From sulphur to selenium, calcium to copper, here’s what your body’s made of – and why it matters

In my youth, I spent an unreasonable amount of time questioning why A-level chemistry was a prerequisite for medical school. Why was it as essential as biology? Why did I need to learn about electrons and entropy? The penny finally dropped when my rather brilliant teachers turned my attention towards the periodic table.

Every single atom in our bodies can be found in the periodic table – from chlorine to chromium, magnesium to manganese. In fact, just six elements make up about 98.5% of our body mass: 65% oxygen, 18% carbon, 10% hydrogen, 3% nitrogen, 1.5% calcium, and just over 1% phosphorus. The remaining 1.5% is made up of trace elements – potassium, sulphur, iron, zinc, copper, and many others – all of which play crucial roles in keeping us alive.

It might be more accurate to describe ourselves as oxygen-based life forms, rather than carbon-based.

The final 1% consists of trace elements. Though they’re present in smaller amounts, they’re no less essential. Many of them come from our diet, which is why we’re advised to balance our meals with sufficient vitamins and minerals.

But what exactly should we be eating to fulfil these requirements – and can you have too much of a good thing?

Calcium

Crucial for healthy bones and teeth, calcium is abundant in dairy products, nuts and leafy greens. It also plays a vital role in nerve and muscle function. When the body is deficient in calcium, numbness, muscle twitching and even seizures may ensue. Dietary supplementation with calcium or vitamin D, which aids calcium absorption, becomes necessary.

However, too much calcium can be just as harmful. In people with cancer, tuberculosis or an overactive parathyroid gland, levels can rise too high, causing kidney stones, depression and abnormal heart rhythms.

Phosphorus

Phosphorus – the same element used in the striking surface of matchboxes – is fundamental to life. It’s a key component of DNA, the blueprint of our being, and of adenosine triphosphate (ATP), the molecule that stores and delivers energy in cells.

Most of us get more than enough phosphorus through our diet – in meat, fish, dairy, grains and nuts. It’s also added as phosphate to many processed foods and fizzy drinks.

Magnesium

From the same periodic group as calcium, magnesium plays a role in muscle and nerve function, and contributes to bone health. You’ll find it in plant-based foods like beans and grains.

Magnesium supplements are widely available, but most people don’t need them. Some people are at a greater risk of magnesium deficiency, including those with chronic alcoholism or malabsorption disorders.

While toxicity from dietary sources is rare, excessive magnesium from supplements can lead to diarrhoea, nausea and, in severe cases, cardiac complications.

Sodium, potassium and chloride

Sodium and potassium share a role in electrical activity within neurons and muscle cells, including those in the heart. Sodium also regulates fluid balance within the body.

The body maintains these minerals within a tight range to ensure optimal function. Too much sodium or potassium can be extremely dangerous. In fact, the traditional lethal injection protocol in the US involved an intravenous dose of potassium to stop the heart.

Deficiencies of sodium and potassium can cause multiple symptoms, including muscle weakness, confusion and other neurological symptoms.

Dietary sources of potassium include bananas and potatoes. For sodium and chloride (the latter also being involved in fluid regulation and stomach acid production), the most familiar source is table salt. We do need some, but no more than 6g a day. High salt intake is linked to high blood pressure and cardiovascular disease.

Sulphur

The smell of sulphur (or more precisely, sulphur-containing compounds) will be familiar to anyone who remembers the acrid odour of school chemistry labs: think rotten eggs, overcooked cabbage and bad breath. Unsurprisingly, cabbage, garlic and onions are rich in sulphur.

Sulphur is found in certain amino acids (protein building blocks) and is essential for growth and development. A diet with lean protein and vegetables usually provides everything you need.

Trace minerals

So far, we’ve looked at macrominerals, those needed in larger quantities. But the trace minerals, needed in smaller amounts, are no less vital.

Take iron, crucial for the production of red blood cells, which carry oxygen throughout the body. Iron deficiency (common in children, menstruating women and people with restrictive diets) can cause anaemia, plus symptoms like fatigue, dizziness and shortness of breath. Iron is plentiful in red meat, legumes and green vegetables.

Other essential trace elements include zinc, which supports immune function, wound healing and cell growth and iodine, needed for the production of thyroid hormones, which both regulate metabolism. Selenium, rich in Brazil nuts, acts as an antioxidant and supports reproductive and thyroid health, while fluoride helps strengthen tooth enamel and prevent decay.

You’ll also find manganese, chromium and copper in the body, all playing key physiological roles. Manganese supports bone development and helps the body metabolise amino acids and carbohydrates. Chromium is involved in glucose regulation through enhancing insulin action. Copper has many varied roles, including iron metabolism, and the maintenance of healthy connective and nervous tissue.

You might even find trace amounts of arsenic, lead or gold in the body – and not just in dental work. These elements are not beneficial. They are toxic rather than therapeutic. Lead can accumulate in bones and organs, interfering with nervous system function. Arsenic, depending on the form, can be carcinogenic and disrupt cellular respiration – the process cells use to convert oxygen and nutrients into energy – essentially poisoning the cell’s energy supply.

So, the periodic table is not just a baffling grid of letters and numbers. It’s a map of you, and the body’s delicate balance between minerals that can be both essential in the right doses, and dangerous in the wrong amounts.