The human body consists of 60 different elements, including oxygen, carbon, hydrogen, nitrogen, calcium, phosphorus, potassium, sulfur, sodium, chlorine, magnesium and 49 other elements in trace quantities.
The human body is an intricate piece of art consisting of a multitude of atoms, about 7 × 1027 atoms, to be more precise. In case you were curious, that number would be read as 7 billion billion billion.
However, not all these atoms are the same. Of the 118 known elements, 94 occur naturally, and the human body comprises 60 of these naturally occurring elements (Source).
Based on the number of atoms and their contribution to the total weight of the human body, the elements can be divided into three groups: the main elements, secondary elements, and trace elements.
The main elements, as the name implies, are those that are most essential for human life and the most abundant, followed in volume by the secondary elements. However, regarding trace elements, they are not all known to be involved in the functioning of the human body.
The four main elements in the human body are oxygen, hydrogen, carbon, and nitrogen.
Approximately 60% of the human body is composed of water. Therefore, it shouldn’t come as a surprise that oxygen and hydrogen, the two elements that make up water, are some of the most abundant elements in the human body. Oxygen is the most abundant, while hydrogen occupies the third place in the list.
Water (H2O) is composed of two parts hydrogen and one part oxygen. Hydrogen, therefore, enjoys a greater atomic percentage than oxygen and every other element in the human body. However, considering that oxygen is the heavier element (atomic weight of oxygen is 16.00 amu or 2.6 x 10-23 grams), it contributes the most to the overall weight of a human.
For an average human weighing around 70 kilograms, oxygen alone contributes 43kg (65% of the total body weight), while hydrogen comes in at 7kg (10% of the total body weight). As for the number of atoms, hydrogen tops all elements, with a total atomic percentage of 62%, followed by oxygen at 24%.
Oxygen, in the form of water, helps regulate our body temperature and osmotic pressure, while molecular oxygen (that we inhale) plays a vital role in converting glucose to ATP molecules. Oxygen is also a component of all four major organic compounds (protein, carbohydrates, lipids, and nucleic acids) found in the human body. However, too much oxygen can prove harmful to the human body. Like oxygen, hydrogen is mostly present in the form of water and is found in every single organic compound.
Carbon, the central element of organic compounds, is the second-most abundant element in the human body and contributes roughly 18% of the total body weight. Carbon is the primary element for all life on Earth and is at the base of all organic compounds.
Coming in after carbon and fourth on the list of abundance is nitrogen. This element is responsible for 3% of the total body weight of a human. Nitrogen is the most abundant element in Earth’s atmosphere and sneaks inside our body alongside oxygen with every breath we take. However, the human body has no use for nitrogen in its gaseous state and therefore exhales it immediately, but it accepts nitrogen from food. The element is an important component of amino acids (which are used to build proteins) and nucleic acids like DNA and RNA (genetic material).
Secondary elements include calcium, phosphorus, potassium, sulfur, sodium, chlorine and magnesium.
Partly thanks to calcium powder adverts, you may already know that human bones are primarily composed of calcium. Calcium is the fifth-most abundant element and the most abundant mineral in the human body. It represents approximately 1.5% of the total body weight. While 99% of calcium is found in the bones & teeth (in compounds like hydroxyapatite), the element also plays an important role in contracting muscles and in the regulation of proteins.
Phosphorus follows calcium in the order of abundance (1% of the total body weight) in the human body. It is primarily found in ATP (adenosine triphosphate) molecules and in bones, alongside calcium.
Next up on the list are potassium (0.35% of body weight) and sodium (0.15% of body weight). Their positively charged ions help in the conduction of nerve signals and in regulating the amount of fluid in the human body. Potassium also plays a role in every heartbeat.
Sulfur (0.25% of body weight) is a component of certain amino acids, like cysteine and methionine, and also of vitamin H or B7 (Biotin) and vitamin B1 (Thiamine).
The final two elements with a substantial contribution to the overall mass of the human body are chlorine (0.15% of body weight) and magnesium (0.005% of body weight). Chlorine is found in the stomach in the form of hydrochloric acid, aids in the body’s balance of water & salt, and plays the role of a catalyst in converting ATP to ADP. Magnesium, on the other hand, is involved in multiple metabolic and enzymatic reactions, while also playing a structural role in bones and teeth.
There are 49 other elements found in trace quantities in the human body. However, of these 49 elements, only some are believed to be essential for human life, while some serve no purpose, but do no harm. These substances are considered contaminants. Examples of contaminant elements include aluminum, titanium, cesium, silver, etc.
The trace elements that are essential for human life include iron, zinc, copper, iodine, selenium, chromium, manganese, lithium, molybdenum and cobalt. Iron is perhaps the most important, as it is responsible for transporting oxygen to red blood cells in the form of hemoglobin. Zinc and copper are found in certain proteins, while thyroid hormones triiodothyronine (T3) and thyroxine (T4) comprise iodine.
There are also some elements, such as silicon, boron, nickel and vanadium, that are deemed possibly or probably essential for human life. Elements such as lead, antimony, thallium and radioactive elements like thorium, uranium, and radium are toxic to the human body.
Nonetheless, these 60 elements are responsible for everything that we are as humans!