Vitamin D fights viral infections and boosts the immune system

This article was previously published on June 21, 2020 and has been updated with new information.

Here I interview three vitamin D experts about the importance of vitamin D for improving your immune function and resistance to all kinds of viral infections, including COVID-19.

Bruce Hollis, Ph.D., of the Medical University of South Carolina, has been researching vitamin D since the late 1970s. His research associate at the Medical University of South Carolina is Dr. Carol Wagner, a neonatologist who has been researching vitamin D since 2000.

Carole Baggerly is the director and founder of GrassrootsHealth Nutrient Research Institute, a nonprofit public health research organization dedicated to bringing public health messages related to vitamin D from research to practice. Baggerly received our Game Changer Award in 2018. She started her work in vitamin D in 2005 after breast cancer treatment.

Vitamin D levels correlate with disease severity

GrassrootsHealth conducted a review of an observational study of 212 patients in Southeast Asia who had COVID-19, which found an association between vitamin D levels and disease severity. Those with the mildest disease had the highest vitamin D levels and vice versa.

Of the 212 people, 49 had mild illness; 59 had a common illness; 56 were serious and 48 were critical. In the initial study group of 212 patients (see Table 1 below), 55 had normal vitamin D levels, defined as greater than 30 ng/ml; 80 had insufficient levels of 21 to 29 ng/ml and 77 had insufficient levels less than 20 ng/ml.

Now it’s worth noting that the “optimal” vitamin D level in that study was set at 30 nanograms per milliliter (30 ng/ml), which may actually be sub-optimal. According to GrassrootsHealth’s research, 40 ng/mL is the lower limit of optimal, with 60 ng/mL to 80 ng/mL being ideal for health and disease prevention. Nevertheless, the advantage of a vitamin D level above 30 ng/ml was clear.

vitamin d covid-19 seriousness
descriptive statistics

Vitamin D levels correlate with mortality risk

A second study looked at data from 780 hospital patients in Indonesia. The same limits for vitamin D were used in this study: below 20 ng/ml; between 20 ng/ml and 30 ng/ml; and above 30 ng/ml.

After adjusting for confounding factors, those with vitamin D levels between 20 ng/mL and 30 ng/mL had a seven-fold higher risk of death than those with vitamin D levels above 30 ng/mL. A level below 20 ng/ml was associated with a 12-fold higher risk of death. As Hollis noted, “That’s really strong data.”

It’s Your Vitamin D Blood Level That Matters, Not The Dose

Now, many vitamin D studies conclude that vitamin D supplementation has little or no effect on any particular health problem or condition. But there is a very simple reason for this: Virtually all of these studies use the same dosage or doses for everyone and do not measure the blood levels of the participants.

This is a critical mistake, because it’s really the blood level that has to get over a certain threshold, and the dosage it takes to get there can vary widely. Another problem is the fact that most studies use a dosage that is much too low. If the dosage is too low, you will not be able to get your blood level within the protective range and vitamin D will appear to be useless.

A third factor that can influence the outcome of vitamin D studies is the interaction between vitamin D and other nutrients. Competing deficiencies can affect a particular subcohort or population, obscuring the results.

A fourth factor is how you define deficiency – using a “word” versus a serum level. For the GrassrootsHealth Scientists’ Panel of 48 researchers, the consensus is that the minimum serum level should be 40 ng/ml (100 nmol/L). Wagner explains:

“If you do a PubMed search, you see literally thousands of articles. You see this really rich basic scientific information that has accumulated over the past two decades that strongly supports the role of vitamin D in immunity.

But then, when randomized control trials are done, there are some that suggest vitamin D is effective and others say no. It’s been a controversial issue and I’m sure Bruce and Carole [Baggerly] will agree with me that doing nutrient studies is not the same as doing a pharma study where… they start with zero as the baseline.

[When it comes to] vitamin D [levels], everybody is different. And so, using a biomarker, which we use in our studies, the total circulating 25(OH)D is a much better indicator.”

Hollis adds:

“In nutritional studies with vitamin D, it was always the dosage — how much you’re going to give — without worrying about what the blood levels achieved would be.

In our studies, of course, we always measure blood levels. Those studies that Carol [Wagner] and I performed during pregnancy (in 2003), they were checked by the FDA. We had to get an investigational drug number (IDN) to conduct these studies, and it was unheard of to have to do that…

In the end we proved that [dosage] we [gave] — 4,000 units — was completely harmless as far as the dosage went. But it’s still a battle… We haven’t seen any side effects due to vitamin D in any of the studies that Carol [Wagner] and I’ve performed, not one…”

Laws need to be updated

Unfortunately, with labeling laws as they are, it’s very difficult to get this point across. As noted by Baggerly:

“Great health… [asked] the FDA … for the ability to print on the [label of] any vitamin D supplement that’[Vitamin D] can help to have a healthy pregnancy and [improve] birth outcomes.’ What we were told in that meeting by the FDA person was, “At what dose?”

