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 cell) are not human cells, but bacteria residing in the normal human gastrointestinal tract.
Elements The main elements that the human body comprises (including water) can be summarized as CHNOPS. Element Symbol percentmass percentatoms Oxygen O65.024.0 CarbonC18.512.0 HydrogenH9.562.0 NitrogenN2.61.1 CalciumCa1.3 0.22 PhosphorusP0.60.22 SulfurS0.30.038 PotassiumK0.20.03 SodiumNa0.20.037 ChlorineCl0.20.024 MagnesiumMg0.10.015 All others < 0.1< 0.3
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. 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.
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. 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.
Elemental composition list
The average adult human body contains approximately 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."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:
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.Use WP:CALC for the mean of means for males and females, since the two groups are of about equal size 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.See table 1. here 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 other 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 US National Research Council as beneficial to human health and possibly or probably essential.
Atomic number Element Fraction of mass)Mass (kg)Atomic percentEssential in humansNegative effects of excessGroup 8 Oxygen 0.65 45 26 Yes (e.g. water, electron acceptor and DNA) Reactive oxygen species 16 6 Carbon 0.18 13 9.5 Yes (organic compounds) 14 1 Hydrogen 0.10 7 63 Yes (e.g. water and DNA) Acidosis 1 7 Nitrogen 0.02–0.03 1.8 1.1 Yes (e.g. DNA and amino acids) Nitrogen narcosis 15 20 Calcium 0.011–0.015 1.0 0.21 Yes (e.g. Calmodulin and Hydroxylapatite in bones) Hypercalcaemia 2 15 Phosphorus 5– 0.78 0.12 Yes (e.g. DNA, Phospholipids and Phosphorylation) Hyperphosphatemia 15 19 Potassium 1.5– 0.14 0.029 Yes (e.g. Na+/K+-ATPase) Hyperkalemia 1 16 Sulfur 0.14 0.049 Yes (e.g. Cysteine, Methionine, Biotin, Thiamine) Sulfhemoglobinemia 16 11 Sodium 0.10 0.041 Yes (e.g. Na+/K+-ATPase) Hypernatremia 1 17 Chlorine 0.095 0.027 Yes (e.g. Cl-transporting ATPase) Hyperchloremia 17 12 Magnesium 0.019 < 0.01 Yes (e.g. binding to ATP and other nucleotides) Hypermagnesemia 2 26 Iron* 0.0042 < 0.01 Yes (e.g. Hemoglobin, Cytochromes) Iron overload 8 9 Fluorine 0.0026 < 0.01 Yes (AUS, NZ),Australian National Health and Medical Research Council (NHMRC) and New Zealand Ministry of Health (MoH) No (US, EU),"Fluoride in Drinking Water: A Review of Fluoridation and Regulation Issues" Maybe (WHO) Fluorine: Highly toxic Fluoride: Toxic in high amounts 17 30 Zinc 0.0023 < 0.01 Yes (e.g. Zinc finger proteins) Zinc toxicity 12 14 Silicon 0.0010 < 0.01 Probably 14 31 Gallium 0.0007 < 0.01 No Gallium halide poisoning 13 37 Rubidium 0.00068 < 0.01 No 1 38 Strontium 0.00032 < 0.001 No Calcium replacement 2 35 Bromine 0.00026 < 0.001 Maybe Bromism 17 82 Lead 0.00012 < 0.001 No Lead poisoning 14 29 Copper 0.000072 < 0.001 Yes (e.g. copper proteins) Copper toxicity 11 13 Aluminium 0.000060 < 0.001 No Aluminium poisoning 13 48 Cadmium 0.000050 < 0.001 No Cadmium poisoning 12 58 Cerium 0.000040 < 0.001 No 56 Barium 0.000022 < 0.001 No toxic in higher amounts 2 50 Tin 0.000020 < 0.001 Maybe 14 53 Iodine 0.000020 < 0.001 Yes (e.g. thyroxine, triiodothyronine) Iodine-induced hyperthyroidism 17 22 Titanium 