Vitamins

VITAMINS, organic foodstuffs possessing a specific biological action, the chemical nature of which is still unknown to us, but which are neither proteins, fats, nor carbohydrates in the strict sense of the word; despite the fact that they are contained in food in very small amounts, they are absolutely essential for the animal organism, since in the absence of vitamins in food, one or another avitaminosis disease (see) develops. The name vitamin was introduced by Funk (S. Funk) in 1912, at first for one of them (the antineuritic), and then it was extended to the entire group of vitamins and became generally accepted. Other researchers proposed other names for these substances, for example, "accessory food substances"; Hopkins called them accessory food factors, Hofmeister - akzessorische Nährstoffe, Schaumann and Boruttau - Ergänzungsstoffe, Aron - Extractstoffe, Abderhalden - nutramines, R. Berg - Komplettine, but all these names did not become widespread. The various vitamins appear to be completely different in their chemical nature, but in their physiological action they are sometimes very similar. At present, five vitamins are distinguished, which are conventionally designated by letters of the Latin alphabet: 1. Vitamin A, or anti-xerophthalmic vitamin; its absence in food is the cause of the avitaminotic disease xerophthalmia. 2. Vitamin B [note: historical nomenclature for Vitamin D], or antirachitic, associated with the avitaminosis rickets. * Both of these vitamins (A and B) are soluble in fats, which is why they are also called fat factors. 3. Vitamin B [note: historical nomenclature for Vitamin B1], or antineuritic; its absence in food leads to the disease beriberi, or polyneuritis. 4. Vitamin C, or antiscorbutic, the absence of which causes scurvy. 5. Vitamin E, or the reproduction vitamin, without which animals lose their ability to reproduce. Role, distribution, and properties of Vitamin A. The most characteristic consequences of the absence of Vitamin A in food are: 1) cessation of growth (which is why this vitamin is also called the growth vitamin) and drop in weight, and 2) xerophthalmia and keratomalacia. The first symptoms are not specific; xerophthalmia and keratomalacia are specific precisely to the absence of Vitamin A in food. With a prolonged absence of this vitamin, animals ultimately die. Vitamin A is contained in various fats of animal origin - in milk fat (in cream, in butter), egg yolk, beef fat, liver fat, and other organs (brain, kidneys, heart), and is especially abundant in fish oil. It is absent, or very scarce, in lard and especially in rendered pork fat. In the bodies of mammals, Vitamin A, like other vitamins, is not formed, but can accumulate in them when feeding on food rich in this vitamin; it is formed in plants, which are the source of Vitamin A for animals. Therefore, the vitamin content in products of animal origin (milk, lard) and in animal organs depends on the animals' food and is subject to large fluctuations; in this connection, cow's milk in the summer, when cows graze on meadows and eat fresh plant food rich in vitamins, is richer in vitamins than in the winter during stall feeding. The amount of vitamin in human milk also depends on the food of the nursing woman. Fish oil is rich in Vitamin A because it is abundant in plankton, which the respective fish feed on; plankton animals feed, in turn, on the alga Nitzschia closterium, which, as special studies with pure cultures of this alga have shown, produces large amounts of Vitamin A. Upon prolonged storage of fish oil, the amount of vitamin in it decreases; in addition, various grades of commercial fish oil can generally differ greatly in their Vitamin A content. Among plant products, the green parts of plants are the richest in Vitamin A; spinach is especially rich, followed by green salads, many varieties of clover, various types of cabbage, and rutabagas. There is much less Vitamin A in tubers and root crops, such as beets and sugar beets; exceptions are carrots and yellow sweet potatoes (white potatoes contain only traces of Vitamin A). Tomatoes are rich in vitamins; conversely, grapes, apples, and pears do not contain it at all. The seeds of certain plants (e.g., rye, wheat, millet, corn, flax, hemp) are also quite rich in Vitamin A, but commercial vegetable oils contain almost no vitamins, as do vegetable margarines. In some plants and fats, the Vitamin A content varies in parallel with the content of the yellow pigment carotene: yellow milk and yellow butter are richer in vitamins than white ones; carrots, tomatoes, and corn are richer in vitamins the more carotene they contain. The