Composition of the human body
Body composition may be analyzed in various ways. This can be done in terms of the chemical elements present, or by molecular type e.g., water, protein, 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, connective tissue, 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.
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.
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 common contaminants without function (examples: caesium, titanium), while many others are thought to be active toxins, depending on amount (cadmium, mercury, lead, radioactives). In humans, arsenic is toxic, and its levels in foods and dietary supplements are closely monitored to reduce or eliminate its intake.
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[clarification needed] organisms, and opportunistically in eosinophils in humans. One study has indicated bromine to be necessary to collagen IV synthesis in humans. 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.
Elemental composition listEdit
The average 70 kg (150 lb) adult human body contains approximately 7×1027 atoms and contains at least detectable traces of 60 chemical elements. About 29 of these elements are thought to play an active positive role in life and health in humans.
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. 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, 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.
|Atomic number||Element||Fraction of mass||Mass (kg)||Atomic percent||Essential in humans||Negative effects of excess||Group|
|8||Oxygen||0.65||43||24||Yes (e.g. water, electron acceptor)||Reactive oxygen species||16|
|6||Carbon||0.18||16||12||Yes (organic compounds)||14|
|1||Hydrogen||0.10||7||62||Yes (e.g. water)||1|
|7||Nitrogen||0.03||1.8||1.1||Yes (e.g. DNA and amino acids)||15|
|20||Calcium||0.014||1.0||0.22||Yes (e.g. Calmodulin and Hydroxylapatite in bones)||2|
|15||Phosphorus||0.011||0.78||0.22||Yes (e.g. DNA and phosphorylation)||Hyperphosphatemia||15|
|19||Potassium||2.0×10−3||0.14||0.033||Yes (e.g. Na+/K+-ATPase)||1|
|16||Sulfur||2.5×10−3||0.14||0.038||Yes (e.g. Cysteine, Methionine, Biotin, Thiamine)||16|
|11||Sodium||1.5×10−3||0.10||0.037||Yes (e.g. Na+/K+-ATPase)||1|
|17||Chlorine||1.5×10−3||0.095||0.024||Yes (e.g. Cl-transporting ATPase)||17|
|12||Magnesium||500×10−6||0.019||0.0070||Yes (e.g. binding to ATP and other nucleotides)||2|
|26||Iron*||60×10−6||0.0042||0.00067||Yes (e.g. Hemoglobin, Cytochromes)||8|
|9||Fluorine||37×10−6||0.0026||0.0012||Yes (AUS, NZ), No (US, EU), Maybe (WHO)||toxic in high amounts||17|
|30||Zinc||32×10−6||0.0023||0.00031||Yes (e.g. Zinc finger proteins)||12|
|29||Copper||1×10−6||0.000072||0.0000104||Yes (e.g. copper proteins)||toxic in higher amounts||11|
|56||Barium||310×10−9||0.000022||0.0000012||No||toxic in higher amounts||2|
|53||Iodine||160×10−9||0.000020||7.5×10−7||Yes (e.g. thyroxine, triiodothyronine)||17|
|34||Selenium||190×10−9||0.000015||4.5×10−8||Yes||toxic in higher amounts||16|
|28||Nickel||140×10−9||0.000015||0.0000015||Probably||toxic in higher amounts||10|
|25||Manganese||170×10−9||0.000012||0.0000015||Yes (e.g. Mn-SOD)||7|
|3||Lithium||31×10−9||0.000007||0.0000015||Yes (intercorrelated with the functions of several enzymes, hormones and vitamins)||toxic in higher amounts||1|
|42||Molybdenum||130×10−9||0.000005||4.5×10−8||Yes (e.g. the molybdenum oxotransferases, Xanthine oxidase and Sulfite oxidase)||6|
|27||Cobalt||21×10−9||0.000003||3.0×10−7||Yes (cobalamin, B12)||9|
|79||Gold||3×10−9||2×10−7||3.0×10−7||No||uncoated nanoparticles possibly genotoxic||11|
|23||Vanadium||260×10−9||1.1×10−7||1.2×10−8||Possibly (suggested osteo-metabolism (bone) growth factor)||5|
|4||Beryllium||3.6×10−8||4.5×10−8||No||toxic in higher amounts||2|
|71||Lutetium||Possibly||toxic in higher amounts||4|
*Iron = ~3 g in men, ~2.3 g in women
Of the 94 naturally occurring chemical elements, 61 are listed in the table above. Of the remaining 33, 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 toxic in large amounts, depending on its physical and chemical forms and magnitude, duration, frequency of exposure, and how it was absorbed by the human body. Transferrins can bind aluminium.
The composition of the human body is expressed in terms of chemicals:
- Proteins – including those of hair, connective tissue, etc.
- Fats (or lipids)
- Hydroxyapatite in bones
- Carbohydrates such as glycogen and glucose
- Dissolved inorganic ions such as sodium, potassium, chloride, bicarbonate, phosphate
- Gases such as oxygen, carbon dioxide, nitrogen oxide, hydrogen, carbon monoxide, acetaldehyde, formaldehyde, methanethiol. These may be dissolved or present in the gases in the lungs or intestines. Ethane and pentane are produced by oxygen free radicals.
