Can magnesium be absorbed through the skin?

Posted 16 August 2017

We have pointed out in numerous posts, that there is no proof that magnesium can be absorbed through the skin, and knowing how difficult it is for substances to penetrate skin, that until proof arrives, to not believe any of the health claims being made for magnesium being applied to the skin. I am particularly referring also to Miracle Magnesium products.

It is also very important to point out that there are two arguments to consider:
a.) can magnesium be absorbed through the skin, and,
b.) are the health claims being made for magnesium valid.

To explain: we need proof that magnesium is absorbed through the skin (and in a significant amount), and, in a second and separate argument, even if magnesium is absorbed, is there proof that magnesium will have the health benefits company makes claims for, e.g., cure sinusitis, cancer, or any other of the claims being made.

So a.)  could be true and b.) false – or vice versa. Or both could be true. Or both a.) and b.) could both be false.

The first study evaluating whether magnesium can be absorbed through the skin has been published.[1]

We examine the findings, and although interesting, they fall short of acceptable evidence.

Firstly, some readers have argued that magnesium absorption through the skin has been studied before. The authors state “No previous studies have looked at effects of transdermal Mg2+ in human subjects.”

The authors conclude: “In this pilot study, transdermal delivery of 56 mg Mg/day (a low dose compared with commercial transdermal Mg2+ products available) showed a larger percentage rise in both serum and urinary markers from pre to post intervention compared with subjects using the placebo cream, but statistical significance was achieved only for serum Mg2+ in a subgroup of non-athletes. Future studies should look at higher dosage of magnesium cream for longer durations.”

In other words, this is a ‘nice’ way of saying that the findings seem relevant, when they are in fact not. Read on.

The results showed that “[A]fter the Mg2+ cream intervention there was a clinically relevant increase in serum magnesium (0.82 to 0.89 mmol/l,p = 0.29) that was not seen in the placebo group (0.77 to 0.79 mmol/L), but was only statistically significant (p = 0.02)) in a subgroup of non-athletes”. 

To claim that the results are clinically relevant without proof that it is clinically beneficial, is nonsense, and particularly when the authors themselves point out that it was not statistically significant: these contradict each other. To spell this out: this is like saying that taking supplement x makes your left arm work faster but not significantly different or faster than someone not taking the supplement.

Of course, this does not mean that the results should be dismissed. They are interesting and suggest further study. But here are reasons to consider.

For those who believe that magnesium products on the skin, therefore works, one still has to be cautious about the results of this study for the following reasons:

  1. The authors call this a pilot study. “A pilot studypilot project or pilot experiment is a small scale preliminary studyconducted in order to evaluate feasibility, time, cost, adverse events, and effect size (statistical variability) in an attempt to predict an appropriate sample size and improve upon the study design prior to performance of a full-scale” Sometimes pilot studies cannot be reproduced, sometimes they can.
  2. One of the authors, Dr Rosanoff, has a strong vested interest in a positive outcome (“promoting magnesium“). This does not negate the findings, but has to be considered. How many times have critics argued that “of course Dr X is going to support this drug, because advocates the drug for the Big Pharma company”.
  3. The product is recorded as Mg++ (magnesium). We know from lots of research, that different salts of an ingredients can influence absorption, for example, ferrous iron versus carbonyl iron. Absorption of magnesium chloride is different to that of magnesium sulphate. Therefore the study cannot be extrapolated to every source of magnesium available
  4. The magnesium was applied to the skin as a cream. This has to be applied 2 x 5ml spoonfuls of cream per day for two weeks: applied to the stomach and torso then spread down to the legs. No showering or washing could take place for a minimum of 3 hours after application. Cream applied to the skin ‘sticks’ to the body and therefore applying a cream to such a large area, may have a very different effect compared to spraying the body with a liquid solution of magnesium.
  5. The researchers found that “[T]here was no statistically significant effect of Mg2+ cream on either serum or urinary Mg2+ status. However, after the Mg2+ cream intervention there was a clinically relevant increase in serum magnesium (0.82 to 0.89 mmol/l) that was not seen in the placebo group (0.77 to 0.79 mmol/L), but this was not statistically significant (p = 0.29).”

    What does this mean? Not statistically significant argues that the difference was not large between those receiving the magnesium and those that did not. Somehow the authors claim it is clinically relevant! Very odd. This would suggest that they were able to show that patients with an average magnesium of 0.89 are better off than 0.82 – in a small number of patients. If we compare the two groups, considering that in the placebo group, that the magnesium went up 0.02, one can argue that the increase in the test group was 0.07 from 0.82, a finding that is interesting but certainly not conclusive.
  6. Usually in study groups, one has to be careful of ‘averages’ or ‘mean’. In other words, one can have 20 patients whose magnesium do not change, but one whose does to a degree that gives the impression that the whole group benefited when ‘averaged’. Was this the case here? Yes, the researchers conclude: “Given the high variance in serum Mg2+ of these subjects, we suggest that future research focus on a larger number of human subjects given higher concentrations of Mg2+ cream application administered for longer durations to investigate whether transdermal application may show a significant contribution to improvement in magnesium status.”

In conclusion, this is a pilot study, one that suggests that a certain formulation of magesium may be absorbed through the skin. Whether these findings can be extrapolated to other forms of magnesium is untested and unknown. The dose absorbed is not significant. And, its clinical benefit, has not been established.

Reference: Kass L, Rosanoff A, Tanner A1, Sullivan K, McAuley W, Plesset M. Effect of transdermal magnesium cream on serum and urinary magnesium levels in humans: A pilot study. PLoS One. 2017 Apr 12;12(4):e0174817. doi: 10.1371/journal.pone.0174817.

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