We explained repeatedly that it was not a dose, but a serum level, and the FDA responsible said, “By law, we can only accept recommendations based on dose, and if you can’t give us a dose, we can’t make any recommendations.” to accept.’ So the laws are outdated to say the least.”

Skin Color Affects Your Risk of Vitamin D Deficiency

The color of your skin is related to your vitamin D level and we also see racial differences in COVID-19. As Hollis noted, in Detroit, Michigan, where African Americans make up 14% of the population, they were responsible for 40% of COVID-19 deaths.1

“It was even worse in Sweden, where the Somali population is less than 1%, and they… [account for] 40% of the dead”, says Hollis. “In Britain, of the 24 doctors who died in healthcare, 23 were people of color. It was so bad they pulled those people off the front lines… the doctors and the nurses.”

Vitamin D deficiency likely plays a role in this racial disparity, although diet, obesity and diabetes also contribute to immune dysfunction. It’s important for dark-skinned people to realize that the more melanin you have, the more sun exposure you need to make enough vitamin D.

According to Hollis, it is physiologically impossible for a dark-skinned person in the United States, unless they are in South Florida or Hawaii, to get optimal vitamin D from typical sun exposure.

Daily supplementation can strengthen lung tissue

If for some reason you can’t get regular sun exposure, then vitamin D supplementation is recommended. Ideally, you want to take it daily, rather than taking a large bolus dose once a week or once a month. As Hollis noted, studies have consistently shown that only daily supplementation was effective.

“When they looked at bolus supplementation, the effect on respiratory infections disappeared,” he says. “Taking a bolus dose every other week or once a month, every three months, was not effective in controlling respiratory infections. So we prefer daily [supplementation].”

Baggerly adds:

“The vitamin D component that is produced in the skin as a result of sun exposure is at some point what we take as a supplement, the D3, and that is then metabolized to 25(OH)D, which we measure, for the biggest part.

The D3 and even the 25(OH)D have been considered inactive in the past… In recent studies, and we have it really relatively recently, the D3 itself seems to be active to keep the epithelium strong [to prevent endothelial leakage].”

Vitamin D3’s ability to strengthen the endothelial structure of the lungs may be one way that vitamin D helps protect against COVID-19. “COVID-19 affects the lungs…and vitamin D in this model was shown to stabilize that,” says Hollis.

Vitamin D strengthens and regulates immune function

Vitamin D also has a marked effect on your innate immune system, which is your first line of defense against bacteria and viruses, as well as your adaptive immune system, involving your T-regulatory helper and suppressor cells and natural killer cells.

They all have to be in balance, explains Wagner. If an imbalance occurs, you can end up with a cytokine storm. According to Wagner, vitamin D is very effective for regulating and balancing adaptive immunity. An example that demonstrates the elegance of this system is pregnancy. Wagner explains:

“You go from a very active immune system where, if the egg is fertilized, you have an invasion of the uterine wall. You have to take that into account, [and] it is a very pro-inflammatory condition. Then, in order to allow fetal growth, you have to rest from that [proinflammatory state].

You see shifts in the T cell populations, the phenotypes, but also in the monocyte-macrophage population, their activity. And then, at the time of delivery, you go back to a pro-inflammatory state [when you] going into labor and expelling the fetus and placenta. So it’s a very elegant process.

We know that when it’s disturbed, we get conditions like preeclampsia. You get a vasculitis all over the body and it can lead to the death of both the mother and the fetus, and you have a cytokine storm in the process. So COVID-19 is not like a foreign alien; it takes advantage of the immune system that we have in our bodies and that makes sense.

Although this particular virus is new, it takes up systems in our body that are old and that contain a very old pre-pro-hormone, namely vitamin D.

So it makes sense to me, as a physician and as a scientist, that those individuals who have balance in their bodies, and in this case vitamin D balance, will do better than if they were deficient. [because then] they can’t mobilize it [immune] cells. Those cells will no longer function.”

Research has also shown that pregnant women with optimal vitamin D levels significantly reduce their child’s risk of developing type 1 diabetes, an autoimmune disease. As noted by Baggerly:

“We’re working with the Diabetes Research Center to see if, even after the child is born, as long as it doesn’t have full-blown type 1 diabetes, what can we do to stop it? And it turns out that the combination of vitamin D and omega -3 really matters.”