As you’ve been reading here and in much of the latest COVID-19 news, vitamin D plays a unique and crucial role in supporting your immune system and protecting you against severe disease. However, what many experts appear to forget is that it is not a “cure-all.”

Many are searching for a single answer to the pandemic, which may be why they are hesitant to consider vitamin D. It’s clear from years of scientific evidence that vitamin D plays a vital role in your health, and while data show that those with higher serum levels have a lower risk of severe disease, making sure your levels are adequate is one of the simplest, easiest and most cost-effective ways you can protect your health.

The Data Are Mounting: Vitamin D Helps Reduce Mortality

A recent population study from Israel, published in the FEBS Journal, adds to the mounting body of evidence that demonstrates vitamin D plasma levels are an independent indicator of the risk for infection and hospitalization from COVID-19.1 Researchers studied 14,000 members of a health service who were tested for the virus from February 1, 2020, to April 30, 2020.

They identified suboptimal or low plasma levels as concentrations below 30 nanograms per milliliter (ng/mL). Within the study group, 10.1% tested positive for COVID-19 and 89.9% were negative.

The data showed that the mean plasma vitamin D level in those who tested positive was significantly lower than in those who tested negative. The association with a low plasma level increased the likelihood of infection and the risk of hospitalization.

Additionally, the data showed other comorbid conditions that raised the risk of infection included age (50 years and older), being male and having low to medium socioeconomic status. Those who were 50 and older had a higher risk of hospitalization. Dr. Eugene Merzon, leader of the study, commented:2

“The main finding of our study was the significant association of low plasma vitamin D level with the likelihood of COVID-19 infection among patients who were tested for COVID-19, even after adjustment for age, gender, socio-economic status and chronic, mental and physical disorders.

Furthermore, low vitamin D level was associated with the risk of hospitalization due to COVID-19 infection, although this association wasn’t significant after adjustment for other factors.”

Merzon advised that the amount of vitamin D should be “personalized, with patients’ age, gender, race and ethnicity, nutritional status and health condition taken into account.”3

The results of the study were also published in Medscape Medical News. A member of the research team, Milana Frenkel-Morgenstern, Ph.D., said the results indicated that clinicians should “test patients’ vitamin D levels and keep them optimal for the overall health — as well as for a better immuno-response to COVID-19.”4

Optimizing your vitamin D levels may be the most accessible way to take control of your health — it’s easily accomplished, cost effective and has a long line of research to back its reputation as an infection fighter.

A study published in the Irish Medical Journal noted that people living in southern latitude countries that normally received sun, such as Spain and Northern Italy, had low mean concentrations of vitamin D and the highest infection and death rates in Europe.5 Medscape Medical News notes these countries do not fortify their food or suggest that people should take vitamin D supplements.6 The researchers concluded:7

“Optimising vitamin D status to recommendations by national and international public health agencies will certainly have benefits for bone health and potential benefits for Covid-19. There is a strong plausible biological hypothesis and evolving epidemiological data supporting a role for vitamin D in Covid-19.”

Serum Vitamin D Levels Predict Disease Severity

Results from further research have demonstrated that a person’s serum vitamin D level is predictive of their disease severity. In a study from England, data were collected from 134 patients who tested positive for COVID-19 and had serum vitamin D levels drawn when they were admitted to the hospital.8

The researchers found that the mean levels were comparable between those in the Intensive Care Unit (ICU) and those treated in the medical unit. However, those in the ICU were more likely to have a deficiency. Interestingly, there was no association with fatalities, which the researchers theorize had to do with the prompt diagnosis and treatment of vitamin D deficiency after admission.

In one review paper, researchers concluded that those at risk for influenza and/or COVID-19 should consider administration of 10,000 IU/d of vitamin D3 to quickly raise concentrations with the goal of reaching 40 ng/mL to 60 ng/mL.9 In a retrospective study involving 212 patients with confirmed COVID-19, the data showed a correlation between vitamin D and disease severity.10

GrassrootsHealth defines the lower edge of an optimal vitamin D level as 40 ng/mL.11 As I’ve written before, I believe to improve your immune function and lower your risk of viral infections, you’ll want to raise your vitamin D to a level between 60 ng/mL and 80 ng/mL (150 nmol/L and 200 nmol/L).

