{"id":786668,"date":"2026-09-29T19:28:09","date_gmt":"2026-09-29T19:28:09","guid":{"rendered":"https:\/\/www.newsbeep.com\/uk\/786668\/"},"modified":"2026-09-29T19:28:09","modified_gmt":"2026-09-29T19:28:09","slug":"scarlett-johansson-swears-by-magnesium-but-can-supplements-really-help-with-digestion-muscle-pain-anxiety-and-sleep-melissa-davey","status":"publish","type":"post","link":"https:\/\/www.newsbeep.com\/uk\/786668\/","title":{"rendered":"Scarlett Johansson swears by magnesium. But can supplements really help with digestion, muscle pain, anxiety and sleep? | Melissa Davey"},"content":{"rendered":"

Dietitian Danielle Shine says her Instagram inbox was filled with questions after actor Scarlett Johansson was quoted in the Daily Mail<\/a> and other publications recently saying she takes magnesium to improve her digestion and sleep.<\/p>\n

\u201cI know that everybody is taking magnesium now. It\u2019s so helpful,\u201d Johansson reportedly told beauty publication<\/a> Byrdie.<\/p>\n

Shine says celebrity endorsement of supplements is persuasive and always leads to an uptick in questions.<\/p>\n

\u201cThe general sentiment was, \u2018If she [Johansson] takes magnesium and says it works for her, then maybe I should be taking it too,\u2019\u201d Shine says.<\/p>\n

But celebrity and influencer endorsement<\/a> aside, what does the evidence say?<\/p>\n

Magnesium is important<\/p>\n

Magnesium is an essential mineral that the body needs for blood pressure regulation, bone health and many other important functions. Because the body doesn\u2019t produce it, diet is critical, with nuts, seeds, legumes, leafy greens and brown rice among good sources.<\/p>\n

But magnesium deficiency is not common in Australia, and is more likely in people with certain conditions such as diabetes or bowel disease. Despite this, it is promoted widely as a good supplement anybody can take for a range of conditions.<\/p>\n

Limited evidence for sleep<\/p>\n

Shine says some studies have reported improvements in certain aspects of sleep when taking magnesium supplements, \u201cbut the findings are inconsistent\u201d.<\/p>\n

\u201cStudies are generally small, short-term and use different forms and doses of magnesium, which makes it difficult to draw firm conclusions about whether supplementation reliably improves sleep,\u201d she says.<\/p>\n

Sports dietitian Dr Evangeline Mantzioris says another difficulty is studies measure sleep quality differently, with some examining sleep duration, time taken to fall asleep, or depth of sleep. But there are not enough consistent, strong findings to show strong cause and effect, she says.<\/p>\n

If someone was struggling with sleep, \u201cWe would want to look at sleep hygiene first, such as lights and devices off, and no caffeine,\u201d she says, along with stress and other factors.<\/p>\n

What about digestion and gut health?<\/p>\n

Shine says some forms of supplemental magnesium draw water into the intestine, and this has a laxative effect. The British Dietetic Association names magnesium oxide as an evidence-based treatment option<\/a> for adults with constipation.<\/p>\n

Mantzioris says people who exercise regularly need to be careful of this, because taken wrongly, magnesium can cause nausea, abdominal cramping and diarrhoea.<\/p>\n

This is because intense exercise jolts the intestines while diverting blood away from them, making the gut extra sensitive to magnesium and giving a laxative double-whammy effect.<\/p>\n

\u201cWe always say in sports that you don\u2019t want to take magnesium when you know you\u2019re going to be out training the next day,\u201d she says.<\/p>\n

Can magnesium help exercise recovery?<\/p>\n

Magnesium is important for metabolism and muscle contraction, Shine says, \u201cbut its role in these processes doesn\u2019t mean that supplementation will improve recovery\u201d, including from muscle pain and damage.<\/p>\n

\u201cThe Australian Institute of Sport classifies magnesium as a Group C<\/a> supplement, a category where the scientific evidence doesn\u2019t support a benefit among athletes or is insufficient to draw firm conclusions,\u201d she says.<\/p>\n

There\u2019s also no good evidence<\/a> magnesium supplementation prevents muscle cramps, Mantzioris says. While soaking in a warm magnesium salt bath may bring relief, it is more likely the warm water<\/a> rather than the magnesium doing the heavy lifting.<\/p>\n

Will it calm my nerves?<\/p>\n

Shine says marketing of magnesium products exploits it being \u201cessential\u201d to calming the nervous system, with suggestions supplementation is also essential to preventing and treating stress and anxiety.<\/p>\n

\u201cMagnesium is involved in processes including nerve transmission and regulation of neuronal activity, helping nerves communicate throughout the body,\u201d she says.<\/p>\n

\u201cHowever, there\u2019s no strong evidence that magnesium supplementation provides broad benefits for nervous-system function.\u201d<\/p>\n

Mantzioris says supplement companies play on people\u2019s real-life stressors and \u201cthey capture our fear that we might be deficient in something, and try to sell that this might explain why we\u2019re stressed or tired\u201d.<\/p>\n

\u201cBut the reason many of us are stressed and tired is because we work too much<\/a>, which magnesium can\u2019t fix.\u201d<\/p>\n

Those with a genuine deficiency may benefit<\/p>\n

People at risk of deficiency or worried can see a doctor<\/a> who can order a blood test and recommend the best way to increase intake. There is also no strong evidence<\/a> to show that routine oral magnesium supplementation during pregnancy is beneficial.<\/p>\n

Taking magnesium in the absence of a known deficiency has some risks, Shine says.<\/p>\n

\u201cVery high doses can cause toxicity, including low blood pressure, breathing problems, abnormal heart rhythms and, in severe cases, cardiac arrest,\u201d she says.<\/p>\n

Melissa Davey is Guardian Australia\u2019s medical editor<\/p>\n

Antiviral<\/a> is a fortnightly column that interrogates the evidence behind the health headlines and factchecks popular wellness claims<\/p>\n

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