Science · Class 9-10 · Chapter 1 · 1.1 Food and nutrition
Food and nutrition.
The book's definition packs four jobs into one sentence: those edible things which, through nutrition, make a living body grow, produce its energy, resist disease and repair its wear are called food. Growth, energy, resistance and repair: those four come back again and again through this chapter.
1. Food, nutrient, nutrition
Three words that sound near neighbours and are not the same. Food is what goes on the plate, the whole of it. A nutrient is the organic or inorganic part of that food which supplies the life of the body. Rice is a food; the starch inside the rice is a nutrient. One food may hold several nutrients, and usually does.
And nutrition is not an event but a process that runs on: the taking in of food, its digestion, its absorption and its assimilation, by which the body's wants are met. Nutrition does not end when the eating does; that is where the real work begins.
step by stepgo on to the next
From food to nutrition
Taking it in. Taking the food into the mouth, chewing it and swallowing. The saliva starts work here; some of the starch in the rice begins to break down in the mouth, which is why rice chewed a while tastes faintly sweet.
Digestion. Breaking the large molecules small enough to enter the blood. Starch to glucose, protein to amino acids, and fat to fatty acids and glycerol.
Absorption. The small molecules pass through the wall of the small intestine into the blood. It is at this step that the food first gets inside the body in any real sense.
Assimilation. The blood carries them to the cells, and the cells make energy of them or make good their own wear. This step is the nutrition itself; all the rest was preparation for it.
What is left over. Whatever was not digested, the fibre of the greens for instance, goes out by way of the large intestine. That indigestible part is the roughage, which has a section of its own later on.
The remark about chewed rice tasting sweet looks forward to the chapter on digestion; it is here only to make the step recognisable.
2. Six components, in two groups
There are six: carbohydrate, protein, fat, vitamins, mineral salts and water. There is no need to learn the six separately, because one question divides them: does it give calories? Carbohydrate, protein and fat do; vitamins, minerals and water do not, and cannot be done without.
Roughage is part of the food but not a nutrient, so it stands outside the list of six. The book gives it a section of its own, and on the tree below it has a branch of its own.
branchestap a branch to open it
What food is made of
The components of food
Those that give energy and build they give calories
Carbohydrate the chief fuel, 4 kcal a gram
Protein building and repair, 4 kcal a gram
Fat stored energy, and the absorbing of A, D, E and K; 9 kcal a gram
Those that help and protect they give no calories
Vitamins they keep the chemistry running, and resist disease
Mineral salts bone, blood, nerve and muscle
Water solvent, carrier and regulator of heat; 60 to 75 per cent of the body
Outside the list part of the food, but not a nutrient
Roughage it gives no nourishment, and keeps the digestion moving
the energy in themtap a component
How much in a gram
About 4 kcal a gram. The body's readiest fuel, and the first thing a cell burns. The largest share of the day's calories comes from here.
About 4 kcal a gram. It does give energy, but that is not its proper work; its proper work is building and repair. The body burns protein only when the carbohydrate has run out.
About 9 kcal a gram. Weight for weight, more than twice what carbohydrate gives. Which is why the body stores its spare energy as fat: more energy in less room.
None at all. Not a grain of energy. And they cannot be done without, because the body's chemistry will not run without them. A very little does the work.
None at all. Building bone, making blood, the work of nerve and muscle: all of it leans on the minerals. As fuel they have no part at all.
None at all. Sixty to seventy five per cent of the body is water. Solvent, carrier and regulator of heat, all three; but not energy.
None at all. It is not digested at all, so the question of energy does not arise. It is kept in the diet because it keeps things moving.
Only three of the seven give energy, and of those three, fat alone gives more than twice what either of the others does. The remaining four give none at all, and three of the body's four jobs want them.
These figures for the energy in a gram are rounded, and the same ones are used right through the chapter.
3. Food is not only energy
If the only work of food were to give energy, rice and oil alone would do. But three of the four jobs in the definition, the growth, the resisting of disease and the repair, want the components that carry no energy at all. Which is why undernourishment is not simply eating too little: too little, too much, and in the wrong proportion are all of them undernourishment.
