American Journal of Therapeutics 0, 1–9 (2017) Magnesium Supplementation in Vitamin D Deficiency Pramod Reddy, MD* and Linda R. Edwards, MD Background: Vitamin D and magnesium (Mg) are some of the most studied topics in medicine with enormous implications for human health and disease. Majority of the adults are deficient in both vitamin D and magnesium but continue to go unrecognized by many health care professionals. Areas of Uncertainty: Mg and vitamin D are used by all the organs in the body, and their deficiency states may lead to several chronic medical conditions. Studies described in the literature regarding these disease associations are contradictory, and reversal of any of these conditions may not occur for several years after adequate replacement. One should consider the supplementation therapy to be preventative rather than curative at this time. Data Sources: PubMed search of several reported associations between vitamin D and Mg with diseases. Results: Vitamin D and Mg replacement therapy in elderly patients is known to reduce the non- vertebral fractures, overall mortality, and the incidence of Alzheimer dementia. Conclusions: Vitamin D screening assay is readily available, but the reported lower limit of the normal range is totally inadequate for disease prevention. Based on the epidemiologic studies, ;75% of all adults worldwide have serum 25(OH)D levels of ,30 ng/mL. Because of the recent increase in global awareness, vitamin D supplementation has become a common practice, but Mg deficiency still remains unaddressed. Screening for chronic magnesium deficiency is difficult because a normal serum level may still be associated with moderate to severe deficiency. To date, there is no simple and accurate laboratory test to determine the total body magnesium status in humans. Mg is essential in the metab- olism of vitamin D, and taking large doses of vitamin D can induce severe depletion of Mg. Adequate magnesium supplementation should be considered as an important aspect of vitamin D therapy. Keywords: vitamin D, magnesium, secondary hyperparathyroidism, ionized magnesium, Intracellu- lar Electrolytes and Magnesium test INTRODUCTION vitamin D deficiency (VDD) and Mg deficiency are often associated with hypocalcemia. Chronic hypocal- Magnesium (Mg) and vitamin D directly regulate bone cemia may lead to secondary hyperparathyroidism and and muscle metabolism throughout the life span of the the resulting elevation in parathyroid hormone (PTH) musculoskeletal system and are also essential for the increases the bone resorption in efforts to restore the absorption of dietary calcium and phosphorus. Chronic serum calcium levels. This process may lead to a gener- alized decrease in bone mineral density, resulting in osteopenia and osteoporosis (osteodystrophy). Patients may present with bone pain, tenderness, muscle weak- Division of General Internal Medicine, UF Health Jacksonville, ness, and difficulty walking with an increased risk of Jacksonville, FL. falls and fractures. The authors have no conflicts of interest to declare. In this review article, we briefly discuss the homeo- *Address for correspondence: 653-1 West 8th St, 3rd floor, Faculty stasis and interactions between Mg and vitamin D Clinic, Jacksonville, FL 32209. E-mail: [email protected] along with diagnostic and treatment options. 1075–2765 Copyright © 2017 Wolters Kluwer Health, Inc. All rights reserved. www.americantherapeutics.com Copyright Ó 2017 Wolters Kluwer Health, Inc. Unauthorized reproduction of this article is prohibited. 2 Reddy and Edwards Mg HOMEOSTASIS Vitamin D is known to be utilized by the earliest life forms throughout the evolution for nearly a billion 10 Recommended daily allowance (RDA) for men is years. Vitamin D supplements are available in 2 nat- 5–6 mg/kg body weight (eg, 70 kg male needs 350– ural inactive forms. Vitamin D2 (ergocalciferol) is not 400 mg of Mg) and 4–5 mg/kg body weight for synthesized naturally in the body and fortified milk, women. Dietary intake of Mg is inadequate in most and supplements are the main source. Vitamin D3 adults because the majority of the Mg is lost during (cholecalciferol) is produced endogenously in human food processing. Although drinking water accounts skin by ultraviolet (UV) radiation after sunlight for ;10% of daily magnesium intake, food (spinach, exposure. Certain dietary sources (dried mushrooms, nuts, and seeds) remain the richest source of Mg.1 salmon) and vitamin supplements are also the sources Only approximately 30% of the total dietary magne- of vitamin D3. Caucasians can generate approximately sium is absorbed in the small intestine, but higher 20,000 IU of vitamin D3 after full-body exposure for – absorption is possible in deficiency states. Magne- 10 15 minutes. Prolonged exposure to sunlight does sium excretion is mainly regulated by the kidney, not produce toxic amounts of vitamin D3 because the where 70% of the filtered Mg is reabsorbed in the excess precursors convert into biologically