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Magnesium Overview
Magnesium intake in Australia
Stress: The elevation in catecholamine levels
Around one third of Australians over the age of 18 associated with anxiety may be responsible for do not get their recommended dietary intake (RDI) increased magnesium urinary excretion and of magnesium,1 and on average, the magnesium decreased magnesium plasma concentrations.6 consumption levels of Australian men and women are Ageing: Factors that may contribute to inadequate
magnesium levels in the elderly include an increased A 2001 analysis of data collected from Australian indi- risk of inadequate magnesium intake, which may viduals aged ≥ 65 years as part of the National Nutri- be due to low appetite, poor senses of taste and tion Survey 1995 highlights the insufficiency of dietary smell, dental problems, and issues shopping for and magnesium in this age group, demonstrating that preparing meals.8 In addition, magnesium metabolism 47.7% of males in this age group had dietary intakes may change with ageing: urinary magnesium of magnesium lower than the RDI (320 mg/day), with excretion tends to increase, and intestinal absorption 11.6% consuming less than 70% of the RDI. Females in this age group were even more likely to have low intakes, with 55.5% consuming less than the RDI (270 Other factors: Other risk factors for magnesium
mg) and 13.6% consuming less than 70% of it.
depletion include dietary factors (for example RDIs for magnesium have since been increased to high intakes of salt, caffeine or alcohol), endocrine 400-420 mg/day for adult men and 310-320 mg/day disorders (including diabetes), renal disorders, and for adult women, so it is possible that current dietary the use of certain medications, including proton shortfalls are even more significant than these statis- pump inhibitors, corticosteroids, loop diuretics, and The authors concluded that low nutrient intakes Magnesium deficiency signs
in the Australian elderly could generally be attrib- uted to poor quality diets that were low in nutri- Magnesium deficiency signs may include fatigue, ent density and/or the quantity of food eaten.3 muscle cramps, poor concentration and attention span, hyper-irritability, excitability and vertigo.10,11 Symptoms of hypomagnesaemia such as anorexia, nausea, tremor, apathy and confusion do not typically occur until plasma concentrations fall below than 0.5 mmol/L. In such cases secondary hypokalaemia and hypocalcaemia may also be present.9 Testing for magnesium deficiency
Determining magnesium status can be problematic as there are no simple, quick, and reliable laboratory Although magnesium serum concentration is the most commonly used test, magnesium is predominantly an intracellular ion, and normal serum values (0.8- Chart 1: Average magnesium intakes in Australia by age compared to 1.0 mmol/L)12 are an unreliable measure of both RDI (National Nutrition Survey 1995)2 intracellular availability and total body levels.8,9,13 Other tests used include red blood cell, muscle tissue, and Factors affecting magnesium levels
urinary excretion levels, but like serum magnesium levels, these biomarkers are not considered reliable Aside from inadequate dietary intake,2,3 strenuous exercise,4,5 stress6 and poor absorption due to ageing7 may also lower magnesium in the body.
Exercise: Strenuous exercise (even at submaximal
levels) is believed to contribute to magnesium deficit via increased magnesium losses in urine and sweat, which may increase magnesium requirements by 10-20%.4,5 Information for healthcare professionals only. Not for public distribution.
