Magnesium participates in numerous physiological and biochemical reactions in the human body. A deficiency can lead to issues with the nerves, muscles, heart, or the overall nervous system. Adequate magnesium intake is even linked to the regulation of blood pressure and blood sugar. Consequently, “magnesium” health supplements are becoming increasingly common. What forms of magnesium supplements are available, which is the most effective, and what are the effects of taking too much? Heho Dietitian Wu Yiting provides a comprehensive summary.
High-Magnesium Ingredients in the Diet
Food and water are the primary sources of magnesium. These include nuts and seeds (cocoa, pumpkin seeds, flaxseeds), whole grains (whole-wheat bread, brown rice), leafy green vegetables, meat, seafood, and soy products—with cocoa having the highest magnesium content. However, the magnesium content decreases significantly after food processing and cooking. Modern refined diets, combined with diseases, certain medications, and alcohol consumption, make magnesium deficiency more likely. According to the 2013–2016 Nutrition and Health Survey in Taiwan, adults aged 13–44 only reach about 60–80% of the daily recommended intake, with deficiency being more severe in women than in men.
Forms of Magnesium Supplements
The absorption rate of magnesium is influenced by many factors. The average absorption rate is about 30–50%; however, the higher the intake of magnesium ions, the lower the absorption rate becomes (and vice versa). Among different forms of supplements, organic forms like Magnesium Chloride and Magnesium Aspartate have higher bioavailability. Below are common forms and their potential therapeutic uses:
- Magnesium Chloride and Magnesium Aspartate: High bioavailability.
- Magnesium Hydroxide: Lower absorption rate; commonly used in antacids or laxatives.
- Magnesium Citrate: Easily soluble in water with higher absorption than magnesium oxide. High doses may help prevent migraines.
- Magnesium Oxide: Poorest bioavailability, though the absorption rate of effervescent tablets is better than that of standard tablets.
- Magnesium Orotate: Potentially useful for heart failure.
- Magnesium Glycinate or Magnesium Taurate: Used in the treatment of depression.
Magnesium Oils and Creams: Efficacy of Topical Application Yet to Be Proven
A 2017 study published in PLOS One suggested that magnesium creams might increase serum magnesium levels through skin absorption (n=20). Consequently, magnesium oils and creams have entered the market claiming to regulate blood pressure via transdermal absorption. However, scientific research has yet to provide strong evidence for this.
A paper titled “Myth or Reality—Transdermal Magnesium?” published in the journal Nutrients in 2017 challenged this hypothesis. The authors noted that magnesium in cells exists in ionic form and cannot pass through the lipophilic (fat-loving) layer of the skin. Furthermore, magnesium absorption occurs via specific transport proteins rather than simple diffusion, and no magnesium transport proteins have been found in epithelial cells (except potentially in small areas of sweat glands and hair follicles). Given the very small sample sizes in current transdermal studies, more research is needed. Therefore, absorbing magnesium through the skin is not currently recommended.
Note: “Magnesium oil” is not actually an oil; it is a magnesium chloride solution with an oil-like texture.
How Much Magnesium Should You Take? Overdose Symptoms
According to the Dietary Reference Intakes (DRI) for Taiwan, the recommended daily intake for adults aged 19–50 is 380 mg for men and 320 mg for women. Magnesium is the second most common mineral deficiency in Taiwan (after calcium). While it is almost impossible to overdose via natural foods, hypermagnesemia (excessive magnesium in the blood) can occur in patients with renal insufficiency, those undergoing magnesium sulfate treatment, individuals with hypothyroidism, or due to certain medications.
Symptoms of excessive magnesium intake include:
- Diarrhea
- Drop in blood pressure and dizziness
- Muscle weakness
- Severe back and pelvic pain
- Mental confusion
- Difficulty breathing
- Arrhythmia (irregular heartbeat)
- Other: Drowsiness, lethargy, or worsening kidney function
In cases of mild overdose, symptoms usually resolve by stopping the use of magnesium supplements, laxatives, or antacids, provided there is no kidney damage. However, severe magnesium poisoning requires emergency medical treatment, such as intravenous fluids or diuretics.