Diabetes & Endocrinology

The Multiple Implications of Vitamin D Deficiency

    Vitamin D has long been an area of interest of John P. Bilezikian, MD, Chief Emeritus of the Division of Endocrinology at NewYork-Presbyterian/Columbia University Irving Medical Center and Vice Chair for the Department of Medicine for International Education and Research at Columbia University Irving Medical Center. “Although vitamin D is very important for skeletal health, over the past 20 to 30 years a huge body of compelling evidence, much of it from the laboratory, has implicated vitamin D in the immune system and in our ability to deal with infections by either our innate immunity or acquired immunity,” says Dr. Bilezikian, a noted clinician-scientist, whose more than 900 peer reviewed publications speak to his many investigative initiatives in endocrinology and metabolic bone diseases.

    image of Dr. John Bilezikian

    Dr. John Bilezikian

    In September 2020, Dr. Bilezikian played a major role in the 4th International Conference on Controversies in Vitamin D virtual meeting, which brought together international scientific and medical experts in the field. They gathered to deliberate on improving the management of vitamin D dosing, therapeutic levels, and the form of administering the vitamin in the general population and under various clinical conditions. The results of their presentations and discussions, with Dr. Bilezikian as lead author, were published in the December 2021 issue of Reviews in Endocrine and Metabolic Disorders.

    The researchers recommended taking a tailored approach based on the mechanisms underlying vitamin D deficiency in different diseases. Compared to healthy populations, they noted that higher levels and greater amounts of vitamin D are recommended in individuals with osteoporosis, diabetes mellitus, gastrointestinal diseases, obesity (especially following bariatric surgery), neurological diseases, malignancies, infections, and in those persons treated with glucocorticoids.

    “We know that individuals who are obese generally have lower levels of vitamin D in their blood than those who are not obese,” says Dr. Bilezikian. “Neurocognitive function and our ability to think clearly have been implicated with vitamin D deficiency. There are also epidemiological studies that associate certain kinds of cancers with low levels of vitamin D. However, these are associative relationships, not necessarily causative. When these organ systems become dysfunctional, we don’t know for sure if this is directly related to vitamin D deficiency. But it is intriguing that so many diseases and health issues have been linked in one way or another to a lack of vitamin D.”

    The COVID Connection

    “With the onset of COVID, we began to observe a number of interesting connections with vitamin D that became more apparent as the number of cases of COVID increased around the world,” says Dr. Bilezikian. “It became clear that individuals with COVID tended to have lower vitamin D levels. In countries where COVID was rampant, Italy as one example, the average level of vitamin D was much lower than other European countries.”

    “We know that vitamin D may be important in protecting us from viral infection, and COVID-19 is a viral infection,” notes Dr. Bilezikian. Since the start of the pandemic, many global studies have documented the associations of vitamin D with SARS-CoV-2 infection, including severity of disease, particularly in the elderly, and vitamin D deficiency in patients with diabetes and obesity, which already increase the risk of severe COVID. Additionally, even mild insufficiency was found to predict hospitalization and mortality, and very low vitamin D levels were linked to greater likelihood of an ICU admission and mortality.

    Answers from Armenia

    As Vice Chair for the Department of Medicine for International Education and Research at Columbia, Dr. Bilezikian has taken his investigations to other countries, including Armenia where he has roots. In 2017, he established the Osteoporosis Center of Armenia focused on clinical care, research, and educational outreach.

    “We recently completed a study on vitamin D in Armenia that documented that the average woman there regardless of age – whether pregnant or not – has levels of vitamin D that are barely adequate, with 25 percent clearly deficient,” he says. “By documenting baseline levels of vitamin D in Armenian residents, we were able to establish solid data from which we can now make statements about its role in prevention and other beneficial effects. It's a very exiting area.”

    The results of their study supported a potential role for vitamin D as a risk factor for COVID-19, as suggested in similar studies from Italy and Spain. Dr. Bilezikian and his colleagues continue to lead the way in research on vitamin D and COVID. Based upon what they learned in Armenia, they have begun another study to look at vitamin D replacement in individuals with and without COVID and whether it can help improve the natural course of this disease or prevent it from developing. They are also pursuing additional research to test the hypothesis that COVID might be made worse by those who have vitamin D deficiency.

      Read More

      Vitamin D: Dosing, levels, form, and route of administration: Does one approach fit all? Bilezikian JP, Formenti AM, Adler RA, Binkley N, Bouillon R, Lazaretti-Castro M, Marcocci C, Napoli N, Rizzoli R, Giustina A. Reviews in Endocrine and Metabolic Disorders. 2021 Dec;22(4):1201-1218.

      Patients hospitalized with COVID-19 have low levels of 25-hydroxyvitamin D. Hutchings N, Babalyan V, Baghdasaryan S, Qefoyan M, Sargsyants N, Aghajanova E, Martirosyan A, Harutyunyan R, Lesnyak O, Formenti AM, Giustina A, Bilezikian JP. Endocrine. 2021 Feb;71(2):267-269.

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      Dr. John Bilezikian
      Dr. John Bilezikian
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