( Originally Published 1936 )
Our knowledge of the vitamins has been acquired by observing the results of selected diets on animals and by studying conditions in human beings that were suspected of being caused by dietary deficiencies. Since the effect of diets lacking particular substances in foods, later known as vitamins, was observed in this work the tendency has been to stress the deficiency diseases that developed. These do not develop in human beings, however, except in cases of famine, in isolated districts where the food supply is limited, in communities where poverty causes a lack of food, or among infants where the diet is too restricted. With the exception of rickets, infantile scurvy, and pellagra, deficiency diseases are seldom seen in America.
General Functions. Recently the positive need for vitamins is being stressed. Men engaged in vitamin research work are urging people to use vitamin-rich diets if they wish to enjoy optimum health. In addition to the part they play in preventing certain deficiency diseases, vitamins are necessary for normal growth and development, normal reproduction and lactation, and the maintenance of health. Growth may be checked at will in experimental animals by the use of vitamin-free or vitamin-poor diets. Normal reproduction and lactation in animals does not take place when certain vitamins are lacking. There is increasing evidence that there is greater health and vigor, longer life, and increased resistance to bacterial infection when all vitamins are used in liberal amounts. We believe that all vitamins should be used in more liberal amounts than that necessary to prevent deficiency diseases.
Classification and Properties. Vitamins are classified alphabetically as A, B, C, D, E, and G. Some workers regard G as a part of B, and use the symbols B1 and B2. Vitamins A, D, and E are soluble in fat and found associated with the fat in certain foods. Vitamins B, C, and G are soluble in water, and widely distributed in foods. All vitamins originally come from the vegetable kingdom. Those found in milk, eggs, and fish oils are there because of the green plants eaten by the animals from which they are obtained. Green leaves and growing shoots are richest in vitamins; fruits, roots, and seed embryos are next. Vitamins A, D, E, and G are stored in the body, while B and C are not stored to any extent. In general, with the exception of vitamin C, they are quite stable and not easily destroyed with ordinary cooking temperatures. C is easily destroyed in cooking, particularly in the presence of oxygen. Some of the water soluble ones may be lost if the water used in cooking or canning is discarded. The addition of an alkali may destroy vitamins also, so the common practice of adding soda to vegetables is not recommended.
Vitamin A. This vitamin is found in fish oils, fats from glandular organs, egg yolk, milk, and milk products, yellow and green vegetables and fruits. Fish oils, butter fat, and egg yolk are the best sources. It is quite stable and not affected in ordinary cooking. Considerable may be stored in the body. It closely resembles carotene, the yellow pigment of carrots, and is thought by some to be formed from it in the liver.
Vitamin A has a direct effect upon growth. It was originally discovered by observing that young animals fed experimental diets would grow or cease to grow accordingly as they were fed butter fat or lard. It was soon found that egg yolk and cod liver oil contained fats similar to butter and that most vegetable fats resembled lard.
It was also observed that animals would grow on a low vitamin A diet but have much respiratory disease and poor reproductive powers. This vitamin appears to keep the mucous surfaces of the respiratory tract and alimentary tract in a healthy condition, thus helping to prevent invasion of bacteria into the blood stream. Investigators have reported that many of the deaths seen among children who were afflicted with the eye disease caused by a lack of vitamin A were due to respiratory disease.
This eye condition, known as xerophthalmia, which occurs after a continued lack of vitamin A, is characterized by the eyes becoming dry, swollen, and inflamed. Eventually blindness may develop. This was first observed among Japanese children where it was discovered that fish oils would prevent it. An epidemic was reported in Denmark which was promptly relieved when butter-fat was added to the diet. Night blindness as seen in arctic countries is another condition often due to a lack of vitamin A. Xerophthalmia is seldom seen in this country. Attention should be given to the inclusion of vita-min A in the diet largely because of its growth promoting quality and the protection which it affords against bacteria.
Vitamin B. Vitamin B is a water soluble vitamin. It is fairly stable, more being lost in the water discarded in cooking than by the cooking itself. Soda destroys it to a great extent and should not be used in cooking vegetables. This vitamin is widely distributed in foods and possibly the best sources are the whole wheat products which contain the germ of the wheat, and yeast. Milk, milk products, and eggs are fairly good sources. All vegetables and fruits contain some. It is not found in highly refined foods.
