Vitamin D deficiency occurs when the body doesn’t have enough vitamin D to maintain healthy bone and immune function. Vitamin D plays a vital role in calcium absorption and bone metabolism.1 2
Vitamin D deficiency is a global public health issue. It affects over 1 billion people worldwide and is especially common in regions with limited sunlight exposure. Factors such as age, skin pigmentation, indoor lifestyles, and certain medical conditions can increase the risk. Even in sunny climates, deficiency can occur due to sunscreen use or limited outdoor activity. 3 4 5
Vitamin D deficiency may not always cause noticeable symptoms. However, common signs can include:
Vitamin D deficiency may not always cause noticeable symptoms. However, common signs can include:
Vitamin D deficiency may not always cause noticeable symptoms. However, common signs can include:
Vitamin D deficiency may not always cause noticeable symptoms. However, common signs can include:
Vitamin D deficiency may not always cause noticeable symptoms. However, common signs can include:
Several factors can contribute to low vitamin D levels:
1.National Institutes of Health (NIH) – Office of Dietary Supplements. Vitamin D Fact Sheet for Health Professionals. https://ods.od.nih.gov/factsheets/VitaminD-HealthProfessional/ (Last accessed: April 22, 2025)
2.Holick MF. Vitamin D deficiency. New England Journal of Medicine 2007;357(3):266–281
3.World Health Organization (WHO). Vitamin D supplementation in infants. e-Library of Evidence for Nutrition Actions (eLENA). https://www.who.int/tools/elena/interventions/vitamind-infants (Last accessed: April 22, 2025)
4.Mithal A al. Global vitamin D status and determinants of hypovitaminosis D. Osteoporosis International 2009;20(11):1807–1820.
5.Cashman KD et al. Vitamin D deficiency in Europe: pandemic and strategies for prevention. Clinical Reviews in Bone and Mineral Metabolism 2021;19(2):77–93.
6.Holick MF. Vitamin D: evolutionary, physiological and health perspectives. Current Drug Targets 2010;11(1):4–18.
7.Kennel KA et al. Vitamin D deficiency in adults: when to test and how to treat. Mayo Clinic Proceedings 2010;85(8):752–758.
8.Martineau AR et al. Vitamin D supplementation to prevent acute respiratory tract infections: systematic review and meta-analysis of individual participant data. BMJ 2017;356:i6583.
9.Wacker M, Holick MF. Sunlight and Vitamin D: A global perspective for health. Dermato-Endocrinology 2013;5(1):51–108.
10.Holick MF. High prevalence of vitamin D inadequacy and implications for health. Mayo Clinic Proceedings 2006;81(3):353–373.
11.Malabanan AO et al. Redefining vitamin D insufficiency. The Lancet 1998;351(9105):805–806.
