History of Word Nutrition:

The word nutrition first becomes visible in 1551 and comes from the Latin word nutrire, meaning “to nourish.” Nutritional science covers a wide spectrum of disciplines.

As a result, nutritional scientists can specialize in certain aspects of nutrition biology, physiology, immunology, biochemistry, education, psychology, and sustainability.

Definition of Nutrition:

The process of taking in food and using it for growth and development, metabolism, and repair is known as nutrition.

Here we will discuss the nutrition of animals and components of nutrition in Human

Components of Human Nutrition:

The nutritional requirements of humans and other animals are relatively complex as co animals compared to plants like other animals. The nutrients used by humans are carbohydrates, proteins, lipids, minerals, nucleic acids, and vitamins.


Carbohydrates are the major source of energy for all animals. About half to2/3 of the total calories every animals consume daily are from carbohydrates.glucose is most ordinarily used for energy.

Other carbohydrates useful carbohydrates are lactose, maltose, starch, and sucrose. Carbohydrates contain 4 kilocalories per gm. Humans get carbohydrates from the food s like bean, potatoes, bread, bran, rice, cereals, and pastas, etc.

Carbohydrates are the most common source of energy. Proteins and lipids are vital building components for the body but they can also be used for energy


The lipids present in food are made up of fatty acids bonded to glycerol. The fatty acid of lipids may be unsaturated and saturated.

Unsaturated fatty acids have some of their carbon atoms double-bonded in place of a hydrogen atom.

The lipids containing unsaturated fatty acids are liquid at room temperature

Saturated fatty acids have all of their carbon atoms bonded to hydrogen atoms.

Generally, the lipids containing saturated fatty acids are solid at room temperature.

On the other hand, sunflower oil contains nearly 75% unsaturated fatty acids. Lipids are used to form membranes, the sheaths surrounding neurons, and certain hormones.

Lipid is also extremely useful energy sources. One gm of lipids contains 09 kilocalories of energy. Important sources of lipid include milk, butter,, eggs,, cheese, mutton, fish, coconut and dry fruits, mustard seeds, etc

Saturated fatty acids can increase a person’s cholesterol level. An increased cholesterol level may eventually result in the clogging of arteries and, ultimately, heart disease.


Proteins are composed of amino acids. Proteins are essential components of the cytoplasm membrane and organelles. They are also the major components of muscles, ligaments, and tendons.

So we use proteins for growth. Many proteins play a role as enzymes. Proteins can also be used for gaining energy. 01 gm of proteins contains 04 kilocalories of energy.

Dietary sources of proteins are meat, eggs, grains, legumes, and dairy products such as milk and cheese.

                                     Proteins can be converted into carbohydrates                                


Minerals are inorganic elements that originate in the Earth and cannot be made in the body. They play important roles in various body functions and are necessary to maintain health. Minerals are categorized into major and trace minerals. Major minerals are required in the amounts of 100 mg (milligrams) or more per day, while trace minerals are required in amounts less than 100 mg per day. The roles of major and minor minerals in the human body

              On the nutritional label of a packaged food, the word “Calorie” is equal to a kilocalorie.

                                      Table: Important minerals in the human diet and their roles Nutrition

Role of Calcium and Iron:

Calcium is essential for the development and maintenance of teeth and bones. It is also needed for maintaining cell membranes and connective tissues and for the activation of several enzymes.

Calcium also aids in blood clotting. Humans get calcium from milk, cheese, egg yolk, beans, nuts, cabbage, etc. Deficiency of calcium causes spontaneous discharge of nerve impulses which many result in tetany, bones also become soft, blood clots slowly and wounds heal slowly.

Iron plays a major role in oxygen from red meat, egg yolk, whole wheat, fish, spinach, mustard, etc. Its deficiency is the most common nutrient deficiency worldwide.

Iron plays an important role in the storage and the transport of oxygen. It is a component of hemoglobin in red blood cells and myoglobin in muscle cells. Cellular energy production also requires iron.

It acts as a cofactor for many enzymes of cellular respiration. Iron also supports immune function. Humans get iron from red meat, egg yolk, whole wheat, fish, spinach, mustard, etc.

Its deficiency is the most common nutrient deficiency worldwide. Iron-deficiency causes anemia.

                       Good calcium nutrition, along with low salt and high potassium intake, prevents hypertension and kidney stones.


