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Principles of nutrition – Part 2


Reasons people eat and chemical composition of the human body
Hunger is the commonest reason that people give for eating. The emptiness of the stomach coupled with a feeling of weakness and tiredness together with certain other stimuli cause the brain to give the signal of hunger. Whenever the stomach is filled up, the hunger signal sent out by the brain in response to hunger gets turned off. This happens even before digestion has progressed far enough for absorption of nutrients to have started. In other words, the first thing that happens for the hunger signal to be turned off is the filling of the stomach. The content of the food that fills the stomach is very important.

The body, tissues or organs may be deficient in or require several elements and vitamins and all of them should come from what the individual eats. There are individuals who eat because they like the taste of the food or because they are longing for a particular taste or flavour.


Very few individuals would tell you that they eat to get well or to remain healthy. As important as this third point is, it is unfortunate that not many people know this and so do not pay any particular attention to what they eat. If human beings were to eat for health or to be healed, then such programmed eating as practiced in most homes today would have been relegated to history. There are some other reasons people give for eating but suffice to say that whatever your reason for eating, you may want to know that you eat because your body has a need. For optimal health, wellbeing and wellness, these needs have to be met as they arise. You may not know it, when there is deficiency of one or more minerals; the body enters into a dis-ease mode, which is a warning signal that all is not well. This can be likened to a car in which a red light flashes on the dashboard when there is a minor fault in the engine. Pain anywhere in the body could be a signal that all may not be well in the body.
Chemical composition of the human body

Six elements, carbon, hydrogen, oxygen, nitrogen, phosphorus and calcium make up about 99% of the weight of the body. Another five elements make up 0.85% of the body. These elements are potassium, sodium, sulfur, chlorine and magnesium. 0.15% of the weight of the body is made up of trace elements. These are dietary minerals that are required in very minute quantities in their functions in the body. They function as co-factors in chemical reactions and assist in the physiological function of organs, muscles etc. Trace elements are also required in the physiological functions of the brain and nerves in the central nervous system. The composition of the human body can also be expressed by the molecules in it. For example, the following molecules can be said to be found in the body: water, carbohydrates such as glucose and the glycogen stores, protein, fats and oils etc. This being the case, these different molecules can be broken down into their elemental components. For example, water is made up of 2 atoms of hydrogen and a single atom of oxygen.


A carbohydrate is a macromolecule of carbon (C), hydrogen (H) and oxygen (O). The hydrogen: oxygen ratio is 2:1 as in water and the basic chemical formula of carbohydrate is Cm(H2O)n. The letters m and n may not necessarily be the same but they represent one of the four different groups of carbohydrates. These groups are referred to as saccharides, a synonym of carbohydrate.

The four groups are monosaccharide, disaccharides, oligosaccharides and polysaccharides.

Glucose, the most basic form of carbohydrates is a monosaccharide with the chemical formula C6H12O6. Smaller carbohydrates, monosaccharides and disaccharides are usually referred to as sugars and they commonly end with the prefix “-ose.” For example, we have glucose (grape sugar monosaccharide), sucrose (cane sugar disaccharide) and lactose (milk sugar disaccharide).

Amino acids are the organic compounds that combine together to form proteins.

Chemical composition of amino acids
Amino acids have a basic amino group (-NH2) and a carboxyl acid group (-COOH). Attached to this basic group is an organic R group that confers uniqueness to the amino acid. Carbon, hydrogen, oxygen and nitrogen are the four key elements found in amino acids. After water, amino acids are the most abundant components of proteins found in muscles and cells. They are combined together into peptide chains (polypeptides), which are the building blocks of proteins. Proteins found mostly in the musculature, give structural support to the human body. Enzymes, which are organic catalysts that catalyze the biochemical reactions that take place in the body, are also proteins. On rare occasions, proteins can be broken down for energy generation.


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