Epsom salt is magnesium sulphate (MgSO4). It is sold for use as a laxative and as a ‘soak’ for injuries and muscle recovery.
Look up pictures of Epsom salts and this is what you get:
1. The salts themselves.
2. The generic ‘I love soaking in my bathtub’ picture.
3. (Lots of) Victoria Beckham. At last her secret to slimness – she just craps everything out.
The story behind Epsom salts goes like this… In the 1600s a farmer at Epsom in England found his cows were unhappy drinking the water due to its bitter taste (“cor blimey Ned oooooofff dis water is a bi’ bitter innit?”) and then found that this water (allegedly) healed scratches and rashes. Epsom salts were born. These days they come from mining operations (Europe, South Africa, the States, etc.).
Athletic peeps love using it – runners, bodybuilders, CrossFitters… Everyone swears by it, but is it actually useful?
Some of the theories of how it helps with muscle recovery include:
- Magnesium being absorbed via the skin to the site of injury and then drawing toxins such as lactate from the body;
- Magnesium sedating the nervous system so you don’t feel post-workout pain / DOMS as much;
- Magnesium relaxing the muscle and decreasing inflammation.
So, how many papers are out there supporting the use of Epsom salts with athletic injuries and recovery?
So what has been researched with Epsom salts?
- With arthroscopic knee surgery it was found that magnesium sulphate is a potential intra-articular analgesic agent;
- In diabetic rats magnesium supplementation can improve cutaneous blood flow (possibly via potentiation of the nitric oxide pathway);
- Magnesium supplementation increases both free and total testosterone levels in both sedentary and athletic individuals, with the increases being higher in the athletic group;
- Rats injected with magnesium during exercise had higher blood glucose and lower lactate levels, thereby enhancing exercise performance;
- Gerbils given magnesium then forced to swim (I have images of a gerbil coach on the sideline with a loudspeaker “Swim… SWIM FOR YOUR LIFE!”) had increased release of glucose, thereby providing more energy substrates both for the body and the brain.
From the “Epsom Salt Council” (who knew there was such a thing!) a 2004 study headed by Dr Waring at the University of Birmingham found that soaking for 12 minutes in a warm (50-55 deg C) bath with Epsom salts resulted in a rise in plasma magnesium. The researchers looked at different Epsom salt concentrations and found that maximal benefit would be found with bathing 2-3 times per week using 500-600g Epsom salts each time. There was also descriptive data showing that two volunteers applied a magnesium sulphate patch (instead of bathing in the salts) and found that all their ‘rheumatic pains’ had disappeared. They conclude that “bathing in Epsom salts is a safe and easy way to increase magnesium and sulphate levels in the body”.
I hate to be a killjoy here, but with all this talk of ‘soaking in a warm tub with Epsom salts relaxes you and relieves muscle pain’ has anyone considered that is the WARM WATER that relaxes you. Duh. Nevertheless, if you want to have an Epsom salt soak go right ahead… As yet there are no reports of magnesium overdose just from soaking…
Taking magnesium sulphate ORALLY however is a different matter. People take it as a laxative however you need to be super dooper careful as side-effects (and overdose symptoms) are not fab – they include nausea, vomiting, flushing/ feeling hot, bradycardia (slow heart rate), drowsiness and the ULTIMATE side-effect, death.
There are a couple of articles out there reporting magnesium sulphate overdose: from obstetric patients (MgSO4 is used as seizure prophylaxis in pre-eclampsia, as well as to inhibit preterm labour), to cases of deliberate overdose with Epsom salts (managed with supportive treatment and eventually renal dialysis), to poor patients trying to detox from alcohol addiction and are given the wrong dosage of MgSo4, resulting in death. Major oopsie. Hate that extra zero.
MgSO4 is not just a problem in humans. Apparently horses get backed up from time to time, and vets use MgSO4 to help them – too much however, and the same negative outcomes. I know you needed to know that.
Bottom line: there is no evidence supporting the use of Epsom salts in muscle recovery. I am truly sorry.
Please let me know if you know of any other studies that support its use – I want to believe it works…
Baker JF, Walsh PM, Byrne DP, Mulhall KJ. In vitro assessment of human chondrocyte viability after treatment with local anaesthetic, magnesium sulphate or normal saline. Knee Surg Sports Traumatol Arthrosc. 2011 Jun;19(6):1043-6.
Heidarianpour A, Sadeghian E, Gorzi A, Nazem F. The influence of oral magnesium sulfate on skin microvasculature blood flow in diabetic rats. Biol Trace Elem Res. 2011 Oct;143(1):344-50.
Cinar V, Polat Y, Baltaci AK, Mogulkoc R. Effects of magnesium supplementation on testosterone levels of athletes and sedentary subjects at rest and after exhaustion. Biol Trace Elem Res. 2011 Apr;140(1):18-23.
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Milne H, Dean P, Hughes M. Deliberate overdose with Epsom salts. BMJ Case Rep. 2009;2009. pii: bcr07.2008.0591. doi: 10.1136/bcr.07.2008.0591. Epub 2009 Apr 20.
Simpson KR, Knox GE. Obstetrical accidents involving intravenous magnesium sulfate: recommendations to promote patient safety. MCN Am J Matern Child Nurs. 2004 May-Jun;29(3):161-9; quiz 170-1.
Henninger RW, Horst J. Magnesium toxicosis in two horses. J Am Vet Med Assoc. 1997 Jul 1;211(1):82-5.