Composition of the human body

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Not to be confused with Human anatomy.

The composition of the human body can be looked at from the point of view of either mass composition, or atomic composition. To illustrate both views, the human body is ~70% water, and water is ~11% hydrogen by mass but ~67% hydrogen by atomic percent.[citation needed] Thus, most of the mass of the human body is oxygen, but most of the atoms in the human body are hydrogen atoms. Both mass-composition and atomic composition figures are given below.

Almost 99% of the mass of the human body is made up of the six elements oxygen, carbon, hydrogen, nitrogen, calcium, and phosphorus. Only about 0.85% is composed of another five elements: potassium, sulfur, sodium, chlorine, and magnesium. All are necessary to life. The remaining elements are trace elements, of which more than a dozen are thought to be necessary for life, or play an active role in health (e.g., fluorine, which hardens dental enamel but seems to have no other function).

Not all elements which are found in the human body in trace quantities play a role in life. Some of these elements are thought to be simple bystander contaminants without function (examples: caesium, titanium), while many others are thought to be active toxins, depending on amount (cadmium, mercury, radioactives). The possible utility and toxicity of a few elements at levels normally found in the body (aluminum) is debated. Functions have been proposed for trace amounts of cadmium and lead, but these are almost certainly toxic in amounts normally found in the body. There is evidence that one element normally considered a toxin (arsenic) is essential in ultratrace quantities, even in mammals. Some elements that are clearly used in lower organisms and plants (arsenic, silicon, boron, nickel, vanadium) are probably needed by mammals also, but in far smaller doses. Two halogens used abundantly by lower organisms (fluorine and bromine) are presently known to be used by mammals only opportunistically. However, a general rule is that elements found in active biochemical use in lower organisms are often eventually found to be used in some way, by higher organisms.[citation needed]

Contents

Elemental composition [edit]

Main article: Dietary mineral

The average 70 kg adult human body contains approximately 6.7 x 1027 atoms and contains at least detectable traces of 60 chemical elements. About 24 or 25 of these elements are thought to play an active positive role in life and health in humans.[1]

The relative amounts of each element vary by individual, with the largest contributor due to fat/muscle/bone body composition ratio differences from person to person. The numbers in the table are averages of different numbers reported by different references.

The human body is ~65% water, and water is ~11% hydrogen by mass but ~67% hydrogen by atomic percent.

