Substances the human body needs

Human Body’s Need for Energy and Material

Just as a machine needs an energy source like gasoline, coal, or electricity to operate, the human body also needs certain substances for its energy and heat. Furthermore, the human body expels and discards about three kilograms of harmful substances daily, such as sweat, urine, and similar waste.

Of course, for a person to live, it is essential to take in new substances to replace those expelled from the body: these new materials are food, drink, and air.

The human body temperature must constantly be 37
∘
C (98.6°F). Part of this heat ensures that the water in the body evaporates and exits through the pores beneath the hairs, and another part ensures that the food, drink, and air inside our body are warmed up.

The human body is a constantly moving machine. Even when we stand still, it performs many tasks: it maintains an upright posture, breathes, digests, its heart beats, it thinks, reads—in short, it continues to work.

What Substances is the Human Body Composed Of?

The human body is mainly composed of the following substances: carbon, hydrogen, oxygen, nitrogen, calcium, phosphorus, and iron. Calcium is found especially in bones, carbon, nitrogen, water (i.e., hydrogen and oxygen) are found throughout the body, phosphorus is found especially in the brain, and iron is found especially in the blood.

To maintain human health, the body must be supplied with these substances. Naturally, humans cannot eat stones or other minerals. Only plants can do this. Plants absorb tiny mineral particles with their roots, which penetrate the soil and even the stones and minerals within. Humans, in turn, eat plants and animals, thus providing the minerals found in them to their bodies.

A host of processes take place inside this machine called the human body; the food, drink, and water that enter the body are converted into the materials the body uses up and expels. They become the energy and heat required by the body.

Human Body’s 24-Hour Operational Data

During the 24-hour operation of a person doing normal work, the body:

• Consumes 1.75 kg of food,
• Drinks 1.4 kg of water,
• Breathes 23 thousand times,
• Takes in 12 thousand liters of air, 2,400 liters of which is oxygen,
• Produces 1.8 liters of saliva, and
• Expels 1 liter of sweat.