Vitamins are the chemical compounds that are required in low amounts but are essential for normal growth and metabolism. Vitamins may be divided into two groups: the fat-soluble vitamins (vitamins A, D, E, and K) and the water-soluble vitamins (vitamins B and vitamin C).

     Vitamin A:

Vitamin A was the first fat-soluble vitamin discovered in 1913). It combines with a protein called opsin to form rhodopsin in rod cells of the retina of the eye. When vitamin A is insufficient, the lack of rhodopsin makes it difficult to see in dim light. It is also involved in cell differentiation, a process

                     Cooking or heating destroys the water-soluble vitamins more readily than the fat-soluble vitamins.

           Fat-soluble vitamins are much less excreted from the body as compared to water-soluble vitamins. This means that levels of water-soluble vitamins in the body can decrease more quickly, leading to vitamin deficiency.

                                    Table: Functions, deficiencies and sources of important vitaminsNutrition

Minute quantities of vitamin C are present in muscles. Since meat consists of muscles so it is not a good source of vitamin C.

Humans get vitamin A from leafy vegetables (spinach, carrots), yellow/orange fruits (mango), liver, fish, egg, milk, butter, etc.

The deficiency of vitamin A is the leading cause of blindness in children worldwide. One of the symptoms of vitamin-A deficiency is night blindness.

This is a temporary condition, but if left untreated it can cause permanent blindness. Vitamin-A deficiency can also cause a condition in which hair follicles become plugged with keratin, giving dry texture to skin.

Vitamin C: (Ascorbic Acid)

Vitamin C participates in many reactions. It is needed to form collagen (a fibrous protein) that gives strength to connective tissues. Collagen is also needed for the healing of wounds. Vitamin C in white blood cells boost the immune system to function properly.

We get vitamin C from citrus fruits (e.g. oranges, lemons, and grapefruit), leafy green vegetables, beef liver, etc. The deficiency of vitamin C causes connective tissue changes throughout the body.

The disease is known as scurvy results from lack of vitamin C. In this condition the synthesized collagen is unstable. Symptoms of scurvy include muscle and joint pain, swollen and bleeding gums, slow wound healing, and dry skin.

Vitamin D

The best-known function of vitamin D is to help regulate blood levels of calcium and phosphorous. Vitamin D increases the absorption of these minerals from the intestine and their deposition in bones. Vitamin D is mainly found in fish liver oil, milk, ghee, and butter, etc.

It is also synthesized by skin when ultraviolet (UV) radiations from the Sun are used to convert a compound into vitamin D.

Long-term deficiency of vitamin D affects bones. In a children’s, deficiency of vitamin-D cause l rickets, a condition in which bones weaken and bow under pressure. In adults, vitamin-D deficiency causes osteomalacia, or “softening of bones,” increasing the risk for fractures in bones.


Strictly speaking, water and dietary fiber are not considered as nutrients, but they do play an important role in life.


Almost 60% of the adult human body is composed of water. Nearly all life-sustaining chemical reactions require an aqueous (watery) environment. Water also functions as the environment in which water-soluble foodstuff is absorbed in the intestines and the waste products are eliminated in urine.

Another important role of water is to maintain body temperature through evaporation, as in sweating. Severe dehydration may result in cardiovascular problems. The average water requirement for an adult human is two liters per day. Important sources of daily water intake are natural water, milk, juicy fruits, and vegetables.


Dietary fiber (also known as “roughage”) is the part of human food that is indigestible. It is found only in plant foods and it moves undigested through the stomach and small intestine and into the colon. The insoluble dietary fiber moves quickly through small intestines.

Its sources are cereals, and skins of many fruits and vegetables. The soluble dietary fiber breaks down as it passes through the alimentary canal. Its sources are oats, beans, barley, and many fruits and vegetables.

Fiber prevents and relieves constipation by stimulating the contraction of intestinal muscles. Avoiding constipation reduces the risk of many other diseases. Soluble fiber helps in lowering blood cholesterol and sugar levels. Insoluble fiber speeds up the movement of carcinogens (cancer-causing agents) from the intestine.

Fiber supplements (such as Ispaghol husk) should be used only with a physician’s recommendations. Taken properly, these supplements may help in constipation and in lowering cholesterol levels.