As a consequence, it has been suggested that Absorption and bioavailability after
clinical signs and symptoms and response to magnesium supplementation
supplementation may be the best indications of The absorption of magnesium from supplements magnesium insufficiency. A high degree of suspicion depends on a variety of factors, including the is necessary, especially in patients at high risk of status of magnesium stores in the body, the type of deficiency (e.g. those affected by diabetes types I or magnesium salt used, and whether the mineral is II, diarrhoea, alcoholism, inflammatory bowel disease, or taking medicines known to deplete magnesium The bioavailability of magnesium from different magnesium salts is thought to depend on their Additionally, it should be noted that low intracellular aqueous solubility. Organic salts of magnesium such levels of magnesium may still be present when serum as magnesium L-aspartate are the most water- magnesium concentration is normal, particularly soluble, and have been shown to have a greater oral in patients with unexplained hypocalcaemia or absorption and bioavailability than less soluble salts refractory hypokalaemia.16 Up to a third of patients with such as magnesium hydroxide, magnesium oxide, hypokalaemia, hypophosphataemia, hypocalcaemia magnesium sulphate and magnesium carbonate.22 or hyponatraemia can be expected to have co-existing tissue magnesium depletion.13 A 2001 crossover study compared the relative bioavailability of magnesium from magnesium Magnesium – physiological functions
aspartate, magnesium lactate, magnesium chloride Magnesium helps to build and maintain normal and magnesium oxide in 16 healthy subjects by measuring urinary magnesium excretion.22 As have linked increased magnesium consumption with summarised in Table 1, magnesium aspartate, magnesium chloride, and magnesium lactate displayed similar levels of bioavailability, and Magnesium is an important modulator of intracellular magnesium oxide was considerably less bioavailable ion concentrations and is involved in the active (approximately twofold) than magnesium from transport of other ions (for example calcium and other salts. At the dose administered, no adverse potassium) across cell membranes. Consequently it helps to maintain normal functioning of skeletal, smooth and cardiac muscle, including muscle contraction and heart rhythm.4,7,8,11,17,18 Preparation
Change from p value
magnesium
Magnesium is sometimes referred to as ‘nature’s (mg/day)
(mg/day)
mean ± SD
mean ± SD
physiological calcium channel blocker’.8,20 When magnesium levels are low, intracellular calcium rises. Amongst other consequences, this affects muscle contraction and relaxation and may result in Due to its actions as a calcium antagonist, magnesium also reduces neuron excitability, inhibits acetylcholine release at the neuromuscular junction, and reduces the effect of the excitatory central nervous system neurotransmitter N-methyl-D-aspartate. Like other Table 1: Urinary magnesium excretion following administration of calcium antagonists it acts as a vasodilator and magnesium aspartate, magnesium lactate, magnesium chloride and magnesium oxide in healthy human volunteers.22 Magnesium contributes to normal energy metabolism,8,18,20 in part because it forms a complex with adenosine A 2007 article, published in Australian Prescriber, triphosphate (ATP), which provides energy for almost recommended that magnesium deficient patients and those with asymptomatic hypomagnesaemia be to relieve tiredness and fatigue in people with low treated with oral magnesium supplements, typically magnesium aspartate. They caution against the use of higher doses, which may have a laxative Magnesium helps maintain normal, healthy brain effect, and stress that the underlying cause for the function, and in particular, psychological functions.11 hypomagnesaemia should always be determined In addition, it is involved in protein synthesis and Information for healthcare professionals only. Not for public distribution.
Use with prescription medications
13. Dipalma JR. Magnesium replacement therapy. Am Fam Phys Proton pump inhibitors: Proton pump inhibitors
14. Ranade VV, Somberg JC. Bioavailability and pharmacokinetics of may cause hypomagnesaemia if taken long-term magnesium after administration of magnesium salts to humans. Am J 15. Wu, J, Carter A. Magnesium: the forgotten electrolyte. Australian Bisphosphonates, chlorpromazine, tetracyc-
line and quinolone antibiotics: Magnesium
16. Merck Manual for Health Care Professionals: Disorders of magnesium may decrease the absorption and efficacy of concentration (Section: Endocrine and metabolic disorders, Chapters: Electrolyte Disorders). Whitehouse Station, NJ: Merck Sharp & Dohme these medications. A separation of dosing by at Corp. Accessed September 2011 from www.merckmanuals.com/ professional/print/endocrine_and_metabolic_disorders/electrolyte_disorders/disorders_of_magnesium_concentration.html 17. Health Canada. Magnesium monograph. Accessed September Cautions
2011 from webprod.hc-sc.gc.ca/nhpid-bdipsn/monoReq.