- Many other small molecules, such as amino acids, fatty acids, nucleobases, nucleosides, nucleotides, vitamins, cofactors.
- Free radicals such as superoxide, hydroxyl, and hydroperoxyl.
The estimated gross molecular contents of a typical 20-micrometre human cell is as follows:
|Molecule||Percent of Mass||Mol.Weight (daltons)||Molecules||Percent of Molecules|
Body composition can also be expressed in terms of various types of material, such as:
- Bone and teeth
- Nervous tissue (Brain and nerves)
- Connective tissue
- Body fluids (blood, lymph, Urine)
- Contents of digestive tract, including intestinal gas
- Air in lungs
Composition by cell typeEdit
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 (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.
- M.A. Zoroddu; J. Aashet; G. Crisponi; S. Medici; M. Peana; V.M. Nurchi (June 2019). "The essential metals for humans: a brief overview". Journal of Inorganic Biochemistry. 195: 120–129. doi:10.1016/j.jinorgbio.2019.03.013. PMID 30939379.
- "Arsenic in Food and Dietary Supplements". US Food and Drug Administration. 22 May 2019. Retrieved 20 August 2019.
- 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.
- Nelson, Lehninger, Cox (2008). Lehninger Principles of Biochemistry (5th ed.). Macmillan.CS1 maint: multiple names: authors list (link)
- How many atoms are in the human body?
- "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: 
- Use WP:CALC for the mean of means for males and females, since the two groups are of about equal size
- See table 1. here
- "Guidance for Industry: A Food Labeling Guide 14. Appendix F". US Food and Drug Administration. 1 January 2013. Archived from the original on 4 April 2017.
- 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.
- Thomas J. Glover, comp., Pocket Ref, 3rd ed. (Littleton: Sequoia, 2003), p. 324 (LCCN 2002-91021), which in
- turn cites Geigy Scientific Tables, Ciba-Geigy Limited, Basel, Switzerland, 1984.
- Chang, Raymond (2007). Chemistry, Ninth Edition. McGraw-Hill. p. 52. ISBN 978-0-07-110595-8.
- "Elemental Composition of the Human Body" Archived 2018-12-18 at the Wayback Machine by Ed Uthman, MD Retrieved 17 June 2016
- 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.
- Zumdahl, Steven S. and Susan A. (2000). Chemistry, Fifth Edition. Houghton Mifflin Company. p. 894. ISBN 978-0-395-98581-6.)
- 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.
- Neilsen, cited
- 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.
- 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.
- Code of Federal Regulations, Title 21: Food and Drugs, Ch 1, subchapter B, Part 101, Subpart A, §101.9(c)(8)(iv)
- Australian National Health and Medical Research Council (NHMRC) and New Zealand Ministry of Health (MoH)
- "Fluoride in Drinking Water: A Review of Fluoridation and Regulation Issues"
- "Scientific Opinion on Dietary Reference Values for fluoride" (PDF). EFSA Journal. 11 (8): 3332. 2013. doi:10.2903/j.efsa.2013.3332. ISSN 1831-4732.
- WHO/SDE/WSH/03.04/96 "Fluoride in Drinking-water"
- 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
- Yamada, Kazuhiro (2013). "Cobalt: Its Role in Health and Disease". Interrelations between Essential Metal Ions and Human Diseases. Metal Ions in Life Sciences. 13. pp. 295–320. doi:10.1007/978-94-007-7500-8_9. ISBN 978-94-007-7499-5. ISSN 1559-0836. PMID 24470095.
- 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.
- 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. hdl:11573/780610. ISSN 1998-0124. S2CID 84837060.
- "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.
- 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. PMID 11745751.
- Willhite, Calvin C.; Karyakina, Nataliya A.; Yokel, Robert A.; Yenugadhati, Nagarajkumar; Wisniewski, Thomas M.; Arnold, Ian M.F.; Momoli, Franco; Krewski, Daniel (2014-09-18). "Systematic review of potential health risks posed by pharmaceutical, occupational and consumer exposures to metallic and nanoscale aluminum, aluminum oxides, aluminum hydroxide and its soluble salts". Critical Reviews in Toxicology. 44 (sup4): 1–80. doi:10.3109/10408444.2014.934439. ISSN 1040-8444. PMC 4997813. PMID 25233067.
- 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): 1636–42. doi:10.1107/S090744490503266X. PMID 16301797.
- 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: 
- Daumann, Lena J. (25 April 2019). "Essential and Ubiquitous: The Emergence of Lanthanide Metallobiochemistry". Angewandte Chemie International Edition. doi:10.1002/anie.201904090. Retrieved 15 June 2019.
- Douglas Fox, "The speed of life", New Scientist, No 2419, 1 November 2003.
- Freitas Jr., Robert A. (1999). Nanomedicine. Landes Bioscience. Tables 3–1 & 3–2. ISBN 978-1-57059-680-3.
- Glausiusz, Josie. "Your Body Is a Planet". Retrieved 2007-09-16.
- Wenner, Melinda. "Humans Carry More Bacterial Cells than Human Ones". Retrieved 2010-10-09.