0.000020 < 0.001 No 4 5 Boron 0.000018 < 0.001 ProbablySafe Upper Levels for Vitamins and Mineral (2003), boron p. 164-71, nickel p. 225-31, EVM, Food Standards Agency, UK 13 34 Selenium 0.000015 < 0.001 Yes (e.g. selenocysteine) Selenium toxicity 16 28 Nickel 0.000015 < 0.0001 Maybe Nickel Toxicity 10 24 Chromium 0.000014 < 0.0001 Maybe 6 25 Manganese 0.000012 < 0.0001 Yes (e.g. Mn-SOD) Manganism 7 33 Arsenic 0.000007 < 0.0001 Maybe Arsenic poisoning 15 3 Lithium 0.000007 < 0.0001 Possibly (intercorrelated with the functions of several enzymes, hormones and vitamins) Lithium toxicity 1 80 Mercury 0.000006 < 0.0001 No Mercury poisoning 12 55 Caesium 0.000006 < 0.0001 No 1 42 Molybdenum 0.000005 < 0.0001 Yes (e.g. the molybdenum oxotransferases, Xanthine oxidase and Sulfite oxidase) 6 32 Germanium < 0.0001 No 14 27 Cobalt 0.000003 < 0.0001 Yes (e.g. Cobalamin/Vitamin B12) Cobalt poisoning 9 44 Ruthenium 0.000007 < 0.0001 No 8 51 Antimony 0.000002 < 0.0001 No toxic 15 47 Silver 0.000002 < 0.0001 No 11 41 Niobium 0.0000015 < 0.0001 No 5 40 Zirconium 0.000001 < 0.0001 No 4 57 Lanthanum < 0.0001 No 52 Tellurium < 0.0001 No 16 39 Yttrium < 0.0001 No 3 83 Bismuth < 0.0001 No 15 81 Thallium < 0.0001 No highly toxic 13 49 Indium < 0.0001 No 13 79 Gold < 0.0001 No uncoated nanoparticles possibly genotoxic 11 21 Scandium < 0.0001 No 3 73 Tantalum < 0.0001 No 5 23 Vanadium 0.000020 < 0.0001 Possibly (suggested osteo-metabolism (bone) growth factor) 5 90 Thorium < 0.0001 No toxic, radioactive 92 Uranium < 0.0001 No toxic, radioactive 62 Samarium < 0.0001 No 74 Tungsten < 0.0001 No 6 4 Beryllium < 0.0001 No toxic in higher amounts 2 88 Radium < 0.0001 No toxic, radioactive 2 2 Helium < 0.0001 No inert gas asphyxiation 18 10 Neon < 0.0001 No inert gas asphyxiation 18 18 Argon < 0.0001 No inert gas asphyxiation 18 36 Krypton < 0.0001 No inert gas asphyxiation 18 *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. Transferrins can bind aluminium.
Periodic table
Composition The composition of the human body can be classified as follows: Water Proteins Fats (or lipids) Hydroxyapatite in bones Carbohydrates such as glycogen and glucose DNA and RNA Inorganic ions such as sodium, potassium, chloride, bicarbonate, phosphate Gases mainly being oxygen, carbon dioxide Many cofactors.
The estimated contents of a typical 20-micrometre human cell is as follows: Compound type Percent of mass Mol. weight (daltons) Compound Percent of molecules Water 65 18 98.73 Other inorganics 1.5 N/A 0.74 Lipids 12 N/A 0.475 Other organics 0.4 N/A 0.044 Protein 20 N/A 0.011 RNA 1.0 N/A DNA 0.1 46
Tissues The main cellular components of the human body 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: Muscle Fat Bone and teeth Nervous tissue (brain and nerves) Hormones Connective tissue Body fluids (blood, lymph, urine) Contents of digestive tract, including intestinal gas Air in lungs Epithelium
Composition by cell type
There are many species of bacteria and other microorganisms that live on or inside the average healthy human body. In fact, there are roughly as many microbial as human cells in the human body by number.American Academy of Microbiology FAQ: Human Microbiome January 2014Judah L. Rosner for Microbe Magazine, February 2014. Ten Times More Microbial Cells than Body Cells in Humans? (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 List of organs of the human body 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
References