Epsom salt in your ice bath may improve your mood
Summary
Major depression is associated with magnesium deficiency.
Magnesium supplementation has been shown to improve measures of mental health at least as well as anti-depressants, without deleterious side effects.
Adding Epsom salt to your ice bath may help meet the micronutritional requirements of cold thermogenesis, while enhancing the mood-lifting effects of the ice bath.
How do you measure magnesium deficiency?
Studies of people suffering from major depressive disorder reveal an association with magnesium deficiency (Jacka et al. 2009, Serefko et al. 2013). However, studies based on blood serum concentrations of magnesium yield ambiguous results, mostly because less than 1% of bodily stores of magnesium is found in the bloodstream (Razzaque 2018). For example, in one study, 19 participants who bathed for 12 min in a hot Epsom salt bath showed small increases in blood serum magnesium, but big increases in urine concentrations. On average, magnesium concentrations in urine sampled 2hrs after just one bath doubled, compared to increases of less than 10% in the bloodstream (Waring 2015).
In Magnesium is Critical for Cold Thermogenesis, I described the importance of magnesium in the proper function of mitochondria, the recruitment of new brown fat, and the essential role magnesium plays in correcting metabolic disorders. Moreover, I described the challenge of obtaining enough magnesium to support a regular practice of deliberate cold exposure, given the fact that foods that were historically rich in magnesium, such as green, leafy vegetables, are now impoverished of it (due to soil depletion).
Given that many Americans have an undiagnosed deficiency, adding 3-5lb of pure Espom salt to your Morozko ice bath may be a good way to help meet your bodily needs for magnesium, without risking side effects (like diarrhea) of supplements. Even if you don't soak for 12 minutes at a time, or you are concerned that the magnesium will not be absorbed through pores that are closed up tight by the cold water, you can increase absorption by postponing your shower. That is, shower before your ice bath, and not after. That way, the salt will take on your skin while you rewarm and have longer to enter into your body through hair follicles and sweat glands.
Magnesium for mental health
What I haven't discussed at any length until now is the potential for correction of magnesium deficiency to improve mental health. Although I wrote about the positive effects of deliberate cold exposure on the brain in Cold and Cognition, and described the protective effect that a healthy metabolism has for managing the risk of Alzheimer's dementia in Brown Fat for Brain Health, I didn't discuss the brain boost that Epsom salt can add to your mood.
The first double-blind, controlled trial of magnesium supplementation for treatment of major depression was in 2008. In a group of elderly, Type 2 diabetics who were newly diagnosed with major depression and deficient in blood serum magnesium, administration of magnesium chloride solution was just as effective for treating depression as the popular anti-depressant imipramine (Barragán-Rodríguez 2008). Since then, a number of studies have confirmed the salubrious effects of magnesium on the brain (e.g., Toffa et al. 2019, Botturi et al. 2020).
For example, a controlled study of over 120 patients in Vermont showed that magnesium chloride supplementation improved scores on a standardized questionnaire related to mental health. Subjects in both immediate and delayed treatment groups showed improvement after two to four weeks of taking magnesium, which faded 2-4 weeks after ceasing supplementation, suggesting that improvements were due to oral magnesium supplementation. Moreover, those patients already taking SSRIs were not excluded from the study. In fact, they experienced a greater positive effect. The researchers conclude:
Magnesium supplementation provides a safe, fast and inexpensive approach to controlling depressive symptoms. Magnesium supplements do not come with the added stigma associated with other therapies and, while monitoring response is still important, the risk of side effects is not as great as from antidepressants. Daily supplementation with 248 mg of elemental magnesium as four 500 mg tablets of magnesium chloride per day leads to a significant decrease in depression and anxiety symptoms regardless of age, gender, baseline severity of depression, or use of antidepressant medications. - Tarleton et al. (2017).
Epsom salt ice baths for transdermal absorption
Magnesium comes in many different formulations that are absorbed or partition in the body in different ways. For example, absorption of oral magnesium oxide into the body is poor, but has been used as an effective laxative known as as Milk of Magnesia since it was patented in 1873. By contrast, in rats magnesium-L-threonate (MgT) has been shown to elevate magnesium levels in the brain, leading to "enhancement of learning abilities, working memory, and short- and long-term memory" (Slutsky et al. 2010).
Nonetheless, Dr. Mark Sricus suggests in Transdermal Magnesium Therapy (2011) that oral supplements have complications that don't occur when dosing magnesium through the skin. Sricus points out that oral medicines must pass through the stomach and liver, whereas "transdermal application bypasses the liver, entering tissues and blood more directly." He suggests both soaking in a magnesium salt bath and applying oils infused with magnesium to the skin as effective transdermal dosage pathways.
A group of German researchers agree, writing:
Transdermal magnesium application should be the ultimate way to replenish cellular magnesium levels since every cell in the body bathes in it. It passes directly into the tissues via the skin, where it should quickly be transported to cells throughout the body. Furthermore, the transdermal absorption of magnesium in comparison to oral application is presented as being more effective on the one hand due to nearly 100% absorption, and as presenting fewer side effects on the other hand as it is bypassing the gastrointestinal tract. - Gröber et al. 2017.
Will Espom salt work in cold water?
In Salt Water Cold, I talked about some of the thermodynamic benefits of adding Espom salt to your ice bath and summarized the controversy around transdermal absorption. Back in 2016, researchers in Australia sought to settle the question of transdermal absorption in a series of experiments that established two facts: 1) magnesium ions penetrate human skin, and 2) hair follicles contribute about a third of total magnesium flux (Chandrasekaran et al. 2016).
What they didn't establish was whether the skin remains permeable to magnesium during cold water immersion. Given the fact that pores, sweat glands, and hair follicles all might be closed up during the vasoconstriction that accompanies deliberate cold exposure, it's possible that permeability of magnesium ions through the skin is impaired during an ice bath, compared to during a hot soak.
Nonetheless, we can employ practices that increase magnesium absorption from the Morozko. First, I've dissolved as much as 18lb (as magnesium sulfate) in my 80 gallon tub without ill effects on the tub, the filtration, or the function of the ozone. While starting with 3-5lb is a good idea for softening ice, it is possible to add even more, although I've also noticed that at high concentrations, splash water will leave a white salt residue behind. (Wipe these up with a damp sponge or paper towel). Second, to maximize transdermal absorption, I shower before entering the ice bath, but not after. In theory, toweling off (but leaving the magnesium on the skin) allows it to be transported into my blood stream after I rewarm.
I have yet to conduct intracellular magnesium assays to test the efficacy of this hypothesis about carrying a residue of Epsom salt on my skin all day, so results are not assured. Nonetheless, it reminds me of being a kid at the beach, with my skin covered with ocean salt. It's not exactly the same, because the Epsom salt is much less noticeable than sea salt, but I like the feel of my skin so much that now I feel kind of funny without it.
Regardless, the mood-lifting upside of adding magnesium to your bath could be terrific, and the down-side risk is negligible, so it seems prudent to try it and see how it feels for yourself.
About the Author
Thomas P Seager, PhD is an Associate Professor in the School of Sustainable Engineering at Arizona State University. Seager co-founded the Morozko Forge ice bath company and is an expert in the use of ice baths for building metabolic and psychological resilience.