Vitamin, hormone, and immunomodulator, vitamin D is an essential micronutrient that wears many hats. The critical role of vitamin D in the immune system has been known for decades. Involved in innate and adaptive immune responses, the vitamin D receptor has been discovered in the majority of immune cells, and vitamin D demonstrates immunosuppressant, anti-inflammatory, antibacterial, and antiviral actions.
The novel coronavirus pandemic has ushered in a renaissance of interest globally in this underconsumed fat-soluble vitamin and its place in the immunity puzzle. The role of vitamin D in SARS-CoV-2 is an active area of debate. In a new study linking vitamin D status and COVID-19, researchers from Spain revealed a major vitamin D deficiency problem, a compelling gender difference, and some telling blood test results.
Published in the Journal of Clinical Endocrinology & Metabolism, this study included over 200 hospitalized adult patients with COVID-19. Over 80% were found to have vitamin D deficiency. In research or when you go to the doctor, the blood test used to measure your vitamin D status is serum 25-hydroxyvitamin D, 25(OH)D for short. This particular study chose a 25(OH)D level less than or equal to 20 ng/mL as their cutoff for deficiency. This detail sounds granular, but you’ll see why definitions for deficiency matter if you keep reading.
How was the study conducted?
This retrospective study used a case-control design, matching 216 COVID-19 patients with 197 controls (matched by gender) from the general population. The average 25(OH)D level in COVID-19 patients was 13.8 ng/mL (deficient), which was significantly lower than the control group (20.9 ng/mL). In the coronavirus patients, men were found to have worse vitamin D status than women. This is an important finding considering that amid this pandemic, men have been reported to experience greater COVID-19 disease severity and mortality than women.
Compared to patients with a 25(OH)D level greater than or equal to 20 ng/mL, vitamin D deficient patients experienced a longer stay in the hospital and higher prevalence of hypertension and cardiovascular diseases. Furthermore, lower vitamin D was associated with higher levels of three key lab tests: serum ferritin, troponin, and D-dimer. As it turns out, higher amounts of these biomarkers indicate infection, increased inflammation (the main driver of the “cytokine storm” phenomenon), and greater COVID-19 severity and fatality.
It’s important to point out that almost half (47%) of the healthy control group in this study (i.e., the non-COVID-19 folks from the general population of Spain) were vitamin D deficient. In fact, the prevalence of vitamin D deficiency is 30 to 60% in Western, Southern, and Eastern Europe. While the vitamin D/coronavirus link is a salient research question to examine, are we simultaneously ignoring another pandemic that’s totally fixable? (Enter vitamin D.
A solution to a problem.
Many things in life are not in our control. A pandemic and the complex challenges of 2020 have made that fact abundantly clear. So when an elegant, pragmatic solution exists—a piece to a larger puzzle—it should be shared swiftly and with accuracy.
So here it is: The problem is inadequate vitamin D, and the answer is adequate vitamin D. That sounds annoyingly simple, yet vitamin D deficiency remains widespread across the world, and many people are still confused about how much vitamin D they need.
I’ve seen many articles and news segments through the years (and amid the pandemic) recommending people simply eat more foods containing vitamin D to address the problem of vitamin D deficiency. On its own, unfortunately, that’s bad science and an ineffective public health message to spread.
Diet won’t cut it.
It’s a known scientific fact that vitamin D is naturally found in small amounts in a handful of foods—fatty fish, egg yolk, liver, and certain types of UV-irradiated mushrooms. Fortified options like cereal, milk, and orange juice deliver small amounts of vitamin D, for example 100 IU per 8-ounce cup of milk. Those modest levels are useful for preventing gross vitamin D deficiency and their manifestations (rickets, osteomalacia) but not for moving the needle when it comes to vitamin D status.
In the U.S., nationally representative data demonstrates that 92.5% of adults are consuming less than 400 IU of vitamin D per day from diet alone. Some nutrient deficiencies can be solved with a “food first” approach, a mantra every dietitian learns in school. Vitamin D is not one of those nutrients. Eating your way to a better vitamin D level is like giving someone 10 minutes to complete a marathon. It’s not going to cut it, and here’s why…
The case for vitamin D supplementation.
Sufficient blood levels of 25(OH)D, the measure of vitamin D status, are considered to be greater than or equal to 20 to 30 ng/mL. Why a range? The National Academy of Medicine chose a conservative cut point at 20 ng/mL, while the Endocrine Society says 30 ng/mL. To put this in context, research estimates that 23% of the U.S. population over the age of 1 have 25(OH)D levels less than 20 ng/mL, and 41% of American adults are below 30 ng/mL. These figures consider all vitamin D inputs: sunshine and diet.
