Composition of the human body

Body composition may be analyzed in terms of molecular type e.g., water, protein, connective tissue, fats (or lipids), hydroxylapatite (in bones), carbohydrates (such as glycogen and glucose) and DNA. In terms of tissue type, the body may be analyzed into water, fat, muscle, bone, etc. In terms of cell type, the body contains hundreds of different types of cells, but notably, the largest number of cells contained in a human body (though not the largest mass of cells) are not human cells, but bacteria residing in the normal human gastrointestinal tract.

Elements

Almost 99% of the mass of the human body is made up of 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 11 are necessary for life. The remaining elements are trace elements, of which more than a dozen are thought on the basis of good evidence to be necessary for life. All of the mass of the trace elements put together (less than 10 grams for a human body) do not add up to the body mass of magnesium, the least common of the 11 non-trace elements.

Other elements

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 toxics, depending on amount (cadmium, mercury, radioactives). The possible utility and toxicity of a few elements at levels normally found in the body (aluminium) is debated. Functions have been proposed for trace amounts of cadmium and lead, although these are almost certainly toxic in amounts very much larger than normally found in the body. There is evidence that arsenic, an element normally considered a toxin in higher amounts, is essential in ultratrace quantities, in mammals such as rats, hamsters, and goats.[1]

Some elements (silicon, boron, nickel, vanadium) are probably needed by mammals also, but in far smaller doses. Bromine is used abundantly by some (though not all) lower organisms, and opportunistically in eosinophils in humans. One study has found bromine to be necessary to collagen IV synthesis in humans.[2] Fluorine is used by a number of plants to manufacture toxins (see that element) but in humans only functions as a local (topical) hardening agent in tooth enamel, and not in an essential biological role.[3]

Elemental composition list

The average 70 kg (150 lb) adult human body contains approximately 7×1027 atoms and contains at least detectable traces of 60 chemical elements.[4] About 29 of these elements are thought to play an active positive role in life and health in humans.[5]

The relative amounts of each element vary by individual, mainly due to differences in the proportion of fat, muscle and bone in their body. Persons with more fat will have a higher proportion of carbon and a lower proportion of most other elements (the proportion of hydrogen will be about the same). The numbers in the table are averages of different numbers reported by different references.

The adult human body averages ~53% water. This varies substantially by age, sex, and adiposity. In a large sample of adults of all ages and both sexes, the figure for water fraction by weight was found to be 48 ±6% for females and 58 ±8% water for males.[6] Water is ~11% hydrogen by mass but ~67% hydrogen by atomic percent, and these numbers along with the complementary % numbers for oxygen in water, are the largest contributors to overall mass and atomic composition figures. Because of water content, the human body contains more oxygen by mass than any other element, but more hydrogen by atom-fraction than any element.

The elements listed below as "Essential in humans" are those listed by the (US) Food and Drug Administration as essential nutrients,[7] as well as six additional elements: oxygen, carbon, hydrogen, and nitrogen (the fundamental building blocks of life on Earth), sulfur (essential to all cells) and cobalt (a necessary component of vitamin B12). Elements listed as "Possibly" or "Probably" essential are those cited by the National Research Council (United States) as beneficial to human health and possibly or probably essential.[8]

