Magnesium Oxide vs. Glycinate: The Truth About Bioavailability


Magnesium is an indispensable mineral that plays a vital role in over 300 biochemical reactions within our bodies. It is responsible for supporting nerve and muscle function, maintaining a steady heartbeat, regulating blood sugar levels, and assisting in the production of protein, bone, and DNA. Unfortunately, many individuals fail to meet their daily magnesium requirements through diet alone. As a result, various forms of magnesium supplements have emerged to bridge this gap. Two commonly encountered forms are magnesium oxide and magnesium glycinate. But which is the superior option and why?

Understanding Bioavailability and Its Significance

Bioavailability refers to the extent to which a substance is absorbed by the body and utilized for its intended purpose. In the context of magnesium supplements, higher bioavailability equates to greater absorption and, subsequently, more favorable outcomes. Conversely, lower bioavailability can result in diminished effectiveness and wasted resources. Therefore, it is pivotal to select a magnesium supplement with high bioavailability to maximize the benefits.

The Lowdown on Magnesium Oxide

Magnesium oxide is a form of magnesium often employed in supplements due to its affordability and high elemental magnesium content. However, it suffers from a significant drawback: poor bioavailability, with only about 4% being absorbed by the body. This limited absorption can be attributed to its low solubility in water, which hinders effective absorption. In essence, while magnesium oxide may appear cost-effective, its low bioavailability may hinder desired results.

Exploring Magnesium Glycinate

Magnesium glycinate is a compound formed by combining magnesium with the amino acid glycine. This particular magnesium form enjoys high bioavailability and exerts a gentle effect on the digestive system. Unlike other magnesium forms, magnesium glycinate is less likely to cause gastrointestinal side effects, making it an appealing choice for individuals with sensitive stomachs or bowel issues. Furthermore, the inclusion of glycine in magnesium glycinate may yield additional benefits, such as promoting relaxation and supporting a healthy sleep cycle.

Unveiling the Distinctions Between Magnesium Oxide and Glycinate

The primary disparity between magnesium oxide and magnesium glycinate lies in their molecular composition and, most importantly, their bioavailability. As previously mentioned, magnesium oxide boasts a paltry absorption rate of approximately 4%, while magnesium glycinate demonstrates substantially higher absorption levels, rendering it a more effective form for elevating magnesium levels within the body. Clinical studies and scientific evidence consistently reinforce the assertion that magnesium oxide is an inferior magnesium form. For instance, one study indicated that magnesium oxide exhibited a fractional absorption rate of only 4%, while magnesium glycinate showcased a fractional absorption rate of 18.8%. Another study revealed that magnesium oxide’s bioavailability was significantly lower than that of magnesium citrate, a magnesium form renowned for its greater bioavailability.

Clinical studies and scientific evidence consistently support the notion that magnesium oxide is suboptimal in terms of bioavailability.

The meager bioavailability of magnesium oxide can compromise its efficacy in addressing magnesium deficiencies and providing the associated health benefits. Conversely, magnesium glycinate’s high bioavailability ensures a greater magnesium absorption rate, thereby offering the full range of benefits associated with this essential mineral.


In conclusion, although magnesium oxide may appear attractive due to its affordability and high elemental magnesium content, its subpar bioavailability diminishes its effectiveness. On the other hand, magnesium glycinate, with its superior bioavailability and added advantages stemming from glycine, represents a far superior option for individuals seeking to rectify magnesium deficiencies and enhance their overall well-being.

Related Articles

Back to top button