Composition of the human body

Not to be confused with Human anatomy.

The main elements that compose the human body are shown from most abundant (by mass) to least abundant.

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 adult male human body is approximately 57% water, and water is 11% hydrogen by mass but 67% by count of atoms (i.e. 67 atomic percent). 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 (see pie graphs and table).

Body composition may also be analyzed in terms of molecular type (e.g., water, protein, connective tissue, fats (or lipids) apatite (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 consist of bacteria (bacterial cells) residing in the normal human gastrointestinal tract.

Major, minor and trace elements

File: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).

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 are necessary to live. The remaining elements are trace elements, of which more than a dozen are thought to be necessary for life.

An easy way to remember the six most essential elements in living organisms is CHNOCP (carbon, hydrogen, nitrogen, oxygen, calcium, and phosphorus).

Other elements and questionable human-required 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 (aluminum) 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 toxic in higher amounts, is essential in ultratrace quantities, even in mammals (rats, hamsters, goats).

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. Bromine is used abundantly by some (though not all) lower organisms, and opportunistically in eosinophils in humans. It has recently been found to be necessary to collagen IV synthesis in humans (not yet confirmed). 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 list

Main article: Dietary element

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.

Atomic number	Element	Fraction of mass	Mass (kg)	Atomic percent	Positive health role in mammals	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 are hydrocarbon derivatives)		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)		15
19	Potassium	2.5×10−3	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 (topically hardens teeth)	toxic in high amounts	17
30	Zinc	32×10−6	0.0023	0.00031	Yes (e.g. Zinc finger proteins)		12
14	Silicon	20×10−6	0.0010	0.0058	Yes (probable)		14
37	Rubidium	4.6×10−6	0.00068	0.000033	No (probable)		1
38	Strontium	4.6×10−6	0.00032	0.000033	Possible (suspected bone growth factor)		2
35	Bromine	2.9×10−6	0.00026	0.000030	Yes (not confirmed) Collagen IV crosslink synthetic cofactor.		17
82	Lead	1.7×10−6	0.00012	0.0000045	No, probably (possible NMDA antagonist)	toxic in higher amounts	14
29	Copper	1×10−6	0.000072	0.0000104	Yes (e.g. copper proteins)		11
13	Aluminum	870×10−9	0.000060	0.000015	No		13
48	Cadmium	720×10−9	0.000050	0.0000045	No, probably	toxic in higher amounts	12
58	Cerium	570×10−9	0.000040		No
56	Barium	310×10−9	0.000022	0.0000012	No, probably	toxic	2
50	Tin	240×10−9	0.000020	6.0×10−7	No, probably		14
53	Iodine	160×10−9	0.000020	7.5×10−7	Yes (e.g. thyroxine, triiodothyronine)		17
22	Titanium	130×10−9	0.000020		No		4
5	Boron	690×10−9	0.000018	0.0000030	Yes (probably)		13
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	No, probably		10
24	Chromium	24×10−9	0.000014	8.9×10−8	Yes (not confirmed)		6
25	Manganese	170×10−9	0.000012	0.0000015	Yes (e.g. Mn-SOD)		7
33	Arsenic	260×10−9	0.000007	8.9×10−8	Yes in rats, hamsters, goats. Probably humans.	toxic in higher amounts	15
3	Lithium	31×10−9	0.000007	0.0000015	Yes, probably. Useful medically (mood stabilizer).	toxic in higher amounts	1
80	Mercury	190×10−9	0.000006	8.9×10−8	No	toxic	12
55	Caesium	21×10−9	0.000006	1.0×10−7	No		1
42	Molybdenum	130×10−9	0.000005	4.5×10−8	Yes (e.g. the molybdenum oxotransferases, Xanthine oxidase and Sulfite oxidase)		6
32	Germanium		5×10−6		No, probably		14
27	Cobalt	21×10−9	0.000003	3.0×10−7	Yes (cobalamin, B12)		9
51	Antimony	110×10−9	0.000002		No	toxic	15
47	Silver	10×10−9	0.000002		No		11
41	Niobium	1600×10−9	0.0000015		No		5
40	Zirconium	6000×10−9	0.000001	3.0×10−7	No		4
57	Lanthanum	1370×10−9	8×10−7		No
52	Tellurium	120×10−9	7×10−7		No		16
31	Gallium		7×10−7		No		13
39	Yttrium		6×10−7		No		3
83	Bismuth		5×10−7		No (Useful in small amounts for gastrointestinal pain)		15
81	Thallium		5×10−7		No	toxic	13
49	Indium		4×10−7		No		13
79	Gold	140×10−9	2×10−7	3.0×10−7	No		11
21	Scandium		2×10−7		No		3
73	Tantalum		2×10−7		No		5
23	Vanadium	260×10−9	1.1×10−7	1.2×10−8	Yes (?) (In humans, suggested osteo-metabolism (bone) growth factor)		5
90	Thorium		1×10−7		No	toxic
92	Uranium		1×10−7	3.0×10−9	No	toxic
62	Samarium		5.0×10−8		No
74	Tungsten		2.0×10−8		No		6
4	Beryllium		3.6×10−8	4.5×10−8	No	toxic	2
88	Radium		3×10−14	1×10−17	No	toxic	2

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

Most of the elements needed for life are relatively common in the Earth's crust. There are exceptions: cobalt for instance makes up only about 25 parts per million of the Earth's crust but is essential for human life. Conversely most of the common elements are necessary for life. An exception is aluminum, 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.Transferrins can bind aluminum.

