Who Found the Role of Magnesium, and How Epsom Salt Became a Supplement

Magnesium was a laxative for centuries before researchers identified it as an essential nutrient in 1926. This page traces that path, the absorption question behind the label, and the NIH adult limits for supplements.

The history of magnesium supplements starts with a laxative, not a vitamin shelf. Sulfate-rich mineral waters were used for centuries to move the bowels, and the finding that magnesium is an essential nutrient came much later. According to PubMed, a 1990 historical review in *Magnesium Research* dates that discovery to 1926 ([PubMed](https://pubmed.ncbi.nlm.nih.gov/2132753/)). ## In this article - Centuries of laxative use before any constipation trial - The essential-nutrient finding in 1926 - Which magnesium form the body absorbs - How much you need, and where the supplement ceiling sits - Bottom line and frequently asked questions ## Centuries of laxative use came before any constipation trial Epsom salt is the everyday name for epsomite, the mineral form of magnesium sulfate. A U.S. patent for a bath salt describes "the mineral epsomite, which is commonly called Epsom salt" as one example of magnesium sulfate material ([USPTO, U.S. Patent 10,549,130](https://image-ppubs.uspto.gov/dirsearch-public/print/downloadPdf/10549130)). The popular origin story for the name did not turn up in any primary or institutional source we checked, so this page leaves it out. The timing is the surprise. A 2020 review in *Nutrients* says magnesium sulfate "has a long history in the treatment of" functional constipation, and that sulfate-rich mineral waters "have been used for centuries for their laxative properties." Its authors also write that it appears no clinical study set out to demonstrate these waters' efficacy for constipation before the 21st century ([PubMed](https://pubmed.ncbi.nlm.nih.gov/32664341/); [DOI](https://doi.org/10.3390/nu12072052)). The same review says the laxative effect of magnesium and sulfate "has since been widely demonstrated." For the parallel calcium story, read [how calcium became a supplement](/blog/history/history-of-calcium-supplements-from-chalk-to-bone-trials). The laxative era also has a warning on record. A 2017 case report in *The American Journal of the Medical Sciences* describes a woman with a history of chronic constipation who took magnesium-containing laxatives. Her serum magnesium rose from 2.0 to a peak of 10.8 mg/dL despite hydration and diuresis, and she died two days later ([PubMed](https://pubmed.ncbi.nlm.nih.gov/29661354/); [DOI](https://doi.org/10.1016/j.amjms.2017.08.013)). ## The essential-nutrient finding came in 1926 The turn came in 1926. Kubena and Durlach write that after the discovery of magnesium as an essential nutrient in that year, research focused on acute deficiency and on the requirement for normal growth and reproduction ([PubMed](https://pubmed.ncbi.nlm.nih.gov/2132753/)). Their review adds that research since the 1970s shows the ability to adapt to a marginal magnesium intake is limited, and that marginal intake is commonplace in developed countries. Today the NIH Office of Dietary Supplements calls magnesium a cofactor in more than 300 enzyme systems, with roles in protein synthesis, muscle and nerve function, and blood pressure regulation ([NIH ODS](https://ods.od.nih.gov/factsheets/Magnesium-HealthProfessional/)). The [magnesium monograph](/ingredients/magnesium) covers the current evidence, and the [heart and blood pressure guide](/health/heart-blood-pressure-complete-guide) covers the cardiovascular research. ## Which magnesium form the body absorbs The NIH says the aspartate, citrate, lactate and chloride forms of magnesium "tend to have higher bioavailability than magnesium oxide and magnesium sulfate" ([NIH ODS](https://ods.od.nih.gov/factsheets/Magnesium-HealthProfessional/)). The studies below measure absorption over hours, not health outcomes, so read them as absorption evidence. The 1990 comparison of citrate and oxide started with solubility. Magnesium oxide was "virtually insoluble in water," while magnesium citrate reached 55 percent solubility in water. In normal volunteers, urinary magnesium rose more over the four hours after a 25 mmol load of citrate than after oxide ([PubMed](https://pubmed.ncbi.nlm.nih.gov/2407766/); [DOI](https://doi.org/10.1080/07315724.1990.10720349)). Dose changes the picture too. In a 1991 study, normal subjects ate a standard meal with 0 to 80 mEq of magnesium acetate added. Fractional absorption fell from 65 percent at the lowest intake tested to 11 percent at the highest. Magnesium from almonds was as bioavailable as soluble magnesium acetate, and enteric-coated magnesium chloride was absorbed much less than acetate ([PubMed](https://pubmed.ncbi.nlm.nih.gov/1864954/); [DOI](https://doi.org/10.1172/JCI115317)). A 2024 head-to-head study in *Nutrients* gave 40 healthy women and men four magnesium products after a seven-day low-magnesium diet, then drew blood over six hours. Plasma magnesium rose after magnesium oxide at one hour and after magnesium citrate at four hours. The authors report no significant rise after magnesium bisglycinate. The microencapsulated ingredient they tested rose at every time point. Two of the five authors list Lubrizol Life Science as their affiliation, so read it as a single study with a commercial stake ([PubMed](https://pubmed.ncbi.nlm.nih.gov/39770988/); [DOI](https://doi.org/10.3390/nu16244367)). ## How much you need, and where the supplement ceiling sits | Adult group | Men, RDA | Women, RDA | Pregnancy | Lactation | |---|---|---|---|---| | 19 to 30 years | 400 mg | 310 mg | 350 mg | 310 mg | | 31 to 50 years | 420 mg | 320 mg | 360 mg | 320 mg | | 51 years and older | 420 mg | 320 mg | not listed | not listed | The RDAs count magnesium from every source, including food, beverages, supplements and medicines. The tolerable upper intake level for adults, 350 mg a day, covers only supplements and medicines. The NIH also says roughly 30 to 40 percent of the magnesium in food and beverages is absorbed ([NIH ODS](https://ods.od.nih.gov/factsheets/Magnesium-HealthProfessional/)). Our [Good Magnesium capsule](https://mtangelvitamins.com/products/good-magnesium-chelate-amino-acids?utm_source=learn_hub&utm_medium=content&utm_campaign=blog_post&utm_content=history-of-magnesium-from-epsom-salt-to-essential-mineral) lists 200 mg of magnesium per capsule, as rice protein chelate, at 47 percent of the Daily Value. The product page shows 60 capsules for $21.99, about $0.37 a day at one capsule per serving. The directions say one or more capsules daily, but two capsules would be 400 mg, above the NIH's 350 mg adult supplement limit, so add up every supplement you take. None of the studies on this page tested rice protein chelate, so the form on this label is still an open question. ## Bottom line Read the magnesium milligrams on the Supplement Facts panel, not the total weight of the compound. Add up every supplement and medicine you take, and stay under the NIH's 350 mg adult supplement limit unless a clinician has said otherwise. Treat a form on the label as a reason to compare, not a guarantee, because the form comparisons here measure absorption over hours, not health outcomes. ## Frequently asked questions ### Where did the name Epsom salt come from? Epsom salt is the common name for epsomite, the mineral that a U.S. patent lists as a magnesium sulfate material. The popular origin story for the name did not appear in any primary or institutional source we checked, so this page does not repeat it. What the record does support is the laxative use of sulfate-rich mineral waters, which a 2020 review says has gone on for centuries. That is the part of the story with a paper trail. ### How did magnesium move from laxative to essential nutrient? Two tracks ran side by side. Sulfate-rich mineral waters were used for centuries as laxatives, and a 2020 review says the laxative effect of magnesium and sulfate has since been widely demonstrated. The nutrient track began with the 1926 discovery of magnesium as an essential nutrient, according to a 1990 historical review. Today the NIH says magnesium is a cofactor in more than 300 enzyme systems, so its job reaches well beyond the bowel. ### When did researchers first link magnesium to animal health? The earliest verified date is 1926, when a 1990 historical review says magnesium was discovered to be an essential nutrient. That review covers experimental magnesium deficiency, and it describes the research that followed, which focused on acute deficiency and on the needs of normal growth and reproduction. We could not verify the specific 1930s animal papers in PubMed or NIH sources, so this page does not name them or report their results. ### Why do magnesium products carry so many different forms on labels? The forms differ in how well they dissolve and how well the body absorbs them. The NIH says aspartate, citrate, lactate and chloride forms tend to have higher bioavailability than magnesium oxide and magnesium sulfate. In a 1990 study of normal volunteers, magnesium citrate reached 55 percent solubility in water, while magnesium oxide was virtually insoluble. Start with the milligrams of magnesium per serving, then compare forms, and remember these studies measure absorption over hours, not health outcomes over months. ### How much magnesium comes from food compared with pills? The NIH says roughly 30 to 40 percent of the magnesium in food and beverages is absorbed. The 1991 study used magnesium added to a meal, not a pill, but it shows absorption falling as the dose rises, from 65 percent at the lowest intake tested to 11 percent at the highest. The RDA counts food and supplements together, while the 350 mg adult upper limit counts only supplements and medicines, so the number to add up is the magnesium from every supplement you take. ### What did the 1930s animal work find? The verified summary is narrower. According to the 1990 review, early experiments on marginal magnesium intake reported changes in tissue composition, and research since the 1970s shows the body's ability to adapt to a marginal intake is limited. We could not confirm the specific 1930s animal papers in PubMed or NIH sources, so we do not describe their results here. ### Why does a form like glycinate or citrate change the story? Because absorption depends on the form, and the studies here do not rank every form the same way. The 1990 study found citrate more soluble and more bioavailable than oxide in normal volunteers. A 2024 study found plasma magnesium rose after citrate and oxide, but not after bisglycinate, in 40 people, and two of its authors list Lubrizol Life Science as their affiliation. None of the studies cited on this page tested rice protein chelate. ## Next reads - [The magnesium monograph](/ingredients/magnesium): the evidence, forms and dosing in one place, if you want the full reference. - [How calcium became a supplement](/blog/history/history-of-calcium-supplements-from-chalk-to-bone-trials): the same question for another mineral, from shell and antacids to bone trials. ### Related reading - [The potassium origin story, from wood ash to supplement](/blog/history/history-of-potassium-from-ash-to-supplement)