And knowing what is chief in which food makes the reckoning of a plate easy. Rice, potato and molasses are chiefly carbohydrate; lentils, fish, eggs and milk are protein; oil and ghee are fat; greens and fruit carry the vitamins, the minerals and the roughage. But hardly any food holds only one of them.
sort thema chip, then a bin
Reckoning the plate
Pick up a chip, then drop it in a bin. The question is which component is chief in that food.
Right. Next one.
Not there. Ask what this food mainly gives: fuel, material for building, stored energy, or the things that protect.
All of them. Now hold on to this: the milk went into the protein bin, and milk carries protein, fat, carbohydrate, calcium and water, all five. Chief does not mean only. That will be useful through the whole chapter.
check yourself
One question
Which puts the difference between a food and a nutrient correctly?
The other way round. What goes on the plate is the food; the working part inside it is the nutrient.
Right. The food is what goes on the plate, the whole of it. The nutrient is the part inside that does the work. One food may hold several: milk carries protein, fat, carbohydrate, calcium and water, all five.
They are not the same, and it is this difference that gets asked about. One is the whole thing, the other a part of it.
Plant foods carry them too: the starch of rice, the protein of lentils, the minerals of greens.
4. The words
Six cards for the definitions this section rests on.
cardstap a card
Six words, six definitions
wordFood
definitionThose edible things which, through nutrition, make a living body grow, produce its energy, resist disease and repair its wear.
wordNutrient
definitionThe organic or inorganic parts of a food that supply the life of the body. Rice is the food; its starch is the nutrient.
wordNutrition
definitionThe whole process by which the body's wants are met, through taking food in, digesting it, absorbing it and assimilating it. A process that runs on, not a single event.
wordCalorie
definitionA unit of energy. In nutrition the reckoning is in kilocalories; 1 kcal is 1000 calories. Where a food is labelled in calories, kilocalories are nearly always meant.
wordUndernourishment
definitionGetting nutrients in less than is needed, in more than is needed, or in the wrong proportion. All three, so eating more does not by itself make a diet nourishing.
wordA balanced diet
definitionOne in which all six components stand in the proportion the body needs. The full reckoning comes in section 1.3.
check yourself
Another question
How much energy comes from 50 grams of fat and 50 grams of carbohydrate together?
Four hundred would be right if both were 4 kcal a gram. But fat is 9.
Four fifty is the fat alone. The 200 from the carbohydrate has still to be added.
Right. Fat, 50 × 9 = 450 kcal; carbohydrate, 50 × 4 = 200; together 650. Notice that for the same weight the fat gave more than twice as much. It is why the body stores its spare energy as fat and not as carbohydrate.
Nine hundred would be right if both were 9 kcal a gram. Carbohydrate is 4.
check yourself
Last question
Someone eats a great deal of rice every day and hardly any vegetables, fruit, lentils or fish. What is that called?
Quantity enough does not settle it; a wrong proportion is undernourishment too. The definition holds all three forms.
Right. Undernourishment is not simply eating too little: too little, too much and in the wrong proportion are all of them it. Here the carbohydrate is ample and the protein, vitamins, minerals and roughage are absent. The stomach fills and three of the body's four jobs, growth, resistance and repair, go unserved.
Undernourishment is not measured by weight but by whether the nutrients are being had.
Rice is chiefly carbohydrate. No single food carries all six components.
At a glance
The four jobs of food. Growth, the producing of energy, resistance to disease, and repair.
Three words. The food is the whole thing on the plate; the nutrient is the working part inside it; the nutrition is the whole process.
Five steps. Taking in, digestion, absorption, assimilation, and what is left over.
Six components. Carbohydrate, protein and fat give calories; vitamins, mineral salts and water do not. Roughage stands outside the list.
Undernourishment. Too little, too much, or in the wrong proportion; all three of them.
If your body or your eating is worrying you, talk to an older person at home or to a teacher at school; if it is needed they will take you to a doctor.
Source: Science, Classes 9-10 (NCTB), Chapter 1 “A better way of living”, section 1.1. The figures for energy in a gram are rounded and kept the same right through the chapter.