Should vitamin D supplements be recommended to prevent chronic diseases?

Historically, vitamin D has been shown to be associated with the regulation of bone metabolism and related musculo-skeletal disorders, However, the insightful opinion of the author that currently vitamin D has gained much attention in research and clinical practice as a possible preventive factor for a wide array of chronic diseases [1], has been applauded by several physicians and researchers worldwide. Vitamin D deficiency is now recognised as an epidemic in the United States [2].

A circulating level of 25-hydroxyvitamin D of >75 nmol/L, or 30 ng/mL, is required to maximise vitamin D's beneficial effects for health while in the absence of adequate sun exposure, at least 800-1000 IU vitamin D3/d may be needed to achieve this in children and adults [2].

In recent years several clinical research studies demonstrated the significance of vitamin D deficiency in various disorders including neuropathy [3], malignancy [4], infertility [5], cardiovascular diseases [6, ], kidney diseases [7], glucose metabolism [8], and immunological dysfunctions [9].

Moreover, in vitro studies showed that vitamin D inhibits pro-inflammatory activity of CD4+ Th1 cells and their production of cytokines such as IL-2, interferon (IFN)-γ, and tumor necrosis factor-α [10]. 1,25(OH)2D exerts an inhibitory effect on T cell proliferation, the expression of IL-2 [11] and IFN-γ mRNA and protein in T cells [12].

In addition, vitamin D receptor regulates transcription factors in immune cell lineages, including Th1, Th17, Th2, regulatory T, and natural killer T cells; and (13) the prevalence of vitamin D insufficiency/deficiency in patients with multiple sclerosis, type 1 diabetes mellitus, and systemic lupus erythematosus.

Low level of Vitamin D is now thought to be a risk factor for psychosis [8, 9]. There are systematic review and meta-analysis which are indicative of an association between depression and low Vitamin D levels. [14]

Conclusion: The major cause of vitamin D deficiency is the lack of appreciation that sun exposure in moderation is the major source of vitamin D.[2] Deliberate avoidance of sun exposure is currently a common practice in Jamaica to prevent darker skin pigmentation. Nowadays many schools are no longer promoting outdoor physical education, while most vehicles have tinted window screens to avoid sunlight. If 'bleachers' are taken into account, vitamin D deficiency may reveal its serious impact on immunity, mental health, cancer incidence, arthritic incidences, hormone levels, etc.

In this connection, it is important to mention that we are disappointed because instead of emphasising that large scale studies are urgently needed to substantiate the role of vitamin-D in various extra-skeletal chronic diseases including cancers, the authors unfortunately chose to emphasise the absence of adequate evidence in support of supplementation of vitamin-D for preventing chronic diseases [1]. Absence of sufficient evidence should not be used to misguide the general public and thus we should not ignore the alarm raised about the epidemic of vitamin-D deficiency [2].

Reference:
1. Meyer HE, Holvik K, Lips P. Should Vitamin D Supplements be Recommended to Prevent Chronic Diseases? BMJ 2015; 350: h321.
2. Holick MF1, Chen TC. Vitamin D deficiency: a worldwide problem with health consequences. Am J Clin Nutr. 2008 Apr;87 (4):1080S-6S
3. Agmon-Levin N, Kivity S, Tzioufas AG, et al. Low levels of vitamin-D are associated with neuropathy and lymphoma among patients with Sjogren’s syndrome. J Autoimmun. 2012;39:234–239. [PubMed]
4. Giovannucci E. Vitamin D and cancer incidence in the Harvard cohorts. Ann Epidemiol. 2009;19:84–88. [PubMed]
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10. Alroy I, Towers TL, Freedman LP. Transcriptional repression of the interleukin-2 gene by vitamin D3: direct inhibition of NFATp/AP-1 complex formation by a nuclear hormone receptor. Mol Cell Biol. 1995;15:5789–5799. [PMC free article] [PubMed]
11. Rigby WF, Stacy T, Fanger MW. Inhibition of T lymphocyte mitogenesis by 1,25-dihydroxyvitamin D3 (calcitriol) J Clin Invest. 1984;74:1451–1455. [PMC free article] [PubMed]
12. Reichel H, Koeffler HP, Tobler A, Norman AW. 1 alpha,25-Dihydroxyvitamin D3 inhibits gamma-interferon synthesis by normal human peripheral blood lymphocytes. Proc Natl Acad Sci U S A. 1987;84:3385–3389. [PMC free article] [PubMed]
13. Boonstra A, Barrat FJ, Crain C, Heath VL, Savelkoul HF, O’Garra A. 1Alpha,25-dihydroxyvitamin d3 has a direct effect on naive CD4(+) T cells to enhance the development of Th2 cells. J Immunol. 2001;167:4974–4980. [PubMed]
14. Anglin RES, Samaan Z, Walter SD, McDonald SD. Vitamin D Deficiency and Depression in Adults: Systematic Review and Meta-analysis. British Journal of Psychiatry 2013; 202(2): 100-107.