

Although few natural food products naturally contain vitamin D, some do:

  • Fatty Fish (salmon, tuna, mackerel)
  • Some mushrooms
  • Beef liver
  • Egg yolks

Even vitamin D supplements are generally inert until converted by two organs. The liver and kidneys activate vitamin D by converting it to active forms like 25-hydroxyvitamin D and 1,25-dihydroxyvitamin D, respectively (also known as “calcidiol” and “calcitriol”). As calcidiol is several times more potent than the original vitamin, this explains why those with poorly functioning livers or kidneys are especially deficient.


Vitamin D has been found to reduce inflammation and modulate immune response. This is different from simply strengthening immune response; a body’s excessive reaction to an infection may cause the immune system to go haywire. This produces excessive amounts of proteins called “cytokines” that send immune cells into action. This over-reaction by the body is known as “cytokine storm”. Vitamin D helps prevent cytokine storm while allowing an effective defense.


Serum concentrations of 25-hydroxyvitamin D are a good indicator of whether someone is deficient or not. This is not a standard test done on routine yearly exams, however. What constitutes a normal vitamin D level may be a subject of disagreement among some scientists. I believe that a value of 40 ng/ml is optimal but may rarely be achieved at current recommended daily allowances (RDAs).

Recommended Dietary Allowances (RDAs) for Vitamin D


0–12 months     400 IU daily                

1–18 years         600 IU  daily               

18-70 years       600 IU daily

>70 years           800 IU daily

Like many things in medicine, these numbers are controversial. Many scientists suggest 2000 International Units (IUs) or more (not to exceed 10,000 IUs) is more appropriate for adults receive all the benefits of vitamin D. Reports suggest that, in order to consistently raise serum levels of bioactive vitamin D in those deficient, at least 1,500-2,000 IU/day or more of supplemental vitamin D is needed.

This is likely hard to obtain without a supplement. In supplements and fortified foods, vitamin D is available as either D2 (ergocalciferol) or D3 (cholecalciferol). The two are very similar to each other and are both considered effective. D2 is thought to be less potent at high doses.


Having enough vitamin D in your system might just help avoid the intensive care unit (or worse) if you become infected with COVID-19. Studies from different nations seem to find the sickest patients have some of the same risk factors as those with vitamin D deficiency. Nations with higher percentages of deficiency have higher death rates. Also, places that have the most direct sunlight (near the equator) and those people spending the most hours outside seem to have less fatalities.

The controversy in conventional medicine continues, with more research needed. No treatment studies raising vitamin D levels in sick COVID-19 patients have been done to see its results. It’s also true no evidence exists that having healthy vitamin D levels won’t prevent you from catching the very transmissible virus.

Having said that, it seems that 2000-4000 IUs of vitamin D supplementation isn’t associated with any major complications, and may prevent a severe case of the disease. 4000 IU is the safe upper limit of vitamin D, according to the Institute of Medicine (IOM), but a risk assessment review published in the American Journal of Clinical Nutrition failed to find toxicity at 10000 IU in healthy adults with no underlying health conditons.

Consider asking your physician for a vitamin D test to see whether you might benefit from more vitamin D. In these pandemic times, it’s a good idea.

Joe Alton MD

Joe Alton MD

Learn more about vitamin D deficiency and 150 other medical topics in the latest edition of The Survival Medicine Handbook. Also, check into some of our medical kits and individual supplies from the entire line at!

Hey, don’t forget to check out our entire line of quality medical kits and individual supplies at Also, our Book Excellence Award-winning 700-page SURVIVAL MEDICINE HANDBOOK: THE ESSENTIAL GUIDE FOR WHEN HELP IS NOT ON THE WAY is now available in black and white on Amazon and in color and color spiral-bound versions at

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