Does Magnesium Make You Smarter? Magnesium, Memory and IQ
Does magnesium make you smarter? No good evidence says so. Only a few small trials exist, and a large trial before birth found no IQ gain by school age.
Dr. Russell T. WarneChief Scientist
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Magnesium does not make you smarter, as far as the human evidence can tell. A 2024 systematic review found only three randomized trials of magnesium supplements and cognition in adults, too few and too small to show any effect, and a large trial of magnesium given before preterm birth found no difference in children's IQ at school age.
Magnesium is essential for the brain, and many adults eat less of it than recommended. Those two facts have been stretched into a marketing claim that extra magnesium, especially a form called magnesium L-threonate, sharpens memory and thinking. This page covers the rat study behind that claim, the one small human trial, the population studies linking magnesium to cognition, and the confounds that make those studies hard to read. It describes research and is not medical advice.
Why magnesium gets linked to brainpower
Magnesium helps regulate the "NMDA receptor", a receptor for the chemical messenger glutamate that is central to learning and memory. Slutsky and colleagues built their rat research on this link between magnesium and synaptic plasticity, and it is the starting point for the "smart mineral" story.
The second ingredient is low intake. Rosanoff, Weaver and Rude reported that almost half (48%) of the US population consumed less than the required amount of magnesium from food in 2005-2006. If many people are short, the reasoning goes, topping them up might help the brain. That is a reasonable hypothesis. It is also exactly the kind of claim that needs a randomized trial, because people who eat plenty of magnesium-rich foods such as leafy greens and nuts differ from other people in many ways.
The magnesium L-threonate claims
Most of the "magnesium makes you smarter" marketing traces back to one laboratory. In 2010, Slutsky and colleagues reported in Neuron that a new compound, magnesium L-threonate, raised magnesium levels in the brains of rats. Treated rats learned faster and did better on several memory tests, and aged rats improved on a pattern-completion memory task. The treated rats also had a higher density of synapses (connections between nerve cells) in the hippocampus, a brain region important for memory.
Rat studies are a place to start, not a basis for claims about human intelligence. The human follow-up came in 2016, when Liu and colleagues ran a randomized, double-blind, placebo-controlled trial of MMFS-01, a product containing magnesium L-threonate. The details matter:
• Who took part: 51 adults aged 50 to 70 were enrolled, all with memory complaints, sleep problems and anxiety. 44 were analyzed (23 on the supplement, 21 on placebo) after 12 weeks.
• What it found: The supplement group's composite cognitive score improved more than the placebo group's, with a standardized effect of d = 0.91. On the IQ scale (standard deviation 15), that would equal roughly 14 points, an implausibly large effect for any supplement and a reason to wait for replication.
• The "brain age" figure: The authors converted scores on one timed test, the Trail Making Test Part B, into a "brain age" and reported that the supplement group's average brain age fell by 9.0 years. That number comes from a single test in 23 people, and it is the figure most often repeated in advertising.
• Who ran it: The study was funded by Neurocentria, the company that makes MMFS-01, and the first author was affiliated with that company.
I have not found a large, independent trial that confirms these results. When Chen and colleagues searched the literature for their 2024 systematic review, the three trials they included were small, used different forms and doses of magnesium, and tested people with very different health conditions. Their conclusion was that the trial evidence was insufficient to say whether magnesium supplements affect cognition.
Magnesium, cognition and dementia in population studies
Observational studies are more numerous, and they are where most headlines come from.
• NHANES: Peeri and colleagues analyzed 2,466 US adults aged 60 and over. Those in the highest quarter of total magnesium intake scored 4.34 points higher on the Digit Symbol Substitution Test (DSST), a timed symbol-coding task, than those in the lowest quarter, after adjusting for age, education, physical activity, health conditions and other factors. The study was cross-sectional, so it cannot show which came first.
