A clinical-science review of the 2026 Lopresti and Smith trial, published in Frontiers in Nutrition — a six-week randomized, double-blind, placebo-controlled study examining the effects of Magtein® (magnesium L-threonate) on cognitive performance, sleep quality, and autonomic recovery in 100 healthy adults aged 18 to 45. 

By Rafea Naffa, PhD  —  R&D Director 

Trial at a glance 

• Design: 6-week, randomized, double-blind, placebo-controlled 
• Population: 100 healthy adults aged 18–45 with self-reported dissatisfied sleep 
• Intervention: 2 g/day Magtein® (1 g AM + 1 g PM) vs. placebo 
• Primary endpoint: NIH Toolbox Total Cognition Composite 
• Cognition: Greater improvement vs. placebo (p = 0.043); 7.5-year cognitive-age difference 
• Sleep: Greater improvement in PROMIS Sleep-Related Impairment (p = 0.043) 
• Autonomic: Reduced sleep heart rate (p = 0.030); increased HRV (p = 0.036) 
• Tolerability: Well-tolerated; no treatment-related discontinuations 
• Published: Frontiers in Nutrition (2026), doi: 10.3389/fnut.2025.1729164

The way we study brain health has changed. 

More adults are reporting poor sleep, mental fatigue, and the kind of stress that doesn’t quite clear by morning. As that picture has grown more complex, so has the science designed to support it. 

Modern trials are no longer satisfied with whether a nutrient moves a single questionnaire score. The sharper questions now are: 

• How do you measure cognition meaningfully in healthy adults who already perform well? 

• How do you assess sleep when subjective experience and physiology don’t always align? 

• And how do you bring autonomic recovery — heart rate, HRV, autonomic balance — into a cognitive-health study? 

Why this matters: Most adults aren’t experiencing severe cognitive decline. They’re experiencing subtle dips in focus, recovery, and mental sharpness that don’t register on traditional clinical measures but show up clearly in everyday life. The science has had to evolve to match that reality. 

The 2026 Lopresti and Smith trial, published in Frontiers in Nutrition, set out to address all three within a single study design [1]. 

The randomized, double-blind, placebo-controlled trial examined the effects of Magtein® (magnesium L-threonate) over six weeks in 100 healthy adults aged 18–45 years with self-reported dissatisfied sleep [1]. Participants completed validated assessments covering cognition, sleep quality, wellbeing, and sleep-time autonomic activity. 

It also reflects the growing scientific maturity of the Magtein® (magnesium L-threonate) clinical research program. 

Why has magnesium been difficult to study in brain health? 

Magnesium has historically been difficult to study in brain health because most magnesium forms have limited published evidence supporting meaningful brain magnesium elevation after oral intake. Elevating magnesium in the blood does not necessarily translate to elevated magnesium concentrations within the brain. 

Magnesium itself plays a fundamental role in human physiology. It serves as a cofactor in more than 300 enzymatic reactions, modulates NMDA receptor activity, and supports the synaptic plasticity involved in learning and memory. 

At the same time, inadequate magnesium intake remains common. National Health and Nutrition Examination Survey (NHANES) analyses indicate many US adults fall short of recommended intake [2], and global modeling suggests widespread dietary magnesium inadequacy worldwide [3]. (For background on how magnesium forms differ, see The Different Forms of Magnesium and Why Magtein® Stands Apart.) 

Despite this biological rationale, translating magnesium biology into measurable cognitive outcomes has historically been challenging — in large part because of distribution. Most magnesium forms have limited published evidence supporting meaningful brain magnesium elevation after oral administration [4, 5]. 

Magnesium L-threonate (Magtein®) was developed specifically to address this challenge — a brain-delivery mechanism we explore in more depth in How Magtein® Crosses the Blood-Brain Barrier (and Why It Matters). Preclinical studies have reported that magnesium L-threonate raises brain magnesium concentrations and supports synaptic density and plasticity-related pathways [4, 5]. Importantly, this brain-delivery mechanism has not yet been established in published literature for other commonly used magnesium forms. 

Key takeaway: Raising magnesium in the blood is not the same as raising magnesium in the brain. That distinction is part of what makes magnesium L-threonate a scientifically distinct compound to study. 

That mechanistic foundation is part of why Magtein® has become one of the more clinically studied magnesium forms in cognitive and sleep-health research. 