Whether 20 or 30 ng/mL, let me be clear: These two numbers are not goals to aim for. Rather, they are cutoffs to avoid, since lower levels put you into vitamin D insufficient and deficient categories. You want your serum 25(OH)D level to be higher than 20 to 30 ng/mL, and consistently so. How much vitamin D will that take? Research from the late Robert P. Heaney, M.D., tells us the answer: 100 IU/day of vitamin D increases serum 25(OH)D by about 1 ng/mL in adults.
A little math, y’all: That means you need 2,000 to 3,000 IU/day of vitamin D3 to achieve those minimum cutoffs (20 to 30 ng/mL) of 25(OH)D. A few important notes: First, these intake levels assume no significant sun exposure (true for many of us during this pandemic) and that the person is a healthy weight. If an individual is overweight or obese, they may require two to three times more vitamin D to achieve that same 25(OH)D level. If a person has regular, significant sun exposure (other health considerations like skin cancer risk may come into play), they will need less vitamin D supplementation.
But remember, greater than 20 to 30 ng/mL is our goal for vitamin D status. In fact, some researchers and clinicians, including the Endocrine Society, actually recommend aiming for a higher range of 40 to 60 ng/mL. In adults, that would require 4,000 to 6,000 IU of vitamin D3 each day.
FYI, for all you parents and grandparents out there, the Endocrine Society recommends 1,000 IU per day of vitamin D3 for infants, children, and adolescents (ages 0 to 18) to raise their 25(OH)D levels above 30 ng/mL. For young children, liquid or gummy forms of vitamin D are available. For adults and children, you should know that the vitamin D3 form is superior to D2, as the former raises and maintains serum 25(OH)D levels much more efficiently.
What has worked for me.
Over the years, each time my doctor has tested my 25(OH)D level, it’s always been 50 to 60 ng/mL. That’s not because of my sun exposure or salmon intake. It’s because I take a daily vitamin D supplement.
There are many quality vitamin D3 supplement options and effective forms (softgels, capsules, tablets, gummies, liquids, etc.) out there from reputable brands. For me, I have taken 5,000 IU vitamin D3 softgels for many years. My lab work has proved this to be an effective dose for me personally.
What we know about vitamin D and COVID-19.
Vitamin D sufficiency in isolation is not a pandemic solution. The novel coronavirus SARS-CoV-2 is a complex, formidable virus with multifactorial risk factors and potentially grave outcomes. With that said, vitamin D is known to be an essential player in our immunity, and its relevance to the coronavirus warrants continued investigation.
Research has shown that vitamin D deficiency is common in COVID-19 patients and tied to longer hospital stays and lab tests associated with disease severity. Some studies (but not all) have found lower vitamin D status to be correlated with worse COVID-19 severity and mortality. These are observational findings I’m talking about. What about interventions?
Researchers are just beginning to look at the impact of vitamin D supplementation on coronavirus outcomes. Worldwide, over 20 trials are actively recruiting patients or underway. One pilot study conducted in Spain and published recently in the Journal of Steroid Biochemistry and Molecular Biologyfound that high doses of a 25(OH)D drug (Calcifediol) resulted in a reduction in the need for ICU treatment in hospitalized COVID-19 patients.
The Vitamin D and COVID-19 Trial (VIVID), currently underway at Harvard, will offer cardinal insights on the effects of vitamin D3 on the coronavirus. Estimated to wrap up in January 2021, this randomized, double-blind, placebo-controlled trial will examine how vitamin D3 supplementation affects COVID-19 severity in newly diagnosed patients and prevention of COVID-19 infection in household members. In this four-week intervention, patients will either receive a placebo or vitamin D3—9,600 IU/day on the first two days of the study, followed by 3,200 IU/day on days three through 28.
Vitamin D deficiency is relevant to everybody, and unlike the coronavirus pandemic, the solution is not elusive. Supplementation is an inexpensive and science-based answer to eliminate vitamin D deficiency, in the U.S. and across the globe.
Adults of normal weight need at least 2,000 to 3,000 IU each day of vitamin D3 to prevent insufficiency, and children need 1,000 IU daily. Higher levels of supplementation (greater than or equal to 4,000 IU/day) are likely prudent to ensure vitamin D sufficiency in the long term. Whether for your bone health or immune system, adequate vitamin D is attainable and a no-brainer investment in your wellness.