Atomic number Element Percent of Mass[2][3][4][5][6][7] Mass (kg)[8] Atomic percent Positive health role in mammals[9] Group
8 Oxygen 65 43 24 Yes (water, electron acceptor) /No (Reactive Oxygen Species) 16
6 Carbon 18 16 12 Yes (organic compounds are hydrocarbon derivatives) 14
1 Hydrogen 10 7 63 Yes (e.g. water) 1
7 Nitrogen 3 1.8 0.58 Yes (e.g. DNA and amino acids) 15
20 Calcium 1.4 1.0 0.24 Yes (e.g. Calmodulin and Hydroxylapatite in bones) 2
15 Phosphorus 1.1 0.78 0.14 Yes (e.g. DNA and phosphorylation) 15
19 Potassium 0.25 0.14 0.033 Yes (e.g. Na+/K+-ATPase) 1
16 Sulfur 0.25 0.14 0.038 Yes (e.g.Cysteine, Methionine, Biotin, Thiamine) 16
11 Sodium 0.15 0.10 0.037 Yes (e.g. Na+/K+-ATPase) 1
17 Chlorine 0.15 0.095 0.024 Yes (e.g. Cl-transporting ATPase) 17
12 Magnesium 0.05 0.019 0.0070 Yes (e.g. binding to ATP and other nucleotides) 2
26 Iron* 0.006 0.0042 0.00067 Yes (e.g. Hemoglobin, Cytochromes) 8
9 Fluorine 0.0037 0.0026 0.0012 Yes/No (topically hardens teeth; toxic in higher amounts) 17
30 Zinc 0.0032 0.0023 0.00031 Yes (e.g. Zinc finger proteins) 12
14 Silicon 0.002 0.0010 0.0058 Yes (probable) 14
37 Rubidium 0.00046 0.00068 0.000033 No (?) 1
38 Strontium 0.00046 0.00032 0.000033 No (?) 2
35 Bromine 0.00029 0.00026 0.000030 No (?) 17
82 Lead 0.00017 0.00012 0.0000045 No (?) (toxic in higher amounts) 14
29 Copper 0.0001 0.000072 0.0000104 Yes (e.g. copper proteins) 11
13 Aluminium 0.000087 0.000060 0.000015 No(?) (toxic?) 13
48 Cadmium 0.000072 0.000050 0.0000045 No(?) (toxic in higher amounts) 12
58 Cerium 0.000057 0.000040 No
56 Barium 0.000031 0.000022 0.0000012 No? (toxic) 2
50 Tin 0.000024 0.000020 6.0e-7 No(?) 14
53 Iodine 0.000016 0.000020 7.5e-7 Yes (e.g. thyroxine, triiodothyronine) 17
22 Titanium 0.000013 0.000020 No 4
5 Boron 0.000069 0.000018 0.0000030 Yes (probable) 13
34 Selenium 0.000019 0.000015 4.5e-8 Yes (toxic in higher amounts) 16
28 Nickel 0.000014 0.000015 0.0000015 Yes (e.g. urease) 10
24 Chromium 0.0000024 0.000014 8.9e-8 Yes (not confirmed) 6
25 Manganese 0.000017 0.000012 0.0000015 Yes (e.g. Mn-SOD) 7
33 Arsenic 0.000026 0.000007 8.9e-8 Yes (not confirmed). Toxic in higher amounts 15
3 Lithium 0.0000031 0.000007 0.0000015 Yes (not confirmed). Toxic in high amounts. Useful medically (mood stabilizer). 1
80 Mercury 0.000019 0.000006 8.9e-8 No (toxic) 12
55 Caesium 0.0000021 0.000006 1.0e-7 No 1
42 Molybdenum 0.000013 0.000005 4.5e-8 Yes (e.g. the molybdenum oxotransferases, Xanthine oxidase and Sulfite oxidase) 6
32 Germanium 0.000005 No (?) 14
27 Cobalt 0.0000021 0.000003 3.0e-7 Yes (e.g. vitamin B12) 9
51 Antimony 0.000011 0.000002 No (toxic) 15
47 Silver 0.000001 0.000002 No (toxic) 11
41 Niobium 0.00016 0.0000015 No 5
40 Zirconium 0.0006 0.000001 3.0e-7 No 4
57 Lanthanum 0.000137 8e-7 No
52 Tellurium 0.000012 7e-7 No 16
31 Gallium 7e-7 No 13
39 Yttrium 6e-7 No 3
83 Bismuth 5e-7 No 15
81 Thallium 5e-7 No (toxic) 13
49 Indium 4e-7 No 13
79 Gold 0.000014 2e-7 3.0e-7 No 11
21 Scandium 2e-7 No 3
73 Tantalum 2e-7 No 5
23 Vanadium 0.000026 1.1e-7 1.2e-8 Yes (not confirmed) 5
90 Thorium 1e-7 No (toxic)
92 Uranium 1.3e-7 1e-7 3.0e-9 No (toxic)
62 Samarium 5.0e-8 No
74 Tungsten 2.0e-8 No 6
4 Beryllium 5e-9 3.6e-8 4.5e-8 No (toxic) 2
88 Radium 1e-17 3e-14 1e-17% No (toxic) 2

*Iron = ~3 g in men, ~2.3 g in women

The elements needed for life are relatively common in the Earth's crust, and conversely most of the common elements are necessary for life. An exception is aluminium, which is the third most common element in the Earth's crust (after oxygen and silicon), but seems to serve no function in living cells. Rather, it is harmful in large amounts.[citation needed] Transferrins can bind aluminium.[10]

Periodic table highlighting dietary elements[1]

H   He
Li Be   B C N O F Ne
Na Mg   Al Si P S Cl Ar
K Ca Sc   Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr
Rb Sr Y   Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe
Cs Ba La * Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn
Fr Ra Ac ** Rf Db Sg Bh Hs Mt Ds Rg Cn Uut Fl Uup Lv Uus Uuo
 
  * Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu
  ** Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr
The four organic basic elements Quantity elements Essential trace elements Function suggested from active handling in mammals, but no specific identified biochemical function

Composition by molecule type [edit]

The composition can also be expressed in terms of chemicals, such as:

The composition of the human body can be viewed on an atomic and molecular scale as shown in this article.

