Food is medicine: The science behind magnesium

Key takeaways:

• Magnesium supplementation has been studied for its effects on various health conditions.
• The supplement may offer benefits for bone health and blood pressure, but the evidence is undecided.

Magnesium supplements may help improve bone health and blood pressure, but more studies are needed to confirm any causal associations, according to research.

Magnesium is an essential mineral and “a cofactor for hundreds of enzymatic reactions” that involve energy production, heart rhythm, nerve function, blood pressure regulation, glucose control and muscle contraction, Stefan M. Pasiakos, PhD, director of the NIH’s Office of Dietary Supplements (ODS), told Healio. It may also contribute to bone development and maintenance.

“Legumes, nuts, seeds, whole grains, and green leafy vegetables, such as spinach, are all good sources of magnesium,” Pasiakos said. “Magnesium is also present in some over-the-counter laxatives, antacids and in many dietary supplements, including most multivitamin/mineral products.”

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The recommended dietary allowance (RDA) for magnesium can vary, he said. For most women, the RDA is 310 to 320 mg per day, “with higher amounts during pregnancy,” and for men, the RDA is 400 to 420 mg per day.

“Magnesium supplementation can be used to increase magnesium intake since many people consume less-than-recommended amounts from their diets,” Pasiakos said. “This includes many older adults and teens.”

Among otherwise-healthy people, symptomatic magnesium deficiency resulting from low dietary intake is rare, but chronic low intake, the use of some medications and certain health conditions like alcoholism can lead to a magnesium deficiency, according to the NIH. Early symptoms include weakness, fatigue, loss of appetite and nausea, but more severe signs include tingling, cramps, muscle contractions, seizures, numbness, abnormal heart rhythms, coronary spasms and personality changes.

“Magnesium supplements are often promoted for bone health and blood pressure control,” Pasiakos said. “FDA has approved a qualified health claim for magnesium from foods or dietary supplements to reduce the risk of high blood pressure, but they state that the evidence supporting this claim is inconsistent and inconclusive.”

Summary of evidence

In a 2022 systematic review and meta-analysis of 12 studies that included 92,170 participants, researchers conducted a qualitative analysis that revealed a positive trend between increased magnesium intake and increased hip and femoral neck bone mineral density, or BMD (hip BMD pooled beta = 0.03; 95% CI, 0.01-0.06; BMD in femoral neck partial r = 0.14; 95% CI, 0.001-0.28). They wrote that higher magnesium intake could support an increase in hip and femoral neck BMD for older adults, but more research is needed to make a concrete recommendation. No conclusions could be drawn regarding bone mineral content, total body and lumbar spine BMD, bone turnover markers and fracture risk due to a limited number of studies assessing these outcomes.

Additionally, a 2018 randomized, double-blind, placebo-controlled, multicenter trial including 200 healthy pregnant women showed that 400 mg per day of magnesium supplements did not appear to be beneficial for BP management. There were no differences in the increase in BP, but for those in the intervention group, there was a significant negative correlation between increases in systolic blood pressure and the increase in blood levels of magnesium (P = .042). The researchers wrote that the supplements should not be recommended for the prevention of increasing BP.

Also, researchers leading a 2022 randomized, double-blind, placebo-controlled trial including 164 patients evaluated magnesium citrate, magnetic sulfate and magnesium oxide’s impact on BP and arterial stiffness. They found that, compared with placebo, 24 weeks of 450 mg per day of any form of magnesium supplementation had no impact on BP, arterial stiffness or carotid-to-femoral pulse wave velocity.

Experts have also studied magnesium supplementation’s impact on other conditions, like diabetes. In a small randomized controlled trial conducted in 2018 with 42 patients, researchers found that for patients with type 2 diabetes, oral magnesium supplementation may improve glycemic control indicators and reduce insulin resistance. Specifically, participants who took 250 mg a day of elemental magnesium for 3 months saw significant improvements in insulin levels (15.56 µIUC/mL to 12.18 µIUC/mL) and HbA1c (8.32% to 7.96%). However, in 2013, the American Diabetes Association found “insufficient evidence to support the routine use of micronutrients,” including magnesium, “to improve glycemic control in people with diabetes.”

More information

Like most supplements, excessive magnesium can lead to health problems. For people aged 9 years and older, the tolerable upper intake level (UL) of supplemental magnesium is 350 mg per day, Pasiakos said.

“The UL does not apply to magnesium from food and beverages,” he said. “High doses of supplemental magnesium can cause diarrhea, nausea and abdominal cramps. Extremely high intakes can lead to irregular heartbeat and cardiac arrest.”

Pasiakos also said primary care physicians should note that magnesium status can be “difficult to assess.”

“The most common method to assess magnesium status is serum magnesium concentration, but serum concentrations have little correlation with total body or tissue levels,” he said. “Combining laboratory tests with clinical assessments can help evaluate magnesium status.”

The ODS offers resources for health care providers and consumers. To learn more about magnesium and other products, check out the ODS Fact Sheets.

Editor’s Note: Healio is highlighting the clinical value of various supplements. See other installments of the series here:

• Melatonin
• Omega-3
• Zinc and other supplements for immune function
• Vitamin D
• Calcium
• Ashwagandha
• Folic Acid
• Vitamin B12 
• Iodine
  

References:

• Bullarbo M, et al. J Pregnancy. 2018;doi: 10.1155/2018/4843159.
• ELDerawi WA, et al. Nutrients. 2018;doi:10.3390/nu11010044.
• Evert AB, et al. Diabetes Care. 2013;doi:10.2337/dc13-2042.
• Groenendijk I, et al. Bone. 2022;doi:10.1016/j.bone.2021.116233.
• Schutten JC, et al. J Am Heart Assoc. 2022;doi:10.1161/JAHA.121.021783.