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Short Summary
Main recommendation: Dr. Kim says magnesium glycinate is one of his most-recommended forms because it's highly bioavailable, gentler on the gut, and may support mood, sleep, and vitamin D conversion, provided the product is truly chelated. Dr. Kim says other forms may suit specific goals: citrate for blood pressure and insulin resistance, malate for people with GI upset, and oxide mainly for constipation rather than deficiency.
Key Points
- Magnesium glycinate is well absorbed and causes fewer gastrointestinal side effects such as diarrhea than magnesium oxide or sulfate.
- Magnesium helps convert inactive vitamin D into 25-hydroxyvitamin D; one double-blind randomized controlled trial in people with overweight or obesity found adding magnesium glycinate to vitamin D raised vitamin D levels more than vitamin D alone.
- Magnesium citrate (400 mg daily for 12 weeks) was linked in a small 2021 double-blind randomized trial to lower blood pressure and improved hemoglobin A1C.
- Magnesium L-threonate (magtein) crosses the blood-brain barrier in animal data, but human evidence is small, industry-funded, and confounded by other ingredients, so the speaker does not generally recommend it.
- Magnesium oxide is poorly absorbed and not suitable for treating deficiency, but it was as effective as senna for constipation and showed early migraine-prevention evidence.
Details Worth Noting
- Concrete instructions: Choose a magnesium glycinate product that explicitly lists a chelated form (magnesium bonded to glycine), not a blend of glycine with magnesium oxide or carbonate. Avoid cheap blends, which are less absorbed and more likely to cause diarrhea. If you have gut sensitivity, the speaker suggests magnesium malate as the most tolerable option. Magnesium L-threonate contains very little elemental magnesium, so do not count it toward your daily magnesium intake.
- A quality test published in December 2022 found that most magnesium glycinate products sold on Amazon were not truly chelated.
- The depression benefit of magnesium glycinate rests on a small case study, and the speaker could not find many good-quality studies for that specific form.
- Dr. Kim cites an open-label crossover trial where 248 mg of magnesium chloride for 6 weeks showed clinically significant improvements in depression and anxiety scores.
- Epsom salt (magnesium sulfate) baths and topical magnesium chloride lack evidence that they meaningfully raise body magnesium levels; any benefit may be relaxation.
Bottom Line
The best form depends on your goal and tolerance: glycinate for general use and vitamin D support, citrate for blood pressure and insulin resistance, malate for sensitive stomachs, and oxide mainly for constipation. Verify the chelation claim on any glycinate label, since many products do not deliver it.
