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), 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.

Elements

The main elements that comprise the human body (including water) can be summarized as CHNOPS.

	Element	Symbol	percent mass	percent atoms
	Oxygen	O	65.0	24.0
	Carbon	C	18.5	12.0
	Hydrogen	H	9.5	62.0
	Nitrogen	N	2.6	1.1
	Calcium	Ca	1.3	0.22
	Phosphorus	P	0.6	0.22
	Potassium	K	0.2	0.03
	Sulfur	S	0.3	0.038
	Sodium	Na	0.2	0.037
	Chlorine	Cl	0.2	0.024
	Magnesium	Mg	0.1	0.015
	All others		< 0.1	< 0.3

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]

Zdroj:https://en.wikipedia.org?pojem=Composition_of_the_human_body
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Atomic number	Element	Fraction of mass [11][12][13][14][15][16]	Mass (kg)[17]	Atomic percent	Essential in humans[18]	Negative effects of excess	Group
8	Oxygen	0.65	45	24	Yes (e.g. water, electron acceptor)[19]	Reactive oxygen species	16
6	Carbon	0.18	13	12	Yes[19] (organic compounds)		14
1	Hydrogen	0.10	7	62	Yes[19] (e.g. water)	Acidosis	1
7	Nitrogen	0.02–0.03	1.8	1.1	Yes[19] (e.g. DNA and amino acids)		15
20	Calcium	0.011–0.015	1.0	0.22	Yes[19][20][21] (e.g. Calmodulin and Hydroxylapatite in bones)	Hypercalcaemia	2
15	Phosphorus	5–7×10−3 [22]	0.78	0.22	Yes[19][20][21] (e.g. DNA, Phospholipids and Phosphorylation)	Hyperphosphatemia	15
19	Potassium	1.5–2×10−3[23]	0.14	0.033	Yes[19][20] (e.g. Na+/K+-ATPase)	Hyperkalemia	1
16	Sulfur	2.5×10−3	0.14	0.038	Yes[19] (e.g. Cysteine, Methionine, Biotin, Thiamine)	Sulfhemoglobinemia	16
11	Sodium	1.5×10−3	0.10	0.037	Yes[20] (e.g. Na+/K+-ATPase)	Hypernatremia	1
17	Chlorine	1.5×10−3	0.095	0.024	Yes[20][21] (e.g. Cl-transporting ATPase)	Hyperchloremia	17
12	Magnesium	500×10−6	0.019	0.0070	Yes[20][21] (e.g. binding to ATP and other nucleotides)	Hypermagnesemia	2
26	Iron*	60×10−6	0.0042	0.00067	Yes[20][21] (e.g. Hemoglobin, Cytochromes)	Iron overload	8
9	Fluorine	37×10−6	0.0026	0.0012	Yes (AUS, NZ),[24] No (US, EU),[25][26] Maybe (WHO)[27]	Fluorine: Highly toxic Fluoride: Toxic in high amounts	17
30	Zinc	32×10−6	0.0023	0.00031	Yes[20][21] (e.g. Zinc finger proteins)	Zinc toxicity	12
14	Silicon	20×10−6	0.0010	0.0058	Probably[28]		14
31	Gallium	4.9×10−6	0.0007	0.00093	No	Gallium halide poisoning[29]	13
37	Rubidium	4.6×10−6	0.00068	0.000033	No	Potassium replacement	1
38	Strontium	4.6×10−6	0.00032	0.000033	No	Calcium replacement	2
35	Bromine	2.9×10−6	0.00026	0.000030	Maybe[30]	Bromism	17
82	Lead	1.7×10−6	0.00012	0.0000045	No	Lead poisoning	14
29	Copper	1×10−6	0.000072	0.0000104	Yes[20][21] (e.g. copper proteins)	Copper toxicity	11
13	Aluminium	870×10−9	0.000060	0.000015	No	Aluminium poisoning	13
48	Cadmium	720×10−9	0.000050	0.0000045	No	Cadmium poisoning	12
58	Cerium	570×10−9	0.000040		No
56	Barium	310×10−9	0.000022	0.0000012	No	toxic in higher amounts	2
50	Tin	240×10−9	0.000020	6.0×10−7	Maybe[1]		14
53	Iodine	160×10−9	0.000020	7.5×10−7	Yes[20][21] (e.g. thyroxine, triiodothyronine)	Iodine-induced hyperthyroidism	17
22	Titanium	130×10−9	0.000020		No		4
5	Boron	690×10−9	0.000018	0.0000030	Probably[10][31]		13
34	Selenium	190×10−9	0.000015	4.5×10−8	Yes[20][21] (e.g. selenocysteine)	Selenium toxicity	16
28	Nickel	140×10−9	0.000015	0.0000015	Maybe[1]	Nickel Toxicity	10
24	Chromium	24×10−9	0.000014	8.9×10−8	Maybe[1][20][21]		6
25	Manganese	170×10−9	0.000012	0.0000015	Yes[20][21] (e.g. Mn-SOD)	Manganism	7
33	Arsenic	260×10−9	0.000007	8.9×10−8	Maybe[1][2]	Arsenic poisoning	15
3	Lithium	31×10−9	0.000007	0.0000015	Possibly (intercorrelated with the functions of several enzymes, hormones and vitamins)	Lithium toxicity	1
80	Mercury	190×10−9	0.000006	8.9×10−8	No	Mercury poisoning	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[20][21] (e.g. the molybdenum oxotransferases, Xanthine oxidase and Sulfite oxidase)		6
32	Germanium		5×10−6		No		14
27	Cobalt	21×10−9	0.000003	3.0×10−7	Yes (e.g. Cobalamin/Vitamin B12)[32][33]		9
44	Ruthenium	22×10−9	0.000007		No [34]		8
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	6×10−9	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
39	Yttrium		6×10−7		No		3
83	Bismuth		5×10−7		No		15
81	Thallium		5×10−7		No	highly toxic	13
49	Indium		4×10−7		No		13
79	Gold	3×10−9	2×10−7	3.0×10−7	No	uncoated nanoparticles possibly genotoxic[35][36][37]	11
21	Scandium		2×10−7		No		3
73	Tantalum		2×10−7		No		5
23	Vanadium	260×10−9	0.000020	1.2×10−8	Possibly[10] (suggested osteo-metabolism (bone) growth factor)		5
90	Thorium		1×10−7		No	toxic, radioactive
92	Uranium		1×10−7	3.0×10−9	No	toxic, radioactive
62	Samarium		5.0×10−8		No