Magnesium comes up often enough that most of us already know the basics: it is an essential mineral, a macromineral at that, and it is good for us. What is less clear is what it actually does all day — and where this quiet natural treasure is hiding on our plates.

A young Black woman sitting on the floor by a window, stretching gently on waking in the morning light
Squares of dark chocolate, cocoa beans and cocoa nibs on a linen cloth
Dark chocolate, a concentrated source of magnesium
A young East Asian woman filling a tote bag with lentils at an open-air market stall

Magnesium has a great deal going for it. To begin with, it contributes to normal psychological function, and it does not stop there. It is also involved in normal nerve and muscle function, and it plays a part in bowel function, the cardiovascular system and the way cells use sugar. A magnesium deficiency is sometimes associated with disorders of carbohydrate metabolism, but the direct link with weight gain remains complicated and cannot be reduced to that one mechanism.

You will have gathered that magnesium is precious. Falling short of it can genuinely affect the body, which needs it every single day.

So let's talk about those needs. How much magnesium we require depends on age and sex, and the reference figures vary from one expert body to another. To avoid guesswork, it is best to follow current official guidance: in the UK, NHS advice on vitamins and minerals, and the European Food Safety Authority's (EFSA) dietary reference values, which set out appropriate intakes for each age group and situation. If you are pregnant, breastfeeding, living with a chronic illness, an older adult, or asking on behalf of a child, get medical advice first.

Where do we find magnesium, then? Our bodies cannot make this mineral, so it has to come from what we eat. The ideal is a balanced diet, bearing in mind that some foods are particularly rich in it: unsweetened cocoa is a notable source, and nuts and dried fruit are good sources too, as are cheese, wholemeal bread, shellfish and bananas.

A mug of hot chocolate made with unsweetened cocoa, a concentrated source of magnesium
Unsweetened cocoa, a concentrated hit of magnesium to savour hot

It is worth knowing that a proportion of the population does not reach the recommended intakes of magnesium, but only a medical assessment can establish a deficiency. Over time, insufficient intake can have consequences for health, but it is up to a health professional to judge whether that is the case and how significant it is. Some non-specific signs can accompany a magnesium deficiency: cramps, palpitations, dizziness, nervousness, anxiety, fatigue, tingling in the hands and feet, constipation or diarrhoea. On their own they cannot diagnose a lack of magnesium — for more information, or to have your levels checked, speak to your GP.

Magnesium takes part in many of the body's functions: current evidence suggests it contributes to normal psychological function and normal muscle function. Beyond that, a balanced diet remains the foundation, and if in doubt it is better to ask a doctor. Magnesium is an essential mineral (a macromineral), meaning it is present in the body in relatively large quantities and yet is indispensable to human, animal and plant life. Every essential mineral has its own precise job, bringing its own set of benefits and keeping the body's biological machinery running as it should.

Cramps, tiredness, nervousness: these signs are common and can have plenty of other causes besides low magnesium. Only a health professional can weigh them up, and that goes double if you are on medication or living with a chronic condition — long-term supplementation is not something to start without their advice.

A young mixed-heritage woman at her kitchen table with an unlabelled bottle of supplements and a glass of water

Cost

On the money side, food is often the most economical option: unsweetened cocoa, nuts, pulses and wholegrains deliver a lot of magnesium for a few pounds. If you opt for a supplement, sold in pharmacies, chemists and health food shops, budget somewhere in the region of £5 to £20 for a month's supply, depending on the form of magnesium and the pack size.

Food supplements do not replace a varied, balanced diet and a healthy lifestyle.