Who Found the Role of Potassium, and How Wood Ash Became a Supplement Story
The potassium story starts with wood ash turned into potash for glass at Jamestown in 1608, moves through an 1808 Royal Society lecture, and ends at today's 99 mg supplement rule. Adult adequate intakes are 3,400 mg for men and 2,600 mg for women.
The history of potassium starts with wood ash, not a supplement bottle. In 1608, colonists at Jamestown, Virginia, made glass from sand, burned seaweed, lime from oyster shells and wood ash converted to potash. The National Park Service lists potash as one of four ingredients glass is made from ([NPS glassblowing narration](https://www.nps.gov/jame/learn/education/classrooms/glassblowingnarrration.htm)). The metal inside that potash came later, and its health limits shape the pill on the shelf today. ## Wood ash went into the first English glass The NPS describes the 1608 materials plainly: sand from nearby beaches, seaweed burned for soda ash, wood ash converted to potash, and oyster shells burned in a kiln for lime (same source). Wood was the fuel as well as the ash. The NPS says England had too few hardwood forests to keep glassmaking going by the 1600s, one reason the colonists tried it at Jamestown. Glassmakers there chopped enough wood to build a two-story house and stoked the furnace for almost two weeks to get a melt (same source). The first glass made by Englishmen in the New World was the 1608 "tryal of glasse," and the NPS says the records do not tell what it was ([NPS glassmaking page](https://www.nps.gov/jame/learn/historyculture/glassmaking-at-jamestown.htm)). Glassmaking there did not last. The NPS calls it the first industry attempted in English North America, and it failed (NPS glassblowing narration). ## The metal came later The Royal Society printed Humphry Davy's Bakerian Lecture in 1808. Its title announces "the decomposition of the fixed Alkalies, and the exhibition of the new substances which constitute their bases" ([Royal Society record](https://doi.org/10.1098/rstl.1808.0001)). The title names the fixed alkalies and promises the new substances that form their bases, which is where the potassium story begins. ## What the NIH says adults need An adequate intake is the level assumed to ensure nutritional adequacy when evidence is too thin to set a requirement. The NIH Office of Dietary Supplements lists potassium adequate intakes at 3,400 mg a day for men and 2,600 mg for women from age 19 on ([NIH ODS](https://ods.od.nih.gov/factsheets/Potassium-HealthProfessional/)). A 2019 update by a National Academies committee set those numbers because it could not derive a requirement (same source). The body absorbs about 85 to 90 percent of the potassium people eat (same source). The same intake figures do not apply to people whose potassium excretion is impaired by medical conditions or medicines (same source). ## When intake runs low or high Severe potassium deficiency is called hypokalemia. It affects up to 21 percent of hospitalized patients, usually because of diuretics and other medicines, and it is rare among healthy people with normal kidney function (same source). Thiazide diuretics, which are commonly used to treat high blood pressure, increase potassium loss in urine. Potassium-sparing diuretics do the opposite and can cause hyperkalemia (same source). At the high end, the NIH says severe hyperkalemia can cause muscle weakness, paralysis, heart palpitations and cardiac arrhythmias that could be life threatening (same source). ## Salt substitutes, and the number on the package Many salt substitutes use potassium chloride in place of some sodium chloride. The NIH says their potassium content ranges from about 440 mg to 2,800 mg per teaspoon, so the number on the label matters (same source). Very high amounts from supplements or salt substitutes can exceed what the kidneys can clear, causing acute hyperkalemia even in healthy people, and people with kidney disease or on certain medicines should check with a clinician first (same source). For the wider picture on blood pressure and diet, see the [heart and blood pressure guide](/health/heart-blood-pressure-complete-guide). ## Why potassium pills stay near 99 mg The NIH says most potassium-containing supplements provide no more than 99 mg per serving (same source). The same summary notes that chronic intake of supplement doses as high as 15,600 mg over five days raised blood potassium in healthy people without taking it past the normal range (same source). The ceiling also has a regulatory reason. FDA requires some oral drugs that provide more than 99 mg of potassium to carry a warning, because potassium salts in certain medicines have been linked to injuries in the small intestine (same source). Mt. Angel Vitamins sells a [99 mg potassium citrate capsule](https://mtangelvitamins.com/products/potassium-99mg-citrate-complex?utm_source=learn_hub&utm_medium=content&utm_campaign=blog_post&utm_content=history-of-potassium-from-ash-to-supplement) for about 27 cents a day (live price checked October 22, 2026). Each one-capsule serving lists 99 mg of potassium from potassium citrate. Mineral dose warnings have their own history, and the [iron supplements post](/blog/history/history-of-iron-supplements-and-the-ferritin-test) covers who gets poisoned by iron tablets and why. ## Food, citrate and chloride Fruits and vegetables carry potassium with partners such as phosphate, sulfate and citrate, not chloride, which is the form used in salt substitutes and some supplements (same source). NHANES 2013 to 2014 data, cited by the NIH, show that 12 percent of people aged 2 and older use a supplement containing potassium, and users add a mean of only 87 mg a day to total intake (same source). Food still carries most of the load. For the other mineral many readers compare with potassium, see the [magnesium monograph](/ingredients/magnesium). ## Next reads - [Magnesium: the ingredient monograph](/ingredients/magnesium): the mineral reference page for anyone comparing potassium with magnesium. - [Folate and folic acid, from 1930s Bombay to fortified bread](/blog/history/history-of-folate-from-lucy-wills-to-fortified-bread): another nutrient that moved from a clinical finding into a food fortification program. ### Related reading - [magnesium from Epsom salt to an essential mineral](/blog/history/history-of-magnesium-from-epsom-salt-to-essential-mineral)