One for the medical text books; a 38-year-old male with gallstones presents with dark urine and loss of appetite, and after a few more tests is quickly diagnosed with severe liver damage.

The cause? A two week course of magnesium sulfate, commonly advised by practitioners of naturopathy as a liver "flush".

This particular side effect itself is a medical first. But the case study also provides evidence in support of concerns over the role science plays in alternative medical practices.

Magnesium sulfate – or good old Epsom salts – has its uses as a medical treatment. It's often prescribed in small amounts as a laxative, or injected in controlled doses to treat pregnant women with severe eclampsia.

The science is a little more dubious when it comes to its benefits as a muscle relaxant or as a way to ease aches and pains.

As for gallstones, the research is a ghost town. Not that a lack of scientific evidence stops naturopaths from confidently prescribing it as a way to "cleanse" the liver.  

While advice can vary, in this particular case the gentleman was instructed to dissolve three tablespoons – just under 50 grams – of Epsom salt crystals in lukewarm water each day, and drink the solution.

The intention was for the salts to dilate the bile ducts and help remove the build-up of minerals in the gallbladder that was causing the patient distress. Or something like that.

In worst case scenarios – such as in this 2009 case study of a 46 year old woman who attempted to take her own life by downing 2 kilograms of the stuff – ingestion of magnesium sulfate might result in vomiting, confusion, limb weakness, and changes to the heart's rhythm. Damage to the kidneys is also a real possibility.

For the average person, the worst effects might be a few extra runs to the bathroom that day.

Sadly for the subject in this case study, the results were far worse than diarrhoea.

On the 12th day of his treatment he reported noticing a drop in appetite and a darkening of his urine. Two days after completing the course he saw signs of jaundice – a yellowing of the skin and eyes caused by a change in liver functions.

Scans and blood tests backed up suspicions that his liver was enlarged and struggling to do its job. The man wasn't an alcoholic, and provided no other convenient explanations for his condition.

While none of this is proof positive that the Epsom salts were responsible, a process called the Roussel Uclaf Causality Assessment Method (RUCAM) was used to connect the liver damage with the treatment to the satisfaction of the medical team.

A little over a month later, without further magnesium salt beverages, the man's liver functions returned to normal.

Beyond speculation of the potential influence of fatty liver disease (or steatohepatitis), there's no obvious cause behind this individual's unique reaction.

A typical gall stone usually forms and passes without symptoms. In the few percent of cases it causes problems, it's usually a cramping in the abdomen that soon passes.

Every now and then their presence leads to complications that might require medication or surgical intervention.

For the most part, a short-term course of Epson salts probably wouldn't have caused harm, and would even appear to work, making it seem like a reasonable gamble for those experiencing mild discomfort.

Without making too many assumptions on this specific case, naturopathy tends to be a practice based on the premise that the body heals itself and interventions shouldn't deviate too far from what you'd find in the natural world.

For all of its appeal as a worldview, treatments are rarely based on evidence taken from literature in the medical community. And this can be a problem.  

Tedious, arduous, and expensive as they are, clinical trials are conducted on potential medications (such as Epsom salts) to identify and describe these kinds of risks versus benefits, providing medical practitioners with sufficient information to make fair judgements.

Even something as innocuous as swallowing a glass of magnesium sulfate each day could have a severe impact on a minority of people, a risk many might not be willing to take.

Medicine based on scientific evidence has its fair share of problems. There's no doubt about it. And it's not always easy to know how to make sense of its conclusions or who to trust to communicate advice.

But the scientific process is a useful way to filter out the risks. Hopefully this guy has now learned his lesson.

This case study was published in BMJ Case Reports.