The elemental composition of the human body

I thought it’d be interesting to work out the composition of the elements that make up a human body.

If we assume the average human has a mass of 70 kilograms (kg) , the image below shows a rough breakdown of how much of each of the following elements they’d be comprised of.

You can see ‘the big 6’ elements are oxygen, carbon, hydrogen, nitrogen, calcium and phosphorus:

The composition of the human body by element

The composition of the human body by element

Of course, there are lot’s of elements making up the ‘others’ and although their mass is small, their presence is in most cases probably crucial to our existence. Here’s the mass present for each of the elements that are found in some form in our bodies and the roles some of these elements have:

  • oxygen (43 kg)
    Oxygen is used in cellular respiration and a constituent part of the water molecule. Water makes up some 60% of our bodies.
  • carbon (16 kg)
    Carbon is the basis of all organic molecules and essential to life as we know it.
  • hydrogen (7 kg)
    Like oxygen, hydrogen is found in water and in the majority of carbon-based organic molecules.
  • nitrogen (1.8 kg)
    A major component of all proteins and nucleic acids (which include DNA and RNA) that are essential to our bodies growth, repair and reproduction.
  • calcium (1.0 kg)
    Calcium keeps our bones and teeth healthy, and is involved in muscular contractions.
  • phosphorus (780 g)
    Essential to energy transfer in our bodies, phosphorus is also an essential constituent part of nucleic acids.
  • potassium (140 g)
  • sulphur (140 g)
    Sulphur is found in some of the essential amino acids and the vitamins thiamin (B1) and biotin (B7).
  • sodium (100 g)
  • chlorine (95 g)
  • magnesium (19 g)
    Found in some enzymes and has an important role in bone structure.
  • iron (4.2 g)
    Iron is found in hemoglobin, which helps transport oxygen around our bodies via our bloodstream. Like many metallic elements found in our body, it is also a part of many enzymes that assist in chemical reactions.
  • fluorine (2.6 g)
  • zinc (2.3 g)
    Zinc has some importance in sexual reproduction, and also some enzymes.
  • silicon (1.0 g)
  • rubidium (0.68 g)
  • strontium (0.32 g)
  • bromine (0.26 g)
  • lead (0.12 g)
  • copper (72 mg)
    Found in some enzymes.
  • aluminium (60 mg)
  • cadmium (50 mg)
  • cerium (40 mg)
  • barium (22 mg)
  • iodine (20 mg)
    Iodine is essential in the production of the hormone, thyroxine which plays an important role in the control of our metabolic rate.
  • tin (20 mg)
  • titanium (20 mg)
  • boron (18 mg)
  • nickel (15 mg)
  • selenium (15 mg)
  • chromium (14 mg)
    Chromium helps in the regulation of sugar levels.
  • manganese (12 mg)
  • arsenic (7 mg)
  • lithium (7 mg)
  • cesium  (6 mg)
  • mercury (6 mg)
  • germanium (5 mg)
  • molybdenum (5 mg)
    Found in some enzymes.
  • cobalt (3 mg)
    Cobalt is found in vitamin B12 which plays an important role in brain and nervous system function.
  • antimony (2 mg)
  • silver (2 mg)
  • niobium (1.5 mg)
  • zirconium (1 mg)
  • lanthanium (0.8 mg)
  • gallium (0.7 mg)
  • tellurium (0.7 mg)
  • yttrium (0.6 mg)
  • bismuth (0.5 mg)
  • thallium (0.5 mg)
  • indium (0.4 mg)
  • gold (0.2 mg)
  • scandium (0.2 mg)
  • tantalum (0.2 mg)
  • vanadium (0.11 mg)
  • thorium (0.1 mg)
  • uranium (0.1 mg)
  • samarium (50 µg)
  • beryllium (36 µg)
  • tungsten (20 µg)

The masses above are based on data from; Emsley, John, The Elements, 3rd ed., Clarendon Press, Oxford, 1998

About Derek Shirlaw

I'm passionate about science communication, social media, and my home country, Scotland. In particular, I have a real interest in astronomy, digital marketing, and the great outdoors.
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