Vitamin D in the prevention of cerebrovascular pathologies: results of new clinical trials in light of unexpected developments and probabilities

Leonardo Triggiani

Neurology Operative Unit, Local Health Authority Roma 1, Santo Spirito Hospital, Rome

DOI 10.30455/2611-2876-2020-3e

Ischemic stroke is the main cause of long-term disability and the fourth cause of mortality globally. The World Health Organization (WHO) estimates that approximately 15 million new cases of stroke occur each year, of which 5 million have fatal outcomes and another 5 million produce serious and permanent disability, with significant social costs. It is believed that over the next few years aging populations and the reduction of mortality by stroke will lead to a progressively increasing prevalence of this pathology. Researchers have attempted to create validated systems of risk calculation: they aim to identify both high-risk patients in order to reduce the possibility of the onset of stroke and risk thresholds that make possible the implementation of effective preventive therapies.

Alongside the study of noted risk factors for cerebrovascular pathologies – hypertension, diabetes, dyslipidemia, smoking, and atrial fibrillation – in the last few years particular attention has been paid to identifying new potential risk factors, among which nutritional and dietary factors have become especially important.

Widely used in the prevention and treatment of bone pathologies, in recent years vitamin D has been introduced for the possible prevention of cerebrovascular diseases as well. For over a decade, sales of vitamin D in the U.S. have grown exponentially, making it one of the most commonly used supplements. Its potential benefits have been upheld by ecological studies – both laboratory and observational – although these data have turned out to be inconsistent and insufficient to establish a causal connection. Studies on the usefulness of vitamin D in preventing cerebrovascular diseases, conducted together with secondary or post hoc analyses, have largely produced invalid results. Indeed, all these studies were marred by several limitations: low dosages, inadequate type of study, short duration, and less than optimal verification of the endpoints. No large-scale studies with significantly high doses of vitamin D have been carried out whose primary endpoint is the prevention of cerebrovascular diseases. For this reason, the Institute of Medicine and the Preventive Services Task Force in the U.S. have reached the conclusion that available data do not allow us to definitively verify the efficiency of the use of vitamin D for this purpose or to establish a risk-benefit relationship. The Institute of Medicine has asked the scientific community to undertake clinical trials with high doses of vitamin D (at least double the daily dose of 600-800 IU/day recommended for bone health) in different populations, including African Americans, who tend to have less cutaneous synthesis of vitamin D through exposure to sun with respect to other ethnic groups.

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