Most of the elements needed for life are relatively common in the Earth's crust. Of the remaining 33, it is not known how many occur in the human body. Of the 94 naturally occurring chemical elements, 61 are listed in the table above. Possibly (suggested osteo-metabolism (bone) growth factor) Uncoated nanoparticles possibly genotoxic the molybdenum oxotransferases, Xanthine oxidase and Sulfite oxidase) Yes (intercorrelated with the functions of several enzymes, hormones and vitamins) Yes ( AUS, NZ), No ( US, EU), Maybe ( WHO) Elements listed as 'Possibly' or 'Probably' essential are those cited by the National Research Council (United States) as beneficial to human health and possibly or probably essential. 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 B 12).

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. 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. In a large sample of adults of all ages and both sexes, the figure for water fraction by weight was found to be 48 ☖% for females and 58 ☘% water for males. This varies substantially by age, sex, and adiposity. The adult human body averages ~53% water. The numbers in the table are averages of different numbers reported by different references. 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 relative amounts of each element vary by individual, mainly due to differences in the proportion of fat, muscle and bone in their body. About 29 of these elements are thought to play an active positive role in life and health in humans. The average 70 kg (150 lb) adult human body contains approximately 7 ×10 27 atoms and contains at least detectable traces of 60 chemical elements. Fluorine is used by a number of plants to manufacture toxins but only functions in humans as a local topical hardening agent in tooth enamel. One study has indicated bromine to be necessary to collagen IV synthesis in humans. Bromine is used abundantly by some (though not all) lower organisms, and opportunistically in eosinophils in humans. Some elements (silicon, boron, nickel, vanadium) are probably needed by mammals also, but in far smaller doses. In humans, arsenic is toxic, and its levels in foods and dietary supplements are closely monitored to reduce or eliminate its intake. 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). Not all elements which are found in the human body in trace quantities play a role in 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. 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. Only about 0.85% is composed of another five elements: potassium, sulfur, sodium, chlorine, and magnesium. Pie charts of typical human body composition by percent of mass, and by percent of atomic composition ( atomic percent).Ībout 99% of the mass of the human body is made up of six elements: oxygen, carbon, hydrogen, nitrogen, calcium, and phosphorus. 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.Įlements The main elements that compose the human body molecules (including water) can be summarized as CHNOPS. In terms of tissue type, the body may be analyzed into water, fat, connective tissue, muscle, bone, etc.

This can be done in terms of the chemical elements present, or by molecular type e.g., water, protein, fats (or lipids), hydroxylapatite (in bones), carbohydrates (such as glycogen and glucose) and DNA. Not to be confused with Human anatomy or Body composition (physical fitness).īody composition may be analyzed in various ways.

Atomic weight of magnesium phosphate