December 2011 Issue

Power of Magnesium — A Macromineral That May Improve Heart Health and Stop Diabetes
By Christin L. Seher, MS, RD, LD
Today’s Dietitian
Vol. 13 No. 12 P. 12

Among all the minerals our bodies need to maintain optimal health, magnesium is a fierce contender for first place. After decades of research, it’s become increasingly evident that magnesium, the fourth most abundant mineral in the human body, is absolutely essential for regulating hundreds of biochemical processes and several physiological systems that maintain metabolic and cardiovascular health. Mounting evidence shows this macromineral is much more important than previously thought.

Multifaceted Role
The majority of magnesium in the body is found in the skeletal system, providing strength to bones and serving as a much-needed reserve used to maintain serum levels when necessary. The remaining magnesium is concentrated in the cells of soft tissue such as muscle, the kidneys and liver, and in intracellular fluids. In these cells and intracellular fluids is where magnesium serves its most critical function as a participant in more than 300 biochemical reactions, with notable roles in glycolysis, the tricarboxylic cycle, beta-oxidation, protein synthesis, muscle contractibility, calcium homeostasis, vitamin D hydroxylation, and ion channel regulation. Magnesium is the regulator of blood glucose, plus it keeps the heart beating regularly and supports immunity.

Adequate dietary intake of magnesium, therefore, is imperative for optimal health. However, data indicate most Americans don’t consume enough magnesium-rich foods such as whole grains, leafy green vegetables, and nuts.1,2 Complicating matters, comorbid illnesses like cardiovascular and kidney disease, diabetes, hypertension, or malabsorptive disorders contribute to low magnesium levels, and diuretic medications or excessive alcohol or caffeine consumption can increase urinary excretion, furthering the risk of magnesium deficiency.3 Signs of deficiency range from relatively minor effects such as loss of appetite, nausea, and fatigue to more severe cardiac problems.

Miracle Mineral?
Because of its vital and multitiered role in the biochemical processes of the body, magnesium is well researched with regard to the prevention and treatment of disease. Receiving the most attention is its relationship to diabetes and heart health.

Diabetes Prevention and Management
Epidemiologic evidence strongly suggests that adequate dietary magnesium reduces the risk of type 2 diabetes. A recent meta-analysis of 13 prospective cohort studies examined this association in more than 500,000 subjects of diverse backgrounds. Results clearly demonstrated a significant inverse relationship between dietary magnesium and diabetes risk—a risk that isn’t altered when factors such as sex, geographic region, or family history are added to the model.4 This study confirms previous research that establishes an association between increased dietary magnesium and a reduced risk of diabetes.5

Despite strong epidemiologic evidence, Constance Brown-Riggs, MSEd, RD, CDE, CDN, a national spokesperson for the American Dietetic Association and author of The African American Guide to Living Well With Diabetes, urges RDs to interpret studies of this nature with caution, citing methodological limitations. “It’s important to note that magnesium as a single nutrient wasn’t examined,” she says. “Dietary magnesium accounted for the majority of total magnesium intake in these studies. Therefore, nutrition professionals must be careful to stress meal patterns to their patients that include sufficient amounts of magnesium-rich foods such as whole grains, almonds and other nuts, and green leafy vegetables.”

Researchers agree, noting that intake of dietary magnesium is closely related to other healthful dietary patterns and lifestyle behaviors, so any association must be interpreted cautiously. Nonetheless, evidence suggesting a strong relationship between magnesium intake and diabetes risk remains when researchers are able to control for factors such as smoking, exercise, calcium status, and the consumption of high-fiber cereals.4

Magnesium’s connection to diabetes is most likely through its role in maintaining glucose homeostasis and regulating insulin secretion and sensitivity.6,7 Therefore, it’s not surprising research indicates that individuals show impaired metabolic control (eg, fasting glucose, two-hour postprandial glucose, hemoglobin A1c), decreased insulin sensitivity, or impaired insulin secretion when they have low magnesium levels.8

But even with data supporting an association between magnesium status and glucose homeostasis, little clinical evidence exists on which to base treatment decisions. Some researchers report success in increasing insulin secretion and/or tissue sensitivity with magnesium supplementation, yet these studies are for the most part conducted with participants who don’t have diabetes.6,7 The few studies that examine people with diabetes are promising but far from establishing clinical practice guidelines.2

Heart Health
Magnesium status also appears to play a role in heart health, with epidemiologic evidence suggesting adequate dietary intake can reduce cardiovascular risk factors such as hypertension, atherosclerosis, and metabolic syndrome.2,9 Additionally, research indicates magnesium may be an important protector against sudden cardiac death known to occur in individuals without any history of cardiovascular disease (CVD).9 This is likely related to the potential for cardiac arrhythmia in individuals with hypomagnesia.

