Text № 5 «from the history of vitamins»

1. Прочитайте текст и скажите, какое открытие было сделано польским ученым.

2. Выделите самое главное, говоря о функциях витаминов A, B, C.

In 1911 the young Polish scientist, Casimir Funk, published a book in which he described experiments by means of which he extracted a substance from rice hull¹ which when fed to fowl in very minute quantities cured them of the paralysis of poly-neuritis within a few hours. For this white crystalline substance he gave a name, Vitamine (“Vita” for life, “amine” the name of a certain class of chemical compounds). Though it was soon shown that the life giving material contained no amine the name remained, not only with the researchers but also with the public, and it stayed though it has dropped its “e”. Naturally the first vitamin work was biological. Many organic chemists have attempted to find the exact chemical structures of these extremely complex materials. The principal members of the vitamin groups are A, B, C, D.

For the most part we obtain our vitamins directly from foods but there are amendments to the rules.

Vitamin A can be obtained from fish livers and a variety of other foods of animal origin, or our bodies can manufacture it from carotene found in green leaves and some tubers.

The body can manufacture its own vitamin D from the ergosterol on or near skin, if exposed to sunshine. The functions of the vitamins are very varied, interesting and important.

Vitamin A. It is essential for eyes, nerves growth, reproduction and lactation and the maintenance of bodily vigor at every stage of existence. Life without vitamin A is hardly worth while. Green vegetables, milk, bitter and cod liver oil contain vitamin A.

Vitamin B. The exact amount of vitamin B for optimum human health is not known; but the minimum intake necessary to prevent beriberi or other severe nervous disturbance has been well established.

In common with most of other vitamins vitamin D is necessary for normal growth. There is probably some connection between its growth and appetite-inducing properties.

Vitamin C. The citrus fruits (oranges, lemons, grape-fruits) are sources of vitamin C. Tomatoes, raw cabbage and onions also contain vitamin C. Apples, bananas, carrots and potatoes contain some, but they are important sources only if eaten in large amounts.

If the shortage of vitamin C causes scurvy, the teeth fall out, if the shortage is less, they rot out.

1 – шелуха риса

Text № 6 «b – complex vitamins»

Прочитайте текст и дайте характеристику витаминов группы В.

Thiamine which is designated as B₁, is one of the B vitamins that are often called the B-complex vitamins. Thiamine is destroyed by prolonged heating. The shorter the cooking time and the less the amount of water used, the less is the loss of thiamine. Important sources of thiamine are: whole grain bread and cereals, meat, milk, liver, nuts, vegetables.

Riboflavin is another of the D vitamins and was called vitamin B₂. It is essential to growth and due to it a high level of positive health is maintained. Riboflavin is little affected by heat but easily destroyed by baking soda. It is also readily destroyed by light and is soluble in water. Foods that are good sources of riboflavin are: whole grain or enriched bread and cereals, cheese, eggs, green leafy vegetables¹, meat, liver, milk.

Still another of the B vitamins is niacin. Until it was recognized as vitamin, this substance was known to chemists as nicotinic acid. Niacin is essential for growth and normal functioning of the skin and the digestive tract. Niacin is stable to air, heat and light, however, it is readily soluble in water and especially hot water. Foods that furnish niacin are: enriched or whole grain bread and cereals, meat, liver.

In many states thiamine, riboflavin, niacin, and iron are more and more commonly being added, flour, rice and other processed cereals to enrich them with these needed food constituents.

Pyridoxine, often referred to as vitamin B₆, is essential for good health. It is especially involved in certain cellular activities and in the utilization of other foods by the body. This vitamin is soluble in water and stable to heat, alkalies and acids, however, it oxidizes readily and is destroyed by light. Good food sources are heart, liver, meat, seeds and whole wheat.

Certain relationships among the vitamins make for better use of these nutrients in the body. For example, thiamine, riboflavin, and niacin are all essential in the utilization of carbohydrates. Vitamin B₆ is essential in the utilization of protein. Vitamin D is closely related to the metabolism of calcium and phosphorus and in its absence these minerals are not efficiently used in bone formation.

Many other vitamins than those presented here have been discovered, but their role in nutrition has not been determinated yet.

1 – greenleafyvegetables– овощи со съедобными листьями (напр. салат)