Symposium: Vitamin D Insufficiency: A Significant Risk Factor in Chronic Diseases and Potential Disease-Specific Biomarkers of Vitamin D Sufficiency Vitamin D Intake: A Global Perspective of Current Status 1 Mona S. Calvo,* 2 Susan J. Whiting, † and Curtis N. Barton* *Office of Applied Research and Safety Assessment, Office of Mathematical Assessment and Services, Center for Food Safety and Applied Nutrition, Food and Drug Administration, and † College of Pharmacy and Nutrition, University of Saskatchewan, Canada ABSTRACT Global high prevalence of vitamin D insufficiency and re-emergence of rickets and the growing scientific evidence linking low circulating 25-hydroxyvitmain D to increased risk of osteoporosis, diabetes, cancer, and autoimmune disorders have stimulated recommendations to increase sunlight (UVB) exposure as a source of vitamin D. However, concern over increased risk of melanoma with unprotected UVB exposure has led to the alternative recommendation that sufficient vitamin D should be supplied through dietary sources alone. Here, we examine the adequacy of vitamin D intake worldwide and evaluate the ability of current fortification policies and supplement use practices among various countries to meet this recommendation. It is evident from our review that vitamin D intake is often too low to sustain healthy circulating levels of 25-hydroxyvitmain D in countries without mandatory staple food fortification, such as with milk and margarine. Even in countries that do fortify, vitamin D intakes are low in some groups due to their unique dietary patterns, such as low milk consumption, vegetarian diet, limited use of dietary supplements, or loss of traditional high fish intakes. Our global review indicates that dietary supplement use may contribute 6 – 47% of the average vitamin D intake in some countries. Recent studies demonstrate safety and efficacy of community-based vitamin D supplementation trials and food staple fortification introduced in countries without fortification policies. Reliance on the world food supply as an alternative to UVB exposure will necessitate greater availability of fortified food staples, dietary supplement use, and/or change in dietary patterns to consume more fish. J. Nutr. 135: 310 –316, 2005. KEY WORDS: ● vitamin D intake ● 25-hydroxyvitamin D ● food fortification ● dietary supplements ● vitamin D dietary requirements Controversy over the source of vitamin D Adequate circulating 25-hydroxyvitamin D [25(OH)D] 3 concentrations are critical to maintaining the health and the function of the immune, reproductive, muscular, skeletal, and integumentary system of men and women of all ages and races (1). In most individuals, the majority of the circulating 25(OH)D originates from cholecalciferol or vitamin D-3, which is synthesized in the skin upon exposure to sufficient UV blue light (UVB) to cleave the B steroid ring of 7-dehy- drocholesterol (2). Vitamin D-3 must undergo 2 separate hydroxylation steps to become functional in its primary bio- logical role in calcium and phosphorus homeostasis. After synthesis in the skin, it is transported to the liver, where it is metabolized to 25(OH)D and may be stored or released to circulation. This intermediary metabolite is the major circu- lating and storage form that is delivered to tissue for further activation. When physiological demands for calcium and phosphorus arise, circulating 25(OH)D is metabolized to its biologically active hormonal form, 1,25-dihydroxyvitamin D [1,25(OH) 2 D] primarily in the renal tubular cells (1,2). The best characterized target organs for 1,25(OH) 2 D are the intes- tine, the kidney, and the bone, but nuclear receptors for this secosteroid hormone have been identified for 30 tissues (2); thus it has other important functions in addition to calcium homeostasis. 1 Presented as part of the symposium “Vitamin D Insufficiency: A Significant Risk Factor in Chronic Diseases and Potential Disease-Specific Biomarkers of Vitamin D Sufficiency” given at the 2004 Experimental Biology meeting on April 18, 2004, Washington, DC. The symposium was sponsored by the American Society for Nutritional Sciences and supported in part by educational grants from the Centrum Foundation of Canada and The Coca-Cola Company. The proceed- ings are published as a supplement to The Journal of Nutrition. This supplement is the responsibility of the guest editors to whom the Editor of The Journal of Nutrition has delegated supervision of both technical conformity to the published regulations of The Journal of Nutrition and general oversight of the scientific merit of each article. The opinions expressed in this publication are those of the authors and are not attributable to the sponsors or the publisher, editor, or editorial board of The Journal of Nutrition, and do not necessarily reflect those of the Food and Drug Administration. The guest editors for the symposium publication are Mona S. Calvo, Center for Food Safety and Applied Nutrition, U.S. Food and Drug Administration, Laurel, MD, and Susan J. Whiting, College of Pharmacy and Nutrition, University of Saskatchewan, SK, Canada. 2 To whom correspondence should be addressed. E-mail: mona.calvo@cfsan.fda.gov. 3 Abbreviations used: 1,25(OH) 2 D, 1,25-dihydroxyvitamin D; 25(OH)D, 25- hydroxyvitamin D; UVB, UV blue light. 0022-3166/05 $8.00 © 2005 American Society for Nutritional Sciences. 310 Downloaded from https://academic.oup.com/jn/article/135/2/310/4663649 by guest on 12 February 2022