The 2026 Lopresti and Smith trial builds on earlier human studies in older adults [6], healthy Chinese adults [7], and middle-aged adults [8]. 

What was the design of the trial? 

The 2026 Lopresti and Smith trial was a six-week, two-arm, parallel-group, randomized, double-blind, placebo-controlled trial of Magtein® (2 g/day) versus matched placebo in 100 healthy adults aged 18 to 45. 

The study was prospectively registered with the Australian and New Zealand Clinical Trials Registry (ANZCTR) and approved by the National Institute of Integrative Medicine Human Research Ethics Committee. Recruitment occurred in Australia between April and November 2024. 

Participants were randomly assigned to receive either: 

• 2 g/day of Magtein® (magnesium L-threonate) 

• or matched placebo capsules 

The Magtein® group received 1 g in the morning and 1 g approximately two hours before bedtime, delivering around 145 mg of elemental magnesium daily. 

How were baseline and follow-up visits structured? 

Participants completed an in-person baseline visit, seven days of baseline Oura Ring monitoring, online questionnaires during the intervention, and a final in-person assessment at week six. The trial standardized caffeine, alcohol, exercise, and breakfast timing before visits to reduce variability. 

How was blinding integrity maintained? 

Blinding integrity was formally assessed at study completion. Most participants either guessed incorrectly or were unsure of their group allocation. 

Compliance was high — 96 of 100 participants completed the trial, and 92% of completing participants took more than 80% of their capsules. 

These details matter. Rigorous execution is what gives a small trial real signal value. 

Why did the population selection matter? 

Population selection matters because cognition and sleep trials frequently produce ceiling effects in fully healthy participants, leaving no room to detect measurable improvement. Sleep trials run into the same problem when participants already have objectively healthy sleep architecture. 

To navigate this, the investigators recruited healthy adults with self-reported dissatisfied sleep lasting longer than four weeks. Participants did not have diagnosed neurological, psychiatric, or sleep disorders. 

The result was a cohort with real-world room to improve — without including clinically impaired populations. 

In practical terms, this means studying people who may function normally day to day but who experience subtle issues such as poor sleep quality, reduced mental sharpness, daytime fatigue, or slower cognitive recovery. It’s a more honest reflection of who actually reaches for magnesium in everyday life. 

In plain terms: The people most likely to feel an effect are often those who already sense something is off — undersleeping, foggy, slow to recover — even when everything still looks normal on paper. 

What assessments were used? 

The study combined validated cognitive testing, subjective sleep measures, objective wearable monitoring, and autonomic indicators. 

Cognitive assessments. The primary endpoint was the NIH Toolbox Total Cognition Composite [9], a validated computerized battery assessing working memory, attention, processing speed, episodic memory, language, and inhibitory control. The trial also included Raven’s Progressive Matrices [10], a non-verbal assessment of fluid reasoning. 

Sleep and wellbeing. Subjective sleep outcomes were measured using the PROMIS Sleep Disturbance and Sleep-Related Impairment scales [11], the Restorative Sleep Questionnaire [12], and the WHO-5 Wellbeing Index [13]. 

Objective monitoring. The Oura Ring was used to monitor sleep architecture, sleep heart rate, and heart rate variability (RMSSD) [14]. 

Additional features. The study also incorporated a visuo-motor Aim Trainer task, expectancy-bias controls, and a cognitive-age translation model. 

Together, these tools created a more multidimensional picture than many conventional supplement studies. 

What did the trial report on cognition? 

Participants receiving Magtein® showed a significantly greater improvement in the NIH Total Cognition Composite compared with placebo (p = 0.043). The Magtein® group improved by 8.40 points compared with 5.60 points in the placebo group. 

Where were the strongest cognitive effects observed? 

The clearest signals appeared in working memory and episodic memory-related measures. 

The List Sorting Working Memory task reached statistical significance (p = 0.033), and the Picture Sequence Memory task showed a positive trend. 

Raven’s 2 fluid reasoning scores did not differ between groups. 

That selective pattern is biologically coherent. Working memory and episodic memory rely heavily on prefrontal and hippocampal circuitry — the same systems linked to the synaptic effects observed in Magtein® preclinical research [4, 5]. The synaptic-plasticity story is explored at greater length in The Neuroplasticity Link: How Magnesium L-Threonate Supports Synaptic Flexibility. 

