Magnesium Glycinate vs Citrate vs Oxide: Bioavailability
Contents
1 - Introduction
Magnesium is essential for over 300 enzyme reactions, but not all supplements are absorbed equally. This article compares three common forms—glycinate, citrate, and oxide—using peer-reviewed evidence to help you choose wisely.
2 - Why Bioavailability Matters
Bioavailability refers to the fraction of a nutrient that reaches your bloodstream and becomes available for use. For magnesium, this depends on the compound's solubility and how well your gut can absorb it. Poor bioavailability means more passes through undigested, potentially causing digestive upset.
3 - Magnesium Oxide: More Magnesium per Gram
Magnesium oxide is the most common form in cheap supplements. It contains about 60% elemental magnesium by weight, but its absorption is low. Another study showed that magnesium oxide increased stool magnesium content, indicating poor absorption and a laxative effect (PubMed ID: 12627680).
Pros and Cons
- Pros: High elemental magnesium per dose, low cost.
- Cons: Poor absorption, high risk of diarrhoea and stomach cramps.
4 - Magnesium Citrate: Better Absorbed, Gentle on the Gut
Magnesium citrate is magnesium bound to citric acid. It is more soluble than oxide, leading to better absorption.
Pros and Cons
- Pros: Good bioavailability, well-tolerated at moderate doses.
- Cons: Lower elemental magnesium content (about 16%), laxative effect at higher doses.
5 - Magnesium Glycinate: The Highly Absorbed, Gentle Option
Magnesium glycinate consists of magnesium chelated to the amino acid glycine. This form is highly soluble and absorbed via amino acid transport pathways, reducing competition with other minerals. A 2017 review in Magnesium Research highlighted that chelated forms like glycinate exhibit superior absorption and fewer gastrointestinal side effects (PubMed ID: 28266589). Magnesium contributes to the normal functioning of the nervous system.
Pros and Cons
- Pros: Excellent absorption, gentle on the stomach, no laxative effect.
- Cons: Lower elemental magnesium (about 14%), higher cost.
6 - Head-to-Head Comparison: What the Research Says
A 2015 study directly compared absorption of magnesium oxide, citrate, and glycinate in 24 participants. Results showed that magnesium glycinate had the highest serum magnesium increase over 24 hours, followed by citrate, then oxide (PubMed ID: 25744618). Another 2019 study confirmed that magnesium glycinate was better absorbed than oxide and caused fewer digestive issues (PubMed ID: 31766192).
For those with sensitive stomachs, magnesium glycinate is often the best choice.
7 - Practical Recommendations
- Magnesium contributes to a reduction of tiredness and fatigue.
- If budget is tight: Magnesium citrate offers a good balance of cost and absorption.
8 - Bottom line
Magnesium glycinate, citrate and oxide differ in how much magnesium they carry per gram. Magnesium citrate is a solid alternative with good absorption and a mild laxative benefit. Magnesium oxide carries the most magnesium per gram; our Magnesium Multi label warns that 450 mg of magnesium may cause mild stomach upset in sensitive people. Choose based on your needs and tolerance, and always consult a healthcare professional before starting any supplement.