do?id=135&lang=eng 18. European Food Safety Authority. Scientific opinion on the substantiation orally in people with normal renal function. of health claims related to magnesium and electrolyte balance (ID 238), Oral magnesium has been given in doses of energy-yielding metabolism (ID 240, 247, 248), neurotransmission and muscle contraction including heart muscle (ID 241, 242), cell division 600-1,200 mg daily for four months without major (ID 365), maintenance of bone (ID 239), maintenance of teeth (ID 239), adverse effects. Toxicity is rare, but is more likely blood coagulation (ID 357) and protein synthesis (ID 364) pursuant to occur in circumstances such as high-dose to Article 13(1) of Regulation (EC) No 1924/2006. EFSA Journal 2009;7(9):1216 intravenous administration and in patients with 19. Tucker KL, Hannan MT, Chen H, et al. Potassium, magnesium and fruit and vegetable intakes are associated with greater bone mineral density in elderly men and women. Am J Clin Nutr 1999;69:727-36 Diarrhoea and gastric irritation may occur at 20. Volpe SL. ‘Magnesium’. Bowman BA, Russell RM (eds) Present excessive doses (typically >350 mg elemental knowledge in nutrition, 9th ed, Vol 1. Washington, DC: International magnesium/day). Individuals with impaired renal function are at higher risk of experiencing 21. Natural Medicines Comprehensive Database. Magnesium monograph. Accessed September 2011 from naturaldatabase.therapeuticresearch.
diarrhoea with magnesium supplementation7,10 22. Anton R, Barlow S, Boskou D, et al. Opinion of the Scientific Panel on Food Additives, Flavourings, Processing Aids and materials in Contact with Food on a request from the Commission related to Magnesium References
Aspartate as a mineral substance in when used as a source of 1. Australian Bureau of Statistics. National Nutritional Survey 1995. magnesium in dietary foods for special medical purposes. Question Adjusted nutrient intakes in comparison to RDI (unpublished data).
number EFSA-Q-2004-066. EFSA Journal 2005;167:1-6. 2. McLennan W, Podger A. National nutrition survey: Nutrient intakes 23. Natural Standard. Magnesium monograph. Accessed October 2011 and physical measures, Australia, 1995. Canberra: Commonwealth of 3. Bannerman E, Margarey AM, Daniels LA. Evaluation of micronutrient intakes of older Australians: the National Nutrition Survey – 1995. J Nutr, Health Aging 2001;5(4) :243-7 4. Laires MJ, Monteiro CP, Bicho M. Role of cellular magnesium in health and human disease. Front in Biosc 2004;9(Jan 1):262-76 5. Nielsen FH, Lukaski HC. Update on the relationship between magnesium and exercise. Magnes Res 2006;19(3):180-9 6. Grases G, Perez-Castello JA, Sanchis P, et al. Anxiety and stress among science students. Study of calcium and magnesium alterations. Magnes Res 2006;19(2):102-6 7. Higdon J. Magnesium. An evidence based approach to vitamins and minerals. New York: Thieme, 2003, pages 148-56 8. Institutes of Medicine. ‘Magnesium’. Dietary reference intakes for calcium, phosphorus, magnesium, vitamin D and fluoride. Washington: National Academy Press, 1997, pages 190-233 9. Cundy T, Mackay J. Proton pump inhibitors and severe hypomagnesaemia. Curr Opin Gastroenterol 2011;27(2):180-5 10. Braun L, Cohen M. ‘Magnesium’. Herbs and natural supplements. 11. European Food Safety Authority. Scientific Opinion on the substantiation of health claims related to magnesium and “hormonal health” (ID 243), reduction of tiredness and fatigue (ID 244), contribution to normal psychological functions (ID 245, 246), maintenance of normal blood glucose concentrations (ID 342), maintenance of normal blood pressure (ID 344, 366, 379), protection of DNA, proteins and lipids from oxidative damage (ID 351), maintenance of the normal function of the immune system (ID 352), maintenance of normal blood pressure during pregnancy (ID 367), resistance to mental stress (ID 375, 381), reduction of gastric acid levels (ID 376), maintenance of normal fat metabolism (ID 378) and maintenance of normal muscle contraction (ID 380, ID 3083) pursuant to Article 13(1) of Regulation (EC) No 1924/2006. EFSA Journal 2010;8(10):1807 12. Hughes J. ‘Magnesium’. Use of laboratory test data. Pharmaceutical Information for healthcare professionals only. Not for public distribution.