One of the most important functions of vitamin B is the stimulation of appetite. It indirectly affects growth in this way by increasing the food intake. It is essential for maintaining the normal tone of the digestive tract both in the stomach and intestines. Much of the malnutrition in children is thought to be partly caused by a lack of sufficient vitamin B in their diets. Cereals and breads containing the germ of the wheat have been a valuable contribution to our diet because of their vitamin B con-tent. Foods rich in this substance are used because of their value in stimulating appetite and promoting digestion and intestinal elimination. The vitamins as well as the fiber in the above mentioned foods may be a factor in the prevention of constipation.
Vitamin B was discovered while searching for a cure for beriberi. That there was a relation between diet and this disease was originally discovered in Japan by a Japanese medical officer who did much to eradicate it from the Japanese Navy by improving the diet. It is most common in the Orient and the Philippines where much polished rice is used. According to McCollum it ranks seventh or eighth in importance among the diseases affecting man and is one of the most common causes of infant mortality in the Philippines. The physical manifestations of the disease are seen in the degeneration of the nerves to such a degree that paralysis may result. The heart is often weak and there may be swelling or edema of the body. As with xerophthalmia it is seldom seen in this country, although there may be a definite vitamin B deficiency with the amount of refined foods used.
Vitamin C. Vitamin C is thought to be the same as an organic acid called ascorbic acid. It has been prepared in crystalline form from paprika which is the best source. It is the most unstable vitamin, being easily destroyed by heat, particularly in the presence of oxygen. It is not stored in the body. The best sources among foods are oranges, lemons, grapefruit, strawberries, tomatoes, raw cabbage, and raw onions. Other fruits and vegetables, particularly if eaten raw, are good sources. Vacuum packed commercially canned fruits and vegetables compare favorably with the fresh ones. Home canned fruits and vegetables contain very little. Cooked potatoes, tomatoes, cabbage, and onions are fairly good sources, potatoes being of especial value because of the amount consumed. Vitamin C is better preserved in citrus fruits and tomatoes because of their acid content.
Originally discovered as a specific prevention for scurvy, vitamin C has been found to be essential in many ways. Pediatricians have observed that retardation of growth in children, irritability and general lack of vigor may be directly due to a lack of vitamin C, so fresh fruits and vegetable juices are added to the child's diet very early. The prevalence of infantile scurvy emphasizes the need for greater consumption of foods rich in this vitamin.
Susceptibility to bacterial infection is increased in the presence of scurvy.
The part that vitamin C plays in tooth nutrition was first described in this country by Howe. Its value has been later confirmed by others so that it is thought to be important in tooth nutrition along with vitamins A and D, and calcium and phosphorus. It has been shown that we need twice the amount of vitamin C necessary to prevent scurvy for the normal development of teeth.
Recently a condition of capillary fragility among children, which also develops at times in old age and some diseases, has been observed both in this country and abroad due to a lack of vitamin C. The capillaries allow the escape of blood and minute subcutaneous blood spots develop. In Sweden this condition was commonly seen in children during the late winter and spring months. It was promptly relieved by adding one orange to the daily diet.
With our present knowledge of nutrition, true scurvy is very rare. In the past it was a common disease among members of exploring expeditions, armies, and prison camps. In 1747 James Lind of the British Navy discovered that it could be prevented by the inclusion of fresh food in the diet. This led to the order that all British sailing vessels should carry fresh lime juice. Scurvy is characterized by definite injury to the capillary blood vessels and dentine-forming cells of the teeth. Hemorrhages occur throughout the body, teeth become loose, bones fragile, and a general soreness and stiffness results. When vitamin C is added recovery is rapid.
The free use of vitamin C is necessary at all ages. It is not stored in the body, but must be supplied regularly. Because of its instability in cooking, a portion of raw fruits or vegetables should be included in the diet daily.
Vitamin D. The fat soluble vitamin D is found in association with vitamin A and at first was thought to be identical with it. It was found by treating cod liver oil with heated air that it lost the property of vitamin A which protects against xerophthalmia. The oil thus treated, however, retained the property of protecting against rickets, so the separated factor was called vita-min D. Later it was found that certain foods and the skin upon exposure to sunlight develop the same property. This is due to the presence in them of a substance known as ergosterol which is changed by the ultraviolet light. Irradiated ergosterol dissolved in vegetable oil is known as "Viosterol." This is much more potent in vita-min D than the natural sources and recently a crystalline substance has been prepared which is 40,000 times as strong as cod liver oil. All concentrated sources of vita-min D should be used only upon a physician's advice.