Atomic numberElementFraction of mass[9][10][11][12][13][14]Mass (kg)[15]Atomic percentEssential in humans[16]!!Negative effects of excessGroup
8Oxygen0.654324Yes (e.g. water, electron acceptor)[17]Reactive oxygen species16
6Carbon0.181612Yes[17] (organic compounds)14
1Hydrogen0.10762Yes[17] (e.g. water)1
7Nitrogen0.031.81.1Yes[17] (e.g. DNA and amino acids)15
20Calcium0.0141.00.22Yes[17][18][19] (e.g. Calmodulin and Hydroxylapatite in bones)2
15Phosphorus0.0110.780.22Yes[17][18][19] (e.g. DNA and phosphorylation)white allotrope highly toxic15
19Potassium2.0×10−30.140.033Yes[17][18] (e.g. Na+/K+-ATPase)1
16Sulfur2.5×10−30.140.038Yes[17] (e.g. Cysteine, Methionine, Biotin, Thiamine)16
11Sodium1.5×10−30.100.037Yes[18] (e.g. Na+/K+-ATPase)1
17Chlorine1.5×10−30.0950.024Yes[18][19] (e.g. Cl-transporting ATPase)17
12Magnesium500×10−60.0190.0070Yes[18][19] (e.g. binding to ATP and other nucleotides)2
26Iron*60×10−60.00420.00067Yes[18][19] (e.g. Hemoglobin, Cytochromes)8
9Fluorine37×10−60.00260.0012Yes (AUS, NZ),[20] No (US, EU),[21][22] Maybe (WHO)[23]toxic in high amounts17
30Zinc32×10−60.00230.00031Yes[18][19] (e.g. Zinc finger proteins)12
14Silicon20×10−60.00100.0058Possibly[8]14
37Rubidium4.6×10−60.000680.000033No1
38Strontium4.6×10−60.000320.000033——2
35Bromine2.9×10−60.000260.000030——17
82Lead1.7×10−60.000120.0000045Notoxic14
29Copper1×10−60.0000720.0000104Yes[18][19] (e.g. copper proteins)11
13Aluminium870×10−90.0000600.000015No13
48Cadmium720×10−90.0000500.0000045Notoxic12
58Cerium570×10−90.000040No
56Barium310×10−90.0000220.0000012Notoxic in higher amounts2
50Tin240×10−90.0000206.0×10−7No14
53Iodine160×10−90.0000207.5×10−7Yes[18][19] (e.g. thyroxine, triiodothyronine)17
22Titanium130×10−90.000020No4
5Boron690×10−90.0000180.0000030Probably[8][24]13
34Selenium190×10−90.0000154.5×10−8Yes[18][19]toxic in higher amounts16
28Nickel140×10−90.0000150.0000015Probably[8][24]toxic in higher amounts10
24Chromium24×10−90.0000148.9×10−8Yes[18][19]6
25Manganese170×10−90.0000120.0000015Yes[18][19] (e.g. Mn-SOD)7
33Arsenic260×10−90.0000078.9×10−8Possibly[1][8]toxic in higher amounts15
3Lithium31×10−90.0000070.0000015Yes (intercorrelated with the functions of several enzymes, hormones and vitamins)toxic in higher amounts1
80Mercury190×10−90.0000068.9×10−8Notoxic12
55Caesium21×10−90.0000061.0×10−7No1
42Molybdenum130×10−90.0000054.5×10−8Yes[18][19] (e.g. the molybdenum oxotransferases, Xanthine oxidase and Sulfite oxidase)6
32Germanium5×10−6No14
27Cobalt21×10−90.0000033.0×10−7Yes (cobalamin, B12)[25][26]9
51Antimony110×10−90.000002Notoxic15
47Silver10×10−90.000002No11
41Niobium1600×10−90.0000015No5
40Zirconium6×10−60.0000013.0×10−7No4
57Lanthanum1370×10−98×10−7No
52Tellurium120×10−97×10−7No16
31Gallium7×10−7No13
39Yttrium6×10−7No3
83Bismuth5×10−7No15
81Thallium5×10−7Nohighly toxic13
49Indium4×10−7No13
79Gold3×10−92×10−73.0×10−7Nouncoated nanoparticles possibly genotoxic[27][28][29]11
21Scandium2×10−7No3
73Tantalum2×10−7No5
23Vanadium260×10−91.1×10−71.2×10−8Possibly[8] (suggested osteo-metabolism (bone) growth factor)5
90Thorium1×10−7Notoxic, radioactive
92Uranium1×10−73.0×10−9Notoxic, radioactive
62Samarium5.0×10−8No
74Tungsten2.0×10−8No6
4Beryllium3.6×10−84.5×10−8Notoxic in higher amounts2
88Radium3×10−141×10−17Notoxic, radioactive2

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

Of the 94 naturally occurring chemical elements, 60 are listed in the table above. Of the remaining 34, it is not known how many occur in the human body.

