Jarrow Formulas MagMind

Magnesium L-threonate (Magtein)· evidence: Limited

Magnesium L-threonate, sold under the trade name Magtein, is magnesium bound to threonic acid. It is marketed for the brain because animal studies suggested it raises magnesium levels in the brain more than other forms. In people, the evidence is a handful of small trials, several funded by the ingredient's maker, so it is far from settled. Claims about memory, focus, brain health or sleep are not authorised.

It is also a low-strength way to get magnesium: 2,000 mg of Magtein provides only about 144 mg of elemental magnesium (38% NRV), at several times the price of citrate or glycinate. If you simply want to top up your magnesium intake, other forms are much better value.

Typical dose: Trials have used about 1.5–2 g of magnesium L-threonate a day, giving roughly 100–144 mg of elemental magnesium.

Safety: Generally well tolerated; some people report headaches or drowsiness. Keep total magnesium from supplements within the EFSA upper level of 250 mg a day unless advised otherwise. Take apart from tetracycline or quinolone antibiotics and bisphosphonates. Speak to your GP first if you have kidney disease.

Research we looked at:
Slutsky I et al. (2010). Enhancement of learning and memory by elevating brain magnesium. Neuron 65(2):165–177.
Liu G et al. (2016). Efficacy and safety of MMFS-01, a synapse density enhancer, for treating cognitive impairment in older adults. J Alzheimers Dis 49(4):971–990.
EFSA NDA Panel (2015). Scientific opinion on dietary reference values for magnesium. EFSA Journal 13(7):4186.

Magnesium· evidence: Moderate

Magnesium is an essential mineral found in green vegetables, nuts, seeds, wholegrains and beans. UK surveys show that some groups, particularly teenagers and some adults, eat less than the recommended amount. A supplement reliably raises intake, and people with a low intake or a diagnosed deficiency are the ones most likely to notice a difference. Most people eating a varied diet get enough from food.

Labels often show the weight of the whole compound (for example 1,000 mg of magnesium citrate), but only part of that is magnesium itself. What matters is the elemental magnesium per daily dose, compared with the NRV of 375 mg. Organic forms such as citrate, glycinate (bisglycinate), malate and taurate are generally absorbed a little better than oxide in small studies, but differences between them are modest and no form has been shown to be better for any particular use.

Magnesium is widely sold for sleep, stress and cramp. These are not authorised claims. Reviews have found the evidence for sleep is of low quality, and a Cochrane review found magnesium is unlikely to prevent ordinary muscle cramps in older adults.

Typical dose: Most supplements give 100–400 mg of elemental magnesium a day (NRV 375 mg). The NHS says adults need about 270–300 mg a day in total, mostly from food.

Safety: High doses loosen stools or cause diarrhoea, especially citrate and oxide. EFSA sets an upper level of 250 mg a day of magnesium from supplements, and the FSA advises that up to 400 mg a day from supplements is unlikely to cause harm. Magnesium can reduce absorption of some antibiotics (tetracyclines, quinolones) and osteoporosis drugs (bisphosphonates), so take them a few hours apart. Speak to your GP first if you have kidney disease.

Research we looked at:
NHS. Vitamins and minerals: others – magnesium. nhs.uk.
EFSA NDA Panel (2015). Scientific opinion on dietary reference values for magnesium. EFSA Journal 13(7):4186.
Expert Group on Vitamins and Minerals (2003). Safe upper levels for vitamins and minerals. Food Standards Agency.
Garrison SR et al. (2020). Magnesium for skeletal muscle cramps. Cochrane Database Syst Rev 9:CD009402.

Cost per daily dose lets you compare packs of different sizes fairly.Worked out from our current prices.