The effect of magnesium supplementation on cognitive performance and sleep quality

A placebo-controlled study published in Nutrition shows that magnesium supplementation can improve memory, reaction time, other cognitive skills, and heart rhythm during sleep.

Magnesium is one of the minerals we need in the largest amounts. It is involved in more than 300 enzymatic processes and plays an overall role in energy metabolism, the nervous system, the cardiovascular system, muscles, blood sugar, and bones. Although magnesium is found in multiple foods such as whole grains, seeds, nuts, cabbage, and dark green vegetables, around 30–50 percent of the world’s population is thought to be deficient in magnesium. This is not only due to unbalanced and refined diets but also because crops contain less magnesium as a result of pesticides and intensive farming methods. Antacid medications can inhibit absorption. In addition, stress, insulin resistance, and diuretic medications can increase the need for the nutrient.
Many people suffer from poor sleep quality as well as concentration difficulties and loss of cognitive abilities as a result of lacking magnesium. Therefore, the researchers behind the new study wanted to investigate the effect of magnesium supplementation on these conditions.

Magnesium supplementation improves cognitive performance

The new study included 100 healthy men and women aged 18–45, all of whom had experienced poor sleep quality for more than four weeks. This was assessed using a specific questionnaire called PROMIS Sleep. At baseline, the participants were required to perform various cognitive tests according to another questionnaire (NIH Toolbox), which included memory, concentration, reaction time, and language. The participants also had to wear a special monitor (Oura Ring) for seven days to record their sleep data, including resting heart rate (HR) and heart rate variability (HRV), which measures the time interval between each heartbeat. This is because heart rate normally decreases during sleep, when the body relaxes and the parasympathetic nervous system is dominant.
After the seven days, the participants were given magnesium supplementation and were instructed to take one capsule in the morning and one capsule two hours before bedtime for six weeks. Each capsule contained 145 mg of magnesium in the form of magnesium L-threonate, which is believed to be more easily absorbed in the brain. There was also a corresponding group that received a placebo. During the course of the study and at the end, the cognitive tests were repeated for both groups.
The study showed that six weeks of magnesium supplementation was associated with significant improvements in working memory and other cognitive abilities in young and middle-aged adults. The participants also experienced faster reaction times, including improved hand–eye coordination. Overall, it appeared that participants who received magnesium supplementation showed signs of reduced cognitive decline that otherwise often occurs with aging.

Magnesium’s effect on sleep quality

According to the study, the participants did not appear to achieve improved sleep quality based on the questionnaire parameters. Nevertheless, magnesium supplementation appeared to lower resting heart rate and increase HRV, as a sign of activation of the parasympathetic nervous system, which is fundamental for good sleep.
Other studies have also shown that there may be a clear association between magnesium deficiency and sleep disturbances. It is also possible that higher doses (250–500 mg) taken before bedtime may have a better effect if the cause of the sleep disturbances is magnesium deficiency.
In any case, it is important to choose a magnesium supplement with high bioavailability. Supplements containing inorganic magnesium oxide, in contrast, should be avoided, as they are absorbed very poorly and primarily have a laxative effect.

References:

Adrian L Lopresti et al. The effects of magnesium L-threonate (Magtein) on cognitive performance and sleep quality in adults: a randomized, double-blind, placebo-controlled trial. 2025

Caijun He et al. The Mechanism of Magnesium in Sleep Disorders. Nat Sci Sleep 2025