Most of the elements needed for life are relatively common in the Earth's crust. Aluminium, the third most common element in the Earth's crust (after oxygen and silicon), serves no function in living cells, but is harmful in large amounts.[30] Transferrins can bind aluminium.[31]

Periodic table

Periodic table highlighting dietary elements

H He
LiBe BCNOFNe
NaMg AlSiPSClAr
KCaScTiVCrMnFeCoNiCuZnGaGeAsSeBrKr
RbSrYZrNbMoTcRuRhPdAgCdInSnSbTeIXe
CsBaLa*HfTaWReOsIrPtAuHgTlPbBiPoAtRn
FrRaAc**RfDbSgBhHsMtDsRgCnNhFlMcLvTsOg
 
 *CePrNdPmSmEuGdTbDyHoErTmYbLu
 **ThPaUNpPuAmCmBkCfEsFmMdNoLr
The four organic basic elements Quantity elements Essential trace elements Possible structural or functional role in mammals

Molecules

The composition of the human body is expressed in terms of chemicals:

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:[33]

MoleculePercent of MassMol.Weight (daltons)MoleculesPercent of Molecules
Water65181.74×101498.73
Other Inorganics1.5N/A1.31×10120.74
Lipids12N/A8.4×10110.475
Other Organics0.4N/A7.7×10100.044
Protein20N/A1.9×10100.011
RNA1.0N/A5×1073×10−5
DNA0.11×101146*3×10−11

Tissues

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

  • Muscle
  • Fat
  • Bone and teeth
  • Nervous tissue (Brain and nerves)
  • Hormones
  • Connective tissue
  • Body fluids (blood, lymph, Urine)
  • Contents of digestive tract, including intestinal gas
  • Air in lungs
  • Epithelium

Composition by cell type

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[34][35] (much less by mass or volume). Some of these symbionts are necessary for our health. Those that neither help nor harm humans are called commensal organisms.

