Mind & Body

These Are the Elements That Make Up the Human Body — And What They Do

Take a peek at the periodic table of elements and then look at your body. Every ingredient within you can be found on that chart. But do you actually know what, say, sulfur does in your body? How about magnesium? Potassium? Apart from a daily multivitamin or sprinkling some sodium chloride on your eggs, how much contact do you have with the elements?

The human body is made up of 60 chemical elements, but as it turns out, the vast majority of your body (nearly 96 percent!) is made up of just four elements: oxygen, carbon, hydrogen, and nitrogen — and a lot of that comes in the form of water. The remaining 4 percent is just a smattering of other members of the periodic table.

Oxygen: 65 Percent

You've got a lot of this one. Oxygen makes up a whopping 65 percent of the human body by weight. But that doesn't mean you're just full of air. Most of the oxygen in your body is bound to hydrogen in the form of water. You've heard it before, but it's true that the human body is around 60 percent water, and that's most of your oxygen. That water is more than weight — it helps the body to regulate temperature and osmotic pressure.

Oxygen is mostly found in your lungs and blood. That's because oxygen is a central element in aerobic cellular respiration, where the mitochondria in your cells use oxygen to break down glucose (sugar) and produce adenosine triphosphate, also known as ATP. ATP is the molecule that transports energy from food to other cellular processes in your body.

Oxygen oxidizes, and most of the time, that's a good thing. But too much oxygen can cause oxidative damage to cells and tissues.

Carbon: 18 Percent

Carbon is a distant second to oxygen in the elements race. It makes up 18 percent of your body. Carbon is said to be "synonymous with life" because its four bonding sites allow the building of long, sinewy molecule chains. These are known as organic molecules and include things like carbohydrates, lipids (aka fats), proteins, and nucleic acids (which make up DNA and RNA). There's a reason that astronomers get excited when they find organic molecules on distant planets — these carbon-based molecules are a building block of life.

Hydrogen: 10 Percent

Hydrogen is the most common element in the universe, but in the human body, it only takes third place — it makes up 10 percent of you. You probably know that every molecule of water (H2O) has two hydrogen atoms and one oxygen atom. It follows, then, that if oxygen is the most plentiful element in the human body and most of that oxygen is in the form of water, so is most of the body's hydrogen. Perhaps the coolest role hydrogen plays in the body is in DNA: hydrogen bonds are what give DNA its double-helix shape.

Nitrogen: 3 Percent

The air around you is about 78 percent nitrogen, so technically, your nitrogen levels fluctuate with every breath. But that nitrogen doesn't stick around — the bit that you do have comes from your food. That nitrogen is mostly found bonded to other elements in organic molecules, but it makes up just 3 percent of the human body on its own. Nitrogen pops up in amino acids, which build peptides and proteins, and in nucleic acids, which make up DNA and RNA.

... And the Other 4 Percent?

The rest of the body is mostly made up of calcium, phosphorus, potassium, sulfur, sodium, chlorine, and magnesium. Those elements keep muscles working, build proteins, and aid digestion, among other things. They may be small, but those elements are mighty.

But that's not all. Here are the elements that make up less than 0.01 percent of the human body, known as trace elements: boron, cadmium, chromium, cobalt, copper, fluorine, iodine, iron, manganese, molybdenum, selenium, silicon, tin, vanadium, and zinc. There's still more, but those remaining elements make up even less of you. Still, just because they're trace doesn't mean they're unimportant — while some of their functions are still a mystery, many of them are absolutely essential to your survival. From gallons of water to the tiniest particles of gold, every ingredient in your body helps to make you, you.

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Learn even more about what makes you tick in "The Story of the Human Body: Evolution, Health, and Disease" by Daniel Lieberman. We handpick reading recommendations we think you may like. If you choose to make a purchase, Curiosity will get a share of the sale.

Written by Kelsey Donk October 4, 2019

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