How much magnesium the body absorbs when we take a supplement depends on the form (ie complex) the magnesium is delivered in (think glycinate, oxide, etc), but also on our internal magnesium levels or status. Someone who is deficient in magnesium (has a blood serum level below 0.75mmol/L) will generally absorb more of the mineral than someone who is not.
Infusing a bit more nuance into assessing magnesium levels in the body, Ferira shares that “some health professionals, especially those with a functional or integrative approach, choose to assess magnesium status with red blood cell (RBC) levels rather than plasma or serum due to the higher magnesium content in red blood cells, but even that test has its challenges in capturing the state of magnesium status throughout the body.”
It is a complex mineral. Used for over 300 essential cellular pathways in the body, it’s no wonder we benefit from a sufficient supply of magnesium on a daily basis. “Your body is constantly consuming magnesium and the amount it stores is regulated,” Registered Dietitian Tracey Frimpong, RD, he tells mbg. On average, he adds, about 40% of the magnesium we consume is absorbed in the upper GI tractwhile 5% is absorbed further down the large intestine (ie colon).
One of the reasons it can be challenging to accurately measure magnesium levels in the blood is because of where it is preferentially concentrated in the body. “Curiously, 99% of the ore it is found in our bones (about 50 to 60%), while the rest is found in the muscles and other soft tissues,” explains Ferira.
This ongoing process of absorption and utilization is quite rapid, so it’s important to make sure you’re always giving your body the magnesium it needs. “Most magnesium will stay in the body for 12 to 24 hours. So it’s not something you can take once, see results, and then not take again,” explains the registered dietitian. Amanda Li, RD
This means that if you’re looking to meet your nutritional needs through rich dietary sources (such as green leafy vegetables, legumes, nuts, seeds, and whole grains) and high-quality supplements, you’ll want to take advantage of that magnesium supplement. at least once a day.
Although the exact rate will depend on what form you’re taking, whether it’s magnesium bisglycinate, citrate, chloride, etc., or even a multivitamin contains magnesium, and what you are taking it for.
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