Nutrition is defined as ” the science of food and its relationship to health”; and health is defined as the state of physical mental and social well-being. Hence the importance of this topic needs no elaboration.
The concepts in nutrition may have changed with time but the emphasis on nutrition and nutrients was always there. Historically in every culture there has been good food and bad food, hot food and cold food, illness producing food etc, although now scientific assessments have taken over.
Nutrition is a multistep process concerned with the intake of food, metabolism of food in organs and cells and its utilisation. Proper nutrition can keep us fit and healthy whereas improper and inadequate diet will reduce fitness and cause disease.
Diet and balanced diet
During a human beings whole life it partakes of a diet of its choice and taste but there is a major difference between this and a balanced diet.
A balanced diet is one that contains all the principle constituents of food in optimum quantities.
Apparently balanced diet appears to be something expensive and exotic but this is not so. On the other hand balanced diet is only composed of locally available native foodstuff which has been mixed and matched intelligently with an eye towards its taste and palatability.
Constituents of balanced diet
1. Carbohydrates for energy
2. Proteins for building up of body
3. Fats for storage of energy
4. Vitamins for biochemical reactions
5. Minerals for maintenance, functioning of organs and adequate water electrolyte balance
Besides these key components two extremely important requirements of balanced diet are –
(a) Roughage to facilitate removal of waste
(b) Water for transportation of material, digestion of food and waste disposal
Formation of balanced diet
Once man knew the constituents of balanced diet a search began for their sources amongst various available foodstuff. It was found that the whole spectrum of components of diet is available in varying quantities in different foodstuff. For example legumes contain protein; rice, bread, potato etc contain carbohydrates but rice is poor in protein and most of the legumes are poor in fat and carbohydrates. All these foods do not contain vitamin A and C but coriander is very rich in both of these. This knowledge brings us to the simple fact that if a person is eating daal, chawal and chutney (legume, rice and coriander paste) he is partaking a reasonably balanced diet.
It is also important while selecting different food items for our diet we have to guard against the possibility of over intake of a particular variety of food and risk out on something else.
Classification of food
There are many ways of classifying food.
(a) By origin – animal origin and plant origin
(b) By chemical composition – protein, fats, carbohydrates, minerals and vitamins
(c) By function – body building food, energy giving food and protective food
(d) By nutritive value – macronutrients and micronutrients
These are the main sources of energy providing 4 Kcal per gram. Carbohydrates are composed of carbon, hydrogen and oxygen. There are three main sources of carbohydrates viz starch, sugar and cellulose. Starch is basic to human diet and found in abundance in serials, roots and tubers. Sugars are the composed of saccharides (mono, di and polysaccharides). Cellulose has no nutritive value but contributes to dietary fibre.
The word protein means “which is of first origin”. They are complex organic nitrogenous compounds. Protein is the element utilised in growth and development and constitutes about 20% of body weight in an adult. The basic units of proteins are called amino acids. Although it is not their primary function but proteins also give energy at the rate of 4 Kcal per gram. Main sources of protein are milk, egg, cheese, meat, fish and fowl, pulses, beans, nuts etc.
Fats and oils are composed of carbon, hydrogen and oxygen. They are calorie giving and storing foods. They can supply 9 Kcal per gram. Most of the body fat stored as adipose tissue is in form of triglyceride. The adipose tissue contributes 10-15% of body weight. The basic unit of fat are fatty acids, which are divided into saturated and unsaturated types. The dietary source of fats are ghee and butter, milk, cheese, eggs, fish oils, groundnut, mustard, coconut etc.
They are a class of organic compounds very essential but required only in micro quantities. Vitamins are divided in two groups (a) Fat soluble – A, D, E, K (b) Water soluble – B, C. Different vitamins are derived from various sources.
More than 50 chemical elements are required for growth, repair and regulation of vital body functions. They can be subdivided in (a) major minerals – Calcium, Sodium, Phosphorous (b) trace elements – Iron, Iodine, Fluorine etc.
Nutritional profile of principal food
Cereals – Rice is the staple food of more than half the human race; wheat and maize rank second and third in consumption.
Millets – They are smaller grains, which are eaten without removing outer layer. Jowar, Bajra, Ragi, Kodo are common examples of millets eaten in India.
Pulses – Commonly used pulses are bengal gram (chana), red gram(tuar), green gram(moong), black gram(urad) etc. For a vegetarian they are the largest source of protein and that’s why they are called “poor man’s meat”.
Vegetables – They are protective food specially green leafy vegetables like spinach, fenugreek (methi) etc.
Nuts and oil seeds – Included in this group are groundnut, cashew, walnut, coconut etc. All these contain good amount of fat and proteins in a relatively small bulk.
Fruits – They are protective foods and are good sources of vitamins and minerals. A daily intake of at least 85 gm of fresh fruit is recommended for maintenance of good health.
