Highlights
- An essential mineral, Magnesium is needed for cellular energy production, DNA/RNA synthesis and bone health and the function of the body’s major antioxidant glutathione
- In clinical trials people with the highest magnesium levels had the lowest risk of cardiovascular disease and diabetes
- US National Academies recommends an intake of 420 mg for men and 320 mg for women over the age of 30 from all food and supplement sources
Magnesium is a cofactor (helper) in more than 300 enzymes that regulate diverse physiological functions ranging from muscle and nervous system, blood glucose regulation and blood pressure control. Serum magnesium levels are highly correlated with better cardiovascular and metabolic health. In addition, an estimated 48% of people in the US take less than the estimated average requirement of Magnesium.
The biology
Magnesium is required for cellular energy production. It is required for bone growth and maintenance, synthesis of RNA and DNA and the production of glutathione, the body’s most abundant antioxidant. It plays critical roles in ion transport required for nerve conduction, muscle contraction and heart rhythm.
Clinical evidence
Several large clinical trials have examined the association between magnesium levels and heart disease. The largest among them tracked 88,000 female nurses in the United states and tested their serum magnesium levels over every two to four years. Over a 26 years follow-up subjects in the highest quartile of plasma magnesium levels had a 77% lower risk of sudden cardiac death compared to subjects in the lowest quartile. A meta-analysis of 16 different clinical studies comprising 313,041 subjects also came to the same conclusion, that circulating and dietary magnesium levels are inversely correlated with cardiovascular disease risk.
We find a similar story with type 2 diabetes and magnesium intake. A meta-analysis of seven of these studies which included 286,668 subjects over 6 to 17 years of follow-up found that 100 milligrams per day increase in total magnesium intake reduced the risk of diabetes by 15%. Another meta-analysis of eight studies came to a similar conclusion, that there is an inverse correlation between magnesium intake from food and the risk of type 2 diabetes. This study found a 23% reduction in risk between the high magnesium and low magnesium groups.
These are fairly convincing studies on magnesium levels in serum with reduced risk of diabetes. What is the clinical evidence that magnesium supplementation, and not just the serum levels, improves cardiometabolic health? Clinical studies on magnesium supplementation so far have been insufficiently powered to conclusively show that supplementation alone reduces the risk of diabetes. The large studies I talk about above, show that high serum magnesium levels are associated with reduced risk of diabetes. As a result, the American Diabetes Association has stated that there is insufficient evidence to conclude that magnesium supplementation improves glycemic control.
Among its many important roles, Magnesium is involved in vitamin D and parathyroid hormone regulation which are critical for bone health. Magnesium is also critical for the proper functioning of cells involved in bone formation and bone remodeling. Not surprisingly, high serum magnesium levels are associated with higher bone density. As for magnesium supplementation: a small study found that 290 milligrams per day of elemental magnesium supplemented as magnesium citrate for 30 days in post-menopausal women, decreased bone loss (n=20).
So do we need to supplement? Or can magnesium be obtained just from our diets alone? With a diet rich in leafy greens, legumes, nuts, seeds and whole grains, chances are good that we are getting our recommended daily allowance of magnesium. That said, if you want to supplement, clinical studies have shown that magnesium supplementation elevates serum magnesium levels.
Guidelines for taking magnesium:
Recommended daily allowance from all food sources:
- Men 19-30: 400mg
- Women 19-30: 310mg
- Men 30+: 420mg
- Women 30+: 320mg
Tolerable upper intake levels (UL) for supplementation;
- Men: 350 mg
- Women: 350 mg
NOTE: The upper intake level is set for supplementation alone and does not include total magnesium intake from all food sources. This can be confusing since in some cases the RDA can be higher than UL, but this is because UL is based on supplementation alone while RDA is food plus supplementation.
Safety
Excessive Magnesium from food does not pose a health risk since the kidneys have an efficient way to remove excess magnesium. But high doses of magnesium taken as a supplement may cause diarrhea. This is the effect caused by the laxative Milk of Magnesia. This is due to the unabsorbed salts in the GI tract that retain fluids and cause increased GI motility. Very large doses of magnesium, usually more than 5000mg/day have been associated with magnesium toxicity. The kidneys cannot eliminate that large a dose and the risk of toxicity is higher in people with compromised kidney function.
Some drug interactions worth noting here include: bisphosphonate (Fosamax) whose absorption is decreased by magnesium. Don’t take a magnesium supplement within two hours of taking oral bisphosphonate. Similarly, if you are on an oral antibiotic, don’t take a magnesium supplement within either two hours before or four to six hours after. Other drugs can deplete magnesium from the body; examples are oral diuretics such as Furosemide (Lasix) and Proton pump inhibitors (e.g. Nexium, and Prevacid). A more complete list can be found at WebMD and NIH-ODS
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Food Sources
Top food sources of Magnesium are pumpkin seeds, chia seeds, spinach, almonds, cashews, black beans, soy milk and edamame (soy beans), peanut butter (peanuts), brown rice.
Supplementation
Magnesium citrate, glycinate, L-threonate, oxide and taurate are among popular choices available in pill form. Among these, the citrate form has a laxative effect so it might be appropriate for those who need this added benefit. The glycinate and L-threonate forms are chelated to amino acids and are thought to be better absorbed orally. Oxide form is poorly absorbed. Another option worth considering is magnesium taurate, based on a pre-clinical study that compared oral bioavailability of various magnesium salts and found that taurate has the second highest oral bioavailability and the highest permeability in the brain
Chiuve, S. E., Korngold, E. C., Januzzi, J. L., Jr., Gantzer, M. L., & Albert, C. M. (2011, February). Plasma and dietary magnesium and risk of sudden cardiac death in women. The American Journal of Clinical Nutrition. https://pmc.ncbi.nlm.nih.gov/articles/PMC3021423/
Del Gobbo, L. C., Imamura, F., Wu, J. H., de Oliveira Otto, M. C., Chiuve, S. E., & Mozaffarian, D. (2013, July). Circulating and dietary magnesium and risk of cardiovascular disease: a systematic review and meta-analysis of prospective studies. The American Journal of Clinical Nutrition. https://pmc.ncbi.nlm.nih.gov/articles/PMC3683817/
Jahnen-Dechent, W., & Ketteler, M. (2012, February). Magnesium basics. Journal of Internal Medicine. https://onlinelibrary.wiley.com/doi/10.1111/j.1365-2796.2007.01840.x
Lopez-Ridaura, R., Willett, W. C., Rimm, E. B., Liu, S., Manson, J. E., Stampfer, M. J., & Hu, F. B. (2004, January 12). Magnesium Intake and Risk of Type 2 Diabetes in Men and Women. Archives of Internal Medicine. https://jamanetwork.com/journals/jamainternalmedicine/fullarticle/412391
Al-Ghamdi, S. M., Akmal, M., & Khanna, S. (2009, August 12). Magnesium: the forgotten electrolyte—a review on hypomagnesemia. Biological Trace Element Research. https://link.springer.com/article/10.1007%2Fs12011-009-8416-8
Magnesium: Overview, Uses, Side Effects, Precautions, Interactions, Dosing and Reviews. WebMD. https://www.webmd.com/vitamins/ai/ingredientmono-998/magnesium
Magnesium – Health Professional Fact Sheet. National Institutes of Health (NIH) Office of Dietary Supplements (ODS). https://ods.od.nih.gov/factsheets/Magnesium-healthProfessional/
Gröber, U., Schmidt, J., & Kisters, K. (2015, September 23). Magnesium in Prevention and Therapy. Nutrients. https://pubmed.ncbi.nlm.nih.gov/29679349/