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

“I know that everybody is taking magnesium now. It’s so helpful,” Johansson reportedly told beauty publication Byrdie.

Shine says celebrity endorsement of supplements is persuasive and always leads to an uptick in questions.

“The general sentiment was, ‘If she [Johansson] takes magnesium and says it works for her, then maybe I should be taking it too,’” Shine says.

But celebrity and influencer endorsement aside, what does the evidence say?

Magnesium is important

Magnesium is an essential mineral that the body needs for blood pressure regulation, bone health and many other important functions. Because the body doesn’t produce it, diet is critical, with nuts, seeds, legumes, leafy greens and brown rice among good sources.

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.

Limited evidence for sleep

Shine says some studies have reported improvements in certain aspects of sleep when taking magnesium........

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