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 0.654524 Yes (e.g. water, electron acceptor) [19] Reactive oxygen species 16
6 Carbon 0.181312 Yes [19] (organic compounds)14
1 Hydrogen 0.10762 Yes [19] (e.g. water) Acidosis 1
7 Nitrogen 0.02–0.031.81.1 Yes [19] (e.g. DNA and amino acids)15
20 Calcium 0.011–0.0151.00.22 Yes [19] [20] [21] (e.g. Calmodulin and Hydroxylapatite in bones) Hypercalcaemia 2
15 Phosphorus 5–7×10−3 [22] 0.780.22 Yes [19] [20] [21] (e.g. DNA, Phospholipids and Phosphorylation) Hyperphosphatemia 15
19 Potassium 1.5–2×10−3 [23] 0.140.033 Yes [19] [20] (e.g. Na+/K+-ATPase) Hyperkalemia 1
16 Sulfur 2.5×10−30.140.038 Yes [19] (e.g. Cysteine, Methionine, Biotin, Thiamine) Sulfhemoglobinemia 16
11 Sodium 1.5×10−30.100.037 Yes [20] (e.g. Na+/K+-ATPase) Hypernatremia 1
17 Chlorine 1.5×10−30.0950.024 Yes [20] [21] (e.g. Cl-transporting ATPase) Hyperchloremia 17
12 Magnesium 500×10−60.0190.0070 Yes [20] [21] (e.g. binding to ATP and other nucleotides) Hypermagnesemia 2
26 Iron*60×10−60.00420.00067 Yes [20] [21] (e.g. Hemoglobin, Cytochromes) Iron overload 8
9 Fluorine 37×10−60.00260.0012Yes (AUS, NZ), [24] No (US, EU), [25] [26] Maybe (WHO) [27] Fluorine: Highly toxic

Fluoride: Toxic in high amounts

17
30 Zinc 32×10−60.00230.00031 Yes [20] [21] (e.g. Zinc finger proteins) Zinc toxicity 12
14 Silicon 20×10−60.00100.0058 Probably [28] 14
31 Gallium 4.9×10−60.00070.00093No Gallium halide poisoning [29] 13
37 Rubidium 4.6×10−60.000680.000033No Potassium replacement1
38 Strontium 4.6×10−60.000320.000033No Calcium replacement2
35 Bromine 2.9×10−60.000260.000030Maybe [30] Bromism 17
82 Lead 1.7×10−60.000120.0000045No Lead poisoning 14
29 Copper 1×10−60.0000720.0000104 Yes [20] [21] (e.g. copper proteins) Copper toxicity 11
13 Aluminium 870×10−90.0000600.000015No Aluminium poisoning 13
48 Cadmium 720×10−90.0000500.0000045No Cadmium poisoning 12
58 Cerium 570×10−90.000040No
56 Barium 310×10−90.0000220.0000012Notoxic in higher amounts2
50 Tin 240×10−90.0000206.0×10−7Maybe [1] 14
53 Iodine 160×10−90.0000207.5×10−7 Yes [20] [21] (e.g. thyroxine, triiodothyronine)Iodine-induced hyperthyroidism 17
22 Titanium 130×10−90.000020No4
5 Boron 690×10−90.0000180.0000030 Probably [10] [31] 13
34 Selenium 190×10−90.0000154.5×10−8 Yes [20] [21] (e.g. selenocysteine) Selenium toxicity 16
28 Nickel 140×10−90.0000150.0000015 Maybe [1] Nickel Toxicity 10
24 Chromium 24×10−90.0000148.9×10−8 Maybe [1] [20] [21] 6
25 Manganese 170×10−90.0000120.0000015 Yes [20] [21] (e.g. Mn-SOD) Manganism 7
33 Arsenic 260×10−90.0000078.9×10−8 Maybe [1] [2] Arsenic poisoning 15
3 Lithium 31×10−90.0000070.0000015 Possibly (intercorrelated with the functions of several enzymes, hormones and vitamins) Lithium toxicity 1
80 Mercury 190×10−90.0000068.9×10−8No Mercury poisoning 12
55 Caesium 21×10−90.0000061.0×10−7No1
42 Molybdenum 130×10−90.0000054.5×10−8 Yes [20] [21] (e.g. the molybdenum oxotransferases, Xanthine oxidase and Sulfite oxidase)6
32 Germanium 5×10−6No14
27 Cobalt 21×10−90.0000033.0×10−7 Yes (e.g. Cobalamin/Vitamin B12) [32] [33] 9
44 Ruthenium 22×10−90.000007No [34] 8
51 Antimony 110×10−90.000002 No toxic15
47 Silver 10×10−90.000002No11
41 Niobium 1600×10−90.0000015No5
40 Zirconium 6×10−90.0000013.0×10−7No4
57 Lanthanum 1370×10−98×10−7No
52 Tellurium 120×10−97×10−7No16
39 Yttrium 6×10−7No3
83 Bismuth 5×10−7No15
81 Thallium 5×10−7Nohighly toxic13
49 Indium 4×10−7No13
79 Gold 3×10−92×10−73.0×10−7Nouncoated nanoparticles possibly genotoxic [35] [36] [37] 11
21 Scandium 2×10−7No3
73 Tantalum 2×10−7No5
23 Vanadium 260×10−90.0000201.2×10−8 Possibly [10] (suggested osteo-metabolism (bone) growth factor)5
90 Thorium 1×10−7Notoxic, radioactive
92 Uranium 1×10−73.0×10−9Notoxic, radioactive
62 Samarium 5.0×10−8No
74 Tungsten 2.0×10−8No6
4 Beryllium 3.6×10−84.5×10−8Notoxic in higher amounts2
88 Radium 3×10−141×10−17Notoxic, radioactive2
2 Helium 20.39×10−212.4×10−141×10−17Nonoble gas18
10 Neon 8.5×10−231×10−141×10−17Nonoble gas18
18 Argon 4.25×10−230.5×10−141×10−17Nonoble gas18
36 Krypton 2.125×10−230.25×10−141×10−17Nonoble 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]
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: [46]

