Saturday, June 9, 2012

FOODS


FOODS
Food has been a basic part of our existence. Through the centuries we have acquired a wealth of information about the use of food to ensure growth of children and youth, to maintain good health through life, and to meet special needs of pregnancy and lactation and to use it to recover from illness.
When you study food composition you will know the nutritional contribution of foods. You may have been told that certain foods are very important for maintaining good health, while others are harmful. As you study the science of Foods and Nutrition, you will need to examine the ideas you have about foods very carefully and accept or reject these in the light of the knowledge you will acquire. Whatever you learn in this area should be used and applied in your personal life.
A large part of your food heritage is scientifically beneficial and needs to be retained; some aspects may need to be modified in the view of the changes in our lifestyle.
Food is an important topic of conversations, articles in newspapers and magazines, as also of advertisements. Some of this information may be correct but a large part of it may not be. As you learn this subject, you will be able to spread the knowledge gained to those around you, so that they discard false ideas about food, which interfere with their food selection and affect their health.
Food, nutrition and health are intimately connected aspects of our life. Let us start our study by defining these and related terms.
Food is that which nourishes the body. Food may also be defined as anything eaten or drunk, which meets the needs for energy, building, regulation and protection of the body. In short, food is the raw material from which our bodies are made. Intake of the right kinds and amounts of food can ensure good nutrition and health, which may be evident in our appearance, efficiency and emotional well-being.
FUNCTIONS OF FOOD
There are three types of foods are as follows:
1.      Physiological functions of food
2.      The Social functions of food.
3.       The psychological functions of food
Physiological functions of food: The first function of the body is to provide energy. The body needs energy to sustain the involuntary processes essential for continuance of life to carry out professional, household and recreational activities, to convert food ingested into usable nutrients in the body, to grow and to keep  warm. The energy needed is supplied by the oxidation of the foods consumed.
The foods we eat become a part of us. Thus one of the most important functions of food is building a body.  A newborn baby weighing 2.7-3.2 kg can grow to its potential adult size of  55-60 kg  if the right  kinds  and amounts of foods are eaten from the birth to adulthood. The food eaten each day helps to maintain the structure of the adult body, and to replace worm out cells of the body.
The third function of food is to regulate activities of the body.  It includes regulation of such varied activities as:
·         Bearing of the heart
·         Maintenance of the body  temperature
·         Muscle contraction
·         Control of Water balance
·         Clotting of blood
·         Removal of  Waste products from the body
The fourth function of food is to improve our body’s resistance to disease.
The Social Functions of Food: Food has always been a central part of our social existence. It has been a part of our community, social, cultural and religious life. Special foods are distributed as a benediction or Prasad in the religious functions home, temples and churches. Feasts are given at specific stages of life such as birth, naming ceremony, birthdays, marriages, etc. Most of the religious festivals also call for feasts and feeding of specific segments of the population. Certain menus are associated with most of these feasts in each region.
Food has been used as an expression of love, friendship and social acceptance. It is also used as a symbol of happiness at certain events in life, for example, pedhas are distributed to announce success in examinations, or the birth of a baby; laddus are associated with the celebration of EID Festival, Deepavali and marriages, cakes are associated with Christmas and birthdays and tilgul with sankranti the festival of friendship. At EID day the Muslims are prepared very delicious and rich dishes and share their foods with relatives and poor peoples in the society.
As food is an integral part of our social existence, this function is important in daily life. Refreshments served at get-togethers or meetings create a relaxed atmosphere. The menu for such get-together, should bring the people together, rather than divide them. This basic aspect should be considered in planning menus for such occasions.
The Psychological Functions of Food: In addition to satisfying physical and social needs, food must satisfy certain emotional needs. These includes a sense of security, love and attention.  Thus familiar foods make us feel secure. Thus familiar foods make us feel secure. Anticipating needs and fulfilling these are expressions of love and attention. These sentiments are the basis of the normal attachment to the mother’s cook. Sharing of food is a token of friendship and acceptance. Sharing of foods is a token of friendship and acceptance. It must be noted that even a nutritionally balanced meal may not be satisfying to the individual, if the foods included are unfamiliar or distasteful to him /her. With time and repeated experience, strange foods become familiar and new tastes are formed.
These aspects are important in food acceptance and must be considered in planning meals, which are not only nutritionally adequate, but also enjoyable for the group for whom they are intended.

