The headline is partly valid but oversimplified. Magnesium is an essential mineral, and supplements can be useful in some circumstances. The main concern is that excess supplemental magnesium can accumulate when the kidneys cannot remove it effectively. ODs+1
The two groups that need particular caution
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People with kidney disease or reduced kidney function
The kidneys normally eliminate excess magnesium. With impaired kidney function, high-dose supplements or magnesium-containing laxatives/antacids can cause magnesium toxicity, potentially leading to low blood pressure, weakness, breathing problems, abnormal heart rhythm, and, in extreme cases, cardiac arrest. ODs+1
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Older adults
Older people are more likely to have reduced kidney function and to take several medications, making excessive supplementation and drug interactions more concerning. This doesn’t mean older adults should avoid magnesium altogether—rather, unnecessary high-dose supplementation should be discussed with a clinician or pharmacist. ODs+1
How much is too much?
For healthy adults, the U.S. NIH sets an upper limit of 350 mg/day of magnesium from supplements and medications (not magnesium naturally present in food). Higher amounts may be appropriate under medical supervision for particular conditions. Excess supplemental magnesium commonly causes diarrhea, nausea, and abdominal cramping. ODs
Magnesium can also interfere with the absorption of certain antibiotics and osteoporosis medicines, so timing may matter. ODs+1
Bottom line: Magnesium from foods such as nuts, seeds, legumes, whole grains, and leafy greens is generally safe. The biggest caution is with high-dose supplements, particularly in people with kidney problems.
If you tell me your age, whether you have kidney problems, and the magnesium product/dose you’re considering, I can tell you whether that particular dose deserves caution.