Humans require different types of nutrients to keep them healthy and fit. These nutrients should be taken appropriately in diet. A balanced diet is defined as the one which contains all the essential nutrients in the correct proportion for the normal growth and development of the body… It should include different types of nutrients and should be according to the energy requirements. The following chart shows some of the common foods, taken in, and the percentage of carbohydrates, lipids, and proteins in each of them.nutrition

Relation of balanced diet with age, gender, and activity;

During the growth period of the body, there is a higher metabolic rate in body cells and so the body needs a balanced diet that contains more energy. Adults need less proteins per kilogram body weights, but a growing boy or girl needs more proteins per kilogram weight. Similarly, children need more calcium and iron for their growing bones and red blood cells respectively

Let thy food be thy medicine”:                                                                                                                                               Hippocrates

Gender has an impact on the requirements of a balanced diet. Women have comparatively fewer metabolic rates than men of the same age and weight. So men need a balanced diet that provides comparatively more energy. Different people have different lifestyles and varied nature of work. A man with stationary habits does not require as much energy as the man who is on his feet most of the time in a day.

       Table: Estimated energy requirements (in Kilocalories) according to age, gender and activity



Problems related to nutrition are grouped as malnutrition. It often refers to undernutrition resulting from inadequate consumption, poor absorption, or excessive loss of nutrients. Malnutrition also contains over-nutrition, resulting from overheating or excessive intake of specific nutrients.

Usually, malnourished people either do not have enough calories in their diet, or eat a diet that doesn’t contain protein, vitamins, or trace minerals. Malnutrition weakens the immune system, impairs physical and mental health, slows thinking, stunts growth and affects fetal development.

Common forms of malnutrition include protein-energy malnutrition (PEM), mineral deficiency disease (MDD), and over-intake of nutrients (OIN).

a- Protein-Energy Malnutrition:

Protein-energy malnutrition means inadequate availability or absorption of energy and proteins in the body. It is the major cause of death in children in developing countries. It may lead to diseases such as Kwashiorkor and marasmus.

Kwashiorkor is due to protein deficiency at the age of about 12 months when breastfeeding is It can also develop at any time during a child’s growing years. Children may grow to normal height but are abnormally weak.

Marasmus normally develops between the ages of six months and one year. Patients lose all their body fat and muscle strength and acquire a skeletal appearance. Children with marasmus show poor growth and look small for their age

b- Mineral Deficiency Diseases:

Diseases resulting from the deficiency of a mineral are comparatively rare among humans. Some examples are given below;

Goiter is a condition caused by an insufficient amount of iodine in the diet. Iodine is used by the thyroid gland to produce hormones that control the body’s normal functioning and growth. If sufficient iodine is not available in a person’s diet, the thyroid gland becomes enlarged and it results in swelling in the neck. This condition is known as goiter.

Anemia is the most common of all mineral deficiency diseases. The term anemia literally means“a lack of blood.” It is caused when the number of red blood cells is reduced than normal

. If the body fails to receive sufficient amounts of iron, the adequate number of hemoglobin molecules are not formed. In this case, there are not enough functioning of red blood cells. The patient is weak and there is a shortage of oxygen supply to the body’s cells.

c- Over-Intake of Nutrients:

Over-intake of nutrients (OIN) is a form of malnutrition in which more nutrients are taken than the amount required for normal growth, development, and metabolism. The effects of over-intake of nutrients are usually intensified when there is a reduction in daily physical activity (decline in energy expenditure).

Over-intake of nutrients causes several health problems. For example, a high intake of carbohydrates and fats leads to obesity, diabetes, and cardiovascular problems. Similarly, a high dose of vitamin A causes loss of appetite and liver problems. Excess intake of vitamin D can lead to the deposition of calcium in various tissues.


An extended period of malnutrition can lead to problems like starvation, heart diseases, constipation, and obesity.                                                                                                                                                                  Starvation: is a severe reduction in nutrient and energy intake and is the most horrible effect of malnutrition. In humans, prolonged starvation causes permanent organ damage and eventually results in death.

Heart diseases: are also increasing on the global level. One of the causes of heart diseases is malnutrition. People who take an unbalanced diet (high in fats) are more exposed to heart problems.

Constipation: Malnutrition often leads to situations where people cannot schedule their meals.This irregularity results in many health problems including constipation.

Obesity: This means becoming over-weight and it may also be due to malnutrition. People who take food that contains energy more than their requirement and do very little physical work can become obese. Obesity is known as mother-disease and may lead to heart problems, hypertension, diabetes.


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