Magnesium is easy to overlook. Yet it powers more than 300 chemical reactions in the body, from making energy to steadying the heartbeat.
The NIH Office of Dietary Supplements says dietary surveys in the United States consistently show intakes lower than recommended. Most Americans of all ages take in less than their target amount from food alone.
The recommended dietary allowance for adults is 400 to 420 mg a day for men and 310 to 320 mg for women. About 30 to 40 percent of the magnesium in food is absorbed.
Full-blown deficiency is uncommon in healthy people because the kidneys hold on to magnesium when stores run low, according to the NIH fact sheet. Certain health conditions, heavy alcohol use and some medicines can tip that balance.
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8 signs that may point to low magnesium
The NIH lists loss of appetite, nausea, vomiting, fatigue and weakness among the early signs. As the deficit deepens, numbness, tingling, muscle contractions and cramps, seizures, personality changes, abnormal heart rhythms and coronary spasms can appear.
Cleveland Clinic's clinical guidance on hypomagnesemia adds tremors and tetany, meaning muscle spasms in the hands and feet, among mild symptoms. In severe cases the clinic points to generalized tonic-clonic seizures, delirium and arrhythmia.
The eight signs most commonly flagged across the two authorities:
- Loss of appetite
- Nausea or vomiting
- Fatigue and weakness
- Muscle cramps, spasms or tremors
- Numbness or tingling in the hands or feet
- Abnormal heart rhythms or palpitations
- Personality changes or delirium
- Seizures
None of these signs is unique to low magnesium. Serum magnesium is not part of routine electrolyte testing in hospitals and clinics, the NIH notes, and blood levels correlate poorly with total body stores. A clinician is the person to work out what is behind persistent symptoms.
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Who is most likely to fall short
The NIH names four groups at elevated risk of magnesium inadequacy.
Group | Why the risk is higher |
|---|---|
Older adults Also read: Your daily multivitamin may be doing more for your memory than you think | Lower dietary intake, less absorption in the gut and more urinary loss with age |
People with type 2 diabetes | Higher blood glucose drives magnesium out in the urine |
People with GI diseases such as Crohn's and celiac Also read: How eating dates every day can affect your gut, heart and blood sugar | Chronic diarrhea and fat malabsorption deplete magnesium over time |
People with alcohol dependence | Poor intake, vomiting, diarrhea, kidney losses and vitamin D shortfall combine |
Cleveland Clinic reports that low blood magnesium affects 30 to 80 percent of people with alcohol use disorder and 25 percent of those with poorly managed diabetes. In the general US population the figure is about 2 percent.
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Where magnesium actually comes from
Magnesium is widely distributed in whole foods, according to the NIH. Good sources include spinach, almonds, cashews, peanuts, black beans, soymilk, edamame, whole-wheat bread, avocado, brown rice and low-fat yogurt.
An ounce of dry-roasted almonds supplies 80 mg, about a fifth of the daily value. Half a cup of boiled spinach delivers 78 mg, and an ounce of dry-roasted cashews adds 74 mg.
Supplements come in many forms including magnesium oxide, citrate and chloride, and absorption differs by form. The NIH sets the tolerable upper limit for supplemental magnesium in adults at 350 mg a day.
The fact sheet also flags interactions with bisphosphonates, some antibiotics and diuretics. Anyone considering a supplement, especially with kidney disease or on prescription medicine, should raise it with a doctor first.
This article is made and published by Emil Martesen, who may have used AI in the preparation.