inactive thick ascending limb of the loop of Henle. Mg is crit- compounds. The amount of vitamin D3 production ical for adenosine triphosphate (ATP) production, varies with the amount of skin pigmentation, body DNA/RNA synthesis, and glucose metabolism. Mg mass, the amount of skin exposed, and the extent of also serves as a cofactor for hundreds of metabolic UV protection, including clothing and sunscreens. reactions in the body, including the vitamin D metab- Absorbed inactive vitamin D is bound to vitamin D olism. Mg is also essential for the regulation of blood binding proteins in the circulation and requires 2 hy- pressure, cardiac excitability, nerve transmission, and droxylations in the liver and kidney to become the neuromuscular conduction.2–4 active form of vitamin D (Figure 1). 25(OH)D serves as vitamin D reserve (4 weeks of half-life) in the body, Normal levels of Mg and the 1,25(OH)2D is considered the active form of The adult human body contains approximately 24 g of vitamin D (15 hours of half-life), which functions via magnesium mostly (99%) contained in the bone, the activation of the vitamin D receptors (VDRs) in the 11–13 muscles, and soft tissues. Only a small fraction of the target tissues. total body magnesium is present in the serum, which Extrahepatic and extrarenal hydroxylations can do not accurately reflect the total body stores. A normal occur in a number of tissues (pancreas, prostate, colon, serum Mg level (1.5–2.5 meq/L) may still be associated skin, and osteoblasts), where intact vitamin D can be with moderate to severe deficiency.5–7 metabolized directly to the active hormone; for exam- ple, prostate cells and dermal keratinocytes are capa- Causes of magnesium deficiency in general ble of both 25 and 1-alpha hydroxylation of the intact population vitamin D.14–16 This local tissue ability to metabolize Most adult humans do not get their recommended vitamin D is considered vital for the maintenance of RDA via diet. Patients who are on chronic proton pump tissue health, and VDD is implicated in the develop- inhibitor therapy may develop magnesium deficiency ment of various diseases and cancers (Table 1). Most of 8,9 these associations are unproven at this point, and there from decreased absorption. Patients on chronic loop 17 and thiazide diuretics may have increased renal Mg is a need for larger, randomized, multicenter studies. losses. Heavy alcohol consumption impairs the absorp- Vitamin D and Mg interactions tion and enhances the excretion of Mg. Consuming large doses of vitamin D products may induce deple- Several steps in the vitamin D metabolism depend on tion of Mg. magnesium as a cofactor, such as vitamin D binding to vitamin D binding protein, 25(OH)D synthesis, 1,25 (OH)2D synthesis, 25-hydroxylase synthesis, and VITAMIN D HOMEOSTASIS VDR expression for cellular effects (Figure 1). Mg defi- ciency can also decrease PTH synthesis and secretion Vitamins are by definition organic compounds that and also the number of available VDRs in target cannot be synthesized by an organism but required cells.18–21 Serum 1,25(OH)2D concentrations frequently to maintain good health. Vitamin D has been misclas- remain low in patients with Mg deficiency despite sified as a fat-soluble vitamin since its discovery in vitamin D intake22–24 Mg deficiency is also known to 1928, but it should be considered as a hormone cause vitamin D–resistant hypocalcaemia, which can because dermal synthesis is the major natural source. only be corrected after the proper replacement of Mg. American Journal of Therapeutics (2017) 0(0) www.americantherapeutics.com Copyright Ó 2017 Wolters Kluwer Health, Inc. Unauthorized reproduction of this article is prohibited. Magnesium and Vitamin D 3 FIGURE 1. Vitamin D metabolism and Mg interaction. Taking large doses of vitamin D without Mg replace- D production progressively declines with the course of ment has been shown to induce atherosclerosis in the disease. Patients with malabsorption syndromes are swine coronary arteries.25 often unable to absorb the fat-soluble vitamin D. Pa- tients on anticonvulsants (eg, phenytoin) and antiretro- Causes of VDD in general population viral medications enhance the catabolism of 25(OH)D Caucasians can generate approximately 20,000 IU of vita- and 1,25(OH)2D. Patients with chronic granulomatous min D3 after full-body exposure for 10–15 minutes. But, disorders (sarcoidosis, tuberculosis, and chronic fungal wearing a sunscreen (protection factor of 30) reduces infections), lymphomas, and primary hyperparathy- vitamin D synthesis in the skin by more than 95%. roidism have increased metabolism of 25(OH)D to Certain Caucasians have variable responsiveness to 1,25(OH)2D, which may lead to VDD. UV-B radiation, resulting in VDD despite abundant sun exposure. Cutaneous production of vitamin D also de- clines with age.26 Individuals with darker skin pigmen- ASSESSMENT OF VITAMIN D tation may require 5–10 times more exposure to generate STATUS vitamin D compared with Caucasians.