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Magnesium: Could Supplements Help You?

A look at magnesium deficiency, supplementation, and toxicity.

Contributor Stefanie Schwartz, MS, RD, CDN


Magnesium, a mineral that has been recognized as a dietary essential since the 1920s, is currently “having a moment.”[1] It appeared in the Forbes list of nutrition and fitness trends and the “magnesium” hashtag has over a billion views on the social media platform TikTok. [2] It has long been known for a host of roles, including bone health and muscle and nerve function, but it is now also being promoted as a quick fix for problems ranging from anxiety and depression to sleep disorders.[3] Why has a nutrient that has been studied for a century emerged as a modern social media trend? The answer is more likely related to consumers’ interest in managing their own well-being and manufacturers’ interest in increasing supplement sales than to advances in our understanding of the role of magnesium in health.


 Functions of Magnesium

About half of the magnesium in the body is in bone where it helps maintain structure. Magnesium is also found in cells and fluids throughout the body where it acts as a cofactor in numerous enzyme systems and is required for the synthesis of protein, DNA, and RNA.  Magnesium also forms a complex with ATP and is therefore needed in every reaction that uses or generates ATP. Magnesium plays a role in the active transport of calcium and potassium across cell membranes, which is important for nerve impulse conduction, muscle contraction, blood pressure regulation, and normal heart function.[4]


Sources of Magnesium 

Magnesium is found in small amounts in a variety of foods (see photo). It is part of the structure of chlorophyll so is found in green vegetables. Legumes, nuts, peanut butter, seeds, and bananas are also good plant sources. Animal sources include milk, meat, poultry, and fatty fish, such as salmon.  Whole grains are a good source but refined grains, such as white bread, are poor sources because magnesium is contained in the bran and germ, which are removed during processing; a cup of whole-wheat flour contains six times the amount of magnesium found in a cup of white flour. Some foods such as breakfast cereals are fortified with magnesium. Water can also be a significant source. Certain laxatives and antacids contain magnesium, and it is available as a dietary supplement. 


Magnesium Intake and Health 

Despite the variety of food sources, dietary surveys suggest that as many as half of Americans consume less than the Recommended Dietary Allowance (RDA) for magnesium, which for adults over the age of 30 years is 420 mg for men and 350 mg for women.[4]  Early symptoms of magnesium deficiency include loss of appetite, nausea, and fatigue; if magnesium deficiency worsens, numbness, muscle cramps, seizures, abnormal heart rhythm, and personality changes can occur.[5] Symptomatic magnesium deficiency is uncommon in healthy people because the kidneys limit urinary excretion of this mineral when levels are low. However, subclinical deficiency can occur in individuals who typically consume insufficient amounts and in those with conditions that reduce absorption and/or increase excretion such as aging, gastrointestinal diseases, alcohol use disorder, and type 2 diabetes. [5]. 


Low magnesium intake is associated with an increased risk of several chronic diseases including osteoporosis, hypertension, heart disease, and type 2 diabetes.[5-8]  For example, a low intake of magnesium is correlated with lower bone mineral density and a higher risk of osteoporosis.[9] Adequate magnesium is needed to keep blood pressure in the normal range and magnesium deficiency is linked to high blood pressure. Higher intakes of magnesium are associated with a reduced risk of hypertension as well as heart disease and stroke.[5,10] With respect to diabetes, a meta-analysis found that magnesium levels in people with prediabetes are significantly lower than levels in healthy adults, suggesting that low magnesium may play a role in the development of prediabetes and its progression to diabetes.[11] 


Based on these correlations, it is not surprising that magnesium supplements have been investigated for their effectiveness in preventing and treating these chronic diseases. Magnesium supplementation has been found to benefit bone mineral density and fracture risk.[9] Some, but not all studies have found a reduction in blood pressure with magnesium supplements in individuals with and without hypertension.[12] Because studies of magnesium supplementation in cardiovascular disease  have used small sample sizes and varying types, doses, and durations of supplements it is difficult to determine if supplements provide a benefit.[13]  A few small studies have shown that magnesium supplements may improve glycemic control in Type 2 diabetes. [5,14]


Are Magnesium Supplements Safe? 

