Over 80 percent of 200 COVID-19 patients in a hospital in Spain have vitamin D deficiency, according to a new study published in the Endocrine Society’s Journal of Clinical Endocrinology & Metabolism. Vitamin D is a hormone the kidneys produce that controls blood calcium concentration and impacts the immune system. Vitamin D deficiency has been linked to a variety of health concerns, although research is still underway into why the hormone impacts other systems of the body. Many studies point to the beneficial effect of vitamin D on the immune system, especially regarding protection against infections.

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