USE OF FOOD IN THE BODY


USE OF FOOD IN THE BODY
Use of food in the body involves three processes --- digestion, absorption and utilization of nutrients in the body.
Digestion is the process, which releases many nutrients in the forms the body can use, by breaking up food in the intestinal tract.
Absorption is the process which carries these nutrients into the circulation system and delivers them to the cell.
Utilization: Cell is the functional unit of life. Hence a large number of the chemical reactions in the cell utilize the nutrients absorbed to produce materials needed for our existence.
Mechanical processes involved in digestion include chewing of food, swallowing of food, churning action in the stomach and rhythmic contraction of the intestinal tract. 
The digestive tract consist of mouth, Esophagus, Liver, Gall bladder, Stomach, Pancreas, Longitudinal muscle, Circular muscle, Duodenum, Jejunum, Large intestine, Ileum, Small intestine, Appendix, Anal Sphincter, Rectum.
Chewing of food reduces the food particles in size, mixes these with saliva and dilutes it with water, so that it is easy to swallow. The food swallowed is mixed with enzymes and acid by the churning action in the stomach. Further the rhythmic contraction of the intestine, help to break the food into small particles and move the food mass forward through the digestive tract.
Chewing of food reduces the food particles in size, mixes these with saliva and dilutes it with water, so that it is easy to swallow. The food swallowed is mixed with enzymes and acid by the churning action in the stomach. Further the rhythmic contraction of the intestine, help to break the food into small particles and move the food mass forward through the digestive tract.
Chemical reactions in digestion process: The first reaction is hydrolysis or splitting with the help of water, Carbohydrates, fats, and proteins break up with the addition of water into smaller molecules, which the tissues can use.
The chemical reactions are accelerated by enzymes, which are secreted in the mouth, stomach and small intestine. Enzymes are living catalysis, that increase the speed of biological reactions, without being a part of compound formed. The enzymatic reactions, which take place in the digestion processes are presented in the table.
As you may know, enzymes are proteins by nature. Their name indicates substance on which they can act, for example, sucrose act on sucrose. Enzymes are specific in their actions. An enzyme, which hydrolyses protein, will not act on starch. Each enzyme acts optimally at a certain pH, e.g., amylase acts only in alkaline medium.
Someone enzymes need another group, known as a coenzyme, to be attached to it to aid their function. For example, B-vitamin serve as a coenzymes in the reactions, which release energy from glucose. In enzyme reactions, mineral elements are essential as cofactors. Thus normal body metabolism is dependent on the presence of appropriate enzymes, coenzymes and cofactors specific to each reaction.
The digestive enzymes are only one group of a large number that are essential to regulate body processes. Other enzymes are present in various tissues of the body and help in the utilization of food that has been absorbed.
Carbohydrates
The digestion process begins with chewing the food in the mouth. The enzyme ptyalin starts the digestion of starch in the mouth. It hydrolyses stars to dextrin, isomaltose and maltose in  neutral or alkaline pH in the mouth. The food tastes sweet due to these products of hydrolysis. The activity of amylase continues in its movement from the mouth to the upper part of the stomach. But as soon as the food mass comes in contact with hydrochloric acid secreted there, this action ceases. Very little digestion of carbohydrates occurs in the stomach as the pH is unfavorable.
The food mixed with gastric juice forms a semi-fluid mass called chime. It takes about three to five hours to form chime. Small portion of chime are released through the pyloric sphineter into the duodenum, the first part of the small intestine.
Proteins: Digestion of proteins starts in the stomach, which serves as a storehouse, where some protein hydrolysis begins. Milk is clotted by a special enzyme rennin and acid is added.
Lipids: The stomach lipase does act on emulsified fats in milk, cream, butter, and egg yolk, but most of the hydrolysis of fats takes place in the small intestine.

