Massage therapists tend to suggest to their clients to take an Epsom salt bath to alleviate muscle soreness or to “detoxify” their muscles and tissues after a massage or a workout. A quick search on Google yields many articles and claims that Epsom salt baths and treatments can work the proposed wonders. How much of this is based on science and science-based evidence? Are the benefits of Epsom salt based on proven facts, or are they based on myths that are perpetrated among the industry and the public?
Epsom salt is an inorganic salt that is composed of magnesium (Mg), sulfate (SO4), and seven water molecules (heptahydrate). Named after the town Epsom in England where the saline mineral water was boiled by the locals for their use, Epsom salt is commonly used as a laxative in medical practices and sometimes as a disinfectant to wounds. However, there is no evidence to support the benefits that some professionals and health gurus claim.
A search on scientific literature websites, including PubMed and Research Gate, yields no evidence or research supporting the claims of Epsom salt. However, there are a few researches that examined magnesium sulfate’s effect on low blood magnesium, severe tetanus, irregular heart rhythm, and ecalmpsia, according to science writer and registered massage therapist Paul Ingraham. Even so, he proposed that the lack of research in the claimed benefits of Epsom salt may be that “researchers just aren’t ‘interested’ or they simply can’t get funding for the work.”
The only study that showed any relevance to the subject was conducted at the University of Birmingham in the U.K. In the study, 19 subjects, who are the staff of School of Biosciences of the university, all took an Epsom salt bath for 12 minutes at a water temperature of between 50 to 55 degrees Celsius (122 to 133 degrees Fahrenheit) over seven consecutive days. Blood samples were taken before the first bath, at the second hour after the first bath, and at the second hour after the seventh bath. Urine samples were collected before and at the second hour of every bath.
At the end of the study, all but two of the subjects had higher magnesium concentration in their blood. Those who didn’t have higher blood magnesium concentration had higher magnesium in their urine. Sulfate levels were high both in blood and urine of all subjects. Researchers concluded that “magnesium ions had crossed the skin barrier and had been excreted via the kidney” and that Epsom salt bath “is a safe and easy way to increase sulfate and magnesium levels in the body.”
Not everyone accepts that this is a valid evidence that Epsom salt could penetrate the skin and provide its benefits. “This seems like a poor quality study,” said massage therapist Samuel McCracken, who practices in Brisbane, Australia. “There’s no control group, and an assumption that it was absorbed through the skin and not inhaled or ingested. And (there is) no proposed mechanism.”
The lack of a control group already made the study’s claims less valid. “The importance of having a control group could be shown this way. What if I had a hot bath with no Epsom salts and (researchers) measured my magnesium levels and found they were elevated afterwards due to dehydration by sweating in the hot bath? This could lead to a higher concentration of blood magnesium.”
Runners Connect also did a brief review of the study and find no credible reasons to support or believe the study. The website stated that the amount of salt needed to elicit osmotic pressure to move in the right direction is over half a pound, based on the “back-of-the-envelope chemistry calculations.” This is much more than the concentration used in the study, which was 0.08 pounds per gallon. “There is nothing special about Epsom salt in this respect,” Runners Connect stated. “Regular table salt would work fine, too, when it comes to osmosis.” The British study was never published nor was it was peer-reviewed.
“Detox” and osmosis
Paul Ingraham stated that poor understanding of the terms “detoxification” and “osmosis” are used to explain the benefits of Epsom salt, and these explanations are based more on myths and beliefs rather than hard facts and evidence. Proponents of Epsom salt usage presume that either osmosis is the means in which the salts can “get into the body and then have a detoxifying effect,” or osmosis is actually the detoxification process itself. However, osmosis is about the movement of water, not the ions or compounds, across a thin membrane, moving from an area of low concentration of solvents to a higher concentration of solvents. Therefore, if the salts do get absorbed into the body, it is not done by osmosis. Detoxification and osmosis do not provide an explanation for Epsom salt “benefits.”
Ingraham also wrote that the human skin is almost completely waterproof — very possibly Epsom salt proof, too. The top layer of the skin, called the stratum corneum, is mostly made up of dead skin cells and is coated with an oily secretion called sebum that is produced in the sebaceous glands of the skin. “Ions and molecules dissolved in water cannot generally pass through the stratum corneum because there is virtually no water in the outer layers of skin for them to diffuse through.”
The skin, however, is fat permeable, which is why certain plant oils cause skin rashes and certain drugs can be absorbed into the skin (e.g. nicotine patches). Even if magnesium is mixed with lotions, the element still doesn’t get absorbed into the skin — at least not among Israeli soldiers. In a study published in the January 2009 issue of Military Medicine, 34 healthy soldiers applied the magnesium-laden lotion on their skin to see if it would improve protection against certain nerve agents. Researchers found that “no serious adverse effects were recorded and the lotion did not interfere with daily tasks” and no magnesium toxicity were found.
Even if Epsom salt could be absorbed into the body, what is the significance and relevance of increasing magnesium and sulfate levels in the body? Ingraham stated that there is “no information about what it is, how it works, what it works for, how strong the effects are, what side effects there might be.” Based on current medical uses of Epsom salt, “there is definitely no particular reason so far to believe that having more magnesium or sulphate in your blood is going to be much use to you — unless you have eclampsia or tetanus or autism,” Ingraham wrote. In fact, according to a study published in Anaesthesia (May 1985), physically fit patients who were given magnesium sulfate intravenously had no decrease of muscle pain while undergoing minor surgery. These patients also suffered “unpleasant side effects.”
Muscle pain and soreness is not fully understood, and there are many factors contribute to pain, such as nerve pathways, disease, stress, and the perception of pain. With no credible evidence supporting the claimed benefits of Epsom salt, it is very difficult to advocate or justify using it for muscle soreness or “cleansing” the body. Thus, the benefits of Epsom salt claimed by some massage therapists and other healthcare professionals should be treated more like a myth rather than a fact.
By Nick Ng