Magnesium Forms Explained: Which One Actually Absorbs?
Magnesium is one of the most popular supplements in Estonia - and one of the most confusing to buy. Walk through any pharmacy or browse maxfit.ee and you will see oxide, citrate, malate, glycinate, bisglycinate, and "triple" blends. They are not interchangeable. The form on the label largely determines how much magnesium your body actually absorbs and what it feels like to take.
Why magnesium form matters
Magnesium supplements are always a magnesium salt - the mineral bound to another molecule. That partner molecule changes two things: bioavailability (how much crosses the gut wall) and tolerability (whether it upsets your stomach).
Magnesium oxide is the cheapest and most common form, but it is poorly absorbed. Studies estimate its bioavailability at roughly 4% under some conditions, far below organic forms (Schuchardt & Hahn, 2017). Worse, the unabsorbed magnesium draws water into the bowel - which is exactly why magnesium oxide is sold as a laxative. A high "elemental magnesium" number on an oxide label can be misleading if most of it passes straight through.
Organic forms - citrate, malate, glycinate - bind magnesium to an organic acid or amino acid. A classic randomized trial found magnesium citrate significantly more bioavailable than oxide (Walker et al., 2003). Schuchardt and Hahn's 2017 review concluded that organic magnesium compounds are generally better absorbed than inorganic ones, although the absolute differences are smaller than marketing suggests.
The main forms, compared
Magnesium malate binds magnesium to malic acid, a compound involved in cellular energy production. It is well absorbed and gentle on the stomach, and is often chosen by people who take magnesium during the day for muscle function and fatigue. MST Magnesium Malate 60caps offers this form in a convenient capsule, while OstroVit Magnesium Malate 120g Naturaalne is an unflavored powder for those who prefer to adjust their own dose.
Magnesium glycinate (bisglycinate) binds magnesium to the amino acid glycine. It is highly bioavailable, very gentle on digestion, and glycine itself has a mild calming effect - which is why glycinate is the form most often recommended for evening use and sleep support.
Magnesium citrate is well absorbed and moderately priced, but at higher doses it has a noticeable laxative effect.
Blended formulas combine several forms. OstroVit Triple Magnesium + B6 P-5-P 90caps pairs three magnesium sources with the active P-5-P form of vitamin B6, which supports magnesium's role in the nervous system. Blends aim to balance absorption, cost, and tolerability in one capsule.
You can browse all of these in the magnesium category at maxfit.ee.
How much magnesium do you need?
The recommended daily intake for adults is around 300-400 mg of elemental magnesium. Many Europeans fall short, and subclinical deficiency is common - DiNicolantonio et al. (2018) argued it is widespread enough to be a public health concern. Athletes lose magnesium through sweat and may have higher needs; a review by Zhang et al. (2017) noted that magnesium status can influence exercise performance, with the clearest benefits in people who were deficient to begin with.
Stress also matters. A systematic review by Boyle et al. (2017) found that magnesium supplementation may modestly reduce subjective anxiety in people prone to it - one reason demand for magnesium spikes during the dark Nordic winter.
Read the label for "elemental magnesium," not the total weight of the salt. A 1,000 mg magnesium glycinate capsule may provide only around 100-150 mg of actual magnesium.
Practical advice
- For daytime use, muscle cramps, and general supplementation: malate or citrate
- For evening use, sleep, and stress: glycinate
- Avoid relying on oxide alone unless you specifically want a laxative effect
- Split larger doses across the day to improve absorption and reduce digestive upset
- Take with food if any form bothers your stomach
Magnesium is safe for most people, but those with kidney disease should consult a doctor, since impaired kidneys cannot clear excess magnesium efficiently.
FAQ
Which magnesium form is best for sleep?
Magnesium glycinate is the usual recommendation for evening use. The glycine component has a mild calming effect, and the form is gentle enough not to disturb the night with digestive discomfort. Magnesium's role in the nervous system also supports relaxation (Boyle et al., 2017).
Why does magnesium sometimes cause loose stools?
Unabsorbed magnesium pulls water into the intestine. This is most pronounced with magnesium oxide and citrate at higher doses. Switching to a well-absorbed form like glycinate or malate, or splitting the dose, usually solves the problem (Schuchardt & Hahn, 2017).
Do athletes need more magnesium?
Possibly. Magnesium is lost in sweat, and low magnesium status has been linked to reduced exercise performance - though supplementation mainly helps those who are already deficient (Zhang et al., 2017). A varied diet plus a modest supplement covers most athletes.
References
- Boyle, N. B., Lawton, C., & Dye, L. (2017). The effects of magnesium supplementation on subjective anxiety and stress - a systematic review. Nutrients, 9(5), 429.
- DiNicolantonio, J. J., O'Keefe, J. H., & Wilson, W. (2018). Subclinical magnesium deficiency: a principal driver of cardiovascular disease and a public health crisis. Open Heart, 5(1), e000668.
- Schuchardt, J. P., & Hahn, A. (2017). Intestinal absorption and factors influencing bioavailability of magnesium - an update. Current Nutrition & Food Science, 13(4), 260-278.
- Walker, A. F., Marakis, G., Christie, S., & Byng, M. (2003). Mg citrate found more bioavailable than other Mg preparations in a randomised, double-blind study. Magnesium Research, 16(3), 183-191.
- Zhang, Y., Xun, P., Wang, R., Mao, L., & He, K. (2017). Can magnesium enhance exercise performance? Nutrients, 9(9), 946.
