I’ve been contributing to this blog since 2010, and fourteen years later, I’m hitting my 345th post and still seem to have have an endless supply of topics. I can thank Facebook for many of them. Pseudoscience springs eternal. Today’s topic was forwarded to me, and I have to admit, I had never heard of magnesium oil until I saw this:
Facebook won’t let me embed the reel itself, but it’s just a guy massaging his foot. There is a lot to unpack here – even ignoring the antiperspirant/aluminum angle. The main claims seem to be:
- Body odour is a sign of magnesium deficiency
- 3/4 of the waste in your lymph expels through your left armpit
- rubbing magnesium oil will eliminate body odour
- magnesium oil will help your body “detox properly”
- magnesium oil will restore your magnesium levels
A quick search of the internet and a browse of TikTok suggests that magnesium oil is marketed as a sort of panacea. Not only does it apparently help with sleeping, it also apparently helps muscle cramp, skin conditions, and yes, detoxification.
The Role of Magnesium
Magnesium is an abundant mineral in the body and critical to hundreds of cellular actions, including DNA and RNA synthesis, muscular contraction, blood pressure, insulin metabolism, and more. We obtain magnesium from our diet. Normal absorption is about 24%–76% of what’s ingested, which varies based on whether the body is deficient. Major sources of magnesium in the diet are water (particularly if you have “hard” water), chlorophyll from leafy greens, and then nuts, whole grains, and legumes. In general, foods high in fibre tend to be good sources of magnesium. Dietary surveys suggest that many “Western” diets provide lower than recommended intakes of magnesium.
Our bodies contain about 24-25g of magnesium, roughly divided equally between the skeleton and tissue. Magnesium on the surface of bone can be released quickly to maintain magnesium levels in the rest of the body. Elimination of magnesium is via the kidneys.
Magnesium supplements, conversely, tend to be poorly absorbed. Because these products tend to cause diarrhea, magnesium products like magnesium citrate are used primarily for this reason. It’s use as a laxative is one of the medical conditions for which magnesium supplements are demonstrably effective. That and treating low magnesium levels. Even conditions for which magnesium supplements are taken widely, like muscle cramps or insomnia, are not backed by convincing evidence. Consequently, there is little role for supplementation in the absence of a documented deficiency, or in circumstances where a medical condition (e.g., celiac disease) or a medication (e.g., a proton pump inhibitor) may be interfering with dietary magnesium absorption.
Topical Magnesium’s Achilles’s Heel: Absorption
While there may be some health benefits from taking magnesium supplements orally, there is a lack of evidence to show that magnesium is absorbed to any meaningful extent when it is applied to the skin. This makes sense, because the skin is an excellent barrier against radiation, chemicals and allergens, while conserving against the loss of water and electrolytes. In order for magnesium to be absorbed, it would have to penetrate the stratum coneum – 15-20 layers of cells that are water repellent. Drug absorption is only possible for fat-soluble drugs – not ionized chemicals like magnesium chloride solution (the typical form found in topical products). The only way magnesium could potentially be absorbed would be through sweat glands or hair follicles. But it isn’t. Extensive evidence show that magnesium is not absorbed through the skin. The one study that seems to be quoted widely to “demonstrate” that topical magnesium is effective for fibromyalgia didn’t have a control group and didn’t measure magnesium levels, and so can be discounted as evidence. Another study that looked at neuropathy also lacked a placebo control – so it is also not persuasive.
Another popular source of topical magnesium are epsom salts or magnesium sulfate heptahydrate. The effectiveness of epsom salts has been extensively analyzed by friend-of-the-blog Paul Ingraham, and I encourage you to read his very long article about them. In short, everything you think you know about epsom salts is probably wrong.
Facebook Fact Check
With the knowledge above, it’s fairly easy to break down this video. In reality, body odour is caused by bacteria on the surface of the skin breaking down the protein molecules in sweat. Low magnesium is associated with muscular tremor, cramping, seizures, cardiac arrhythmia, and conditions like low calcium and low potassium. It is not associated with body odour. The lymphatic system is a network in the body that collects plasma and liquid that has leaked out of capillaries and returns it to the bloodstream. This liquid, called lymph, moves through tubes to one of two major ducts where it returns to the bloodstream: the lymphatic duct, and the thoracic duct. While there are lymph nodes in both armpits, there is no expulsion of lymph from the left armpit, an observation that should be apparent to anyone with armpits. Given magnesium oil isn’t absorbed to any meaningful extent, massaging it into your feet will have zero effects on the physiology of your body or its ability to “detox”. If you have kidneys and a liver that are functioning normally, then you have a detox system that’s working fine.
Conclusion: No evidence of effectiveness
All the anecdotes and videos about topical magnesium can’t refute physics – magnesium isn’t absorbed through the skin, so any effects attributed to magnesium oil are placebo. Striving to eat a diet rich in magnesium is a good idea, however, and there are some circumstances where magnesium supplements are medically appropriate.