Other elements

Of the 94 naturally occurring chemical elements (which now include Neptunium and Plutonium) 60 are listed in the table above. Of the remaining 34, it is not known how many occur in the human body. For some of these elements, numbers for concentrations in various tissues or organs is available, typically from studies involving small population sample sizes.

Noble Gases

Concentration of noble gasses in whole blood.

Atomic number	Element	Fraction of volume	Atomic percent	Positive health role in mammals	Negative effects of excess	Group
2	Helium	37×10−9			asphyxiant	18
10	Neon	138×10−9			asphyxiant	18
18	Argon	230×10−6			asphyxiant	18
36	Krypton	550×10−9			asphyxiant	18
54	Xenon	9.7×10−9			asphyxiant	18
86	Radon*	700×10−21			highly radioactive	18

* hypothetical value for radon based on 10 Bq/m³ and 0.4 blood/air partition coefficient.

Lanthanides

Of the seventeen rare earth elements (REEs), fifteen belong to the lanthanide series. The other two, scandium and yttrium, are listed in the table above, as are three lanthanides: lanthanum, cerium, and samarium. Of the remaining twelve lanthanides, eleven are listed below. No information is available regarding the remaining lanthanide, promethium.

Concentration of rare earth elements / lanthanides in blood serum.

Atomic number	Element	g/ml-1 blood serum	Atomic percent	Positive health role in mammals	Negative effects of excess	Group
59	Praseodymium	11×10−12			low to moderate toxicity	n/a
60	Neodymium	33.7×10−12			low to moderate toxicity	n/a
63	Europium	82×10−12			comparable to other heavy metals	n/a
64	Gadolinium	7.2×10−12			free ions highly toxic	n/a
65	Terbium	1.3×10−12			low to moderate toxicity	n/a
66	Dysprosium	9.6×10−12			mildly toxic when ingested	n/a
67	Holmium	2.55×10−12			low acute toxicity	n/a
68	Erbium	9.5×10−12			low to moderate toxicity	n/a
69	Thulium	1.69×10−12			soluble salts slightly toxic in large amounts	n/a
70	Ytterbium	13.2×10−12			all compounds highly toxic	n/a
71	Lutetium	2.46×10−12			oxide powder is toxic	n/a

Essential elements on the periodic table

Periodic table highlighting dietary elements

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	*	Lu	Hf	Ta	W	Re	Os	Ir	Pt	Au	Hg	Tl	Pb	Bi	Po	At	Rn
Fr	Ra	**	Lr	Rf	Db	Sg	Bh	Hs	Mt	Ds	Rg	Cn	Uut	Fl	Uup	Lv	Uus	Uuo
			*	La	Ce	Pr	Nd	Pm	Sm	Eu	Gd	Tb	Dy	Ho	Er	Tm	Yb
			**	Ac	Th	Pa	U	Np	Pu	Am	Cm	Bk	Cf	Es	Fm	Md	No

The four organic basic elements

Quantity elements

Essential trace elements

Possible structural or functional role in mammals

Composition by molecule type

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

• Water
• Proteins – including those of hair, connective tissue, etc.
• Fats (or lipids)
• Apatite in bones
• Carbohydrates such as glycogen and glucose
• DNA
• Dissolved inorganic ions such as sodium, potassium, chloride, bicarbonate, phosphate
• Gases such as oxygen, carbon dioxide, nitrogen oxide, hydrogen, carbon monoxide, 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 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:

Molecule	Percent of Mass	Mol.Weight (daltons)	Molecules	Percent of Molecules
Water	65*	18*	1.74×1014	98.73
Other Inorganics	1.5	N/A	1.31×1012	0.74
Lipids	12	N/A	8.4×1011	0.475
Other Organics	0.4	N/A	7.7×1010	0.044
Protein	20	N/A	1.9×1010	0.011
RNA	1.0	N/A	5×107	3×10−5
DNA	0.1	1×1011	46*	3×10−11

*The amount of water is highly dependent on body composition and amount of fat. In adults in developed countries it 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. DNA: A human cell also contains mitochondrial DNA. Sperm cells contain less mitochondrial DNA than other cells. A mammalian red blood cell normally contains no nucleus in adulthood, and thus no DNA. However, nucleated red blood cells, or NRBCs, are present in the fetal and neonatal circulations, and may appear in mature mammals when disease is present.

Materials and tissues

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

• Muscle
• Fat
• Bone and teeth
• Brain and nerves
• Hormones
• Connective tissue
• Blood – 7% of body weight.
• Lymph
• Contents of digestive tract, including intestinal gas
• Urine
• Air in lungs

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 (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

• Hydrostatic weighing
• Dietary element
• Composition of blood
• List of human blood components
• Body composition
• Abundance of elements in Earth's crust
• Abundance of the chemical elements