Composition of the human body

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Pie charts of typical human body composition by percent of mass, and by percent of atomic composition (atomic percent) Two pie graphs about the composition of the human body.png
Pie charts of typical human body composition by percent of mass, and by percent of atomic composition (atomic percent)

Body composition may be analyzed in various ways. This can be done in terms of the chemical elements present, or by molecular structure e.g., water, protein, fats (or lipids), hydroxyapatite (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.

Contents

Elements

The main elements that comprise the human body (including water) can be summarized as CHNOPS.
201 Elements of the Human Body.02.svg ElementSymbolpercent
mass		percent
atoms
OxygenO65.024.0
CarbonC18.512.0
HydrogenH9.562.0
NitrogenN2.61.1
CalciumCa1.30.22
PhosphorusP0.60.22
SulfurS0.30.038
PotassiumK0.20.03
SodiumNa0.20.037
ChlorineCl0.20.024
MagnesiumMg0.10.015
All others< 0.1< 0.3
Parts-per-million cube of relative abundance by mass of elements in an average adult human body down to 1 ppm Element abundance human body ppm chart.svg
Parts-per-million cube of relative abundance by mass of elements in an average adult human body down to 1 ppm

About 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. [1] 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 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. [2]

Some elements (silicon, boron, nickel, vanadium) are probably needed by mammals also, but in far smaller doses. Bromine is used by some (though not all) bacteria, fungi, diatoms, and seaweeds, and opportunistically in eosinophils in humans. One study has indicated bromine to be necessary to collagen IV synthesis in humans. [3] Fluorine is used by a number of plants to manufacture toxins but in humans its only known function is as a local topical hardening agent in tooth enamel. [4]

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. [5] About 29 of these elements are thought to play an active positive role in life and health in humans. [6]

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. [7] 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. [8] 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, [9] 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 US National Research Council as beneficial to human health and possibly or probably essential. [10]

Atomic numberElementFraction of mass
[11] [12] [13] [14] [15] [16] 		Mass (kg) [17] Atomic percent Essential in humans [18] Negative effects of excess Group
8 Oxygen 0.654526 Yes (e.g. water, electron acceptor and DNA) [19] Reactive oxygen species 16
6 Carbon 0.18139.5 Yes [19] (organic compounds)14
1 Hydrogen 0.10763 Yes [19] (e.g. water and DNA) Acidosis 1
7 Nitrogen 0.02–0.031.81.1 Yes [19] (e.g. DNA and amino acids)15
20 Calcium 0.011–0.0151.00.21 Yes [19] [20] [21] (e.g. Calmodulin and Hydroxylapatite in bones) Hypercalcaemia 2
15 Phosphorus 5–7×10−3 [22] 0.780.12 Yes [19] [20] [21] (e.g. DNA, Phospholipids and Phosphorylation) Hyperphosphatemia 15
19 Potassium 1.5–2×10−3 [23] 0.140.029 Yes [19] [20] (e.g. Na+/K+-ATPase) Hyperkalemia 1
16 Sulfur 2.5×10−30.140.049 Yes [19] (e.g. Cysteine, Methionine, Biotin, Thiamine) Sulfhemoglobinemia 16
11 Sodium 1.5×10−30.100.041 Yes [20] (e.g. Na+/K+-ATPase) Hypernatremia 1
17 Chlorine 1.5×10−30.0950.027 Yes [20] [21] (e.g. Cl-transporting ATPase) Hyperchloremia 17
12 Magnesium 500×10−60.019< 0.01 Yes [20] [21] (e.g. binding to ATP and other nucleotides) Hypermagnesemia 2
26 Iron*60×10−60.0042< 0.01 Yes [20] [21] (e.g. Hemoglobin, Cytochromes) Iron overload 8
9 Fluorine 37×10−60.0026< 0.01Yes (AUS, NZ), [24] No (US, EU), [25] [26] Maybe (WHO) [27] Fluorine: Highly toxic

