Magnesium citrate is a manufactured compound, not something mined from the earth or extracted from a single natural source. It’s created by combining two ingredients: a magnesium source (typically magnesium carbonate or magnesium oxide) and citric acid. The reaction between these two raw materials produces the finished salt you find in supplements and laxative preparations. Both starting ingredients, however, trace back to distinctly different origins in nature.
The Two Raw Ingredients
Magnesium citrate is the product of a straightforward acid-base reaction. When citric acid is dissolved in water and a magnesium compound like magnesium carbonate is added, the mixture fizzes as carbon dioxide escapes, and what remains is magnesium citrate in solution. Once the water is removed through crystallization or spray drying, you get the powder used in tablets, capsules, and liquid preparations.
The magnesium half and the citric acid half come from completely different supply chains, and each has its own story.
Where the Magnesium Comes From
The magnesium used in supplement manufacturing starts as a simple inorganic compound, most often magnesium carbonate or magnesium oxide. These compounds are derived from mineral deposits, brine pools, or seawater. In the United States, seawater and natural brines accounted for about 64% of magnesium compound production in 2021. Companies in California and Delaware recover magnesium oxide from seawater, while operations in Michigan pull it from underground well brines and facilities in Utah harvest it from the Great Salt Lake.
The process for extracting magnesium from seawater works because magnesium is the third most abundant dissolved element in ocean water. Manufacturers add a base to the water, which causes magnesium hydroxide to precipitate out as a solid. That solid is then filtered, dried, and converted into magnesium oxide or carbonate for industrial use.
On the mining side, a mineral called magnesite (a naturally occurring form of magnesium carbonate) is another source. One company in Nevada mines magnesite directly. Globally, identified magnesite resources total around 13 billion tons, with additional billions of tons available in dolomite, evaporite minerals, and brine deposits. Some newer operations are even exploring ways to recover magnesium from coal fly ash and old asbestos mine tailings.
Where the Citric Acid Comes From
The citric acid half of the equation has a surprisingly biological origin. While citric acid occurs naturally in citrus fruits, virtually all of the citric acid produced industrially today comes from microbial fermentation. A fungus called Aspergillus niger, a common black mold, is the workhorse of the citric acid industry. The fungus is fed a sugar source, often molasses or corn-derived glucose, and as it metabolizes those sugars, it produces citric acid as a byproduct.
This fermentation process has been the dominant production method for over a century. The citric acid is then purified, crystallized, and sold as a dry powder ready to be reacted with magnesium compounds.
How the Final Product Is Made
In an industrial setting, the two ingredients are combined in water. The citric acid dissolves first, then the magnesium source is added. The resulting solution contains dissolved magnesium citrate, which can be finished into a product through a couple of routes. Slow evaporation or cooling produces crystals of magnesium citrate nonahydrate (a form that holds water molecules in its crystal structure). Spray drying, where the solution is blasted through hot air as a fine mist, produces anhydrous magnesium citrate powder without the bound water.
The finished powder must meet pharmaceutical purity standards before it can be sold as a supplement or medication. U.S. Pharmacopeia guidelines set strict limits on contaminant metals: arsenic must stay below 1.5 parts per million, lead below 1 part per million, and cadmium below 0.5 parts per million, among others.
It Doesn’t Exist in Nature
Magnesium citrate is not found as a mineral or in food. Your body does encounter both magnesium and citric acid through diet. Magnesium is present in nuts, seeds, leafy greens, and whole grains. Citric acid is abundant in lemons, oranges, and other fruits. But these two compounds don’t naturally bond together into magnesium citrate in any meaningful quantity outside of a manufacturing process.
The reason manufacturers go through the trouble of creating this specific compound is absorption. Organic magnesium salts like citrate dissolve far more readily in the gut than inorganic forms like magnesium oxide. Studies comparing the two consistently show that magnesium citrate produces higher magnesium levels in both blood and urine after a single dose, indicating that more of it actually makes it into circulation. The tradeoff is that citrate delivers less elemental magnesium per gram of powder than oxide does, so the tablets or doses tend to be physically larger.
Environmental Considerations
The magnesium supply chain carries a notable environmental footnote. When magnesium metal is processed in its molten state, manufacturers have historically used sulfur hexafluoride (SF6) as a protective cover gas. SF6 has 23,500 times the global warming potential of carbon dioxide and persists in the atmosphere for roughly 1,000 years. In 2022, SF6 emissions from the U.S. magnesium industry were equivalent to 1.1 million metric tons of CO2. The industry has been working since 1999 to transition to alternative gases that break down more quickly, though this effort primarily affects magnesium metal production rather than the magnesium compounds used in supplements.
Seawater extraction, by contrast, is considered a relatively low-impact process since it draws on an essentially limitless source without traditional mining. Several newer projects around the world are focused on recovering magnesium from industrial waste products like mine tailings and coal ash, turning pollution cleanup into a raw material source.