Carbohydrates in human nutrition: Role and other functions

carbohydrates in human nutrition


Food is the main source of survival for the living world and the only source of nutrition for animals and the human body. After taking food in the form of solid, semi-solid, or liquid, it is digested in the human body through various processes. The human body needs energy for various physiological functions. Thus all the organic and inorganic elements present in the food increase the work efficiency of the body. Help in performing the basic functions of the organism, and maintains good health. There are different types of food with different types of components. The function of each component is also different. One such component of the food is carbohydrates, which are used in large quantities in the daily food chart. The source and role of carbohydrates in human nutrition are discussed below (2) & (5).


According to nutrition science, carbohydrates are the main source of energy in the body. Carbohydrates are polyhydroxy aldehydes or polyhydroxy ketones or substances.

The chemical formula of carbohydrates is C₆H₁₂O₆. Carbohydrate words come from the Latin word “carbo” and the Greek word, “hydro”. The word “carbo” means carbon and the word, “hydro” means water. A carbohydrate molecule contains 6 carbon atoms, 12 hydrogen atoms, and 6 oxygen atoms (4).


1. Carbohydrate is an organic element.

2. The empirical formula of common carbohydrate is (CH₂O)

3. This type of food generates energy in the human body. Nearly 1 gm of carbohydrate provides 4 kcal of energy.

4. The ratio of hydrogen and oxygen in carbohydrates is 2:1.

5. This type of food is broken down by amyl lytic enzymes in the human body.

6. Carbohydrates are made up of hydrogen, oxygen, and carbon.

7. The structure of carbohydrates is both chain-shaped and ring-shaped.

8. Carbohydrates are colorless crystalline compounds with a sweet taste.

9. Chemically carbohydrates are polyhydric alcohol compounds (4) & (6).

Source of carbohydrates

Carbohydrates are mainly found in both vegetable and animal sources. There are a variety of foods in nature that contain carbohydrates.

1. Plant source

Rice, wheat, corn, potato, sweet potato, beetroot, dates, grapes, apples, ripe mango, banana, orange, papaya, sugarcane, molasses, sugar, vegetables, watermelon, cereals, millet, pulses, nuts, roots, potato, flour, sago, barley, etc. are the plant sources of carbohydrates

2. Animal source

Goat liver, cow’s and buffalo’s milk, etc. are the animal sources of carbohydrates (3) & (6).

Classification of carbohydrates

There are three types of carbohydrates. All carbohydrates are organic compounds consisting of carbon, oxygen, and hydrogen, in which carbohydrates are divided into three types based on the number of molecules in the carbon.

1. Monosaccharide

The simple carbohydrates that are made up of a single molecule are called monosaccharides. That means, no simple sugar compounds are found when monosaccharides are analyzed.

They are classified based on the number of carbon, which is between 3 to 10. If the number of carbon molecules is 3 then it is called triose, if it is 4 then it is tetrose, if it is 5 then it is a pentose, if the carbon number is 6 then it is called hexose. Monosaccharides are a form of carbohydrates and are grouped into aldoses and ketoses (3) & (5).


Glucose, fructose, galactose, ribose, etc. are examples of monosaccharides.

Ribose is called pentose because ribose is made up of five carbon atoms.

Glucose, fructose, galactose are called hexose because they are made up of six carbon atoms.

Glucose and galactose are called aldohexose and fructose are called ketohexose for the presence of aldehyde and ketone groups.

Fructose is found in fruits, Glucose is found in honey, sweets, fruits, and Galactose is found in milk (2) & (5).

2. Disaccharide

The carbohydrates that are made up of two monosaccharide molecules are called disaccharides. This type of carbohydrate is formed by the combination of two monosaccharides (4).





1. MaltoseMaltose is found in germinated seeds. During the germination of grains, some starch is converted into maltose.Glucose + glucose
2. SucroseSucrose is found in Sugarcane, molasses, sugar, date’s juice.Glucose + fructose
3. LactoseLactose is a milk carbohydrate. Cow and buffalo milk contains 4% lactose and breast milk contains 7% lactose (3).Glucose + galactose

3. Polysaccharide

Carbohydrates that are made up of more than ten monosaccharides are called polysaccharides. Polysaccharides are complex carbohydrates. The common symbol of polysaccharides is (C₆H₁₂O₅) n. Monosaccharides 1, 4, and 1, 6 are joined by linkage to form polysaccharides (2).


Examples of polysaccharides are starch, glycogen, cellulose, dextrin, etc. The following is a description of some polysaccharides.

1. Starch

This type of polysaccharide is less soluble in water. Starch is found in rice, wheat, flour, flattened rice, potato, barley, green apples, banana, popcorn, puffed rice, sweet potato, carrots, papaya, etc. When the fruit ripens, the starch is dissolved. People can live for a long time without consuming protein and eating only a lot of starch foods (4) & (5).

