If a magnesium supplement has ever sent you running for the bathroom, you are not imagining it. The form of magnesium makes a real difference to how gentle it is on the stomach. Here is what is going on and which forms tend to be the most comfortable.
Why some magnesium upsets the stomach
The key is absorption. When a magnesium form is poorly absorbed in the small intestine, more of it travels onward to the bowel, where it draws in water and can have a laxative effect. So the forms most associated with loose stools are generally the ones that are absorbed least efficiently. Better-absorbed forms leave less magnesium behind to cause that effect.
What the absorption research shows
According to a bioavailability study retrieved from PubMed comparing commercial magnesium preparations, magnesium oxide showed relatively poor bioavailability, with a fractional absorption of only around 4 percent, while several other salts were absorbed substantially better (Firoz & Graber, 2001, PubMed). That poorly-absorbed oxide form is exactly the kind that leaves more magnesium in the gut. It is also, unfortunately, one of the cheapest and most common forms in budget supplements.
The gentler forms
Generally speaking, the better-absorbed organic forms tend to be gentler on the stomach because less magnesium is left to reach the bowel. Magnesium glycinate (magnesium bound to the amino acid glycine) is widely regarded as one of the gentlest, which is a big part of why it is popular for evening and everyday use. We compare it directly with another common form in magnesium glycinate vs citrate.
Practical tips for comfort
Beyond choosing a well-absorbed form, a few simple habits help: take magnesium with food, start with a sensible dose rather than a large one, and split the dose across the day if you take a higher amount. Individual tolerance varies, so a little experimentation within sensible limits is reasonable.
What magnesium is authorised to support
Magnesium carries several authorised UK and EU health claims, including contributions to normal muscle function, the reduction of tiredness and fatigue, normal functioning of the nervous system, and normal psychological function. These recognised functions apply regardless of form, which is why getting a form you can take comfortably and consistently matters.
How our magnesium is formulated
Our Magnesium is built around well-absorbed forms including magnesium glycinate, chosen specifically for comfort and consistent daily use. We explain the formula in what is a 3-in-1 magnesium supplement.
The takeaway
The gentlest magnesium is generally a well-absorbed form, because poorly absorbed forms (like magnesium oxide) leave more magnesium in the bowel, where it can have a laxative effect. Magnesium glycinate is widely considered one of the gentlest. Taking it with food and at a sensible dose helps further.
Sources retrieved from PubMed; see linked reference above. This article is for general information, not medical advice. Food supplements should not be used as a substitute for a varied, balanced diet and a healthy lifestyle. If you are pregnant, breastfeeding, taking medication or managing a medical condition, speak to your GP or pharmacist before starting a new supplement. Signed, Dr. Miron, Founder of Pure Vitamins UK.
