Magnesium is one of the most abundant minerals in the human body, yet deficiency is quietly common across Australia. It sits behind muscle contraction, nerve signalling, energy production, and bone formation. Without enough of it, the body starts to show the strain in ways that are easy to misread: disrupted sleep, muscle cramps, low energy, and a poor stress response. Many Australians chalk these up to busy lives rather than a fixable nutritional gap.
What magnesium actually does in the body
The body uses magnesium in more than 300 enzymatic reactions. That figure isn't an abstraction. It means magnesium is directly involved in how your cells generate energy, how your muscles relax after contracting, and how your DNA is synthesised and repaired. The heart muscle depends on magnesium to maintain a steady rhythm. Bones hold roughly 60 per cent of the body's total magnesium, with most of the rest stored in muscle tissue.
Magnesium also plays a role in regulating cortisol, the hormone your body releases under pressure. When magnesium levels drop, the body's stress response tends to become more reactive. If you've read about what cortisol does to your body, you'll understand why keeping that system well-regulated matters for long-term health. Low magnesium doesn't cause cortisol to spike on its own, but it removes one of the mechanisms that helps buffer the response.
Sleep is another area where magnesium has a documented effect. The mineral activates receptors in the brain that support the nervous system's ability to wind down. It's one reason why low magnesium is frequently linked to insomnia and poor sleep quality, and why sleep hygiene interventions sometimes produce limited results when an underlying deficiency is present.
Why deficiency is so common
Australia's soils have been under sustained agricultural pressure for decades. Intensive farming strips topsoil of minerals, and magnesium is among the first to go. This means leafy greens, nuts, and whole grains grown in depleted soils contain less magnesium than the same foods grown a generation ago. You can eat a textbook diet and still fall short.
Processing makes it worse. Refining wheat into white flour removes around 80 per cent of its magnesium. Boiling vegetables leaches the mineral into the cooking water. Alcohol and high doses of caffeine both increase urinary excretion of magnesium. Together, these factors mean that even people with reasonable diets are often running below optimal levels.
The Australian Government's Healthdirect resource on minerals lists magnesium as essential and notes that the recommended daily intake sits at 320 milligrams for adult women and 420 milligrams for adult men. Most Australians don't consistently hit those numbers through food alone.
Signs you might not be getting enough
Deficiency rarely announces itself clearly. The symptoms overlap with fatigue, overwork, and poor sleep, which is exactly why it goes unnoticed. The most common signs include muscle cramps, particularly in the legs at night, persistent tiredness, difficulty concentrating, irritability, and headaches. Constipation is also associated with low magnesium, since the mineral plays a role in bowel motility.
A blood test can check serum magnesium, but it's an imperfect measure. The body prioritises keeping blood levels stable by drawing magnesium from bone and muscle, so serum levels can appear normal even when tissue stores are depleted. If symptoms are present and diet is poor, a clinician will often consider deficiency regardless of what the blood test shows.
Where to find magnesium in food
The richest dietary sources are relatively accessible. Dark leafy greens like spinach and silverbeet are high in magnesium. So are pumpkin seeds (one of the most concentrated food sources at around 150 milligrams per 30-gram serving), almonds, cashews, black beans, edamame, and whole grains like brown rice and oats. Dark chocolate with a high cocoa content also contributes meaningfully.
Variety matters more than any single food. Relying on one source creates a ceiling. A diet that rotates nuts, legumes, leafy greens, and whole grains across the week gives the body consistent exposure. Cooking methods matter too: steaming vegetables rather than boiling them, and choosing minimally processed grains over refined alternatives, preserves more of the mineral content.
Should you take a supplement?
Supplements can correct a genuine deficiency, but the form of magnesium matters. Magnesium oxide is cheap and widely available, but the body absorbs it poorly, only around 4 per cent of the dose. Magnesium glycinate and magnesium citrate absorb much better and are gentler on the digestive system. Magnesium malate is preferred by some practitioners for fatigue-related presentations. High doses of any form can cause loose stools, so starting low and building gradually is the sensible approach.
Anyone taking prescription medications should check with a GP or pharmacist before supplementing. Magnesium can interact with certain antibiotics and medications for osteoporosis or type 2 diabetes by affecting how quickly they're absorbed.
Magnesium and long-term health
Population studies consistently find that higher dietary magnesium intake is associated with lower rates of type 2 diabetes, hypertension, and cardiovascular disease. These are associations, not proof of direct causation. But the mechanisms are plausible: magnesium improves insulin sensitivity, relaxes blood vessel walls, and reduces inflammatory markers. A 2021 meta-analysis published in the European Journal of Nutrition found that each 100-milligram increase in dietary magnesium intake was associated with a 7 per cent lower risk of type 2 diabetes.
Bone health is the other long-term consideration. Most people focus on calcium and vitamin D for bone density, but magnesium is equally necessary. It converts vitamin D into its active form, and without adequate magnesium, vitamin D supplementation works less effectively. The three nutrients are interdependent, not interchangeable.
Getting magnesium from food is the most reliable approach. Supplements fill gaps when diet falls short. Either way, it's a mineral worth paying closer attention to than most Australians currently do.