Magnesium — the mineral involved in 300 processes that half the population isn't getting enough of
Magnesium deficiency is one of the most common and most underdiagnosed nutritional inadequacies in the developed world. Standard blood tests miss it almost entirely. Its effects span sleep, anxiety, blood pressure, insulin sensitivity and energy production.
nutrition
is the fourth most abundant cation in the human body and a cofactor in over 300 enzymatic reactions — including every step of ATP production, DNA replication and repair, synthesis, and the regulation of neuromuscular function. Without the Krebs cycle cannot operate efficiently, muscles cannot relax after contraction, and the electrical signalling that coordinates the heartbeat becomes unstable. It is not a supplementary mineral — it is a structural requirement for basic cellular function.
Estimating true deficiency is harder than it should be. Serum — the standard clinical test — reflects less than 1% of total body and is tightly regulated by the kidneys, remaining apparently normal even when intracellular stores are substantially depleted. Red blood cell and urinary after an oral load are more accurate measures but are rarely ordered. This means deficiency is consistently underdiagnosed in clinical settings, and prevalence estimates from serum testing significantly understate the actual burden.
Population studies using dietary intake data rather than serum levels consistently find that 45 to 60% of adults in Western countries consume less than the estimated average requirement. The primary reasons are the displacement of whole foods by refined foods — which strip during processing — and the decreasing content of soil and therefore crops over the past five decades due to intensive agricultural practices
is required to activate vitamin D — specifically to convert it to its active form, calcitriol, in the liver and kidneys. People supplementing vitamin D without adequate status may find that vitamin D levels rise but biological effects remain blunted. This interaction is particularly relevant given the widespread co-occurrence of low vitamin D and low in the same populations
regulates the NMDA receptor, the primary receptor for glutamate — the brain's main excitatory neurotransmitter. At physiological concentrations, blocks the NMDA receptor channel, preventing excessive glutamate signalling. Low reduces this blocking effect, leading to heightened neuronal excitability that manifests clinically as anxiety, irritability, hyperreactivity to sensory input and difficulty sleeping
deficiency disrupts ATP-sensitive channels in pancreatic beta cells, impairing insulin secretion. It also reduces insulin receptor sensitivity in peripheral tissues. Hypomagnesaemia is reported in 14 to 48% of people with type 2 diabetes, compared to 2.5 to 15% in the general population, and may further worsen hyperglycaemia and insulin resistance — creating a cycle where metabolic disease depletes and depletion worsens metabolic disease
promotes melatonin secretion and modulates GABA activity — the primary inhibitory neurotransmitter — which explains its role in sleep quality. A 2025 randomised controlled trial found that bisglycinate supplementation significantly improved sleep onset, sleep duration and subjective sleep quality in healthy adults with self-reported poor sleep, compared to placebo. Stress, alcohol and caffeine all deplete which may partly explain why these are also associated with poor sleep
The best dietary sources of are dark leafy greens — spinach and Swiss chard are among the richest sources — followed by pumpkin seeds, almonds, black beans, dark chocolate, avocado, whole grains and fatty fish. Notably, these are the foods most displaced by ultra-processed food consumption, which provides almost no while simultaneously increasing demand for it through the stress of processing refined
If supplementation is considered, form matters. oxide — the cheapest and most widely sold form — has poor bioavailability, typically 4% absorbed. citrate, glycinate and malate are substantially better absorbed and better tolerated. L-threonate is the only form demonstrated to cross the blood-brain barrier effectively and is the form studied specifically for neurological and sleep effects. The choice depends on what is being addressed — gut motility, muscle function, sleep, or neurological symptoms.