2. Glycogen

Glycogen is stored in the liver and muscles of animals. It is water-soluble. Glycogen contains fewer glucose molecules than starch. It is a type of stored carbohydrate. Glycogen is also found in fungi and yeasts (5).

3. Cellulose

It is found in paper, grass, cotton, vegetables, etc. Cellulose is not digested in the human body. The cell of all plants is made up of cellulose. This type of polysaccharide is insoluble in water. Animals can take cellulose as food (3) & (4).

4. Dextrin

Dextrin is a special type of polysaccharide. It is produced as a result of the digestion of starch or glycogen. It is not found in nature. Dextrin is the intermediate state between starch and sugar. Dextrin is also produced by toasting the bread (2).

5. Inulin

Inulin is also a type of polysaccharide. The only source of inulin is plant source. There are over 4000 sources of these carbohydrates. It is found in the roots of puffed tubers, dahlia, onions, garlic, etc. Hydrolysis of inulin produces fructose (2).

The daily amount of carbohydrates in the diet

There is a definite need for carbohydrates in the daily diet of the human body. It acts as a source of energy. The body needs carbohydrates for the oxidation of fats and the synthesis of some amino acids (2). The amount of carbohydrates required to be included in the daily diet chart is described below:

Name of different groupsThe required amount of carbohydrates
1.     Adult males and females60 – 70%
2.     Pregnant and maternity woman50 – 70%
3.     Children (up to 1-year-old)40 – 50%
4.     Preschool children40 – 60%
5.     Teenagers (males and females)50 – 70%

Carbohydrates in human nutrition

It has an essential role in the human body. It is one of the most significant nutrients for the human. The amount of carbohydrates is also the highest in the daily diet chart of human beings. The function of carbohydrates in human nutrition is very important.

  • Excess carbohydrates taken with food are stored in the liver and muscles in the form of glycogen. It also turns into fat in the body’s fatty tissue and liver and stores energy for the future.
  • The primary function of carbohydrates food is to provide heat energy for various biological activities. The caloric value of carbohydrates is 4.1 kcal/gm.
  • Carbohydrates play a significant role in the metabolism of amino acids. In animals, the metabolic substances of carbohydrates can lead to the formation of some unnecessary hydrocarbon structures of amino acids.
  • Excessive intake of carbohydrates reduces the metabolism of protein in the body. This is why dietary carbohydrates reduce the body’s need for protein.
  • Carbohydrates prevent ketosis disease. The deficiency of carbohydrates in the diet increases the breakdown of body fat. The breakdown of the fat results in the production of ketone bodies in the body and ketosis is observed in the body.
  • The galactose produced by the hydrolysis of lactose plays a very important role in the development of the brain.
  • The carbohydrates called cellulose present in vegetables formed feces as dietary fiber. It helps in intestinal compression of the digestive tract and relieves constipation.
  • The human body produces organic acids, fatty acids, amino acids, etc. from carbohydrates by metabolism. All these acids play a special role in protein synthesis and fat synthesis.
  • In the presence of carbohydrates, a type of bacteria produces vitamin K and vitamin B complex in the human intestine.
  • Carbohydrates help in the combustion of fats.
  • Carbohydrates such as glycoproteins and glycolipids participate in the structure of cell membrane systems (4) & (1).

Effects of excessive carbohydrates are on the body

Any food should not be taken in large quantities. The main 6 elements in the food need to be in the right amount of the body. If for some reason the amount of carbohydrates in the body increases, then there are various problems in the body.

  • When large amounts of carbohydrates are consumed, it stays in the intestines. Lactose or cellulose produces gas in the stomach.
  • Excess carbohydrates create fat in the body, resulting in decreased energy, increasing the number of triglycerides in the blood in some cases.
  • Eating large amounts of sugar (carbohydrates) can lead to tooth decay.
  • Due to the intake of more carbohydrates, the body cannot absorb the protein, minerals, vitamins properly. So malnutrition is seen and the body’s immunity is reduced (2).

So it is important to keep the right amount of carbohydrates in the daily diet chart. Carbohydrates should not be eating in large quantities and even if eating in small quantities, it causes various diseases in the body.

Among the nutrients in food, fats produce the most heat and energy in the body. The presence of carbohydrates is essential for this heat and energy supply. In case of a deficiency of carbohydrates, the combustion process is not completed. This causes the body to produce some toxins called ketone bodies. These ketone bodies cause ketosis disease in the body. Ketosis causes excessive fatigue and a lack of electrolysis in the body. Many times hypoglycemia (decreases the amount of sugar in the blood) occurs (2) & (1).

Written By: Manisha Bharati


1. Ajoy Paul. Zoology Honours (volume 1). Books and Allied (P) Ltd., Kolkata (India). Chapter: Carbohydrates. Page no: 747 to 760.

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