:Composition of the human body

File:element_abundance_human_body_ppm_chart.svg 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, & 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.

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.{{cite web |title=Arsenic in Food and Dietary Supplements |url=https://www.fda.gov/food/metals/arsenic-food-and-dietary-supplements |publisher=US Food and Drug Administration |access-date=20 August 2019 |date=22 May 2019}}

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.{{Cite journal|vauthors=McCall AS, Cummings CF, Bhave G, Vanacore R, Page-McCaw A, Hudson BG |title = Bromine Is an Essential Trace Element for Assembly of Collagen IV Scaffolds in Tissue Development and Architecture|journal = Cell|volume = 157|issue = 6|pages = 1380–92|year = 2014|pmid = 24906154|doi=10.1016/j.cell.2014.05.009|pmc=4144415}} 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.{{cite book|first1=David L |last1=Nelson|last2= Cox |first2=Michael M|title=Lehninger Principles of Biochemistry |publisher=Macmillan |edition=8th|isbn=978-1-319-23090-6|location=New York |date=2021}}

{{main article|mineral (nutrient)}}

The average {{convert|70|kg|abbr=on|adj=on}} adult human body contains approximately {{val|7|e=27}} atoms and contains at least detectable traces of 60 chemical elements.{{Cite web|url=https://education.jlab.org/qa/mathatom_04.html|title=Questions and Answers - How many atoms are in the human body?|website=education.jlab.org|accessdate=4 April 2023}} 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: [http://hdl.handle.net/10113/46493]

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. [http://ajcn.nutrition.org/content/33/1/27.full.pdf 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 element.

The elements listed below as "Essential in humans" are those listed by the US Food and Drug Administration as essential nutrients,{{cite web|url=https://www.fda.gov/Food/GuidanceRegulation/GuidanceDocumentsRegulatoryInformation/LabelingNutrition/ucm064928.htm|archive-url=https://wayback.archive-it.org/7993/20170404170950/https://www.fda.gov/Food/GuidanceRegulation/GuidanceDocumentsRegulatoryInformation/LabelingNutrition/ucm064928.htm|url-status=dead|archive-date=4 April 2017|title=Guidance for Industry: A Food Labeling Guide 14. Appendix F|publisher=US Food and Drug Administration|date=1 January 2013}} 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.{{cite book|author=Institute of Medicine|title=Dietary Reference Intakes: The Essential Guide to Nutrient Requirements|url=https://books.google.com/books?id=dYZZTgjDeccC&pg=PA415|access-date=21 June 2016|date=29 September 2006|publisher=National Academies Press|isbn=978-0-309-15742-1|pages=313–19, 415–22}}

*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.{{cite journal | last1=Willhite | first1=Calvin C. | last2=Karyakina | first2=Nataliya A. | last3=Yokel | first3=Robert A. | last4=Yenugadhati | first4=Nagarajkumar | last5=Wisniewski | first5=Thomas M. | last6=Arnold | first6=Ian M.F. | last7=Momoli | first7=Franco | last8=Krewski | first8=Daniel | title=Systematic review of potential health risks posed by pharmaceutical, occupational and consumer exposures to metallic and nanoscale aluminum, aluminum oxides, aluminum hydroxide and its soluble salts | journal=Critical Reviews in Toxicology | volume=44 | issue=sup4 | date=2014-09-18 | issn=1040-8444 | doi=10.3109/10408444.2014.934439 | pages=1–80|pmid=25233067|pmc=4997813}} Transferrins can bind aluminium.{{Cite journal | last1 = Mizutani | first1 = K. | last2 = Mikami | first2 = B. | last3 = Aibara | first3 = S. | last4 = Hirose | first4 = M. | title = Structure of aluminium-bound ovotransferrin at 2.15 Å resolution | doi = 10.1107/S090744490503266X | journal = Acta Crystallographica Section D | volume = 61 | issue = 12 | pages = 1636–42 | year = 2005 | pmid = 16301797}}

{{Periodic table (for higher organisms)}}

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:{{cite book |first=Robert A. |last=Freitas Jr. |title=Nanomedicine |url=http://www.foresight.org/Nanomedicine/Ch03_1.html |publisher=Landes Bioscience |year=1999 |isbn=978-1-57059-680-3 |no-pp=true |pages=Tables 3–1 & 3–2 |access-date=2011-04-06 |archive-date=2018-04-16 |archive-url=https://web.archive.org/web/20180416233300/http://www.foresight.org/Nanomedicine/Ch03_1.html |url-status=dead}}

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

{{main|List of distinct cell types in the adult human body}}

{{main|Human microbiome#Relative numbers}}

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.American Academy of Microbiology [http://academy.asm.org/index.php/faq-series/5122-humanmicrobiome FAQ: Human Microbiome] {{Webarchive|url=https://web.archive.org/web/20161231092333/http://academy.asm.org/index.php/faq-series/5122-humanmicrobiome |date=31 December 2016}} January 2014Judah L. Rosner for Microbe Magazine, February 2014. [http://www.asmscience.org/content/journal/microbe/10.1128/microbe.9.47.2 Ten Times More Microbial Cells than Body Cells in Humans?]{{Cite journal|last1=Gilbert|first1=Jack|last2=Blaser|first2=Martin J.|last3=Caporaso|first3=J. Gregory|last4=Jansson|first4=Janet|last5=Lynch|first5=Susan V.|last6=Knight|first6=Rob|date=2018-04-10|title=Current understanding of the human microbiome|journal=Nature Medicine|volume=24|issue=4|pages=392–400|doi=10.1038/nm.4517|issn=1078-8956|pmc=7043356|pmid=29634682}}{{Cite journal |vauthors=Sender R, Fuchs S, Milo R |date=January 2016 |title=Are We Really Vastly Outnumbered? Revisiting the Ratio of Bacterial to Host Cells in Humans |journal=Cell |volume=164 |issue=3 |pages=337–40 |doi=10.1016/j.cell.2016.01.013 |pmid=26824647 |doi-access=free}}

(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.

• 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

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Category:Biochemistry

Category:Human anatomy

Category:Human physiology