FOOD COMPOSITION


FOOD COMPOSITION
Most food contain more than one nutrient. The nutrient contents of foods have been determined by analyzing these in the laboratory. The composition of over 650 Indian foods has been determined.
The food composition tables give the concentration of nutrients in 100 g of the edible portion of the food. Therefore it is important to know how much of the food purchased is edible. In some foods, such as milk, butter, sugar, the edible portion is 100 percent. In fruits and vegetables, it varies from 65 percent in bananas to 98 percent in tomatoes.
The values for nutrients given in food composition tables are averages of the results obtained by analyzing a large number of samples of each food. Therefore the figures in such tables give a fairly good idea of the composition of each food.
Foods are grouped in the food value tables, on the basis of the plant from which the food is derived, for example, seeds, roots, leaves, fruits, etc. Animal foods are grouped on the basis of species and the product used.
It is interesting to note that there are inherent similarities in the composition of foods in each group.  In the table 1.1 the composition of various foods has been presented to illustrate this  point. For example, the protein content of cereals varies from 7 to 12, and that of dals and legumes from 17 to 25 per cent. This information has important applications in practical usage of tables. It is possible to predict the overall nutrient content of combinations used, if we know the amounts of individual foods used. If the composition of a particular food is not found in the tables, you can roughly predict its nutrient combination, by knowing the group to which it belongs.
You may observe from Table 1.1, that cereals and dals do not contain vitamins A and C. Therefore you will realize how important it is to include vegetables and fruits, which are rich source of these two vitamins, in our daily menu of cereals and dal. Most of the vegetables and fruits, as you will observe from Table 1.1 , are low n calories. Oils, fats and sugars are mainly sources of calories. Thus you get an idea of the contribution of various foods by studying Table 1.1.



Table 1.1: Food Composition at a glance
( Approx, Group Values per 100 g E.P)
Foods
Moisture
Calories
Protein (g)
Vit.  A (mcg)
Vit. C
(mg)
Minerals and Vit. B-Comp.
Cereals-rice, Wheat, bajra, Jowar
10
340
7 to 12
---
---
Some
DAls, Legumes
10
340
17 to 25
---
---
Some
Milk
85
70
3
48
---
Some
Eggs
75
170
13
960
---
Some
Meat, fish, poultry
75
100-190
18
Some
---
Some
Leafy & Orange-yellow Vegetables & Fruits
90
20
2
1800
30
Some
Fruits-Vit. C - rich
85
50
1
Some
50
Some
Other Vegetables
90
30
2
Some
Some
Some
Other Fruits
85
50
1
Some
Some
Some
Roots & tubers
60-85
50-100
1
Some
Some
Some
Oils & Fats
0
900
--
750
---
---
Sugar, Jaggery
0
400
---
---
---
---

Most of analytical work on Indian foods was carried out in various laboratories under the auspices of Indian Council of Medical research (ICMR). A compilation of results is published as the Nutritive Value of Indian Council of Medical Research. A number of new varieties of food with high contents of certain nutrients, have been developed at research centers under the auspices of the Indian Council of Agricultural Research. You get a number of those foods in the market and use these in your dietary. The nutritive value of these new varieties of foods needs to be included in the book of Nutritive Value of Indian Foods. There are two International Food Value tables published by the Food & Agriculture Organization (FAO). It is good to remember that the nutritive value of natural foods does not vary a great for a particular variety of the same food from one country to another. But there is a great variation in the composition of prepared foods such as bread, biscuits, cakes, etc., due to variation in recipes and the basic ingredients used from one region to another.