Cations, Anions, and the Human Body
Dietary minerals are mainly inorganic ions. They are essential nutrients that must be obtained from the diet. Following is a list of some of the more important ions in the cells and fluids of our bodies:
- Sodium ions
are the principal cations found outside cells in the body. They help regulate and control the level of body fluids. Too little
leads to diarrhea, anxiety, a decrease in body fluids, and circulatory failure. However, most people have the opposite problemtoo much sodium ioningested mainly as table salt and salty snack foods. Too much
increases water retention, leading to high blood pressure (hypertension). About 50 million people in the United States suffer from hypertension. Uncontrolled hypertension can lead to stroke, heart attack, kidney failure, or heart failure. Antihypertensives are among the most prescribed drugs in the United States.
- Potassium ions
are the principal cations found inside cells in the body. Bananas, orange juice, and potatoes are good sources of
Potassium ions help regulate cellular functions, including nerve impulses and heartbeats, and the level of body fluids.
- Chloride ions
are the principal anions found outside cells in the body. They serve as counterions (ions necessary to balance electrical charge) for
in the extracellular fluid and for
in gastric juice. Like
chloride ions are ingested mainly as table salt. Like sodium and potassium ions, chloride ions are involved in maintaining acidbase and fluid balances. It is difficult to separate the effect of too much
from that of too much
both seem to be involved in hypertension. Too little dietary
is rare, but it can result from heavy sweating, chronic diarrhea, and vomiting.
- Calcium ions
occur mainly in the skeleton and account for 1.52% of body mass.
is therefore essential for building and maintaining bones and teeth. Also,
plays a crucial role in blood clotting, muscle contraction, and the transmission of nerve signals to cells. An adequate supply of
is especially important during pregnancy and in growing children. It helps to prevent osteoporosis in older people. Good sources of calcium are milk and other dairy products, nuts, and legumes.
- Magnesium ions
like
are found mainly in the bones, but they are also vital components of many enzymes, which are substances our bodies need in order to release energy from the food we eat. Good sources of
are green vegetables (
is a component of the chlorophyll in all green plants), milk, bread, cereals, and potatoes.
- Phosphate ions exist mainly as
and
in body fluids. About 85% of the phosphorus-containing ions in the body are in the bones, where they act as the counterions for
Also, they play an important role in energy production from food. Good sources of phosphate are milk and other dairy products, cereals, and meat.
- In addition to the above ions, the body needs smaller amounts of ions found in trace minerals. These include the ions iron(II), chromium(III), copper(II), zinc, fluoride, iodide, and bicarbonate, as well as the hydrogen ion. Also required are compounds of manganese, molybdenum, and selenium, although these are not necessarily in the form of simple ions. These trace minerals play a variety of roles, several of which are discussed in other chapters.
Knowledge of ions is important not only to your success in a chemistry course but also to an understanding of many critical life processes.