Today in "I understand why it happens but it's still frustrating"
I've been looking into topical magnesium, more commonly known as an "epsom salt bath". And, like, on the one hand, "alternative medicine" is a great source of ideas for treating medical conditions, and basically every single existing non-alternative medicine has been the result of doing some science on "alternative medicine" techniques. And on the other hand, the placebo effect is both strong and very real, and humans are terrible at understanding randomness, which is why we even invented science. You really do gotta check, you always gotta check. AND, back on the first hand, humans are eerily good at finding patterns, to the point where there probably ought to be a Humans Are Space Orcs story about it, and a lot of humans, whose conceptions of reality have been put through some pretty intensive stress testing, believe that epsom salt baths work. AND, on the second hand, we invented science, we have science, we ought to use science.
So anyway, several studies have looked into whether topical magnesium has any effect, and in 2017 someone went through and did a meta-analysis of it, and admittedly some of the studies were insufficient to draw any conclusions from them, but still, none of them showed any kind of evidence that there was enough happening here that it was worth looking into further. Since (despite our best efforts) you can't test everything, it makes sense to prioritize doing real amounts of research on things that are showing promise in the initial trials.
EXCEPT
none of those studies, nor the meta analyses, acknowledge that (quoting directly from the National Institute of Health)
Assessing magnesium status is difficult because most magnesium is inside cells or in bone. The most commonly used and readily available method for assessing magnesium status is measurement of serum magnesium concentration, even though serum levels have little correlation with total body magnesium levels or concentrations in specific tissues [https://ods.od.nih.gov/factsheets/Magnesium-HealthProfessional/, accessed 2023-03-28]
All of them checked whether topical magnesium influenced the amount of magnesium in the blood. And it does not. But that result is entirely consistent with the expected result if topical magnesium is absorbed into the skin: if your soft tissues, which hold 39-49% of your magnesium, are deficient, then you would expect it to stay in the nearest tissues, and not make it to the blood.
Which is not to say that this proves epsom salt baths work: this is the same result you'd expect if they don't work at all. Which is to say, the experiment would be expected to have the same result regardless of whether the hypothesis was accurate or not, which is to say, this was bad science. It tells us absolutely nothing. And it's especially frustrating because an experiment to test the actual claim would have been quite a bit easier -- measuring range of motion and muscle pliability is much cheaper than taking blood samples. A double-blind, randomized controlled trial would have been actually quite straightforward to carry out.
All of which is to say, I'm kinda thinking about buying 100 lbs of magnesium sulfide and finding myself some test subjects
