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Most Hospitalized COVID Patients Have Vitamin D Deficiency, Study Suggests

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Key Takeaways

  • A new study found that more than 80% of people hospitalized with COVID-19 were deficient in vitamin D.
  • The research didn't establish a link between vitamin D levels and severity of COVID-19 infection, but the findings support the case for taking vitamin D supplements as part of the fight against the coronavirus.

Scientists have been researching a possible link between COVID-19 and vitamin D deficiency for months, and the latest study found that more than 80% of hospital patients with the virus lack the crucial “sunshine vitamin.”  

Study Findings

The research, published in the Endocrine Society's Journal of Clinical Endocrinology & Metabolism, found that 82.2% of 216 COVID-19 patients at Hospital Universitario Marqués de Valdecill in Cantabria, Spain, were deficient in vitamin D. By comparison, only 47% of a control group of people who didn’t have COVID-19 were deficient.

However, it didn't find a relationship between vitamin D levels and the severity of COVID-19 (such as ICU admission or the need for mechanical ventilation), or deaths from COVID-19.

The University of Cantabria researchers recommended vitamin D treatment for "high-risk individuals," such as the elderly and patients with comorbidities, as well as COVID-19 patients.

J. Patrick Whelan, PhD

People who are vitamin D deficient are very over-represented among the COVID-19-susceptible populations. The effectiveness of vitamin D (as well as vitamin C and zinc) in protecting us against other viral infections suggests it is likely to be of benefit when it comes to COVID-19 as well.

— J. Patrick Whelan, PhD

Why We Need Vitamin D

Vitamin D isn’t like other vitamins, because it functions as a hormone. “Vitamin D, which we get from sun exposure, diet, and supplements, is a steroid hormone that modulates expression of genes involved in the immune defense system,” says Marilyn Tan, MD, an endocrinologist with Stanford Health Care in Stanford, California. “It’s important for bone health and calcium balance.”

Low vitamin D is a risk factor for osteoporosis (a condition that weakens the structure of the bone) in adults, and severe vitamin D deficiency can have adverse effects on the skeleton.

Vitamin D deficiency has also been associated with poorer health outcomes. “There is ongoing research investigating the association between vitamin D levels and multiple health conditions including type 2 diabetes and certain cancers,” Dr. Tan says. “This is not to say that vitamin D deficiency is the cause of these chronic medical conditions, per se, but there is an association between very low vitamin D levels and those who are chronically ill.”

Vitamin D deficiency may also be associated with symptoms like mood changes, bone pain, fatigue, malaise, and muscle weakness.

Vitamin D and COVID-19

Pediatric rheumatologist J. Patrick Whelan, PhD, points out that we don't yet have good prospective studies yet to show that vitamin D supplementation decreases the risk of coronavirus infection.

However, he believes there is "tremendous circumstantial​ evidence" to support its use. "People who are vitamin D deficient are very over-represented among the COVID-19-susceptible populations," he says. "The effectiveness of vitamin D (as well as vitamin C and zinc) in protecting us against other viral infections suggests it is likely to be of benefit when it comes to COVID-19 as well."

Another study, published in BMJ Nutrition Prevention and Health, found that higher levels of vitamins A, E and D are linked to fewer "respiratory complaints" in adults. U.K. researchers analyzed the data of 6,115 adult participants of the government’s 2008–2016 National Diet and Nutrition Survey Rolling Programme – which collected annual data on all food and drink consumed by around 1,000 randomly-selected people living in private households across the UK.

It found that vitamin A and E intake from both diet and supplements was associated with a lower prevalence of respiratory complaints, while vitamin D intake from supplements only was associated with the same.

Marilyn Tan, MD

Vitamin D, which we get from sun exposure, diet, and supplements, is a steroid hormone that modulates expression of genes involved in the immune defense system. It’s important for bone health and calcium balance.

— Marilyn Tan, MD

Vitamin D Supplements: Yes or No? 

Whether a supplement is needed depends on your baseline vitamin D level, which can vary by season (sun exposure is one of the main sources, remember). 

Nonetheless, Whelan thinks everyone should take a vitamin D supplement because of the associations with improved immune responses to viruses and less autoimmunity, plus the benefits to bone health.

“There is very little vitamin D in the diets of most people, particularly since 90% of adults in the world are lactase deficient (also known as lactose intolerant) and don't get it from drinking milk,” Whelan says. “Fish oil is a good dietary source of vitamin D, so people who eat fatty fish like salmon probably don't need to worry as much.” 

Whelan adds that most of us don't spend enough time outdoors, meaning we don't give our skin a chance to make the vitamin D we need.

Men vs. Women

The new study also found that men had lower levels of the vitamin than women. Whelan thinks this is because men are less likely than women to take supplements or pay attention to their health.

"Most people think of osteoporosis as a women's problem, but there are plenty of men coming into the emergency room with hip fractures due to fragile bones," Whelan says. "Older men are at particular risk because they are often more sedentary, which means less sun exposure and less exercise to strengthen their bones."

What This Means For You

If you think you might be deficient in vitamin D, you can get a supplement from all good health food stores – just run it past your doctor first.

Remember, no supplement can protect you from COVID-19, so continue to follow the guidelines from your local health department to help curb the spread of the virus and keep you and your family safe and healthy.

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  1. Hernández, J et al. Vitamin D status in hospitalized patients with SARS-CoV-2 infection. The Journal of Clinical Endocrinology & Metabolism. 2020 Oct. doi: 10.1210/clinem/dgaa733 

  2. Pike JW, Christakos S. Biology and mechanisms of action of the Vitamin D HhormoneEndocrinol Metab Clin North Am. 2017;46(4):815-843. doi:10.1016/j.ecl.2017.07.001

  3. MedlinePlus. Vitamin D Deficiency. Updated June 12, 2020.

  4. Cleveland Clinic. Vitamin D deficiency. Updated October 16, 2019.

  5. Almoosawi, S and Palla, L. Association between vitamin intake and respiratory complaints in adults from the UK National Diet and Nutrition Survey years 1–8. BMJ Nutrition, Prevention & Health. 2020 Oct. doi: 10.1136/bmjnph-2020-000150