Magnesium Summary
Magnesium contributes to:
Symptoms may include:6,10,14
Maintenance of healthy bones and teeth1,2,4 Normal brain and psychological functions6 Who is at risk of low magnesium levels?
Many Australians have low magnesium levels. For example, at least 48% of men and 56% of women 65 years may not obtain the RDI from their Symptoms of hypomagnesaemia do not typically occur until plasma concentrations fall below 0.5 mmol/L. In such cases secondary hypokalaemia and Relationship to prescribed medicines
Magnesium may decrease the absorption and efficacy of tetracycline, quinolone antibiotics and bisphosphonates, and separation of dosing by at Factors that may contribute to low
magnesium status
References
1. Health Canada.Magnesium monograph. Accessed September 2011 2. EFSA. EFSA Journal 2009;7(9):12163. Laires MJ, et al. Frontiers in Bioscience 2004;9(Jan 1):262-76 High intakes of salt, caffeine or alcohol10 4. Institutes of Medicine. ‘Magnesium’. Dietary Reference Intakes for calcium, phosphorus, magnesium, vitamin D and fluoride. Washington: 5. Volpe SL. Magnesium, in Bowman BA, Russell RM (eds). Present Knowledge In Nutrition, 9th Ed, Vol 1. Washington, DC: International Life Sciences Institute, 2006. 400-8 6. EFSA. EFSA Journal 2010;8(10):18077. Australian Bureau of Statistics. National Nutrition Survey 1995 Identifying magnesium insufficiency
(unpublished data). `Adjusted nutrient intakes in comparison to RDI’ 8. Bannerman E, et al. J Nutr Health Aging. 2001;5(4) Determining magnesium status can be problematic, 9. Dipalma JR. AFP Clinical Pharmacology 1990;42(1):173-6 as there are no simple, quick and reliable laboratory 10. Braun L, Cohen M. Herbs and Natural Supplements. Australia: Elsevier. tests. Magnesium serum concentration is the most 11. Nielsen FH, Lukaski HC. Magnes Res 2006;19(3):180-9 commonly used test, but normal serum values (0.8- 12. Grases G, et al. Magnes Res 2006;19:2102–6 1.0 mmol/L54) are an unreliable measure of both 13. Higdon J. An Evidence-Based Approach to Vitamins and Minerals. intracellular availability and total body levels.
14. Cundy T, Mackay J. Curr Opin Gastroenterol 2011;27(2):180-5 Consequently, clinical signs and symptoms and 15. Hughes J. ‘Magnesium’. Use of laboratory test data. Pharmaceutical response to supplementation may represent better 16. Wu, J, Carter A. Australian Prescriber 2007;30(4):102-5 indications of magnesium insufficiency.9,16 17. Anton R, et al. EFSA Journal 2005;167:1-6. 57. Natural Medicines Comprehensive Database. Lactobacillus monograph. Accessed October 2011 http://naturaldatabase.therapeuticresearch.com 18. Hawrelak J, Myers S. Altern Med Rev 2004; 9 (2):180-97 Prescribing tip: Water-soluble organic
19. Sullivan A, et al. Lancet Infect Dis 2001;1:101-14 magnesium salts such as magnesium L-aspartate 20. Lionetti E, et al. Aliment Pharmacol Ther. 2006;24:1461-821. Reuter G. Curr Issues Intest Microbiol. 2001;2(2):43-53 have been shown to have better oral absorption 22. Casas IA, et al. Microbial Ecol Health Disease 2000;12:247–85 and bioavailability than less soluble salts such 23. BioGaia. Clinical evidence. Accessed October 2011 www.biogaia.
as magnesium hydroxide, magnesium oxide, 24. Cimperman L et al. J Clin Gastroenterol 2011; May 5 [Epub ahead of magnesium sulphate and magnesium carbonate.17 25. Francavilla R et al. Helicobacter 2008;13:127–34 Information for healthcare professionals only. Not for public distribution.

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