Fluoride: Toxic in high amounts

17
30 Zinc 32×10−60.0023< 0.01 Yes [20] [21] (e.g. Zinc finger proteins) Zinc toxicity 12
14 Silicon 20×10−60.0010< 0.01 Probably [28] 14
31 Gallium 4.9×10−60.0007< 0.01No Gallium halide poisoning [29] 13
37 Rubidium 4.6×10−60.00068< 0.01No Potassium replacement1
38 Strontium 4.6×10−60.00032< 0.001No Calcium replacement2
35 Bromine 2.9×10−60.00026< 0.001Maybe [30] Bromism 17
82 Lead 1.7×10−60.00012< 0.001No Lead poisoning 14
29 Copper 1×10−60.000072< 0.001 Yes [20] [21] (e.g. copper proteins) Copper toxicity 11
13 Aluminium 870×10−90.000060< 0.001No Aluminium poisoning 13
48 Cadmium 720×10−90.000050< 0.001No Cadmium poisoning 12
58 Cerium 570×10−90.000040< 0.001No
56 Barium 310×10−90.000022< 0.001Notoxic in higher amounts2
50 Tin 240×10−90.000020< 0.001Maybe [1] 14
53 Iodine 160×10−90.000020< 0.001 Yes [20] [21] (e.g. thyroxine, triiodothyronine)Iodine-induced hyperthyroidism 17
22 Titanium 130×10−90.000020< 0.001No4
5 Boron 690×10−90.000018< 0.001 Probably [10] [31] 13
34 Selenium 190×10−90.000015< 0.001 Yes [20] [21] (e.g. selenocysteine) Selenium toxicity 16
28 Nickel 140×10−90.000015< 0.0001 Maybe [1] Nickel Toxicity 10
24 Chromium 24×10−90.000014< 0.0001 Maybe [1] [20] [21] 6
25 Manganese 170×10−90.000012< 0.0001 Yes [20] [21] (e.g. Mn-SOD) Manganism 7
33 Arsenic 260×10−90.000007< 0.0001 Maybe [1] [2] Arsenic poisoning 15
3 Lithium 31×10−90.000007< 0.0001 Possibly (intercorrelated with the functions of several enzymes, hormones and vitamins) Lithium toxicity 1
80 Mercury 190×10−90.000006< 0.0001No Mercury poisoning 12
55 Caesium 21×10−90.000006< 0.0001No1
42 Molybdenum 130×10−90.000005< 0.0001 Yes [20] [21] (e.g. the molybdenum oxotransferases, Xanthine oxidase and Sulfite oxidase)6
32 Germanium 5×10−6< 0.0001No14
27 Cobalt 21×10−90.000003< 0.0001 Yes (e.g. Cobalamin/Vitamin B12) [32] [33] 9
44 Ruthenium 22×10−90.000007< 0.0001No [34] 8
51 Antimony 110×10−90.000002< 0.0001 No toxic15
47 Silver 10×10−90.000002< 0.0001No11
41 Niobium 1600×10−90.0000015< 0.0001No5
40 Zirconium 6×10−90.000001< 0.0001No4
57 Lanthanum 1370×10−98×10−7< 0.0001No
52 Tellurium 120×10−97×10−7< 0.0001No16
39 Yttrium 6×10−7< 0.0001No3
83 Bismuth 5×10−7< 0.0001No15
81 Thallium 5×10−7< 0.0001Nohighly toxic13
49 Indium 4×10−7< 0.0001No13
79 Gold 3×10−92×10−7< 0.0001Nouncoated nanoparticles possibly genotoxic [35] [36] [37] 11
21 Scandium 2×10−7< 0.0001No3
73 Tantalum 2×10−7< 0.0001No5
23 Vanadium 260×10−90.000020< 0.0001 Possibly [10] (suggested osteo-metabolism (bone) growth factor)5
90 Thorium 1×10−7< 0.0001Notoxic, radioactive
92 Uranium 1×10−7< 0.0001Notoxic, radioactive
62 Samarium 5.0×10−8< 0.0001No
74 Tungsten 2.0×10−8< 0.0001No6
4 Beryllium 3.6×10−8< 0.0001Notoxic in higher amounts2
88 Radium 3×10−14< 0.0001Notoxic, radioactive2
2 Helium 20.39×10−212.4×10−14< 0.0001Nonoble gas18
10 Neon 8.5×10−231×10−14< 0.0001Nonoble gas18
18 Argon 4.25×10−230.5×10−14< 0.0001Nonoble gas18
36 Krypton 2.125×10−230.25×10−14< 0.0001Nonoble gas18