Key takeaway: The cognitive gains clustered exactly where magnesium’s biology would predict — plasticity-driven domains like working memory and episodic memory — rather than fixed reasoning ability. That coherence between mechanism and outcome strengthens the trial’s interpretation. 

What did the cognitive age analysis show? 

One of the most discussed findings from the study was the “cognitive age” translation. 

The trial reported a 2.24-point between-group difference on the NIH Change Sensitive Score at week six. Using NIH normative references, this translated to approximately 7.5 years on the normative cognitive-aging curve [15]. This is a derived statistical interpretation, not a direct measurement of biological cognitive age. It’s best read as an intuitive way of contextualizing what the cognitive differences mean in everyday terms — a concept we discuss further in Magtein® and a Healthier Brain Age. 

What new measurement approach did the study introduce? 

The study also reported significant improvements in a digital visuo-motor Aim Trainer task. According to the authors, this represents one of the first uses of a digital visuo-motor performance assessment within a magnesium clinical trial — opening an interesting direction for future cognitive-performance research. 

What did the trial report on sleep? 

The Magtein® group reported significantly greater improvement in PROMIS Sleep-Related Impairment versus placebo (p = 0.043), with the strongest effects in participants who started the trial with poorer baseline sleep. 

The sleep findings revealed an important subjective–objective pattern. Objective sleep architecture did not differ significantly between groups, and some subjective scales remained non-significant in the full cohort. 

This pattern likely reflects population selection. Participants entered with subjective sleep dissatisfaction but relatively healthy baseline objective sleep metrics — sleep efficiency averaged 86%, and average total sleep time was nearly seven hours [1]. That left limited room for major objective changes to surface. 

What did the sleep subset analysis show? 

The most notable sleep findings emerged in participants with lower sleep quality. In this subgroup, the study reported significant improvements in sleep disturbance and stronger improvements in sleep-related impairment. 

In plain terms: The more unsettled someone’s sleep was at baseline, the more visible the effect. In a group of mostly healthy sleepers, the signal was easier to feel than to measure on a ring. 

What did the trial report on heart rate and HRV? 

The trial reported reduced sleep-time heart rate (p = 0.030) and increased RMSSD heart rate variability (p = 0.036) in the Magtein® group compared with placebo. 

These measures matter because autonomic balance influences how well the body transitions into recovery mode during sleep — a process closely linked to stress resilience, next-day energy, and cognitive performance. 

RMSSD is commonly used as an indicator associated with parasympathetic nervous system activity. The combination of lower sleep heart rate and higher HRV is broadly consistent with a more recovery-oriented physiological state [16]. 

Why this matters: HRV isn’t just a fitness metric. It’s one of the clearest windows we have into the body’s capacity to shift into recovery — the state in which sleep restores and stress resolves [17]. A nutrient that may support that shift is asking a different scientific question than one that only moves a cognitive score. 

These findings open a new physiological dimension for future Magtein® research. 

What did the trial report on tolerability? 

Magtein® was generally well tolerated. Treatment-related adverse-event rates were similar between groups, 98% of Magtein® participants rated tolerability as good or excellent, and no participant discontinued due to a treatment-related adverse event. 

Why does this trial matter? 

Beyond the individual findings, the 2026 Lopresti and Smith trial represents an important step in the evolution of cognitive-health nutraceutical research. 

It demonstrates: 

• rigorous methodology 

• thoughtful cohort design 

• multidimensional outcome selection 

• expectancy-bias controls 

• objective wearable integration 

• and a clinical-neuroscience lens 

The findings are also broadly consistent with previous Magtein® human studies conducted across different populations [6, 7, 8]. 

For researchers, the study offers a strong design template. 

For formulators, it reinforces the growing clinical evidence base supporting the 2 g/day Magtein® protocol. 

For integrative clinicians, it suggests that individuals experiencing dissatisfied sleep may represent a particularly relevant target population — the place where the effect is most likely to be felt. 

Most importantly, the study reflects the continued maturation of the Magtein® research platform. Magtein® remains one of the more clinically studied magnesium forms in cognition and sleep-health research, with a growing body of human and preclinical evidence behind it. 

Further replication, longer durations, and broader populations may still be needed. But this trial adds another layer of human evidence to the relationship between magnesium status, brain function, sleep quality, and autonomic recovery — and gives the next generation of studies a stronger foundation to build on. 

FAQs 

What is magnesium L-threonate? 

