Magnesium Supplementation: The Importance of Chemical Form and Bioavailability

When selecting magnesium supplements, the chemical form is often more critical than the total milligram dosage listed on the label. While many products display the amount of elemental magnesium, the bioavailability—the rate and extent to which the nutrient is absorbed by the body—varies significantly depending on the compound used.

Magnesium oxide is a common, inexpensive form that offers high elemental content but possesses low bioavailability, with absorption estimates around 4 percent. In contrast, forms such as magnesium citrate, bisglycinate, and magnesium glycinate are noted for higher solubility and better absorption. Magnesium glycinate, specifically, uses glycine chelation to create a highly absorbable complex that may also reduce gastrointestinal discomfort.

Different delivery methods also impact intake. Ready-to-drink cans typically provide 100mg to 180mg per serving, while powders can offer between 148mg and 375mg. Consumers are advised to distinguish between the total weight of a compound and the actual amount of elemental magnesium it contains, as a portion of the weight in compounds like magnesium bisglycinate is attributed to the glycine molecule.