Proponents of Epsom salt baths believe that when added to warm water, the magnesium dissolves and is absorbed into the body through the skin—allowing a whole host of benefits.
Why is magnesium helpful, especially for workout recovery? "Magnesium is an essential mineral present in our bodies that assists with normal muscle function including contraction and relaxation", said Dennis A. Cardone, DO, a sports medicine specialist and team doctor for athletic programmes, including a major tennis championship. In fact, the nutrient keeps not just your muscles healthy and functioning, but also your bones, heart and almost every other organ in your body.
"Sometimes people who are deficient in magnesium have issues with muscle cramping or muscle pain", said Jason Machowsky, CSCS and exercise physiologist. One small study of professional male cyclists even found that magnesium supplementation helped recovery after strenuous exercise and had a "protective effect on muscle damage". Machowsky cautions that supplements should be taken under the guidance of a doctor or dietician. Luckily, it's naturally found in many foods like green leafy vegetables, legumes, nuts, seeds and wholegrains.
The only problem: "The fact that soaking in a warm bath of Epsom salt results in actually getting that magnesium into your body remains to be seen", Machowsky said. "We don't have any research showing Epsom salt can be absorbed through the skin in significant enough quantities to affect blood levels of magnesium", he said.
"The benefits of an Epsom salt bath appear to be wholly related to the soaking in warm water", adds Cardone. "While ice baths have recently become popular to reduce inflammation, a hot bath can improve blood flow—delivering oxygen and nutrients to the muscles—and elasticity of the connective tissue", Cardone said. This can help ease pain caused by delayed-onset muscle soreness, or DOMS.
There's another indirect recovery benefit, both Cardone and Machowsky said. "Perhaps most important is that soaking in a warm bath can be relaxing and benefit our mental and emotional health", Cardone said.
Research shows that warm baths can decrease cortisol, a stress hormone. "A 2019 study in the journal Sleep also found that a 10-minute warm bath an hour or two before bed can help you fall asleep faster and improve sleep quality—and a good night's sleep that spans eight to nine hours is important for muscle recovery and performance", Cardone said.
"Given the kind of stressful world that we live in, anything we can do to promote a calm environment for ourselves, including time to actively relax and allow your body to rest and recover, is important—regardless of whether you put the salts in", Machowsky said.
Plus, there's the power of the brain-body response known as the placebo effect. Researchers have found placebos (or inactive treatments, such as a sugar pill) can lead to real, measurable physiological changes providing similar benefits to medications. In other words, thinking that Epsom salt baths are soothing or improving muscle pain or speeding up your recovery might be reason enough to keep using them. "If you believe it's going to help you, odds are it may help you", even if we don't have good data to say the direct cause is the magnesium sulphate, Machowsky said.
