Dr. Naoki Omida: For Kidney Patients, Beware of High Doses of Magnesium Supplements
Dr. Wala’a Hafez
In recent years, magnesium has rapidly risen to the top of the list of the most popular dietary supplements, driven by its association with improved sleep and relaxation, support for muscle and nerve health, as well as discussions regarding its benefits for migraines, heart health, and bone health. However, behind this popularity, the scientific picture appears more balanced than some claims suggest. Magnesium is an essential element that the body requires for many of its vital functions; however, obtaining it from food sources remains the best option for most people. The popularity of supplements does not mean they are necessary or suitable for everyone.
Why does the body need magnesium?
Magnesium is one of the essential minerals that the body cannot do without. It participates in hundreds of biochemical reactions, contributing to energy production, protein and DNA synthesis, and the regulation of nerve and muscle functions. It also plays a role in bone health, blood pressure regulation, glucose levels, and supporting heart and cardiovascular functions. A recent review published this year in *Current Nutrition Reports* indicates that magnesium plays an important role in many physiological and metabolic processes, while low levels have been linked to cardiovascular diseases, metabolic disorders, bone problems, and certain neurological conditions. However, researchers emphasize that determining magnesium levels in the body is not a simple matter, and true, obvious deficiency is less common than might be suggested by the widespread commercial advertising of its supplements.
Does everyone need magnesium supplements?
The answer is no. Most healthy individuals can meet their magnesium needs through a balanced diet, particularly through nuts, seeds, legumes, whole grains, and leafy vegetables. Medical sources indicate that magnesium naturally present in food usually does not pose a problem for people with normal kidney function, as the body eliminates excess amounts through urine. Here lies an important point: the upper limit of 350 mg per day for adults does not include magnesium naturally found in foods, but applies to magnesium obtained from dietary supplements and medications. Dr. Naoki Omida, an integrative medicine specialist at Cleveland Clinic, who is board-certified in internal medicine, gastroenterology, hepatology, and integrative medicine, warns against overconsumption of magnesium supplements, noting that scientific evidence for some common uses of these supplements remains limited. Dr. Omida summarizes his stance by saying, “Do not treat it as a magic solution.”
Magnesium and Migraines
Migraines are among the areas where magnesium has received the most attention from researchers. Some evidence suggests it may be useful in preventing migraine attacks and reducing their frequency in some patients. Joint guidelines from the American Academy of Neurology and the American Headache Society concluded that magnesium is “probably effective” in preventing migraines. Furthermore, a recent systematic review found evidence supporting its use for this purpose, though it remains insufficient to consider it a definitive treatment suitable for all sufferers. Its benefit may be more pronounced in some migraine sufferers experiencing “aura,” which are temporary neurological symptoms that may precede or accompany an attack, such as visual or sensory disturbances, as well as in those suffering from menstrual-related migraines. However, the doses used for migraine prevention may exceed the usual upper limit for magnesium from dietary supplements; therefore, they should be taken under medical supervision and not considered a general dose suitable for everyone.
Laxative Effect
When taken as a supplement in high doses, magnesium can act as a laxative, causing diarrhea, cramps, abdominal spasms, and nausea. The U.S. National Institutes of Health (NIH) clarifies that some forms of magnesium are more likely than others to cause diarrhea, including magnesium carbonate, chloride, gluconate, and oxide. This is not merely due to “stomach sensitivity”; rather, unabsorbed magnesium salts remain in the intestines, drawing water to them via osmotic pressure, which increases the liquidity of their contents. It may also contribute to stimulating gastrointestinal motility, explaining its laxative effect. This effect is medically known; some magnesium salts are primarily used in constipation treatments. Therefore, overconsumption or use in inappropriate doses can turn a “healthy supplement” into a cause of diarrhea and gastrointestinal disturbances.
Types of Magnesium Are Not Alike
Not all magnesium supplements are the same; their effects vary depending on the compound type, dosage, and the body’s absorption rate. For example, medical sources indicate that “magnesium citrate” has good absorption but may also have a laxative effect, whereas “magnesium oxide” is used in some cases as a laxative or antacid and may cause diarrhea. According to Cleveland Clinic, a recent systematic review of studies on magnesium for migraine prevention showed that gastrointestinal disturbances were among the most prominent side effects associated with supplements, including loose stools, diarrhea, and stomach irritation, which were mostly mild and temporary in most cases.
Excessive Dosage
The acceptable upper limit for magnesium from dietary supplements and medications for adults is set at 350 mg per day, primarily based on the likelihood of gastrointestinal side effects, not because exceeding this amount necessarily means poisoning or diarrhea. Conversely, a scientific review published in *Advances in Nutrition* called for re-evaluating this limit, after showing that several studies using higher doses did not record a significant increase in diarrhea cases compared to control groups. These results suggest that the relationship between dosage and side effects is not fixed; magnesium tolerance varies from person to person and is affected by the type of supplement, its formulation, and the dose used. Therefore, 350 mg should not be treated as a “toxic dose,” nor does this mean it can be exceeded arbitrarily; it represents a precautionary limit for magnesium obtained by healthy adults from supplements and medications, not from natural food sources.
Kidney Patients: Greater Caution
Greater caution is needed when taking magnesium supplements in people with kidney problems, as kidneys play a primary role in eliminating excess amounts. When kidney function weakens, magnesium may accumulate in the blood, making high doses potentially dangerous. According to the U.S. National Institutes of Health (NIH), severely elevated magnesium levels can lead to low blood pressure, muscle weakness, vomiting, irregular heartbeats, and difficulty breathing. In severe cases, poisoning can lead to cardiac arrest. Magnesium supplement warnings are not limited to high doses; they can also interfere with the absorption of certain medications, including some antibiotics and osteoporosis treatments. Therefore, timing of intake should be considered, and consultation with a doctor or pharmacist is advised when using them concurrently with other medications. Regarding the use of magnesium to improve sleep, Dr. Omida emphasized that available scientific evidence remains limited, noting that most studies are small and that more research is needed before recommending it routinely for sleep disorders. He also advised against exceeding 350 mg per day of magnesium from dietary supplements without medical recommendation.
Food First
Dr. Omida summarizes the picture by saying, “Magnesium is not an enemy, nor is it a magic supplement.” It is an essential mineral that the body needs daily, playing important roles in muscle and nerve functions, bone health, energy production, as well as heart and cardiovascular functions. Evidence also points to potential benefits for certain uses, such as migraine prevention. However, the most important rule is that increasing the dose does not mean increasing the benefit. Overconsumption of supplements or use of certain types of magnesium can lead to diarrhea, cramps, and nausea, while the need for caution increases among those with impaired kidney function or individuals taking medications that may interact with it.