The preferred way to increase nutrient intake is with food, which provides a variety of nutrients that collectively work together in maintaining health. However, there is little risk from consuming the Tolerable Upper Intake Level (UL) for magnesium of 350 mg/day from supplements and there is evidence this UL value, established in 1997, is set too low and that taking supplemental doses greater than 350 mg is safe.[15] For example, several of studies discussed here used magnesium supplements in doses that exceeded the UL with few side effects. The side effects for healthy adults, if they do occur, are generally limited to mild, reversible diarrhea. In fact, magnesium-based laxatives have been used for years as a treatment for constipation and there has been a recent resurgence in interest in the use of magnesium oxide as a safe, convenient, low cost treatment for chronic constipation. The recommendation is to start with 1000 mg taken in 3-4 doses throughout that day and if needed increase to up to 2000 mg/day. (See  Editor’s Note). Magnesium oxide is most effective as a laxative because it is poorly absorbed; it draws water into the intestine, which helps to promote bowel movements. Well-absorbed forms of magnesium supplements,  such as magnesium citrate, glycinate, orotate, and carbonate, are more effective in supporting the systemic roles of magnesium inside the body. [16]


Even though magnesium supplements are generally safe, very large doses (more than 5,000 mg/day) from magnesium-containing laxatives and antacids have been associated with magnesium toxicity symptoms including hypotension, nausea, vomiting, lethargy, muscle weakness, irregular heartbeat, and, possibly, cardiac arrest. [5,16] Magnesium supplements of any dose should be used with caution by people with kidney disease because poor kidney function can limit excretion of excess magnesium. Magnesium supplements can also interact or interfere with certain medications. For example, supplements reduce the absorption of bisphosphonates, which are used to treat osteoporosis.  


Trending Roles for Magnesium Supplements

If you acquire your nutrition recommendations from social media, you are likely to be taking a magnesium supplement to improve your mood, ease your stress, sleep better, or lessen leg cramps. Although social media is not a reliable source for health information, there is some promising scientific evidence for these benefits.  


Anxiety and Depression  A review of studies investigating the effects of magnesium supplements on anxiety found modest support for a beneficial effect with doses of up to 300 mg/day in individuals with mild to moderate levels of anxiety.[17]  A scientific review of magnesium and mental health found a correlation between low magnesium levels and depression and a beneficial effect of magnesium supplements on depression when taken alone or in combination with antidepressant medications. [18] For example, one study that provided 248 mg of supplemental magnesium for 6 weeks reported significant improvement in depression scores. [19] However, the review also suggests that more long-term, well-controlled studies are needed to definitively recommend supplementation for depression and anxiety.


Stress  Stress triggers physiological and psychological responses in the body. In the short-term stress causes the release of adrenaline to increase heart rate and cortisol to increase blood sugar to help us escape from the perceived threat. When stress becomes chronic, it can worsen existing health problems and also cause or exacerbate anxiety and depression. Stress increases the release of magnesium into the blood stream and eventually causes magnesium loss as it is excreted by the kidneys. Low magnesium status is common in individuals suffering from psychological stress and this may be due in part to magnesium loss via the kidneys. Magnesium supplementation in the range of 300-400 mg/day has shown benefits in stressed but otherwise healthy subjects. [20] 


Sleep Disorders  Magnesium is a popular internet treatment for sleep disorders, including difficulty falling asleep and/or staying asleep.  Observational studies have shown low magnesium status in individuals with sleep disorders, particularly in older adults and those suffering from high levels of stress. [20]  Although currently there is not sufficient evidence from well-controlled clinical trials make to support the role of magnesium in sleep disorders, magnesium supplementation is a low cost, low risk option worth trying to improve sleep. [21,22]


Muscle Cramps  A deficiency of magnesium can cause muscle twitching, cramping, and even seizures. However, in the absence of a deficiency, magnesium has not been shown to be effective at easing cramping. A review of magnesium supplementation of 100 to 520 mg/day found that it is unlikely that magnesium supplements provide a benefit in reducing leg cramps.[23]


Migraines Although it is known that magnesium is important for energy homeostasis in the brain, the exact connection between magnesium and headaches has yet to be determined. A review of studies on headaches and magnesium suggests supplementation of 300 mg twice daily is a well-tolerated option in treating migraine and in enhancing the effects of typical antimigraine medications. [24]


Conclusion


The ability of social media to swiftly disseminate information may be promoting benefits of magnesium supplements more rapidly than the science can advance to back them up. The studies reviewed here do not provide adequate evidence based on well-designed research on magnesium supplementation to make specific recommendations. That said, in healthy adults there are many potential benefits and few risks associated with supplemental magnesium at doses less than 5000 mg.


Editor’s note: Clinicians have started prescribing daily magnesium supplementation for chronic constipation.  The long term effects of this supplementation is not known. Although studies have shown that 1,000 mg of magnesium supplementation for chronic constipation is safe, consider starting with magnesium oxide 400 mg daily and titrating slowly upward.  Monitoring of serum magnesium levels may be warranted when using greater than this dosage.  Patients with renal disease or patients on digitalis may be at risk for hypermagnesemia.


References:


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