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 [47] [48] [49]
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. [47] [50] [51] [52] [53] (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

Related Research Articles

<span class="mw-page-title-main">Calcium</span> Chemical element with atomic number 20 (Ca)

Calcium is a chemical element; it has symbol Ca and atomic number 20. As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride layer when exposed to air. Its physical and chemical properties are most similar to its heavier homologues strontium and barium. It is the fifth most abundant element in Earth's crust, and the third most abundant metal, after iron and aluminium. The most common calcium compound on Earth is calcium carbonate, found in limestone and the fossilised remnants of early sea life; gypsum, anhydrite, fluorite, and apatite are also sources of calcium. The name derives from Latin calx "lime", which was obtained from heating limestone.

<span class="mw-page-title-main">Chromium</span> Chemical element with atomic number 24 (Cr)

Chromium is a chemical element; it has symbol Cr and atomic number 24. It is the first element in group 6. It is a steely-grey, lustrous, hard, and brittle transition metal.

<span class="mw-page-title-main">Fat</span> Esters of fatty acid or triglycerides

In nutrition, biology, and chemistry, fat usually means any ester of fatty acids, or a mixture of such compounds, most commonly those that occur in living beings or in food.

<span class="mw-page-title-main">Iodine</span> Chemical element with atomic number 53 (I)

Iodine is a chemical element; it has symbol I and atomic number 53. The heaviest of the stable halogens, it exists at standard conditions as a semi-lustrous, non-metallic solid that melts to form a deep violet liquid at 114 °C (237 °F), and boils to a violet gas at 184 °C (363 °F). The element was discovered by the French chemist Bernard Courtois in 1811 and was named two years later by Joseph Louis Gay-Lussac, after the Ancient Greek Ιώδης, meaning 'violet'.

<span class="mw-page-title-main">Nutrition</span> Provision to cells and organisms to support life

Nutrition is the biochemical and physiological process by which an organism uses food to support its life. It provides organisms with nutrients, which can be metabolized to create energy and chemical structures. Failure to obtain the required amount of nutrients causes malnutrition. Nutritional science is the study of nutrition, though it typically emphasizes human nutrition.

<span class="mw-page-title-main">Dietary fiber</span> Portion of plant-derived food that cannot be completely digested

Dietary fiber or roughage is the portion of plant-derived food that cannot be completely broken down by human digestive enzymes. Dietary fibers are diverse in chemical composition and can be grouped generally by their solubility, viscosity and fermentability which affect how fibers are processed in the body. Dietary fiber has two main subtypes: soluble fiber and insoluble fiber which are components of plant-based foods such as legumes, whole grains, cereals, vegetables, fruits, and nuts or seeds. A diet high in regular fiber consumption is generally associated with supporting health and lowering the risk of several diseases. Dietary fiber consists of non-starch polysaccharides and other plant components such as cellulose, resistant starch, resistant dextrins, inulins, lignins, chitins, pectins, beta-glucans, and oligosaccharides.

A nutrient is a substance used by an organism to survive, grow and reproduce. The requirement for dietary nutrient intake applies to animals, plants, fungi and protists. Nutrients can be incorporated into cells for metabolic purposes or excreted by cells to create non-cellular structures such as hair, scales, feathers, or exoskeletons. Some nutrients can be metabolically converted into smaller molecules in the process of releasing energy such as for carbohydrates, lipids, proteins and fermentation products leading to end-products of water and carbon dioxide. All organisms require water. Essential nutrients for animals are the energy sources, some of the amino acids that are combined to create proteins, a subset of fatty acids, vitamins and certain minerals. Plants require more diverse minerals absorbed through roots, plus carbon dioxide and oxygen absorbed through leaves. Fungi live on dead or living organic matter and meet nutrient needs from their host.