A team of scientists from Indonesia found that “Vitamin D status is strongly associated with COVID-19 mortality outcome …”12 In yet another study posted on the preprint portal Medrxiv, Northwestern University researchers found a correlation between severe vitamin D deficiency and higher mortality rates in countries around the globe.13

This is just an example of data being gathered and published that show there is a strong correlation between vitamin D levels and the risk of infection and the severity of disease. Some experts warn that observational studies, in which researchers gather data and observe an effect without changing the environment, limit the ability to use the data.14

The concern is that observational data cannot rule out other factors that may explain the results. Yet, despite the fact there may be other confounding factors, it’s vital to realize that data have been gathered in multiple countries, in multiple studies, and all the results are pointing in the same direction.

Mainstream Media Associating Low Vitamin D With Severe Disease

As some challenge the mounting evidence that vitamin D may contribute to changing the course of the disease, mainstream media are catching on to the evidence from science.

USA Today ran an article in June in which they gave an explanation of the importance of vitamin D to the immune system, how it affects the innate and adaptive immune system and the role it may play in COVID-19.15

Although they also point out the limitations of observational studies, the reporter included the high number of people who are deficient and wrote, “Most commonly, low levels of vitamin D are caused by insufficient exposure to sunlight.”

A piece in The New York Times covered several of the studies that associated low vitamin D with greater disease severity and two studies using the same data that were not as positive.16 In the negative studies, the association disappeared after the data were adjusted for age, race and obesity. An “ask-the-doctor” piece in Today reported mixed opinions.17

Dr. JoAnn Manson from Harvard Medical School and Brigham and Women’s Hospital believes the observational studies demonstrate the potential that vitamin D is beneficial. She is organizing a randomized clinical trial to test vitamin D in relation to the severity of COVID-19.

Conversely, private practice internal medicine physician Dr. Pieter Cohen “strongly discourages people from getting a vitamin D blood test right now.”18 He adds:

“We don’t recommend vitamin D to our patients and I see no credible evidence that vitamin D has a role in either preventing or treating COVID-19. We might have evidence in the future that evolves and would change our opinion, but that’s the status here.”

Manson has a more balanced view, saying:19

“We also know that vitamin D has an immune-modulating effect and can lower inflammation, and this may be relevant to the respiratory response during COVID-19 and the cytokine storm that’s been demonstrated.”

She recommends:20

“For patients who are unable to be outdoors and also have low dietary intake of vitamin D, it’s quite reasonable to consider a vitamin D supplement. The recommended dietary allowance of vitamin D is 600-800 IU/daily, but during this period, a multivitamin or supplement containing 1000-2000 IU/daily of vitamin D would be reasonable.”

Combine These Strategies With Raising Your Vitamin D Level

I strongly believe that vitamin D optimization is a powerful and beneficial strategy to protect your health. In my free report on vitamin D I’ve developed a resource you can use to share and help educate others. The only way you’ll know your vitamin D level is to test it. GrassrootsHealth has a home test kit that is simple to use and provides you with results at home.21

You’ll find a calculator at that will help you use your current weight, serum level and daily supplement intake to estimate how much vitamin D3 you need to reach your desired vitamin D level.22 Yet, while crucial, it’s not the only thing available to help protect your health.

I believe it is highly important to become metabolically flexible to help reduce the severity of a COVID-19 infection. The single most important step to attaining and maintaining metabolic flexibility is to reduce the number of hours during the day in which you eat.

When you do this, you decrease insulin resistance. In my book Fat for Fuel I discuss how to become metabolically flexible, including using intermittent fasting and cyclical nutritional ketosis.

The use of molecular hydrogen is another strategy, as it’s a powerful antioxidant and an anti-inflammatory agent. Using quercetin with zinc can further lower your risk. Quercetin acts as a zinc ionophore23 and has its own antiviral effects.24

If you are hospitalized, early treatment is essential. There is controversy over which is best, but clinical evidence has suggested mechanical ventilation should be avoided. I discuss the reasons for this in “Ventilators May Increase Risk of Death From COVID-19.”

One of the best treatments today is the MATH+ Protocol, first developed by the Front Line Covid-19 Critical Care Alliance.25 It’s designed to be used when someone is hospitalized and needs supplemental oxygen. You’ll find further information about each of these strategies in “How to Fix the COVID-19 Crisis in 30 Days.”

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