Quick Answer
Should you take magnesium glycinate or threonate?
Choose glycinate if your primary goal is sleep quality or anxiety reduction — it has the strongest clinical evidence for these outcomes and costs significantly less. Choose threonate if you want brain-penetrant magnesium for cognitive performance and working memory. Both are more bioavailable than magnesium oxide, which should be avoided.
The magnesium supplement market has expanded considerably since researchers at MIT demonstrated in 2010 that a novel magnesium chelate — magnesium L-threonate — could raise cerebrospinal fluid magnesium levels and improve synaptic density in the prefrontal cortex and hippocampus of rodents. That study, published in Neuron, catalysed commercial interest in brain-targeted magnesium and created a market bifurcation that continues today.
This article evaluates the two forms on the dimensions that matter: absorption, brain penetration, clinical evidence, and cost.
What is the difference between magnesium glycinate and threonate?
The fundamental difference is in the chelating ligand — the molecule bonded to the elemental magnesium ion.
Glycinate uses glycine, the simplest amino acid. The glycine molecule is small, electrically neutral at physiological pH, and carried across the intestinal wall via the PepT1 transporter, bypassing the competitive absorption pathway that limits inorganic magnesium uptake. The result is an estimated 80% absorption rate versus 4–30% for magnesium oxide.
Threonate uses threonic acid, a metabolite of Vitamin C. Threonate’s mechanism is different: rather than optimising intestinal absorption (both forms absorb well), threonate’s proposed advantage is facilitating transport across the blood-brain barrier through a transporter system that appears to be threonate-specific. This produces a disproportionate increase in brain magnesium relative to serum magnesium.
What does the research say about magnesium threonate for cognition?
The foundational paper (Slutsky et al., Neuron 2010) showed that magnesium-deficient rats given threonate had significantly higher CSF magnesium, higher synaptic density in the prefrontal cortex, and better performance on spatial memory tasks. Crucially, the same improvements were not seen in rats given magnesium chloride at the same dose, suggesting the threonate ligand itself contributes.
Human data is limited but positive. A 2016 randomised controlled trial in older adults with cognitive complaints showed significant improvements in executive function, working memory, and attention after 12 weeks of supplementation. A 2022 study found improvements in sleep quality and cognitive performance in middle-aged adults with self-reported memory complaints.
When should you choose glycinate?
Glycinate is the right choice when:
- Your primary goal is sleep quality (strongest RCT evidence)
- You have anxiety or elevated evening cortisol
- Budget is a consideration (typically 3–5x cheaper per dose)
- You have sensitive digestion (glycinate has no osmotic laxative effect)
When should you choose threonate?
Threonate is the right choice when:
- You specifically want brain-penetrant magnesium
- Your primary goals are cognitive: working memory, learning, attention
- You are already meeting sleep quality goals via other means
- You are willing to pay the premium for the BBB penetration evidence
Sources
- Slutsky I, et al. “Enhancement of learning and memory by elevating brain magnesium.” Neuron. 2010;65(2):165–77.
- Liu G, et al. “Efficacy and Safety of MMFS-01, a Synapse Density Enhancer, for Treating Cognitive Impairment in Older Adults.” J Alzheimers Dis. 2016;49(4):971–90.
- Zhang C, et al. “A Magtein supplement improves cognitive abilities in adults with cognitive impairment.” Front Aging Neurosci. 2022;14.
Thorne Magnesium Bisglycinate
Thorne
1,240 reviews
The most rigorously tested magnesium bisglycinate on the market. NSF Certified for Sport, manufactured in a cGMP facility, and formulated for maximum elemental magnesium delivery per capsule.
Pros
- + NSF Certified for Sport
- + 200 mg elemental magnesium per 3-capsule serving
- + No fillers or unnecessary excipients
- + Bisglycinate form — stable and well-absorbed
Cons
- − Premium price point ($0.53/day at standard dose)
- − Capsules, not powder — harder to titrate dose
Frequently Asked Questions
Does magnesium threonate actually cross the blood-brain barrier?
Yes, in animal studies magnesium L-threonate raises CSF magnesium concentrations more effectively than other forms, including glycinate and citrate. The mechanism is the threonate ligand, which appears to facilitate active transport across the blood-brain barrier. Human trials showing cognitive improvement are promising but smaller than animal data.
Is magnesium glycinate safe to take every night?
Yes. Magnesium glycinate is well-tolerated for long-term nightly use at doses up to 350 mg elemental magnesium/day. Unlike magnesium oxide or citrate, the chelated glycinate form has minimal osmotic effect in the gut, making it the form least likely to cause loose stools.
What is the difference between magnesium bisglycinate and glycinate?
Magnesium bisglycinate (diglycinate) has two glycine molecules chelated to each magnesium ion, versus one in the standard glycinate form. The bi- form is more stable in the digestive tract and typically has higher elemental magnesium content per gram of chelate.
Can I take magnesium glycinate and threonate together?
Yes, they can be taken together, though it's generally not necessary. Some people stack glycinate at night for sleep and threonate in the morning for cognitive effects. Monitor total elemental magnesium intake across both supplements to stay within the 350 mg/day supplemental UL.
How quickly does magnesium threonate improve memory?
Human trials show measurable improvements in cognitive test scores within 12 weeks of consistent magnesium threonate supplementation. Animal data shows more rapid improvements, but human timelines are longer. Do not expect overnight cognitive enhancement.