Yet not all evidence supports magnesium’s association with heart health. A major study last year from the Framingham Heart Study Offspring Cohort failed to find an association between baseline serum magnesium and future development of hypertension or CVD.10 Clinical evidence links those with hypomagnesia with dyslipidemia; however, whether this is a direct consequence of inadequate magnesium intake or mediated through the mineral’s effect on insulin is unknown.7

Is More Better?
The Recommended Daily Allowance (RDA) for magnesium for individuals under the age of 18 ranges from 80 mg/day for a 1-year-old child to 410 mg/day for an 18-year-old young man. An Adequate Intake of 30 to 75 mg/day is recommended during the first year of life.11 The RDA of magnesium for women and men aged 19 to 30 are 310 mg/day and 400 mg/day, respectively.11 The RDA for women aged 31 and older is 320 mg/day; for men, it’s 420 mg/day.11

The amount of magnesium necessary for disease prevention and treatment hasn’t been established. Epidemiologic data suggest that for every 100 mg/day increase in dietary magnesium, the risk of developing type 2 diabetes decreases by approximately 15%.4,5 The few clinical studies showing efficacy in improving insulin sensitivity with magnesium supplementation have used doses between 300 and 365 mg/day.7,12 Improvement in lipid profiles has been demonstrated using 365 mg/day.12 As mentioned earlier, however, these studies look promising, but they’re too few on which to base treatment recommendations.

Individuals choosing supplemental magnesium should avoid taking it with a multivitamin that contains other minerals, such as iron, calcium, phosphorous, or potassium, as this may result in decreased absorption and efficacy.1 Similarly, consuming high levels of phytates and fiber also will impede magnesium absorption.

Potential Side Effects
Since the body can both swiftly and effectively remove excess magnesium via the kidneys, toxicity due to increased dietary consumption is unlikely to occur except in individuals with underlying kidney disease. Excessive consumption of magnesium salts (3 to 5 g), however, can result in diarrhea and dehydration; more serious side effects such as nausea, weakness, double vision, slurred speech, or paralysis have been reported in people who’ve reached toxicity from excessive intravenous administration.1 As a result, a Tolerable Upper Intake Level from nonfood sources has been set at 350 mg/day although certain populations, including those with cardiac arrhythmias, coronary artery disease, and hyperlipidemia, may benefit from supplementation above 350 mg/day.11

Bottom Line
Diets high in magnesium-rich foods appear to be protective against chronic disease, and low magnesium status is increasingly being linked to disease risk and impaired disease management. RDs should encourage their patients to consume diets rich in whole grains, green leafy vegetables, nuts, and legumes but keep in mind that there isn’t enough evidence to make treatment recommendations.

For additional information, visit http://ods.od.nih.gov/factsheets/magnesium to review the Office of Dietary Supplements’ magnesium fact sheet.

— Christin L. Seher, MS, RD, LD, is founder of Strategic Health Solutions, LLC, serving northeastern Ohio.

 

References
1. Ford ES, Mokdad AH. Dietary magnesium intake in a national sample of U.S. adults. J Nutr. 2003;133(9):2879-2882.

2. Office of Dietary Supplements. Dietary supplement fact sheet: Magnesium. Available at: http://ods.od.nih.gov/factsheets/magnesium. Accessed October 2011.

3. Gropper SS, Smith JL, Groff JL. Advanced Nutrition and Human Metabolism, 4th ed. Florence, Ky.: Thomson/Wadsworth; 2005.

4. Dong JY, Xun P, He K, Qin LQ. Magnesium intake and risk of type 2 diabetes: Meta-analysis of prospective cohort studies. Diabetes Care. 2011;34(9):2116-2122.

5. Larsson SC, Wolk A. Magnesium intake and risk of type 2 diabetes: A meta-analysis. J Intern Med. 2007;262(2):208-214.

6. Rodríguez-Morán M, Guerrero-Romero F. Insulin secretion is decreased in non-diabetic individuals with hypomagnesaemia. Diabetes Metab Res Rev. 2011;27(6):590-596.

7. Guerrero-Romero F, Tamez-Perez HE, González-González G, et al. Oral magnesium supplementation improves insulin sensitivity in non-diabetic subjects with insulin resistance. A double-blind placebo-controlled randomized trial. Diabetes Metab. 2004;30(3):253-258.

8. Sales CH, Pedrosa LF, Lima JG, Lemos TM, Colli C. Influence of magnesium status and magnesium intake on the blood glucose control in patients with type 2 diabetes. Clin Nutr. 2011;30(3):359-364.

9. Peacock JM, Ohira T, Post W, Sotoodehnia N, Rosamond W, Folsom AR. Serum magnesium and risk of sudden cardiac death in the Atherosclerosis Risk in Communities (ARIC) study. Am Heart J. 2010;160(3):464-470.

10. Khan AM, Sullivan L, McCabe E, Levy D, Vasan RS, Wang TJ. Lack of association between serum magnesium and the risks of hypertension and cardiovascular disease. Am Heart J. 2010;160(4):715-720.

11. Institute of Medicine. Dietary Reference Intakes: The Essential Guide to Nutrient Requirements. Washington, D.C.: National Academies Press; 2006.

12. Mooren FC, Krüger K, Völker K, Golf SW, Wadepuhl M, Kraus A. Oral magnesium supplementation reduces insulin resistance in non-diabetic subjects—a double-blind, placebo-controlled, randomized trial. Diabetes Obes Metab. 2011;13(3):281-284.

 

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