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Settled ground

Magnesium's blood-pressure average is its least useful number

Over 8,610 people the upper reading fell 1.25 points. Among those taking 400mg a day for at least 12 weeks it fell 6.38, a number found by looking back through the data, not tested head on.

Magnesium

Magnesium and blood pressure usually arrives as a single number, and that number is small: averaged across 8,610 people, 1.25 points off the upper reading. In the slice that took 400mg a day or more for at least 12 weeks the drop reached 6.38, a number picked out of the data afterwards rather than tested on its own. None of these trials counted heart attacks or strokes. Where you start, and how long you keep going, decides how much the average has to do with you.

The findings behind this

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Physical & bodyBlood pressure barely moved on average, more at 400mg a day

Averaged over 8,610 people, magnesium lowered the upper reading by 1.25 points. In the slice taking 400mg a day or more for at least 12 weeks it was 6.38, a figure found by looking back.

★★★Well replicated — this finding’s sources average out to meta-analyses, systematic reviews or high-powered trials.The larger figures come from a slice of the data examined after the fact rather than the review's main comparison, which makes them the weaker number even though they are the more striking one. The ten pooled reviews overlap, so some of the same original trials are counted more than once. And blood pressure is a stand-in here: none of these trials counted heart attacks or strokes.Click to keep this openSupport heart and blood flowMagnesium
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Physical & body4 points came off blood pressure in people already at risk

In 543 people with prediabetes, poor blood-sugar control or another long-term condition, 365 to 450mg of magnesium a day lowered the upper reading by 4.18 points over one to six months.

★★☆Single study — solid evidence, such as one good trial or a large observational dataset, but not replicated at the top tier.Everyone in these trials already had one of those conditions, so a healthy adult has no reason to expect the same shift. The trials ran between one and six months, which says nothing about a year on it. And 543 people across 11 trials is a modest base for a figure this precise.Click to keep this openAge wellMagnesium

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