anti-xerophthalmic vitamin is soluble in fats and fat solvents. It is thermolabile, but not to the extent recently thought; it is more sensitive to oxidation. If oil is heated without access to air, it endures heating for 4 hours at 120° without harm to the vitamin; if, however, a stream of air is passed through the oil during heating, the vitamin is destroyed. Vitamin A is not destroyed during the saponification of oil if it is carried out not in an aqueous solution and without access to oxygen, and after saponification, it remains in the unsaponifiable residue. Products rich in Vitamin A give several color reactions, which can be considered qualitative reactions for the anti-xerophthalmic vitamin. Thus, for example, according to Drummond, when one drop of vitamin-containing oil is mixed with 1 cubic centimeter of arsenic trichloride, a dark blue coloration is obtained, which after a few seconds turns to purple, and after 5 minutes discolors; this reaction is very sensitive (0.05 mg of fish oil gives it) and can, according to Drummond, serve for the colorimetric determination of the vitamin content. According to Bezssonov, the substance under study is dissolved in benzene and 3 cubic centimeters of the solution are shaken with 12 drops of Folin's reagent (a solution of phosphotungstic acid, used to determine uric acid); in the presence of the vitamin, a blue coloration appears. The chemical nature of Vitamin A has not yet been finally elucidated; it is certain that this vitamin is not a fat. All vitamin preparations obtained so far do not represent pure vitamins. The most purified preparation was obtained by Takahashi from fish oil and was named by him biosterin; its composition is C₂₇H₄₄O₂, molecular weight is 340. Biosterin, according to Takahashi, contains two alcohol groups - one tertiary and one primary or secondary - and is close to cholesterol. 1 mg of biosterin per 1 kg of vitamin-free food ensures normal growth of rats. Role and distribution of Vitamin B [antirachitic]. Vitamin B [antirachitic], which plays an important role in the etiology of rickets (see Avitaminoses), is distinct from the Vitamin A just considered. Butter, rich in Vitamin A, is very poor in the antirachitic vitamin. Fish oil, rich in Vitamin A, is the product richest in Vitamin B. The yolk of a chicken egg is rich in the antirachitic vitamin. Of vegetable oils, only coconut oil may contain a little of this vitamin (it does not contain the anti-xerophthalmic vitamin). The green parts (leaves) of plants are rich in Vitamin B; from leaves, Vitamin B can be extracted with alcohol, ether, and acetone. Regarding the content of Vitamin B in various plant products, there are still very few studies; however, it can be said that many plant products rich in the anti-xerophthalmic vitamin are poor in or completely devoid of Vitamin B. In the absence of the latter in food, in rickets, the phosphorus content in the blood drops sharply. The introduction of Vitamin B into the organism brings the phosphorus content in the blood to normal. The presence of Vitamin B in food makes possible the complete utilization of phosphoric acid and normal calcium deposition in bone tissue. In its properties, Vitamin B is distinct from Vitamin A; thus, for example, if a current of air heated to 100° is passed through fish oil for 12–20 hours, Vitamin A is destroyed, and fish oil loses its ability to cure keratomalacia, whereas the antirachitic vitamin remains untouched, and fish oil retains its previous antirachitic properties. In elucidating the chemical nature of Vitamin B, an important role was played by the studies of Hess and others on the effect of ultraviolet rays on various plant and animal products and on the animals themselves, which showed that under the influence of illumination with ultraviolet rays, some substance (provitamins) is transformed into Vitamin B and the products are enriched with Vitamin B. By virtue of this, vegetables grown in beds are always richer in Vitamin B (since they were exposed to the direct action of sunlight) than vegetables grown in greenhouses or hotbeds (under glass), since glass absorbs the ultraviolet rays of the solar spectrum (see Avitaminoses).* According to Windaus's research, the provitamin is a substance close to cholesterol - ergosterol. * Funk recognizes the existence of a special growth vitamin, which, in his opinion, stimulates the growth of yeast; this Funk calls Vitamin D. However, most researchers deny the existence of this vitamin, which is why we call the antirachitic vitamin letter D, as is done following the suggestion of MacCollum by American, English, and German (e.g., Stepp) scientists.