See also

References

  1. Anke M. "Arsenic". In: Mertz W. ed., Trace elements in human and Animal Nutrition, 5th ed. Orlando, FL: Academic Press, 1986, 347-372; Uthus E. O., "Evidency for arsenical essentiality", Environmental Geochemistry and Health, 1992, 14:54-56; Uthus E.O., Arsenic essentiality and factors affecting its importance. In: Chappell W. R., Abernathy C. O., Cothern C. R. eds., Arsenic Exposure and Health. Northwood, UK: Science and Technology Letters, 1994, 199-208.
  2. McCall AS, Cummings CF, Bhave G, Vanacore R, Page-McCaw A, Hudson BG (2014). "Bromine Is an Essential Trace Element for Assembly of Collagen IV Scaffolds in Tissue Development and Architecture". Cell. 157 (6): 1380–92. doi:10.1016/j.cell.2014.05.009. PMC 4144415. PMID 24906154.
  3. Nelson, Lehninger, Cox (2008). Lehninger Principles of Biochemistry (5th ed.). Macmillan.
  4. How many atoms are in the human body?
  5. "Ultratrace minerals". Authors: Nielsen, Forrest H. USDA, ARS Source: Modern nutrition in health and disease / editors, Maurice E. Shils ... et al.. Baltimore : Williams & Wilkins, c. 1999, p. 283-303. Issue Date: 1999 URI:
  6. See table 1. here
  7. "Guidance for Industry: A Food Labeling Guide 14. Appendix F"
  8. Institute of Medicine (29 September 2006). Dietary Reference Intakes: The Essential Guide to Nutrient Requirements. National Academies Press. pp. 313–19, 415–22. ISBN 978-0-309-15742-1. Retrieved 21 June 2016.
  9. Thomas J. Glover, comp., Pocket Ref, 3rd ed. (Littleton: Sequoia, 2003), p. 324 (LCCN 2002-91021), which in
  10. turn cites Geigy Scientific Tables, Ciba-Geigy Limited, Basel, Switzerland, 1984.
  11. Chang, Raymond (2007). Chemistry, Ninth Edition. McGraw-Hill. p. 52. ISBN 0-07-110595-6.
  12. "Elemental Composition of the Human Body" by Ed Uthman, MD Retrieved 17 June 2016
  13. 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.
  14. Zumdahl, Steven S. and Susan A. (2000). Chemistry, Fifth Edition. Houghton Mifflin Company. p. 894. ISBN 0-395-98581-1. )
  15. Emsley, John (25 August 2011). Nature's Building Blocks: An A-Z Guide to the Elements. OUP Oxford. p. 83. ISBN 978-0-19-960563-7. Retrieved 17 June 2016.
  16. Neilsen, cited
  17. Salm, Sarah; Allen, Deborah; Nester, Eugene; Anderson, Denise (9 January 2015). Nester's Microbiology: A Human Perspective. p. 21. ISBN 978-0-07-773093-2. Retrieved 19 June 2016.
  18. Subcommittee on the Tenth Edition of the Recommended Dietary Allowances, Food and Nutrition Board; Commission on Life Sciences, National Research Council (1 February 1989). "9-10". Recommended Dietary Allowances: 10th Edition. National Academies Press. ISBN 978-0-309-04633-6. Retrieved 18 June 2016.
  19. Code of Federal Regulations, Title 21: Food and Drugs, Ch 1, subchapter B, Part 101, Subpart A, §101.9(c)(8)(iv)
  20. Australian National Health and Medical Research Council (NHMRC) and New Zealand Ministry of Health (MoH)
  21. "Fluoride in Drinking Water: A Review of Fluoridation and Regulation Issues"
  22. "Scientific Opinion on Dietary Reference Values for fluoride". EFSA Journal. 11 (8): 3332. 2013. doi:10.2903/j.efsa.2013.3332. ISSN 1831-4732.
  23. WHO/SDE/WSH/03.04/96 "Fluoride in Drinking-water"
  24. Safe Upper Levels for Vitamins and Mineral (2003), boron p. 164-71, nickel p. 225-31, EVM, Food Standards Agency, UK ISBN 1-904026-11-7
  25. Yamada, Kazuhiro (2013). "Cobalt: Its Role in Health and Disease". Metal Ions in Life Sciences. 13: 295–320. doi:10.1007/978-94-007-7500-8_9. ISSN 1559-0836.
  26. Banci, Lucia (18 April 2013). Metallomics and the Cell. Springer Science & Business Media. pp. 333–368. ISBN 978-94-007-5561-1. Retrieved 19 June 2016.
  27. Fratoddi, Ilaria; Venditti, Iole; Cametti, Cesare; Russo, Maria Vittoria (2015). "How toxic are gold nanoparticles? The state-of-the-art". Nano Research. 8 (6): 1771–1799. doi:10.1007/s12274-014-0697-3. ISSN 1998-0124.
  28. "Scientific Opinion on the re-evaluation of gold (E 175) as a food additive". EFSA Journal. 14 (1): 4362. 2016. doi:10.2903/j.efsa.2016.4362. ISSN 1831-4732.
  29. Hillyer, Julián F.; Albrecht, Ralph M. (2001). "Gastrointestinal persorption and tissue distribution of differently sized colloidal gold nanoparticles". Journal of Pharmaceutical Sciences. 90 (12): 1927–1936. doi:10.1002/jps.1143. ISSN 0022-3549.
  30. Aluminum Toxicity
  31. Mizutani, K.; Mikami, B.; Aibara, S.; Hirose, M. (2005). "Structure of aluminium-bound ovotransferrin at 2.15 Å resolution". Acta Crystallographica Section D. 61 (12): 1636. doi:10.1107/S090744490503266X.
  32. Douglas Fox, "The speed of life", New Scientist, No 2419, 1 November 2003.
  33. Freitas Jr., Robert A. (1999). Nanomedicine,. Landes Bioscience. Tables 3–1 & 3–2. ISBN 1-57059-680-8.
  34. Glausiusz, Josie. "Your Body Is a Planet". Retrieved 2007-09-16.
  35. Wenner, Melinda. "Humans Carry More Bacterial Cells than Human Ones". Retrieved 2010-10-09.
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