Vitamin D deficiency
Vitamin D deficiency is increasingly recognized as a widespread health issue, particularly affecting adults over the age of 60, with prevalence rates ranging from 25 to 54 percent in this demographic. Factors contributing to this deficiency include reduced sunlight exposure, malnutrition, and certain medical conditions like Crohn's disease and obesity. Vitamin D, a fat-soluble vitamin, is essential for maintaining calcium and phosphorus levels in the body, playing a crucial role in bone health and mineralization. While it can be obtained through diet—primarily from oily fish, eggs, and fortified foods—much of it is synthesized in the skin when exposed to sunlight. The recommended daily intake varies, with specific guidelines suggesting 600 to 800 IUs for different age groups. Vitamin D deficiency is linked not just to skeletal issues, such as osteoporosis and fractures but also to potential nonskeletal effects, including impacts on mood, cognition, and chronic diseases. Addressing and preventing vitamin D deficiency could significantly enhance the quality of life, particularly among older adults, by mitigating risks associated with depression and other health complications.
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Subject Terms
Vitamin D deficiency
Disease/Disorder
Definition: Illness that results when the body does not have enough vitamin D, a fat-soluble vitamin necessary for normal bone development and maintenance.
Anatomy or system affected: All
Vitamin D has become a popular topic due to its attention in the media and supposed role in prevention and treatment of many chronic diseases. By the 2020s, vitamin D deficiency remained widespread in the United States and globally. Older adults are the most vulnerable population to a vitamin D deficiency due to their decreased exposure to natural sunlight, increased prevalence of malnutrition and intestinal malabsorption. Other groups at risk for vitamin D deficiency include breastfed infants, people with dark skin, individuals with Crohn disease or celiac disease, and those who are obese.
Vitamin D is considered a prohormone, which is an inactive substance that can be converted to a hormone. Vitamin D is a fat-soluble vitamin synthesized in the skin through ultraviolet light and obtained in foods such as oily fish, eggs and fortified foods (milk, eggs, cereals). It can be produced by phytoplankton, zooplankton, and most animals exposed to sunlight. Vitamin D exists in supplemental, pharmaceutical and metabolite forms as vitamin D2 (ergocalciferol) and vitamin D3 (cholecalciferol). Vitamin D2 is synthesized “from yeast and used for food fortification” in comparison to Vitamin D3, which is made in the skin when exposed to ultraviolet rays emitted from sunlight. Vitamin D2 can be ingested through plant sources, while Vitamin D3 is obtained through animal sources.
Vitamin D status is generally defined by the following reference ranges of serum 25-hydroxyvitamin D in nanograms per milliliter (ng/mL) or nanomoles per liter (nmol/L). According to the National Institutes of Health Office of Dietary Supplements (NIH ODS) in 2022, levels below 12 ng/mL (30 nmol/L) are too low, 20 ng/mL is adequate for most people, and levels above 50 ng/mL (125 nmol/L) are too high. In 2010, the Institute of Medicine (IOM) updated the Dietary Reference Intake (DRIs) for calcium and vitamin D. Assuming minimal sun exposure, in the United States and Canada the Institute of Medicine (IOM)'s recommended Dietary Reference Intake (DRI) for vitamin D is 600 IUs per day for those ages 1 to 70 and 800 IUs for those age 71 and older. The NIH ODS also recommended that breastfed infants from birth to twelve months receive a dietary supplement of 400 IU of vitamin D because human breast milk is an inadequate source of the nutrient.
The most efficient and plentiful source of vitamin D is direct sunlight. It is important to note that sunscreens SPF 8 and above prevent vitamin D production. The amount of unprotected sun exposure is dependent upon latitude/climatic locations and skin type. Vitamin D produced in the skin lasts at least twice as long in the blood as vitamin D ingested from the diet.
Vitamin D is naturally present in mushrooms and oily fish (i.e., swordfish, tuna, salmon, sardines) and available in fortified foods such as milk, yogurt, cheese, margarine, orange juice, and breakfast cereals.
Once vitamin D is obtained through endogenous production in the skin through UV rays or consumed through a dietary source, it enters the bloodstream via vitamin D receptors (VDRs). These receptors exist everywhere throughout the body on cells of the target organs such as the kidneys, bone, intestines, and brain. Vitamin D then travels to the liver as a metabolite (25-hydroxyvitamin D) in its major circulating form and to the kidneys where it is converted to its active form (1-25-hydroxyvitamin D). The main function of vitamin D is in the regulation of calcium and phosphorus levels found in the body. This regulation is done in conjunction with parathyroid hormone (PTH). PTH stimulates 1-25-hydroxy vitamin D, the active form of vitamin D, which increases the production of calcium from the intestinal lumen and bone. Likewise, an increase in 1-25-hydroxyvitamin D increases phosphate absorption from the intestine and decreases phosphate urinary excretion while also slightly increasing intestinal calcium absorption.