• Taiwan: Tao and colleagues followed 5,663 adults aged 55 and over for a median of about six years. Higher magnesium intake at the start was linked to lower odds of poor scores later on the Mini-Mental State Examination, a brief screening test, with the clearest results in men. (The paper has a published correction; the main findings quoted here come from its abstract.)
• Rotterdam: Kieboom and colleagues measured blood (serum) magnesium in 9,569 adults without dementia and followed them for a median of 7.8 years. Both low and high serum magnesium were linked to a higher risk of dementia, by about 30% each, compared with the middle group.
Chen's 2024 review pooled such cohorts and found the same U-shaped pattern for serum magnesium, with the lowest dementia risk around 0.85 mmol/L. Dietary magnesium, by contrast, showed inconsistent links with cognitive disorders across studies. A U-shape is a warning against the idea that more is always better.
What the trials in children show
The most rigorous evidence on magnesium and IQ comes from an unexpected place: obstetrics. Magnesium sulfate, the compound in Epsom salt, is given by drip to some women about to give birth very early, because it lowers the child's risk of cerebral palsy. An updated Cochrane systematic review of six trials found that it reduced the risk of cerebral palsy up to about age two (risk ratio 0.71). The evidence on outcomes at school age is less certain.
Doyle and colleagues followed children from one of these trials, ACTOMgSO4, to ages 6 to 11. Of 867 surviving children, 669 were assessed. The magnesium and placebo groups showed little difference on any cognitive outcome, IQ included, and none on academic skills or behavior. This was a large, randomized trial with a long follow-up, and its message for the IQ question is clear: a high dose of magnesium at a critical stage of brain development did not raise later intelligence.
No randomized trial that I am aware of has tested magnesium supplements on IQ in healthy children.
The confounds behind magnesium and intelligence
Observational links between magnesium and test scores are hard to interpret. Diets rich in magnesium tend to be rich in plant foods generally, and people who eat that way are on average better educated and more physically active. Those same factors predict higher test scores on their own. Statistical adjustment helps but never fully removes this kind of confounding, especially when diet is measured once with a questionnaire.
Health matters too. Kidney function and diuretic drugs both change blood magnesium, which is why the Rotterdam team adjusted for them, and poor health in general predicts cognitive decline. That may help explain why both low and high blood magnesium predict dementia. A low reading can be a marker of illness rather than its cause.
Similar patterns appear for other minerals. Our page on zinc and IQ shows how trials of a nutrient that is vital for the brain still found no IQ gain, while iron deficiency and IQ covers a case where correcting a real deficiency matters more. Magnesium may yet turn out to protect thinking in people who are truly deficient, but that has not been shown.
Frequently asked questions
Does magnesium make you smarter?
There is no good evidence that it does. The trials in adults are few and small, and a large randomized trial of magnesium before preterm birth found no IQ difference at school age.
Does magnesium L-threonate improve memory?
It improved memory in rats. The only notable human trial had 44 analyzed participants, was funded by the product's maker and has not been confirmed by a large independent trial.
Can magnesium help with sleep or anxiety?
A meta-analysis of three small trials in 151 older adults found that magnesium shortened the time taken to fall asleep by about 17 minutes, but the evidence was rated low to very low quality. Better sleep can help with day-to-day concentration, which is a different thing from higher intelligence.
Can low magnesium affect thinking?
Population studies link both low and high blood magnesium to higher dementia risk, but they cannot show cause and effect, because illness can change magnesium levels.
Who should I see if I am worried about my magnesium levels?
A GP or family doctor, who can review your diet, medicines and health conditions and decide whether a blood test is useful. Anyone considering supplements, particularly with kidney disease, should talk to a doctor or pharmacist first.
The takeaway
Magnesium matters for the brain, and many people eat less than recommended. That has not translated into evidence that extra magnesium raises intelligence. The supplement claims rest on rat experiments and one small company-funded trial. The largest randomized trial with IQ outcomes found no difference, and the population studies that look more hopeful are confounded by diet quality and health. If you want a reliable measure of your reasoning ability, try an online IQ test built by psychometricians.
