2.2 Major minerals
The major mineral elements, defined here as those where 25 g or more is present in the body, are listed in Table 4.
Table 4 The major mineral elements required by the body. The recommended intakes (RNI) per day for a woman between the ages of 25 and 50 are listed. The approximate adult body content, functions and common food sources of the minerals are also shown.
|Element (symbol)||RNI/g||Body content/g||Functions||Main food sources|
|calcium (Ca)||0.7||1000||major structural component of bones and teeth; necessary for many enzymes, including those of blood clotting, muscle contraction and conduction of nerve impulses||milk, cheese, bread and flour (if fortified),cereals, green vegetables|
|chlorine (Cl)||2.5||100||major negative ion (as chloride,C1 − ) in body fluids; present in stomach secretions as hydrochloric acid (HCl)||main source is salt (sodium chloride, NaCl) used in food processing, cooking,and at the table|
|magnesium (Mg)||0.3||25||present in bone, inside cells and in body fluids; needed for some enzymes||milk, bread and other cereal products, potatoes and other vegetables|
|Phosphorus (P)||0.55||700||present in bones and teeth; essential for ATP and DNA and many other molecules||milk, cheese, bread and cereals, meat and meat products, nuts|
|potassium (K)||3.5||140||main positive ion inside cells; K + also present in extracellular fluids; essential for conduction of nerve impulses, also for the maintenance of ion concentration gradients across cell membranes||widely distributed in vegetables, meat, milk, fruit and fruit juices|
|sodium (Na)||1.6||100||major positive ion in extracellular fluids; Na + also present inside cells; essential for conduction of nerve impulses and active transport of small molecules across cell membranes (e.g. absorption from gut)||main source is salt (sodium chloride, NaCl) used in food processing, cooking, and at the table|
|sulfur (S)||no value set||150||present in proteins||protein-rich foods; meat, fish, eggs, milk, bread, cereals|
You will see that Table 4 is arranged with the elements in alphabetical order.
If the table were to be arranged based on the recommended nutrient intake values, with the highest at the top, which two elements would appear at the top of the table?
If, alternatively, the elements which occurred in the largest amounts in the body were to be at the top, which two elements would be at the top, and which one would appear at the bottom?
The two elements with the highest reference nutrient intake (RNI) values are potassium (3.5 g) and chlorine (2.5 g).
The two elements that occur in the largest amounts in the body are calcium (1000 g or 1 kg) and phosphorus (700 g). The one in the list that occurs in the smallest amounts in magnesium (though there are many more elements that are present in even smaller quantities in the body as you will see later).