Vitamin D is essential for humans. In addition to its recognized roles in calcium and phosphorus metabolism and bone mineralization, vitamin D is also known for its activity at the extra-skeletal level, as many cells throughout the body express the vitamin D receptor and the 1α-hydroxylase enzyme. Extra-skeletal actions of vitamin D are significant in pediatric patients because they have an impact on the normal processes of a child’s development, including those of the immune system, thus promoting good health.
In a review which I prepared in 2017, these were the conclusions I drew on vitamin D in pediatric patients:
- the action of vitamin D may have beneficial effects in the prevention and cure of chronic diseases;
- vitamin D can play a synergic role in the maintaining and developing a child’s immune system;
- it is crucial to maintain normal vitamin D serum levels for clinical efficiency apart from those required for bone metabolism. Even if roughly one-third of the population of western countries, Italy included, has insufficient levels of vitamin D (serum levels < 20 ng/nL – 50 nmol/L), it has been suggested that efficient levels needed to sustain an appropriate response of the immune system should be higher (equal to or higher than 30-40 ng/m – 75-100 nmol/L) (Fig. 1).
Note that these statements are all hypothetical (“can”, “it is possible”, etc.). The aim is to establish the role of vitamin D in chronic diseases, a very controversial and debated topic for which we find contrasting and equivocal data in the literature. Observational studies in adults affected by various pathologic conditions have shown that these diseases are more severe in those subjects with low vitamin D levels. However, very often studies on vitamin D supplementation have produced negative and controversial results and have even provided documented evidence on the inefficiency of vitamin D supplementation in subjects with cardiovascular and oncological diseases. The Vitamin D and OmegA-3 TriaL (VITAL), which investigated whether taking supplements of vitamin D (2.000 IU/day) and omega-3 fatty acids (1 gram/day) would reduce the incidence of cancers or cardiovascular diseases over 5 years, showed that there was no difference between subjects taking the supplement and those taking the placebo. This study suggests a difference between association data compared to those obtained by supplementation.
The aim of this review is, first, to provide a reasoned update of what the literature tells us about the role of vitamin D in pediatric patients; second, to show that levels of dietary vitamin D intake are almost always insufficient at all ages ; and, third, to show that supplementation is the way to obtain adequate levels of vitamin D. It is yet not clear, though, whether achieving adequate levels of vitamin D is associated with a significant clinical improvement.
The recent Nota 96, issued by the Italian Medicine Agency (AIFA) to introduce new regulatory criteria on whether the National Health Service (SSN) will reimburse vitamin D costs for the adult population, does not apply to patients of pediatric age (0-18 years old). For these subjects, reimbursement of vitamin D continues to be completely covered by the SSN (Nota 96, Gazzetta Ufficiale, general series no. 252, 26 Oct. 2019). This regulation could be explained by the higher vulnerability of children with insufficient vitamin D status, a circumstance that necessitates greater elasticity in coverage criteria.