Magnesium is the fourth most abundant mineral in the human body, essential for over 300 enzymatic reactions that regulate vital processes including energy production, muscle function, and bone health. Approximately 60% of the body's magnesium resides in bone tissue, with the remainder supporting muscles, soft tissues, and cellular functions. This mineral acts as a cofactor for DNA synthesis, cellular energy metabolism, and maintaining electrical gradients across cell membranes. Understanding what magnesium does for the body helps explain why deficiency can cause symptoms ranging from muscle cramps to fatigue. Whilst most people obtain sufficient magnesium through a balanced diet, certain populations may require supplementation under medical guidance.

What Does Magnesium Do for the Body

Magnesium is the fourth most abundant mineral in the human body and plays a fundamental role in maintaining health and wellbeing. This essential nutrient is involved in over 300 enzymatic reactions that regulate diverse biochemical processes, from energy production to protein synthesis. Approximately 60% of the body's magnesium is stored in bone tissue, with the remainder distributed in muscles, soft tissues, and bodily fluids.

The mineral acts as a cofactor for enzymes that facilitate critical cellular functions, including DNA and RNA synthesis, cellular energy metabolism, and the maintenance of electrical gradients across cell membranes. Without adequate magnesium, many of these processes cannot function optimally, potentially affecting multiple organ systems.

Magnesium's importance extends to cardiovascular health, nervous system function, muscle contraction and relaxation, bone mineralisation, and glucose metabolism. It works synergistically with other minerals such as calcium, potassium, and phosphorus to maintain physiological balance. The body cannot produce magnesium independently, making dietary intake essential for maintaining adequate levels.

Understanding magnesium's multifaceted roles helps explain why deficiency can manifest in various ways, from muscle cramps to fatigue. For most individuals, obtaining sufficient magnesium through a balanced diet is adequate, though certain populations may require additional supplementation under medical guidance. Magnesium supplements are available as licensed medicines for specific clinical indications and as food supplements for general health.

Essential Functions of Magnesium in Human Health

Energy Production and Metabolism

Magnesium is indispensable for cellular energy production through its role in adenosine triphosphate (ATP) metabolism. ATP, the body's primary energy currency, must bind to magnesium to become biologically active. The mineral facilitates the conversion of food into usable energy by activating enzymes involved in glycolysis and the citric acid cycle. This explains why magnesium deficiency often presents with fatigue and reduced exercise tolerance.

Cardiovascular and Muscle Function

The mineral plays a role in maintaining normal heart rhythm and vascular tone. Magnesium acts as a natural calcium channel blocker, helping to regulate the influx of calcium into cardiac and smooth muscle cells. This mechanism may contribute to blood pressure regulation and muscle contraction. In skeletal muscle, magnesium enables proper muscle relaxation following contraction, which is why deficiency commonly causes cramps and spasms.

Nervous System Regulation

Magnesium modulates neurotransmitter release and neuronal excitability, contributing to normal psychological function and stress response. It acts on N-methyl-D-aspartate (NMDA) receptors in the brain, helping to prevent excessive neuronal firing. Some research suggests a relationship between magnesium status and mood, though there is no established link between supplementation and treatment of mental health conditions.

Bone Health and Structural Support

Approximately 50–60% of the body's magnesium resides in bone tissue, where it influences bone matrix formation and affects the activities of osteoblasts and osteoclasts. Magnesium works alongside calcium and vitamin D to maintain bone density and structural integrity. It also influences parathyroid hormone secretion, which regulates calcium homeostasis. While magnesium is important for bone health, current NICE guidance on osteoporosis (NG226) focuses primarily on calcium and vitamin D rather than magnesium supplementation.

Signs Your Body May Need More Magnesium

Early Warning Signs

Magnesium deficiency, clinically termed hypomagnesaemia, often develops gradually with subtle initial symptoms. Early indicators include persistent fatigue, weakness, and reduced appetite. Many individuals experience muscle twitches, cramps, or spasms, particularly in the legs during night-time. These symptoms occur because magnesium deficiency increases neuromuscular excitability, causing involuntary muscle contractions.

Other early signs may include:

• Persistent eyelid twitching (myokymia)

• Generalised muscle tension or stiffness

• Difficulty sleeping

• Mild mood changes or increased irritability

• Reduced exercise tolerance

Progressive Symptoms

As deficiency becomes more pronounced, symptoms may intensify and affect multiple systems. Cardiovascular manifestations can include palpitations, irregular heartbeat, or chest discomfort. Neurological symptoms may progress to numbness, tingling sensations (paraesthesia), or heightened sensitivity to sensory stimuli. Some individuals report increased headache frequency, though a definitive causal relationship between magnesium deficiency and all headache types has not been established.

When to Seek Medical Advice

Certain symptoms warrant prompt medical evaluation. Contact your GP if you experience persistent muscle cramps unresponsive to simple measures, unexplained fatigue lasting several weeks, or cardiac symptoms such as palpitations or chest pain. Call 999 immediately for severe chest pain, seizures, or severe palpitations with dizziness or fainting. For urgent concerns, contact NHS 111.

