Magnesium participates in many physiological and biochemical reactions in the human body. Magnesium deficiency can lead to issues with the nerves, muscles, heart, or nervous system. Adequate magnesium intake is also associated with the regulation of blood pressure and blood sugar. Consequently, “magnesium” health supplements are becoming increasingly popular. What forms of magnesium supplements are available, and which one is the most effective? What are the effects of excessive intake? Heho Dietitian Yi-ting provides a comprehensive summary here.
Magnesium-Rich Foods in the Diet
Food and water are the primary sources of magnesium intake, including nuts and seeds (such as cocoa, pumpkin seeds, and flaxseed), whole grains (such as whole wheat bread and brown rice), green leafy vegetables, meat, seafood, and soy products. Among these, cocoa contains the highest magnesium content. Processing and cooking can significantly reduce the magnesium content in food. With today’s highly refined dietary patterns, combined with illnesses, medications, and alcohol consumption, magnesium deficiency is becoming more common. According to the 2013–2016 Nutrition and Health Survey in Taiwan, adults aged 13–44 consume only about 60% to 80% of their recommended daily intake, with deficiency being more prevalent in females than in males.
Forms of Magnesium Supplements
The absorption rate of magnesium is influenced by various factors. The average absorption rate ranges from approximately 30% to 50%. Generally, higher intake of magnesium ions leads to lower absorption efficiency, whereas magnesium deficiency in the body triggers higher absorption rates. Among the different forms of magnesium supplements, organic forms like magnesium chloride and magnesium aspartate offer higher bioavailability. Below are common forms of magnesium supplements and their studied potential therapeutic uses:
- Magnesium chloride and magnesium aspartate: Higher bioavailability.
- Magnesium hydroxide: Lower absorption rate, commonly used in antacids or laxatives.
- Magnesium citrate: Highly water-soluble with an absorption rate higher than magnesium oxide. High doses of magnesium citrate may help prevent migraines.
- Magnesium oxide: Poorer bioavailability, though effervescent tablets offer better absorption than standard tablets.
- Magnesium orotate: Potentially beneficial for heart failure.
- Magnesium glycinate or magnesium taurate: Used in the treatment of depression.
Topical Magnesium Oils and Creams: Efficacy Remains Unproven
A 2017 study published in the journal PLOS One indicated that magnesium-containing creams might increase serum magnesium levels through dermal absorption (n=20). Consequently, magnesium oils and creams have entered the market claiming to deliver magnesium transdermally, even suggesting potential blood pressure-regulating benefits. However, scientific evidence supporting these claims remains limited.
A 2017 review paper published in Nutrients titled “Myth or Reality—Transdermal Magnesium?” questioned this hypothesis. The authors noted that magnesium exists as ions in cells and cannot easily penetrate the lipophilic layer of the skin. Furthermore, magnesium absorption occurs via specific transport proteins rather than simple diffusion, and such magnesium transporters have not yet been identified in epithelial cells, except possibly in small areas like sweat glands and hair follicles. Given the very small sample sizes in current transdermal magnesium absorption studies, further research is required to confirm these claims. Therefore, relying on transdermal absorption for magnesium supplementation is not currently recommended.
Note: Magnesium oil is not actually an oil; rather, it is a magnesium chloride solution with an oil-like texture.
Recommended Daily Intake and Overdose Symptoms
According to the Dietary Reference Intakes (DRIs), the recommended daily magnesium intake for adults aged 19 to 50 is 380 mg for males and 320 mg for females, with variations for other age groups. Magnesium is the second most common mineral deficiency among the population (second only to calcium). Intake from natural food sources carries virtually no risk of overdose. Hypermagnesemia typically only occurs in individuals with renal insufficiency, those receiving magnesium sulfate therapy, individuals with hypothyroidism, or due to specific drug interactions.
Symptoms of magnesium overdose include:
- Diarrhea
- Low blood pressure, dizziness
- Muscle weakness
- Severe back pain and pelvic pain
- Mental confusion
- Difficulty breathing
- Cardiac arrhythmia
- Other symptoms: Lethargy, confusion, and deteriorating kidney function
For mild magnesium overdose, stopping the use of magnesium supplements, magnesium-containing laxatives, or antacids is generally sufficient, provided kidney function is unimpeded. However, severe magnesium toxicity requires emergency medical intervention, such as intravenous (IV) fluids or diuretics.