*Iron = ~3 g in males, ~2.3 g in females

Of the 94 naturally occurring chemical elements, 76 are listed in the table above. Of the remaining 18, 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. [38] Transferrins can bind aluminium. [39]

Periodic table

Essential elements for higher organisms (eucarya). [40] [41] [42] [43] [44] [45] [46]
H He
LiBe BCNOFNe
NaMg AlSiPSClAr
KCaScTiVCrMnFeCoNiCuZnGaGeAsSeBrKr
RbSrYZrNbMoTcRuRhPdAgCdInSnSbTeIXe
CsBaLuHfTaWReOsIrPtAuHgTlPbBiPoAtRn
Legend:
  The four basic organic elements
  Quantity elements
  Essential trace elements
  Essentiality or function debated
  Not essential in humans, but essential/beneficial for some non-human eucarya

Composition

The composition of the human body can be classified as follows:

The estimated contents of a typical 20-micrometre human cell is as follows: [47]

Compound typePercent of massMol. weight (daltons)CompoundPercent of molecules
Water 65181.74×101498.73
Other inorganics 1.5N/A1.31×10120.74
Lipids 12N/A8.4×10110.475
Other organics 0.4N/A7.7×10100.044
Protein 20N/A1.9×10100.011
RNA 1.0N/A5×1073×10−5
DNA 0.11×1011463×10−11

Tissues

The main cellular components of the human body [48] [49] [50]
Cells of the human body by mass.svg Cell type % mass % cell count
Erythrocytes (red blood cells)4.285.0
Muscle cells28.60.001
Adipocytes (fat cells)18.60.2
Other cells14.314.8
Extracellular components34.3-

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

Composition by cell type

There are many species of bacteria and other microorganisms that live on or inside the healthy human body. In fact, there are roughly as many microbial as human cells in the human body by number. [48] [51] [52] [53] [54] (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. 1 2 3 4 5 Zoroddu MA, Aaseth J, Crisponi G, Medici S, Peana M, Nurchi VM (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. S2CID   92997696.
  2. 1 2 "Arsenic in Food and Dietary Supplements". US Food and Drug Administration. 22 May 2019. Retrieved 20 August 2019.
  3. ↑ 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.
  4. ↑ Nelson DL, Cox MM (2021). Lehninger Principles of Biochemistry (8th ed.). New York: Macmillan. ISBN   978-1-319-23090-6.
  5. ↑ "Questions and Answers - How many atoms are in the human body?". education.jlab.org. Retrieved 4 April 2023.
  6. ↑ "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:
  7. ↑ Use WP:CALC for the mean of means for males and females, since the two groups are of about equal size
  8. ↑ See table 1. here
  9. ↑ "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.
  10. 1 2 3 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.
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  12. ↑ "Elemental Composition of the Human Body" Archived 2018-12-18 at the Wayback Machine by Ed Uthman, MD Retrieved 17 June 2016
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  19. 1 2 3 4 5 6 7 8 Salm S, Allen D, Nester E, Anderson D (9 January 2015). Nester's Microbiology: A Human Perspective. Mcgraw-hill Us Higher Ed. p. 21. ISBN   978-0-07-773093-2 . Retrieved 19 June 2016.
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  31. ↑ 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
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  43. ↑ McCall AS, Cummings CF, Bhave G, Vanacore R, Page-McCaw A, Hudson BG (June 2014). "Bromine is an essential trace element for assembly of collagen IV scaffolds in tissue development and architecture". Cell. 157 (6): 1380–1392. doi:10.1016/j.cell.2014.05.009. PMC   4144415 . PMID   24906154.
  44. ↑ Zoroddu MA, Aaseth J, Crisponi G, Medici S, Peana M, Nurchi VM (2019). "The essential metals for humans: a brief overview". Journal of Inorganic Biochemistry. 195: 120–129. doi:10.1016/j.jinorgbio.2019.03.013.
  45. ↑ Remick K, Helmann JD (30 January 2023). "The Elements of Life: A Biocentric Tour of the Periodic Table". Advances in Microbial Physiology. 82. PubMed Central: 1–127. doi:10.1016/bs.ampbs.2022.11.001. ISBN   978-0-443-19334-7. PMC   10727122 . PMID   36948652.
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