The estimated gross molecular contents of a typical 20-micrometre human cell is as follows:[12]

Molecule Percent of Mass Mol.Weight (daltons) Molecules Percent of Molecules
Water 65* 18* 1.74e14* 98.73*
Other Inorganics 1.5 N/A 1.31e12 0.74
Lipids 12 N/A 8.4e11 0.475
Other Organics 0.4 N/A 7.7e10 0.044
Protein 20 N/A 1.9e10 0.011
RNA 1.0 N/A 5e7 3e-5
DNA 0.1 1e11 46* 3e-11

Water: Obviously the amount of water is highly dependent on the level of hydration. DNA: A human cell also contains mitochondrial DNA. Sperm cells contain less mitochondrial DNA than other cells. A mammalian red blood cell contains no nucleus and thus no DNA.

Materials and tissues [edit]

Body composition can also be expressed in terms of various types of material, such as:

Composition by cell type [edit]

There are many species of bacteria and other microorganisms that live on or inside the healthy human body. In fact, 90% of the cells in (or on) a human body are microbes, by number[13][14] (much less by mass or volume). Some of these symbionts are necessary for our health. Those that neither help nor harm us are called commensal organisms.

See also [edit]

References [edit]

  1. ^ a b Ultratrace minerals. Authors: Nielsen, Forrest H. USDA, ARS Source: Modern nutrition in health and disease / editors, Maurice E. Shils ... et al.. Baltimore : Williams & Wilkins, c1999., p. 283-303. Issue Date: 1999 URI: [1]
  2. ^ Thomas J. Glover, comp., Pocket Ref, 3rd ed. (Littleton: Sequoia, 2003), p. 324 (LCCN 2002-91021), which in
  3. ^ turn cites Geigy Scientific Tables, Ciba-Geigy Limited, Basel, Switzerland, 1984.
  4. ^ Chang, Raymond (2007). Chemistry, Ninth Edition. McGraw-Hill. p. 52. ISBN 0-07-110595-6. 
  5. ^ Distribution of elements in the human body (by weight) Retrieved on 2007-12-06
  6. ^ Frausto Da Silva, J. J. R; Williams, R. J. P (2001-08-16). The Biological Chemistry of the Elements: The Inorganic Chemistry of Life. ISBN 9780198508489. 
  7. ^ Zumdahl, Steven S. and Susan A. (2000). Chemistry, Fifth Edition. Houghton Mifflin Company. p. 894. ISBN 0-395-98581-1. )
  8. ^ J. Emsley, The Element, 3rd ed., Oxford: Clarendon Press, 1998.
  9. ^ Neilsen, cited
  10. ^ Mizutani, K.; Mikami, B.; Aibara, S.; Hirose, M. (2005). "Structure of aluminium-bound ovotransferrin at 2.15 Å resolution". Acta Crystallographica Section D Biological Crystallography 61 (12): 1636. doi:10.1107/S090744490503266X.  edit
  11. ^ Douglas Fox, "The speed of life", New Scientist, No 2419, 1 November 2003.
  12. ^ Freitas Jr., Robert A. (1999). Nanomedicine,. Landes Bioscience. Tables 3–1 & 3–2. ISBN 1-57059-680-8. 
  13. ^ Glausiusz, Josie. "Your Body Is a Planet". Retrieved 2007-09-16. 
  14. ^ Wenner, Melinda. "Humans Carry More Bacterial Cells than Human Ones". Retrieved 2010-10-09. 
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