<span class="mw-page-title-main">Human nutrition</span> Nutrients supporting human health

Human nutrition deals with the provision of essential nutrients in food that are necessary to support human life and good health. Poor nutrition is a chronic problem often linked to poverty, food security, or a poor understanding of nutritional requirements. Malnutrition and its consequences are large contributors to deaths, physical deformities, and disabilities worldwide. Good nutrition is necessary for children to grow physically and mentally, and for normal human biological development.

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<span class="mw-page-title-main">Choline</span> Chemical compound and essential nutrient

Choline is a cation with the chemical formula [(CH3)3NCH2CH2OH]+. Choline forms various salts, such as choline chloride and choline bitartrate. An essential nutrient for animals, it is a structural component of phospholipids and cell membranes.

A trace element is a chemical element of a minute quantity, a trace amount, especially used in referring to a micronutrient, but is also used to refer to minor elements in the composition of a rock, or other chemical substance.

<span class="mw-page-title-main">Mineral (nutrient)</span> Chemical element required as an essential nutrient by organisms to perform life functions

In the context of nutrition, a mineral is a chemical element. Some "minerals" are essential for life, but most are not. Minerals are one of the four groups of essential nutrients; the others are vitamins, essential fatty acids, and essential amino acids. The five major minerals in the human body are calcium, phosphorus, potassium, sodium, and magnesium. The remaining minerals are called "trace elements". The generally accepted trace elements are iron, chlorine, cobalt, copper, zinc, manganese, molybdenum, iodine, selenium, and bromine; there is some evidence that there may be more.

<span class="mw-page-title-main">Calcium in biology</span> Use of calcium by organisms

Calcium ions (Ca2+) contribute to the physiology and biochemistry of organisms' cells. They play an important role in signal transduction pathways, where they act as a second messenger, in neurotransmitter release from neurons, in contraction of all muscle cell types, and in fertilization. Many enzymes require calcium ions as a cofactor, including several of the coagulation factors. Extracellular calcium is also important for maintaining the potential difference across excitable cell membranes, as well as proper bone formation.

The abundance of the chemical elements is a measure of the occurrences of the chemical elements relative to all other elements in a given environment. Abundance is measured in one of three ways: by mass fraction, by mole fraction, or by volume fraction. Volume fraction is a common abundance measure in mixed gases such as planetary atmospheres, and is similar in value to molecular mole fraction for gas mixtures at relatively low densities and pressures, and ideal gas mixtures. Most abundance values in this article are given as mass fractions.

A bromide ion is the negatively charged form (Br−) of the element bromine, a member of the halogens group on the periodic table. Most bromides are colorless. Bromides have many practical roles, being found in anticonvulsants, flame-retardant materials, and cell stains. Although uncommon, chronic toxicity from bromide can result in bromism, a syndrome with multiple neurological symptoms. Bromide toxicity can also cause a type of skin eruption, see potassium bromide. The bromide ion has an ionic radius of 196 pm.

<span class="mw-page-title-main">Tetrabromobisphenol A</span> Chemical compound

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<span class="mw-page-title-main">Metal toxicity</span> Harmful effects of certain metals

Metal toxicity or metal poisoning is the toxic effect of certain metals in certain forms and doses on life. Some metals are toxic when they form poisonous soluble compounds. Certain metals have no biological role, i.e. are not essential minerals, or are toxic when in a certain form. In the case of lead, any measurable amount may have negative health effects. There is a popular misconception that only heavy metals can be toxic, but lighter metals such as beryllium and lithium can be toxic too. Not all heavy metals are particularly toxic, and some are essential, such as iron. The definition may also include trace elements when abnormally high doses may be toxic. An option for treatment of metal poisoning may be chelation therapy, a technique involving the administration of chelation agents to remove metals from the body.

<span class="mw-page-title-main">Manganese in biology</span> Use of manganese by organisms

Manganese is an essential biological element in all organisms. It is used in many enzymes and proteins. It is essential in plants.

<span class="mw-page-title-main">Copper in biology</span>

Copper is an essential trace element that is vital to the health of all living things. In humans, copper is essential to the proper functioning of organs and metabolic processes. Also, in humans, copper helps maintain the nervous system, immune system, brain development, and activates genes, as well as assisting in the production of connective tissues, blood vessels, and energy. The human body has complex homeostatic mechanisms which attempt to ensure a constant supply of available copper, while eliminating excess copper whenever this occurs. However, like all essential elements and nutrients, too much or too little nutritional ingestion of copper can result in a corresponding condition of copper excess or deficiency in the body, each of which has its own unique set of adverse health effects.

<span class="mw-page-title-main">Selenium in biology</span> Use of Selenium by organisms

Selenium is an essential micronutrient for animals, though it is toxic in large doses. In plants, it sometimes occurs in toxic amounts as forage, e.g. locoweed. Selenium is a component of the amino acids selenocysteine and selenomethionine. In humans, selenium is a trace element nutrient that functions as cofactor for glutathione peroxidases and certain forms of thioredoxin reductase. Selenium-containing proteins are produced from inorganic selenium via the intermediacy of selenophosphate (PSeO33−).

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