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Vitamin D

With summer closing its sunny gates, it is important to bring vitamin D into our awareness.

Getting enough vitamin D is an important part of an overall healthy lifestyle, but many Americans may not be getting enough. One report from the National Center for Health Statistics, which is part of the U.S. Centers for Disease Control and Prevention, found that about 25 percent of the population is at risk for inadequate levels of vitamin D and 8 percent is at risk for deficiency.

Now, new research shows that too-low levels of vitamin D may be linked to a greater risk of testing positive for coronavirus.

Patients with a “likely deficient” vitamin D status had nearly double the likelihood of testing positive for COVID-19 compared to those with a “likely sufficient” vitamin D status, per a study on a single testing center published in the journal JAMA Network Open.

Researchers gathered data from 4,314 patients tested for COVID-19 at the University of Chicago Medicine between March 3 and April 10, 2020. A total of 489 patients had their vitamin D levels measured in the year before getting tested for COVID-19.

Nearly 20 percent of participants whose most recent vitamin D level was deficient tested positive for COVID-19, while only 12 percent of participants whose last vitamin D level was not deficient tested positive.

The Association of Vitamin D Deficiency with COVID-19 Risk Factors

It’s important to keep in mind that vitamin D deficiency may also be heightened by several factors associated with COVID-19 risk, such as age, obesity, diabetes, and chronic illness.

Still, the analysis controlled for many of these factors.

The researchers note that more research may be warranted through randomized clinical trials with varying doses of vitamin D in populations with and without vitamin D deficiency to further understand the link.

“Since African American and Hispanic populations in the United States have both high rates of vitamin D deficiency and bear a disproportionate burden of morbidity and mortality from COVID-19, they may be particularly important populations to engage in studies of whether vitamin D can reduce the incidence and burden of COVID-19,” note the researchers.

Vitamin D for COVID Treatment or Prevention?

This research also suggests that testing vitamin D levels might be an important tool in guiding treatments and prevention strategies for COVID-19.

“Vitamin D strengthens innate immunity, so it might be expected to decrease COVID-19 infection and transmission,” note the researchers. “Vitamin D also affects metabolism of zinc, which decreases replication of coronaviruses.”

Recent studies give credence to vitamin D’s protective potential. A 2021 investigation found that among patients hospitalized with COVID, intake of vitamin D significantly reduced Intensive Care Unit admission and mortality. In this study, of the 447 patients treated with calcifediol, a form of vitamin D, 4.5 percent required the ICU. In contrast, of the 391 patients who were not treated with vitamin D, 21 percent required the ICU.

It’s important to note that because of how vitamin D affects immune function, it may reduce inflammatory responses that cause symptoms of COVID-19. That means that while vitamin D may reduce spread of COVID-19, it might also increase the chances that someone carries it asymptomatically, making it more difficult to track the vitamin’s effect on virus spread, according to study authors.

Since you can transmit COVID-19 even if you don’t have symptoms, it’s important to follow general guidelines for preventing the spread:

  • Maintain a social distance of six feet or more from people outside of your household whenever possible.
  • Wear a mask when out in public and when you can’t be socially distant.
  • Wash your hands or sanitize frequently and disinfect commonly touched surfaces.
  • Avoid large groups or situations when it will be hard to be socially distant.
  • When spending time with others, being outdoors is safer than indoors.

Keep in mind this idea is just a hypothesis and requires further investigation.

Getting Enough Vitamin D

Even though more research is needed to determine the link between vitamin D and COVID-19, it’s still good for overall health to ensure you’re getting enough of the vitamin.

Doing so may play a role in protecting against conditions like heart disease and high blood pressure, diabetes, infections and immune system disorders, certain types of cancer (like colon, prostate, and breast cancers), and multiple sclerosis, according to the Cleveland Clinic.

Although you can get vitamin D through exposure to sunshine (15 to 20 minutes three days per week is typically enough to maintain adequate levels) and nutritional supplements, you can also get it through a healthy diet.

Vitamin D is found in foods like trout and salmon, white mushrooms, fortified milk, eggs (the vitamin is in the yolk), and fortified cereal, per the National Institutes of Health.

If you decide to supplement with vitamin D, keep in mind that a key co-nutrient of vitamin D is vitamin K2, which directs calcium into the bones. As these two vitamins work synergistically, it is important to intake adequate amounts of both. While sufficient intake of vitamin K2 can be reached through diet alone, data suggests that joint supplementation of vitamin D and vitamin K2 might be more effective than taking either one in isolation.

It’s a good idea to talk to your doctor before taking any vitamins and/or supplements as they can potentially interact with your medications.

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Ballegooijen, A et al. “The Synergistic Interplay between Vitamins D and K for Bone and Cardiovascular Health: A Narrative Review.” International Journal of Endocrinology. 2017. doi: https://doi.org/10.1155/2017/7454376.

Meltzer DO, et al. Association of Vitamin D Status and Other Clinical Characteristics With COVID-19 Test Results. JAMA Network Open. September 3, 2020. doi: https://www.doi.org/10.1001/jamanetworkopen.2020.19722.

Nogues, X, et al. “Calcifediol Treatment and COVID-19–Related Outcomes.” The Journal of Clinical Endocrinology & Metabolism. September 27, 2021. doi: https://doi.org/10.1210/clinem/dgab405.

Vitamin D. National Institutes of Health. March 24, 2020. https://ods.od.nih.gov/factsheets/VitaminD-HealthProfessional.

Vitamin D Deficiency. Cleveland Clinic. October 16, 2019. https://my.clevelandclinic.org/health/articles/15050-vitamin-d–vitamin-d-deficiency.

Vitamin D Status: United States, 2001–2006. National Center for Health Statistics. U.S. Centers for Disease Control and Prevention. March 2011. https://www.cdc.gov/nchs/products/databriefs/db59.htm.