What changes occur in the ergosterol molecule during its conversion under the influence of ultraviolet rays into vitamin B is still unknown. Vitamin B, unlike its provitamin ergosterol, is not precipitated by digitonin, which precipitates both cholesterol and ergosterol. Role and distribution of vitamin B. In the absence of vitamin B in food, beriberi (see) or polyneuritis occurs. The initial symptoms are unspecific—loss of appetite, weight loss, followed by metabolic disorders and, as a specific symptom, disorders of the nervous system, convulsions, paralysis. In growing animals, the absence of vitamin B causes first a cessation of growth, and then weight loss, etc. The absence of vitamin B in food is accompanied by a number of metabolic disorders as well; in polyneuritis, gas exchange is reduced (both oxygen consumption and CO₂ output), body temperature is lowered, tissue respiration of polyneuritic pigeons is reduced, as well as the reaction to cysteine, carbohydrate metabolism is impaired (hyperglycemia and impaired glycogen function of the liver), creatine metabolism in the muscles and brain is impaired, cholesterol metabolism is impaired, etc. In experiments with experimental B-avitaminosis, as well as other avitaminoses, it is possible to eliminate the loss of appetite and the resulting decrease in food intake, but even then the characteristic metabolic disorders still take place. The product richest in vitamin B is brewer's yeast. It is abundant in the grains of various cereals, and in the grains of some cereals it is contained, mainly or exclusively, in the outer layer of the grain or in its germ part (rice, wheat, corn), while in others (rye) it is distributed more evenly throughout the grain. In potatoes, vitamin B is not abundant, but still sufficient to cover the daily requirement of this vitamin when consuming significant quantities of potatoes. Carrots are very rich in it, followed by spinach, cabbage, beets, beans, peas, eggplants, oranges, apples (see table). Among animal products, milk (whey) and eggs should be put in first place in terms of vitamin B content, and then certain organs (liver, brain, muscles). Vitamin B is soluble in water, as well as in 95° alcohol. It is fairly stable upon heating: ordinary short-term boiling (especially with an acidic reaction) does not cause noticeable destruction of the vitamin; prolonged boiling or (especially) heating to a higher temperature (up to 120°) destroys vitamin B. A number of researchers * In addition to the data placed in the article Avitaminoses, it should be pointed out that, according to data by Hart, Steenbock, and others, irradiation with ultraviolet rays increases the egg-laying capacity of hens and that the yolk of eggs laid by hens that were irradiated during egg-laying with ultraviolet rays is much richer in vitamin D than ordinary yolk. tried to isolate vitamin B, obtain its pure preparations, and determine its composition and chemical nature. Funk isolated crystalline products possessing strong antineuritic action from yeast and rice bran. Suzuki obtained orizanin; Edie and Ewans isolated from yeast a very active preparation—torulin, of the composition C₆H₁₇N₂O₅; Hofmeister obtained oridin, and so on. But none of them managed to bring the purification of vitamin B to the end and determine its composition. The greatest success in this regard was apparently achieved recently (1927) by Jansen and Donath; they obtained a substance from rice bran which, in an amount of 0.003 mg per day, completely protected birds from beriberi disease (the dose curing beriberi in humans is about 1 mg per day). Repeated analyzes of the hydrochloric acid salt of this substance and its double salt with gold chloride led to the following formula for pure vitamin B: C₆H₁₀ON₂. According to the authors, the molecule of this vitamin contains either an imidazolic or a pyrimidine ring. It should also be pointed out that, according to Jendrassik, it is possible to detect the presence of vitamin B using a special color reaction (solutions of potassium ferricyanide and ferric chloride are added to an acidified aqueous solution of the test substance; in the presence of vitamin B, a blue coloration or blue precipitate appears). Role and distribution of vitamin C. In the absence of vitamin C in the food of humans, the disease of scurvy occurs; children get infantile scurvy, which is better known under the name of Barlow's disease (see Barlow's disease). Research on experimental scurvy in guinea pigs played a very important role in clarifying the role of vitamin C. In experimental scurvy caused by the removal of this vitamin from food, characteristic metabolic disorders are observed: hyperglycemia occurs (A. Palladin), which first increases, reaches a certain maximum, after which it begins to fall; falling, the sugar curve reaches normal (this period coincides with the appearance of external symptoms of scurvy), and then drops even lower—hypoglycemia sets in, increasing up to the death of the animal. Simultaneously, the glycogen function of the liver is impaired; the content of creatine in the muscles increases; creatinuria begins, which increases as scurvy develops; the synthetic abilities of the organism are impaired, etc. Antiscorbutic vitamin C is contained, mainly, in plant products, first of all, in fresh green vegetables—cabbage, lettuce, various varieties of beets, onions, radishes, potatoes, in many fruits, first of all, lemons and oranges (oranges play a major role in the fight against infantile scurvy), further, in eggplants, strawberries, apples, etc. It is also contained in germinating seeds; in resting seeds, on the contrary, vitamin C is completely absent. Among animal products, milk occupies the first place in the content of antiscorbutic vitamin, and the amount of the vitamin in both cow's and human milk depends on the food of the lactating animal; then come various organs (muscles, kidneys, liver), which can also contain certain amounts of this vitamin if fed a diet rich in vitamin C. Vitamin C is soluble in water; it is much more sensitive to various chemical and physical influences than other vitamins. It is very sensitive to the action of high temperatures; even heating to 30–40°, especially for a long time, acts on it in a destructive manner; rapid heating to boiling is less harmful to vitamin C than prolonged heating at lower temperatures. If spinach is boiled for 15 minutes, only 1/12th part of the originally contained amount of vitamin C will remain in it.