Various types of nutrition
As opposed to autotrophic green plants which manufacture their food from simple substances absorbed from their environment, all animals including man are heterotrophic obtaining readymade food from other organisms. Animals can be divided in to several categories according to the nature of food and manner in which they obtain it.
1. Herbivores feed on plants eg cow, horse, rabbit etc. They can be further subdivided in seed eaters, fruit eaters
2. Carnivores feed on animal meat. They are subdivided in to predators which chase and kill their prey eg tiger and owl and scavengers who consume dead meat eg vultures,
3. Parasites live on or inside the body of other animals and absorb or ingest nourishment from their body tissue without necessarily killing eg tapeworm.
4. Symbionts are partners living together who benefit each other eg protozoa living in the gut of termite digest wood both for themselves and their host termites.
5. Omnivores eat both animals as well as plant material as food. Man is also an omnivore.
Nutrition of Indians
As far as man is concerned, food habits are formed by what kind of society he lives in, what is his cultural background and what geographical region he belongs to. Food habits of tribal living only a few hundred miles away from a town may be very different from that of a factory worker living in the town.
There are some unifying principles behind food intake.
In spite of the great variety of races, tribes, social and cultural backgrounds and climate, most of the food of man all over the world comes from only 14 different kinds of crops. Either these crops are consumed directly or some of them are fed to the animals and the latter become the source of meat, milk and eggs.
Energy requirements during different activities
Activity Energy used per/hr/kg body wt.
1. Sleeping 4.62
2. Sitting 6.47
3. Standing still 8.32
4. Mild exercise 16.63
5. Heavy physical work 23.1
Recommended daily energy requirement
Group Body wt.(kg) Energy allowance
Per day (Kcal)
Adult male 60
Light work 2425
Moderate work 2875
Heavy work 3800
Adult female 50
Light work 1875
Moderate work 2225
Heavy work 2925
We have seen that the various nutrients in food have specific roles to play in the functioning, growth and repair of the human body. It is obvious that if a person’s regular diet lacks or has a overage of a nutrient the normal functioning of the body will be hampered, which will show up as a disease. Diseases, which occur due to diet related or nutritional reasons, come under the purview of nutritional problems.
Nutritional diseases are commonly found in third world countries. In India they have yet to be won over. The reasons for prevalence of these diseases range from poverty to ignorance, which anyway is the bane of our country and countries like us.
Most of the western countries suffer from different kind of nutritional problems. Theirs is a problem of plenty hence obesity, hypercholestrolremia etc are their major problems.
Low Birth Weight
About 30% of babies born in India are below 2.5 kg. Although there are many causes for this but maternal malnutrition is a major one amongst them. A LBW infant has less chances of survival and if it survives then the morbidity is high.
Protein Energy Malnutrition
It is an important cause of childhood mortality and morbidity in our country. It also leads to permanent impairment of physical and possibly mental growth of those who survive. Clinically PEM is divided in kwashiorkar and marasmus. Both these variants present with different clinical features but are cured by intake of optimum quantities of protein in a balanced diet.
It is an ocular manifestation of vitamin A deficiency. It is most common in children aged 1-3 years and it is related to faulty weaning. Southern and Eastern states of India are the worst affected. It can be prevented by adequate intake of vitamin A containing foods eg carrots, mango and green leafy vegetables.
It can be defined as “a condition in which the haemoglobin content of blood is lower than normal. This is as a result of a deficiency of one or more essential nutrients regardless of the cause of such deficiency”. Iron deficiency anaemia is the commonest example of this. Copper and Zinc deficiency also may cause nutritional anaemia. To prevent this condition diet rich in mineral containing foods is required. In other words, fruits and vegetables especially green is mainstay of the treatment.
Iodine Deficiency disorder
In the common language it is called as Goitre. An ugly swelling in the front of neck appears due to this. If the deficiency is severe then it effects the central nervous system. In India average goitre prevalence is 36%. Affected children are called cretins. The iodised salt is the best remedy to prevent it. Seafood is also rich in Iodine.
Calcium and Phosphorus deficiency
They are major constituents of bone and teeth, hence their deficiency in the diet causes malformation of these. Inadequate deposition of calcium and phosphorus due to deficiency of vitamin D will result in a disease called Rickets in children and osteomalacia in adults. The bones become bent, as they can not bear body weight. Milk, bajra, ragi etc are good sources of these substances.
Excessive intake related problems
We are all aware of problems associated with excessive intake of fats and carbohydrates. From obesity to heart disease the spectrum is wide. Another lesser-known dietary toxicity is produced by excessive intake of vitamins specially A, D, E and K. This problem is called hypervitaminosis. The features may be related to the accumulation of vitamin or its functional products.
In today’s world hardly any person gets the perfect diet for his body, although everyone should know that it necessary for a healthy living. I hope after reading this article every person would get an idea of what he should take for leading a healthy life.