Carbohydrates: Functions and Food Sources

Carbohydrates: Functions and Food Sources

Carbohydrate refers to a large family of organic compounds essentially made of three elements i.e. carbon, hydrogen and oxygen.

Carbohydrates are widely distributed in plant foods. They are mainly present in these foods in the form of three types of compounds called sugars, starches and fibre. All these carbohydrates are made up of some basic simple units. One prominent example of a basic unit is glucose. Other examples are fructose and galactose.

Table sugar (cane sugar) which we commonly use in our houses is a carbohydrate made up of two basic units i.e. one unit of glucose and one unit of fructose. On the other hand, a starch molecule is very large. It is made up of several basic units of glucose linked together. These chains of glucose can be straight or branched.

Examples of foods rich in starch are rice, wheat, maze and tapioca.

Fibre. like starch, is made up of a number of basic units. The term fibre includes several substances. Cellulose is one example. It is a substance made up of several glucose units. How, then, is it different from starch? It is the type of linkage between glucose units in cellulose that makes all the difference.

All these types of carbohydrates i.e. sugars, starches and fibre can also be classified as available and non-available carbohydrates. Carbohydrates like sugars and starches are digestible in the human digestive tract and hence can be made available to the body for its functioning. These carbohydrates are termed as available carbohydrates. Cellulose and certain other large carbohydrate molecules that cannot be digested in the human digestive tract are collectively referred to as fibre or non-available carbohydrates.

Food Sources

The list includes cereals and millets, roots and tubers, some fruits, sweeteners like cane sugar, jaggery and honey. You will find more details in Table. Cereals and millets are the main source of carbohydrates in Indian diets. All cereals like wheat, rice, and millets e.g. jowar, bajra and ragi contain considerable amounts of starch. So do roots and tubers like potato, tapioca, sweet potato, yam and colocasia. Fruits like mango, banana, sapota are, however, rich in carbohydrates in the sugar form, Cane sugar or cube sugar and other sweeteners like honey and jaggery are 95 per cent to 100 per cent carbohydrate (sugar form).

Carbohydrate Rich food
Food stuff Carbohydrate content per 100gm


Cane Sugar













sweet potato













  • Energy-giving function: The chief function of carbohydrates is to furnish energy for the working of the body. One gram of carbohydrate provides approximately 4 kilocalories (Kcal). Carbohydrate foods are widely distributed in nature and are the cheapest sources of energy. They usually provide 60-70 per cent of the total calories in our diets. The kilocalorie is the unit of measurement of energy. One kilocalorie is the amount of heat required to raise the temperature of 1 kilogram of water by 1 degree centigrade (°C). Do note that in nutrition. kilocalorie and calorie mean one and the same thing.

  • Protein-sparing action: Though proteins can be broken down in the bodv to meet the energy need, this is not their chief function. An insufficient amount of carbohydrates in the diet will force the body to break down proteins for releasing energy instead of using them for the body's growth and development. Carbohydrates. if taken in sufficient amounts to meet the energy needs of the body, spare proteins for their important basic role in the body i.e. supporting growth and body-building. This particular act of sparing proteins for other functions is termed as the protein-sparing action of carbohydrates.

  • Utilization of fats: Some amount of carbohydrate is needed for the proper utilization of fat in the body. Presence of carbohydrates in the diet prevents the body from breaking down too much fat for energy. In case of deficiency of carbohydrates in the diet, more fat will be broken down to meet the energy requirements of the body. Why is this harmful? The reason is that excessive fat breakdown can result in accumulation of by-products of fat metabolism. This accumulations causes a problem and can affect health.

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