Magnesium: Why It Matters and How to Get Enough

Updated September 2026

Magnesium is involved in hundreds of processes in the body, including energy production, muscle and nerve function, blood glucose control and bone development. It's also one of the nutrients Australians most often fall short on.

How common is low magnesium intake in Australia?

National data from the Australian Bureau of Statistics found that around one in three Australians aged two and over (37% of males and 34% of females) did not meet their magnesium requirements from food. Shortfalls were most common in teenagers and older adults, with nearly two in three men aged 71 and over not meeting their needs.¹

Not meeting requirements from food isn't the same as a diagnosed deficiency, which only a doctor can assess. But it does mean many of us have room to improve.

What affects your magnesium intake and levels?

• Diet quality. Refining grains removes much of their magnesium, so diets built around white bread, pasta and packaged foods tend to be lower.
• Alcohol. Regular drinking increases the amount of magnesium lost through urine.
• Certain medications. Long term use of some reflux medications (proton pump inhibitors) and some diuretics can lower magnesium levels.
• Age. Absorption tends to fall and losses tend to rise as we get older.

Signs your intake might be low

Early signs are often vague: tiredness, weakness, muscle cramps or twitches and poor appetite. Because these overlap with many other issues, speak with your GP if they persist rather than self diagnosing.

How much magnesium do you need?

The Nutrient Reference Values for Australia and New Zealand set the Recommended Dietary Intake for adults at:²

• Men: 400 mg a day (19 to 30 years), 420 mg a day (31 years and over)
• Women: 310 mg a day (19 to 30 years), 320 mg a day (31 years and over)

For magnesium from supplements (not food), the upper level of intake for adults is 350 mg a day. Going above this is the most common cause of loose stools and stomach upset.²

Food first

Good food sources include pumpkin seeds, almonds and cashews, leafy greens such as spinach and silverbeet, legumes like black beans and chickpeas, wholegrains such as oats, quinoa and brown rice, dark chocolate and avocado.

Does the form of magnesium matter?

Yes. Magnesium in supplements is bound to different compounds, and some are absorbed better than others. In one study comparing common forms, magnesium oxide had a fractional absorption of just 4%, while magnesium chloride, lactate and aspartate were absorbed significantly better.³

• Magnesium oxide: inexpensive and common, but poorly absorbed. Often used for constipation.
• Magnesium citrate: well absorbed, with a mild laxative effect at higher doses.
• Magnesium glycinate (bisglycinate): magnesium bound to the amino acid glycine. Generally gentle on the stomach, which makes it a popular choice for daily use.
• Magnesium threonate: studied for brain health, but human research is still limited.

Magnesium and sleep

Magnesium plays a role in the nervous system and sleep regulation. In a small randomised, placebo controlled trial of 46 older adults with insomnia, 500 mg of magnesium daily for eight weeks improved sleep efficiency, sleep time and the time taken to fall asleep compared with placebo.⁴ It's a promising result, but the study was small and involved older adults, so it doesn't mean magnesium will improve sleep for everyone.

How to take it

• Stay within the 350 mg supplemental upper level unless your doctor advises otherwise.
• Taking it with food can reduce stomach upset.
• Many people take magnesium in the evening, though taking it consistently matters more than timing.
• If you have kidney disease or take regular medication, check with your GP or pharmacist first, as magnesium can interact with some medicines, including certain antibiotics and osteoporosis medications.

The bottom line

Magnesium isn't a cure all, but it's a foundational nutrient that many Australians don't get enough of from food. Start with magnesium rich whole foods, and if you use a supplement, choose a well absorbed form at a sensible dose.

Where Keeper fits: Keeper Complete Longevity includes 250 mg of magnesium as magnesium glycinate in each daily serve, alongside 17 other ingredients. Every batch is third party tested. See our testing standards.

References

1. Australian Bureau of Statistics. Australian Health Survey: Usual Nutrient Intakes, 2011 to 12.
2. NHMRC. Nutrient Reference Values for Australia and New Zealand: Magnesium.
3. Firoz M, Graber M. Bioavailability of US commercial magnesium preparations. Magnes Res. 2001.
4. Abbasi B et al. The effect of magnesium supplementation on primary insomnia in elderly. J Res Med Sci. 2012.

This article is general information only and isn't a substitute for advice from your healthcare professional.