Тема 4: fats

Active Vocabulary:

fat, fatty; to take in, intake; to protect, protection, protective; to derive, derivative, derivation; to deplete, depletion; layer; amount; excess; equipment; knowledge; essential; extreme; to include, to perform, to refuse, to call on; to prove; to play a part

Animals, human beings included, take in sugars and starches and store the excess as fat. The ability to make fats from carbohydrates or similar materials seems to be a characteristic of most living matter including plants. But man hasn’t been able to perform this task in the laboratory, even when armed with all the equipment and knowledge in the world. The microscopic walls of plant cells are much better laboratories than our scientists have yet been able to make.

The fatty foods perform some very important function in our animal lives; to do without them can be dangerous. Fats form a protective layer around the nerves, apparently to protect them from shocks. One of the characteristic results of semi-starvation is extreme irritability. It has been suspected that this may be due to the depletion of fat around the nerves.

Fats in the form of their derived compounds – phospholipids – also play an important part in our brain and entire nervous system. Another class of compounds derived from the fats and known as the sterols is also essential for the living organism. So one may say that, in its higher forms, life without fat is impossible.

Even admitting these facts, however, one might argue that they do not prove that a diet should contain any large amount of fat, for we make fat out of the carbohydrates we take in, hence sugars might be all that would be necessary to supply energy. As an argument this is unanswerable – but as an observation of facts it is a hundred per cent wrong. There are fats and fats and the human body is quite unable to meet the fat-manufacturing situation by itself. There are some necessary fats that our bodies refuse to, or cannot, manufacture and we need to call on other animals, such as cows, to help us out. Moreover, without fats in the diet we could not get a sufficient amount of the fat-soluble vitamins A, D and E.

There are two fatty acids, linileic and linolenic, which the body must have and which it cannot manufacture itself. These fatty acids get their names from linseed: oil in which they were first discovered. There are several other fats and fatty acids which are essential and which we do not make in our bodies.

Тема 5: proteins

Active Vocabulary:

protein (complete, partially complete, incomplete); to vary variation; to link, to maintain, maintenance, to value, value, valuable; to support; to classify; to result in; to base upon; adequate; to be able, ability

Proteins differ from carbohydrates in that, besides the elements present in sugar and starches, they also contain nitrogen and in most cases sulphur. Phosphorus and iron are also found in some proteins. The importance of nitrogen content commonly varies from 10 to 18 per cent. Proteins are found in foods of both animal and plant origin. Meat, eggs, milk, nuts and certain of cereal foods are high in protein. All those foods contain more than one protein. Milk, for example, contains the proteins, lactalbumin and casein, as well as others of lesser importance.

Proteins are complex in nature, they are composed of a number of amino acids or “building blocks”, linked together, and also of amino acids linked with other substances. Proteins vary in the kind and number of amino acids present. Certain amino acids the body is unable to build. These are known as essential amino acids and must be supplied by the foods eaten.

Variation in the quality of proteins has resulted in their classification as complete, partially complete, and incomplete, based upon their ability to support normal growth and to maintain life even if it is the only protein in the diet. A partially complete protein is one that maintain life but does not support normal growth. An incomplete protein, although valuable in the diet, will by itself neither support normal growth nor maintain life. Most animal proteins are complete. Plant proteins are more or less incomplete, although the soya bean and the wheat grain contain proteins that are complete. Valuable sources of protein are: cereals and cereal products, cheese, eggs, fish, meat, milk, nuts.