Vitamin D promotes skeletal health and bone mineralization. The most established data on the benefits of vitamin D are related to the skeletal system. There is an increasing amount of evidence on the neurological effects of vitamin D. Additionally, vitamin D improves coronary artery disease through lipid-lowering effects, promotes immunomodulation, and aids in the response to viral infections. Evidence has shown that it may also inhibit airway remodeling in chronic obstructive pulmonary disease (COPD), increase peripheral insulin sensitivity, and improve islet beta cell function. Vitamin D has also been shown to have oncologic benefits by altering gene expression and possibly lowering the incidence of colorectal cancer and breast cancer. According to the National Institutes of Health Office of Dietary Supplements in 2011, higher levels of serum vitamin D may be linked to increased risk of pancreatic cancer, however, and more studies are needed to assess the nutrient’s overall effect on cancer risk.
According to Chu, vitamin D3 has skeletal benefits such as fall and fracture risk prevention, as well as for osteoporosis in the older population. Although many findings have been made regarding the skeletal effects of vitamin D, there are still mixed and inconclusive results from numerous studies and testing related to nonskeletal effects. Nonskeletal effects of vitamin D insufficiency are not as widely studied but are being explored, particularly in relation to cardiovascular disease, diabetes mellitus, cancer, and immune dysfunction. Increasing evidence has shown that vitamin D has beneficial neurological effects on cognition, memory, and mood.
By detecting a vitamin D deficiency, primary care providers may be able to prevent conditions in late life, such as depression, and improve quality of life in older patients. Preventing and treating vitamin D deficiency may potentially improve the morbidity and mortality associated with depression and other health outcomes in older adults. This can have a significant impact on medical practice as primary care providers are at the forefront of health promotion, health maintenance and patient education.
Bibliography
Aloia, J. F. “Clinical Review: The 2011 Report on Dietary Reference Intake for Vitamin D: Where Do We Go from Here?” Journal of Clinical Endocrinology & Metabolism, vol. 96, 2011, pp. 2987–2996.
Bailey, R., K. Dodd, J. Goldman, J. Gahche, J. Dwyer, A. Moshfegh, C. Sempos, and M. Picciano. “Estimation of Total Usual Calcium and Vitamin D Intakes in the United States.” The Journal of Nutrition, vol. 140, 2010, pp. 817–822.
Chu, M. P., K. Alagiakrishnan, and C. Sadowski. “The Cure of Ageing: Vitamin D-Magic or Myth?” Postgraduate Medical Journal, vol. 86, 2010, pp. 608–616.
Fiske, A., J. Wetherell, and M. Gatz. “Depression in Older Adults.” Annual Reviews of Clinical Psychology, vol. 5, 2009, pp. 363–389.
Hankey, C., and W. Leslie. “Nutritional Issues and Potential Interventions in Older People.” Reviews in Clinical Gerontology, vol. 21, 2011, pp. 286–296.
Holick, Michael F. The Vitamin D Solution: A 3-Step Strategy to Cure Our Most Common Health Problem. Hudson Street Press, 2010.
Institute of Medicine, Food and Nutrition Board. Dietary Reference Intakes for Calcium and Vitamin D. National Academy Press, 2011.
Nguyen, H. C. T., and A. Chernoff. “Vitamin D3 25-Hydroxyvitamin D.” Medscape Reference: Drugs, Diseases & Procedures, 20 Nov. 2019, emedicine.medscape.com/article/2088694-overview. Accessed 6 Jan. 2025.
Peacock, M. “Calcium Metabolism in Health and Disease.” Clinical Journal of the American Society of Nephrology, vol. 5, 2010, pp. S23–S30.
Phinney, K., M. Bedner, S. Tai, W. Vamathevan, L. Sander, K. Sharpless, S. Wise, J. Yen, R. Schleicher, M. Chaudhary-Webb, C. Pfeiffer, J. Betz, P. Coates, and M. Piacciano. “Development and Certification of a Standard Reference Material for Vitamin D Metabolites in Human Serum.” Analytical Chemistry, vol. 84, 2012, pp. 956–962.
Rosen, C. “Vitamin D Insufficiency.” New England Journal of Medicine, vol. 364, 2011, pp. 248–254.
Ross, A. Catharine, et al. "The 2011 Report on Dietary Reference Intakes for Calcium and Vitamin D from the Institute of Medicine: What Clinicians Need to Know." The Journal of Clinical Endocrinology and Metabolism, vol. 96, no. 1, 2011, pp. 53–58, doi:10.1210/jc.2010-2704. Accessed 6 Jan. 2025.
Tuohimaa, P. “Vitamin D and Aging.” Journal of Steroid Biochemistry and Molecular Biology, vol. 114, no. 1–2, 2009, pp. 78–84.
"25-Hydroxy Vitamin D Test." Rev. by Sandeep K. Dhaliwal, et al. MedlinePlus, NIH National Library of Medicine, 20 May 2024, medlineplus.gov/ency/article/003569.htm. Accessed 6 Jan. 2025.
“Vitamin D: Fact Sheet for Consumers.” National Institutes of Health Office of Dietary Supplements. NIH, 8 Nov. 2022, ods.od.nih.gov/factsheets/VitaminD-Consumer/. Accessed 6 Jan. 2025.
Wilkins, C., Y. Sheline, C. Roe, S. Birge, and J. Morris. “Vitamin D Deficiency Is Associated with Low Mood and Worse Cognitive Performance in Older Adults.” American Journal of Geriatric Psychiatry, vol. 14, no. 12, 2009, pp. 1032–1040.