References
1. Chen, F., Wang, J., Cheng, Y., Li, R., Wang, Y., Chen, Y., Scott, T., & Tucker, K. L. (2024). Magnesium and cognitive health in adults: A systematic review and meta-analysis. Advances in Nutrition, 15(8), 100272. [doi.org/10.1016/j.advnut.2024.100272](. doi.org
2. Doyle, L. W., Anderson, P. J., Haslam, R., Lee, K. J., Crowther, C., & Australasian Collaborative Trial of Magnesium Sulphate (ACTOMgSO4) Study Group. (2014). School-age outcomes of very preterm infants after antenatal treatment with magnesium sulfate vs placebo. JAMA, 312(11), 1105-1113. [doi.org/10.1001/jama.2014.11189](. doi.org
3. Rosanoff, A., Weaver, C. M., & Rude, R. K. (2012). Suboptimal magnesium status in the United States: Are the health consequences underestimated? Nutrition Reviews, 70(3), 153-164. [doi.org/10.1111/j.1753-4887.2011.00465.x](. doi.org
4. Slutsky, I., Abumaria, N., Wu, L. J., Huang, C., Zhang, L., Li, B., Zhao, X., Govindarajan, A., Zhao, M. G., Zhuo, M., Tonegawa, S., & Liu, G. (2010). Enhancement of learning and memory by elevating brain magnesium. Neuron, 65(2), 165-177. [doi.org/10.1016/j.neuron.2009.12.026](. doi.org
5. Liu, G., Weinger, J. G., Lu, Z. L., Xue, F., & Sadeghpour, S. (2016). Efficacy and safety of MMFS-01, a synapse density enhancer, for treating cognitive impairment in older adults: A randomized, double-blind, placebo-controlled trial. Journal of Alzheimer's Disease, 49(4), 971-990. [doi.org/10.3233/JAD-150538](. doi.org
6. Peeri, N. C., Egan, K. M., Chai, W., & Tao, M. H. (2021). Association of magnesium intake and vitamin D status with cognitive function in older adults: An analysis of US National Health and Nutrition Examination Survey (NHANES) 2011 to 2014. European Journal of Nutrition, 60(1), 465-474. [doi.org/10.1007/s00394-020-02267-4](. doi.org
7. Tao, M. H., Chuang, S. C., Wu, I. C., Chan, H. T., Cheng, C. W., Chen, H. L., Lee, M. M., Chang, H. Y., Hsiung, C. A., & Hsu, C. C. (2024). Cross-sectional and longitudinal associations of magnesium intake and cognition in the Healthy Aging Longitudinal Study in Taiwan. European Journal of Nutrition, 63(8), 3061-3073. [doi.org/10.1007/s00394-024-03490-z](. doi.org
8. Kieboom, B. C. T., Licher, S., Wolters, F. J., Ikram, M. K., Hoorn, E. J., Zietse, R., Stricker, B. H., & Ikram, M. A. (2017). Serum magnesium is associated with the risk of dementia. Neurology, 89(16), 1716-1722. [doi.org/10.1212/WNL.0000000000004517](. doi.org
9. Shepherd, E. S., Goldsmith, S., Doyle, L. W., Middleton, P., Marret, S., Rouse, D. J., Pryde, P., Wolf, H. T., & Crowther, C. A. (2024). Magnesium sulfate before preterm birth for neuroprotection: An updated Cochrane systematic review. Obstetrics & Gynecology, 144(2), 161-170. [doi.org/10.1097/AOG.0000000000005644](. doi.org
10. Mah, J., & Pitre, T. (2021). Oral magnesium supplementation for insomnia in older adults: A systematic review & meta-analysis. BMC Complementary Medicine and Therapies, 21(1), 125. [doi.org/10.1186/s12906-021-03297-z](. doi.org
Hero image: CSIRO ScienceImage 937 Coiled magnesium sheets and magnesium ingots, by Mark Fergus, CSIRO, CC BY 3.0. Via Wikimedia Commons.
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