The missing science of Epsom salt baths and why we’ll believe anything we’re told

‘Epsom’ salt is a mineral compound, just like all other salts. Specifically the compound magnesium sulfate. Widely accepted as ‘very good for you’, Epsom salt baths are famous for relieving muscle aches and pains.

But I wanted to investigate the validity of these claims.

Fun fact: Epsom salt gets its name from a market town in Surrey. It was in Epsom’s mineral waters that the salts were originally extracted from centuries ago when the town’s springs made it a fashionable resort.

How people think it works

People claim it works by sucking out the ‘toxins’ such as lactic acid in your muscles – helped by sweating from the heat of the water – whilst your body sucks in the magnesium ions.

Scientifically it turns out this is absurd, as I expected.

I struggled with where to start …

Firstly, sweating out ‘toxins’ is impossible. Designed for cooling us dowwn, sweat is made almost completely of water, with tiny amounts of other chemicals like ammonia, urea, salts, and sugar. (Ammonia and urea are left over when your body breaks down protein.)

Secondly, even if we assume there are ions to attract them (which there are not), the idea that magnesium ions in the water can permeate your sweat glands is the scale equivalent of a charged balloon magically travelling across an entire room to stick to your hair, as Paul Ingraham puts it.

Thirdly, and perhaps most pertinently, your skin is waterproof. Which means it’s osmosis proof. Which means nothing in water can transfer into your skin ever. Unless your skin is broken by a cut or a wound. And even then… (I won’t go into it)

Can you get drunk through your skin? No. So you can’t get magnesium through your skin either.

This is not an exhaustive list. There are many more reasons this is so silly.

So does it have any benefits at all?

Compared to a hot bath with no salts (the benefits of which have been scientifically backed, as I will write about in separate post)?

Absolutely none.

When I looked for scientific evidence I found nothing published that even tested, let alone supported, any claims of its benefits on muscle aches and pains.

If you want to ingest magnesium you must do so orally. Whether it’s through your food or a supplement, there’s only one way in.

And there’s only one way out for the toxins – your liver.

If you take away one thing from this, it should be an extreme scepticism for all things we are told and sold in the health, fitness and beauty industries. As well as an appreciation for just how willingly we buy into the benefits of things that feel good.

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