Lemon juice is well preserved by the addition of 0.06% acid potassium sulfate; in this case, it retains sufficient amounts of the antiscorbutic vitamin for 4 years. Various vegetables do not lose vitamin C to the same degree upon identical heating. The heating to which vegetables are subjected during the preparation of dishes, although it destroys a significant part of the vitamins C in them, still, by virtue of their richness in this vitamin, does not nearly always threaten us with the danger of receiving an insufficient amount of vitamin C. This vitamin is destroyed very rapidly upon heating under pressure at a temperature of 110-130°. By virtue of this, canned foods contain absolutely no vitamin C (tomatoes seemingly represent an exception in this regard). Sterilized and pasteurized milk also do not contain vitamin C, as well as condensed milk. This vitamin also tolerates drying poorly, especially if it is conducted at an elevated temperature: dried vegetables and potatoes usually do not contain this vitamin. But, according to recent data, with very rapid drying at a low temperature (the Just-Hatmaker method), vitamin C can be preserved intact both in vegetables and in dry milk. During prolonged storage of vegetables, the content of vitamin C in them decreases. This vitamin is also destroyed in the presence of minute traces of copper. The chemical nature of the antiscorbutic vitamin has still not been completely elucidated. The reaction for vitamin C proposed by Bessonov, based on the use of a special reagent (phosphomolybdotungstic acid), does not yield a positive effect with all products containing vitamin C. Reproduction vitamin E. During studies on the above-described vitamin, it turned out that sometimes, when the food of animals was seemingly adequate and complete in all respects, the animals lost the ability to reproduce. This occurred, for example, when adult rats were fed exclusively on milk; the addition of cod liver oil and yeast to the food did not improve matters, and only after the introduction into the food of fresh lettuce, sprouted wheat grains, butter in more significant quantities, and egg yolk, did the animals regain their ability to reproduce. From this, Bishop and Evans concluded that the presence of a special vitamin in food is necessary for reproduction, which they named the reproduction vitamin, or vitamin E. The absence of this vitamin causes degeneration of the gonads in males, and in females, the termination of pregnancy already after the implantation of the egg. Vitamin E, as far as is known so far, is contained in cereal seeds (especially in their germ part) and in green plants, in egg yolk, and (in smaller quantities) in butter; it can be extracted from these products using ether, alcohol, acetone, and other similar substances. Vitamin E is absent in cod liver oil. Vitamin E is insoluble in water; it is very stable with respect to the action of high temperatures, light, atmospheric oxygen, acids, and alkalis. Its chemical nature is still unknown. Avitaminosis and resistance to infections. A characteristic consequence of a deficiency of vitamins or their absence in food is a lowered resistance to all kinds of infections; this lowered resistance is observed with a deficiency in the food of any of the vitamins A, B, C, and D. Are vitamins formed in the animal organism? As can be seen from the above, vitamins are generally exogenous substances, since they usually are not formed at all or are not formed in sufficient quantity in the body of animals. However, according to recent data, exceptions must be made to this general conclusion: some vitamins can be formed in the bodies of certain animals. This is indicated by the fact that vitamin C is present in the livers of rats fed a diet devoid of this antiscorbutic vitamin, which apparently is the reason why rats do not contract scurvy. Conversely, vitamin C is not formed in the bodies of humans and guinea pigs. Vitamin D, as we saw above, can also be formed in the animal body under the influence of ultraviolet rays.