Magnesium L-threonate is a magnesium compound bound to L-threonic acid (a metabolite of vitamin C). It was developed to address the challenge that most magnesium forms have limited evidence of meaningfully raising magnesium concentrations inside the brain after oral intake. Magtein® is the proprietary form of magnesium L-threonate used in published clinical trials on cognition and sleep. 

What was the design of the 2026 Magtein® clinical trial? 

The 2026 Lopresti and Smith trial was a 6-week, two-arm, parallel-group, randomized, double-blind, placebo-controlled trial conducted in Australia [1]. One hundred healthy adults aged 18 to 45 with self-reported dissatisfied sleep were randomly assigned to receive either 2 g daily of Magtein® or a placebo [1]. The trial was prospectively registered on ANZCTR and approved by the National Institute of Integrative Medicine Human Research Ethics Committee. 

What dose of Magtein® was used? 

Participants received 2 g/day of Magtein®, split as 1 g in the morning and 1 g approximately two hours before bedtime. This delivered around 145 mg of elemental magnesium daily. 

How long does Magtein® take to work? 

The 2026 Lopresti and Smith trial used a six-week protocol and reported significant cognitive and physiological differences at the end of the study. Earlier sleep research reported subjective improvements emerging within the first one to two weeks. While some consumers have anecdotally reported feeling benefits from the first day, individual responses may vary. From a scientific perspective, two to six weeks of consistent use best reflects the protocols used in published research. 

What was the primary cognitive endpoint? 

The primary endpoint was the NIH Toolbox Total Cognition Composite, a validated computerized battery that evaluates working memory, attention, episodic memory, language, processing speed, and executive function. 

What cognitive findings were reported? 

The trial reported a significantly greater improvement in the NIH Total Cognition Composite in the Magtein® group versus placebo (p = 0.043). The strongest signals appeared in working-memory-related outcomes. 

Did the study report sleep benefits? 

Yes. Participants receiving Magtein® showed greater improvement in PROMIS Sleep-Related Impairment scores versus placebo. Larger effects were observed in participants with higher baseline sleep dissatisfaction. 

Did the study report changes in heart rate variability (HRV)? 

Yes. The trial reported significant between-group differences in sleep heart rate and heart rate variability (HRV). These findings are exploratory and open a new physiological dimension for future Magtein® research to explore. 

Was Magtein® well tolerated? 

Yes. Adverse-event rates were similar between the placebo and Magtein® groups, and 98% of Magtein® participants rated tolerability as good or excellent. 

Does this study apply to other magnesium forms? 

No. The study specifically investigated Magtein® and did not include head-to-head comparisons with other magnesium forms. 

Do other oral magnesium forms have the same level of brain-related clinical evidence? 

Currently, most other oral magnesium forms have limited published clinical evidence supporting brain-related outcomes such as cognition, sleep quality, or brain magnesium elevation. Therefore, the results of this study should be interpreted as specific to Magtein® and should not be assumed to apply to other magnesium forms unless supported by direct clinical evidence. 

Is magnesium glycinate supported by the same level of brain-related clinical evidence? 

No. Magnesium glycinate is commonly positioned for sleep support, but published clinical evidence remains limited. A recent SupplySide Supplement Journal article noted that magnesium glycinate is often associated with sleep claims in dietary supplements, but identified only one published clinical trial to date using magnesium bisglycinate for sleep, and also noted that few clinical trials have studied this form overall [18]. Magtein® has additionally undergone a specific FDA GRAS notification (GRN 499) and EU/UK Novel Food authorizations — regulatory steps that most proprietary magnesium forms have not completed. Magnesium glycinate should not be assumed to have the same brain-related evidence profile or regulatory clearance as Magtein®. (For a fuller comparison, see Magtein® vs. Magnesium Glycinate.) 

Is Magtein® FDA approved? 

Dietary supplements are not “approved” by the U.S. Food and Drug Administration in the way prescription drugs are; supplements are regulated under a different framework. However, Magtein® (magnesium L-threonate) has FDA GRAS status (Generally Recognized As Safe), confirmed by an FDA Letter of No Objection in response to GRAS Notification GRN 499 (2014). This means the FDA reviewed the safety data submitted for Magtein® and raised no questions about its use as a magnesium source in both dietary supplements and conventional foods. Magtein® also holds EU Novel Food authorization (2024) and UK Novel Food authorization (2026). Many proprietary magnesium forms have not completed FDA GRAS notification for food use. 