Risk factors for deficiency include chronic gastrointestinal conditions (Crohn's disease, coeliac disease), type 2 diabetes, long-term use of proton pump inhibitors, thiazide or loop diuretics (such as furosemide), aminoglycoside antibiotics, and alcohol misuse. Older adults and individuals with malabsorption disorders face increased risk. If you have these risk factors and experience suggestive symptoms, discuss magnesium status assessment with your healthcare provider. Diagnosis typically involves serum magnesium measurement, though this may not always reflect total body stores accurately. Hypomagnesaemia often occurs alongside low potassium and calcium levels, requiring comprehensive clinical assessment.

Daily Magnesium Requirements and Food Sources

Recommended Daily Intake

The UK Department of Health establishes Reference Nutrient Intakes (RNIs) for magnesium based on age and gender. Adult men require approximately 300 mg daily, whilst adult women need around 270 mg daily. Requirements during pregnancy remain at 270 mg daily, increasing to 300 mg during lactation. Adolescents have varying requirements: boys aged 15-18 years need 300 mg daily, whilst girls of the same age require 270 mg. Children aged 11-14 years need 280 mg (boys) and 280 mg (girls) daily.

These recommendations assume normal gastrointestinal absorption and kidney function. Individuals with certain medical conditions or taking specific medications may require adjusted intakes under medical supervision.

Magnesium-Rich Food Sources

A varied, balanced diet typically provides adequate magnesium for most people. Excellent dietary sources include:

• Green leafy vegetables: Spinach, kale, Swiss chard (magnesium is central to the chlorophyll molecule)

• Nuts and seeds: Almonds, cashews, pumpkin seeds, sunflower seeds (approximately 80mg in 30g almonds)

• Whole grains: Brown rice, wholemeal bread, oats, quinoa

• Legumes: Black beans, chickpeas, lentils, kidney beans

• Fish: Mackerel, salmon, halibut

• Dark chocolate: 70–85% cocoa content (approximately 95mg in 50g)

• Avocados: One medium avocado contains approximately 58mg

These values are approximate and may vary by product and preparation method.

Optimising Absorption

Magnesium bioavailability varies depending on food source and individual factors. Organic forms found in plant foods are generally well absorbed. However, phytates in whole grains and legumes can reduce absorption, though this effect is typically modest in balanced diets. Magnesium and vitamin D have a bidirectional relationship, with each affecting the metabolism and function of the other.

Food processing and refining significantly reduce magnesium content. White flour contains approximately 80% less magnesium than wholemeal flour, and white rice contains substantially less than brown rice. Choosing minimally processed whole foods maximises magnesium intake. Cooking methods have minimal impact on magnesium content, as the mineral is relatively heat-stable, though boiling vegetables in large volumes of water may cause some leaching into cooking liquid.

When to Consider Magnesium Supplements

Clinical Indications for Supplementation

Whilst dietary sources should be the primary means of obtaining magnesium, supplementation may be appropriate in specific circumstances. Healthcare professionals may recommend supplements for documented deficiency or for individuals with chronic gastrointestinal disorders affecting absorption, such as Crohn's disease or coeliac disease, or those with type 2 diabetes who often exhibit lower magnesium levels.

Long-term use of certain medications can deplete magnesium stores. Proton pump inhibitors (omeprazole, lansoprazole), thiazide and loop diuretics (furosemide), and some antibiotics may warrant monitoring and potential supplementation. The MHRA has issued Drug Safety Updates regarding the risk of hypomagnesaemia with long-term PPI use. Older adults face increased risk due to reduced dietary intake, decreased absorption, and increased urinary losses.

Types of Magnesium Supplements

Various magnesium formulations exist, with differing bioavailability and tolerability profiles:

• Magnesium citrate: Well absorbed, commonly used for general supplementation

• Magnesium glycinate: Highly bioavailable, less likely to cause gastrointestinal upset

• Magnesium oxide: Lower bioavailability but higher elemental magnesium content, often used as a laxative

• Magnesium chloride: Available in oral forms

Topical magnesium products (oils, sprays, bath salts) are available, but evidence for significant systemic absorption through the skin is limited. These products are not licensed medicines for treating deficiency.

Safety Considerations and Interactions

Magnesium supplements are generally well tolerated at recommended doses, though gastrointestinal side effects (diarrhoea, nausea, abdominal cramping) can occur, particularly with magnesium oxide. UK guidance indicates that supplemental magnesium up to 400 mg daily (in addition to dietary intake) is unlikely to cause harm in adults with normal kidney function.

Important contraindications and interactions include:

• Severe renal impairment (risk of hypermagnesaemia)

• Myasthenia gravis (may worsen muscle weakness)

• Heart block or severe cardiac conduction disorders

• Interactions with medications: separate magnesium supplements from levothyroxine, bisphosphonates, and quinolone/tetracycline antibiotics by at least 2-3 hours

If you experience side effects from magnesium supplements, report them through the MHRA Yellow Card Scheme.

When to Consult Healthcare Professionals

Always consult your GP or pharmacist before starting magnesium supplements, particularly if you have existing medical conditions, take regular medications, or are pregnant or breastfeeding. Self-diagnosis of magnesium deficiency is unreliable; proper assessment requires clinical evaluation and potentially laboratory testing. If you experience persistent symptoms suggestive of deficiency despite adequate dietary intake, seek medical advice rather than self-treating. Your healthcare provider can determine whether supplementation is appropriate, recommend suitable formulations and dosages, and monitor for potential adverse effects or interactions.

Frequently Asked Questions