1. FOOD AND NUTRITIONAL SUBSTANCES

1.1. Nutrients1.2. Groups of foods

2. A COMPLETE AND BALANCED DIET

2.1. Criteria for an adequate diet

Nutritional substances are those chemical compounds which are found in food and which we use to obtain energy and to build the matter which goes to make up our cells.

NUTRITIONAL SUBSTANCES

GLUCIDS (also calledSUGARS

or CARBOHYDRATES)

LIPIDS OR

FATSPROTEINS WATER VITAMINS

MINERAL SUBSTANCES

NUTRIENTS

MACRO-NUTRIENTSThey are the majority components of food

MICRONUTRIENTSWe need very small quantities of these substances, but their

absence causes serious disorders.

GLUCIDS LIPIDS PROTEINS WATER VITAMINSMINERAL

SALTSFIBRE

MACRO-NUTRIENTS:

a.1.) Glucids or carbohydrates: their main function in the body is to provide energy. The most common glucids in our diet are starches which can be found in pulses, potatoes, etc., and simple sugars like glucose and saccharose.

Some examples of pulses: chickpeas, beans, …

a.2.) Lipids or fats: they have many functions, but the most important is that of providing energy. They are, together with proteins, which form the cellular membrane of the cells.

They can be found in vegetable oils (olive oil, sunflower oil, etc.) and in animal fats (lard, fat and butter).

a.3.) Proteins: these are necessary for building the matter that forms our cells. We can obtain proteins from foods which have an animal origin (meat, fish and eggs) and a vegetable origin (pulses, cereals, etc.)

a.4.) Water: it is a fundamental component of living matter.

We need to take three litres of water a day: one and half litres comes from food and the rest we must drink.

a.5.) Fibre which comes from vegetables is also a glucid. It is necessary for helping the food to pass through the intestine.

b) MICRO-NUTRIENTS

b.1.)The most well-known micro-nutrients are vitamins. We need very small quantities of these substances, but their absence causes serious disorders.

b.2.)Minerals are also micro-nutrients, chemical elements that we also need in small quantities. Examples: iron (blood), magnesium, sodium, potassium, phosphorous, fluoride, etc.

EXAMPLES OF VITAMINS

VITAMINS Foods where they are found

A( retinol) Carrots, spinach, parsley

B1 (thiamine) Eggs, peanuts, pulses

B6 (pyridoxine)Sardines and fresh anchovies, lentils

C (ascorbic acid)Kiwis, red peppers, citrus fruits

D (calciferol) Produced by the skin

1.2. Groups of foods

There are different ways of grouping together the food we need for a healthy diet: the “FOOD WHEEL” or the “FOOD PYRAMID” are some examples. They help us to choose the adequate food.

We are going to classify as Grande Covian did. He was a Spanish nutritionist. This classification divides food into six groups, according to both their origin and their nutrients.

The six groups are as follows:

GROUP 1. MILK, MILK DERIVATES AND EGGS

These are a source of proteins, vitamins and calcium.

GROUP 2. MEAT, POULTRY AND

FISH

Basically, these provide us with proteins.

GROUP 3. FATS AND OILS

These include animal fats like butter and vegetable oils. Eaten in moderation they

provide the lipids we need.

GROUP 4. CEREALS, PULSES, POTATOES

AND SUGARS

These provide proteins and glucids

GROUP 5. VEGETABLES

These are a source of vitamins and fibre

GROUP 6. FRUIT

These provide glucids, vitamins and fibre

An optimum diet is a complete and balanced diet, complete because it uses foods from each group and balanced because we eat the correct proportion of each food.

The diet varies in each person: the work, the age, illnesses,… and many other factors have influence on diets

To know if our diet is complete and balanced or not, we must use some criteria.

A COMPLETE AND BALANCED DIET (AUDIO):http://lgfl.skoool.co.uk/content/keystage3/biology/pc/learningsteps/ABDLC/launch.html

2.1.Criteria for an adequate diet

Diet should comply with the following key points:- Food should provide just the right amount of energy for carrying out our activities and

for the development of the organism. An excess or defect in this energy supply will be harmful.

- Diet should supply enough proteins, vitamins and minerals. Once again, an excess or defect in this energy supply will be harmful.

- With regard to the distribution of the foods which provide energy, this should be done as follows:

DISTRIBUTION OF FOOD

FOOD PROPORTION

Rich in glucids 55-60% of total number of calories

Rich in lipids 30% of total number of calories

Rich in proteins 15% of total number of calories

Other criteria to bear in mind:

We must eat 22 g of fibre a day which can be obtained from vegetables and fruits

You should not eat more than 3g of salt a day. Any excess may cause problems in the excretory apparatus and increases blood pressure.

Only 10% of calories should be obtained from simple glucids (sugars).

The maximum level of cholesterol per day is 300 g. An excess of this can cause serious problems in the arteries.

Combine animal and vegetable proteins.

However, as you know, the most serious problems are brought through malnutrition. A poor diet with little variation can cause serious illnesses.

MALNUTRITION: http://lgfl.skoool.co.uk/content/keystage3/biology/pc/learningsteps/MALLC/launch.html

Now is your turn!

Make a “FOOD WHEEL” or a “FOOD PYRAMID” for a person of your age following the criteria of a balanced diet.