What was the 7.5-year cognitive age finding? 

The trial reported a 2.24-point group difference at week 6 on the NIH Toolbox Total Cognition Change Sensitive Score (p = 0.043). Applied to the NIH normative decline of approximately 0.3 points per year from age 20, this translates to a group difference of roughly 7.5 years on the normative curve. This is a derived metric expressing a between-group difference in age-equivalent terms. It is not a direct measurement of biological cognitive age. 

Where can I read the full paper? 

The study was published open-access in Frontiers in Nutrition: Lopresti AL, Smith SJ. The effects of magnesium L-threonate (Magtein®) on cognitive performance and sleep quality in adults: a randomised, double-blind, placebo-controlled trial. Front Nutr. (2026) 12:1729164. doi: 10.3389/fnut.2025.1729164 

References 

1. Lopresti AL, Smith SJ. The effects of magnesium L-threonate (Magtein®) on cognitive performance and sleep quality in adults: a randomised, double-blind, placebo-controlled trial. Front Nutr. (2026) 12:1729164. doi: 10.3389/fnut.2025.1729164
2. Tao MH, Liu J, Cervantes D. Association between magnesium intake and cognition in US older adults: National Health and Nutrition Examination Survey (NHANES) 2011 to 2014. Alzheimers Dement (N Y). (2022) 8:e12250. doi: 10.1002/trc2.12250 
3. Passarelli S, Free CM, Shepon A, Beal T, Batis C, Golden CD. Global estimation of dietary micronutrient inadequacies: a modelling analysis. Lancet Glob Health. (2024) 12:e1590–e1599. doi: 10.1016/S2214-109X(24)00276-6 
4. Slutsky I, Abumaria N, Wu LJ, Huang C, Zhang L, Li B, et al. Enhancement of learning and memory by elevating brain magnesium. Neuron. (2010) 65:165–177. doi: 10.1016/j.neuron.2009.12.026 
5. Sun Q, Weinger JG, Mao F, Liu G. Regulation of structural and functional synapse density by L-threonate through modulation of intraneuronal magnesium concentration. Neuropharmacology. (2016) 108:426–439. doi: 10.1016/j.neuropharm.2016.05.006 
6. Liu G, Weinger JG, Lu ZL, Xue F, Sadeghpour S. Efficacy and safety of MMFS-01, a synapse density enhancer, for treating cognitive impairment in older adults: a randomized, double-blind, placebo-controlled trial. J Alzheimers Dis. (2016) 49:971–990. doi: 10.3233/JAD-150538 
7. Zhang C, Hu Q, Li S, Dai F, Qian W, Hewlings S, et al. A Magtein®, magnesium L-threonate-based formula improves brain cognitive functions in healthy Chinese adults. Nutrients. (2022) 14:5235. doi: 10.3390/nu14245235 
8. Hausenblas HA, Lynch T, Hooper S, Shrestha A, Rosendale D, Gu J. Magnesium-L-threonate improves sleep quality and daytime functioning in adults with self-reported sleep problems: a randomized controlled trial. Sleep Medicine X. (2024) 8:100121. doi: 10.1016/j.sleepx.2024.100121
9. Weintraub S, Dikmen SS, Heaton RK, Tulsky DS, Zelazo PD, Bauer PJ, et al. Cognition assessment using the NIH Toolbox. Neurology. (2013) 80:S54–S64. doi: 10.1212/WNL.0b013e3182872ded 
10. Raven J, Rust J, Chan F, Zhou X. Raven’s 2 Progressive Matrices, Clinical Edition (Raven’s 2). San Antonio, TX: Pearson (2018).
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12. Drake CL, Hays RD, Morlock R, Wang F, Shikiar R, Frank L, et al. Development and evaluation of a measure to assess restorative sleep. J Clin Sleep Med. (2014) 10:733–741. doi: 10.5664/jcsm.3860 
13. Topp CW, Ostergaard SD, Sondergaard S, Bech P. The WHO-5 Well-being Index: a systematic review of the literature. Psychother Psychosom. (2015) 84:167–176. doi: 10.1159/000376585 
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18. Gholam, D. (2026, April 27). National Advertising Division rules to change magnesium claims on Nature’s Truth glycinate gummies. SupplySide Supplement Journal. 

These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.