Among foods, milk fat and egg yolk are the best sources. They do not contain a large amount of vitamin D, but because of the quantity used in the diet, are regarded as good sources. Cod liver oil, halibut liver oil, and other fish liver oils are excellent sources. In these fish, vitamin D seems to be concentrated in the liver, while in the salmon it is distributed through the fat in the body of the fish. Salmon is a fairly good source. Vitamin D is stable to heat and can be stored in the body.
The chief function of vitamin D is the part that it plays in the utilization of calcium and phosphorus, and consequently the building of skeletal tissue. It is now thought that it aids in the absorption of these elements as well as their retention after absorption. With a lack of calcium and phosphorus, or vitamin D or sunshine, rickets may develop.
In rickets the bones do not calcify properly and knock knees, bow legs, spinal curvatures, and narrow deformed chest and pelves result. A rachitic child is pigeon-breasted, pot-bellied, and has enlarged joints and beaded ribs. It is estimated that 50 per cent of the children in cities under two years of age are victims of rickets, indicating that there is a deficiency of calcium and phosphorus, and vitamin D or sunshine.
There is no question about the need of extra vitamin D for pregnant and nursing mothers and children to en-sure good development of teeth and to prevent rickets. The average adult possibly secures sufficient from a well balanced diet and from exposure to sunshine. The irradiation of foods, however, may bring about a better distribution of vitamin D for every one. Milk seems to be one of the most successfully irradiated foods.
The value of sunshine should not be overlooked. Rickets is a disease of the Temperate Zones. Children in the tropics are more exposed to the sunlight so benefit with immediate irradiation of ergosterol in the skin. The Eskimos do not have the sunlight, but eat fish oils for their vitamin D.
Sun bathing is sometimes overdone. Only a part of the total skin's surface needs to be exposed and that only for a short time. Ultraviolet rays do not pass through ordinary window glass nor clothing. Special ultraviolet lamps should be used carefully.
The lack of sunshine with dust and smoke in the cities is largely responsible for the deficiency of vitamin D among city children. Better diets and more sunlight for both mothers and children will do much to eradicate rickets and ensure better teeth.
Vitamin E. Vitamin E is a fat soluble vitamin found in wheat germ, egg yolk, milk, and green leafy vegetables.
In animal experimentation work it has been found that a deficiency has resulted in sterility in both sexes. There is little evidence that vitamin E is lacking in the human dietary, however.
Vitamin G (B2). Vitamin G was separated from B. It is a water soluble vitamin and more stable to heat than B. It is found in yeast, germ of wheat, milk, meat, eggs, and leafy vegetables. The banana is a richer source of G than any other fruit. Milk is probably the most important source.
Like A and B it is essential to growth and to general well-being. A deficiency may result in digestive disturbances, inadequate blood formation, a lack of resistance to infectious diseases, and general lack of vitality.
It is the general belief that pellagra, a disease rather common in the mountain districts of the South, is due to a lack of vitamin G, although some believe that there are other factors. It is characterized by a red rash on the skin of the face and hands, sore tongue and mouth, digestive disturbances, and an acute diarrhea. It is true that Goldberger was able to eradicate pellagra from a orphanage by the inclusion of milk, lean meat, eggs, yeast, tomato juice, and canned salmon, and produce it in a prison in six months by feeding them the type of diet eaten by cotton mill workers who had a high incidence of the disease. These diets contained a high percentage of pork and corn.
From recent studies it would seem that vitamin G is the agent through which the unnamed substance in the stomach wall and liver works in correcting the abnormal blood formation in pernicious anemia.
It is not possible or necessary to state definite amounts of foods' that must be included in the diet to meet vita-min requirements. It is obvious that a liberal amount of milk, eggs, vegetables, fruits, and whole grain cereals must be used. A pint of milk is advisable for the adult and a quart for the child. Vegetables should be used twice a day—a leafy vegetable and another, in addition to potato. Whole grain cereals and breads should be given preference to refined ones. An egg should be included daily or several times a week. Some raw fruit or vegetable must be used to supply vitamin C. Fish liver oils or irradiated foods should be used to supply the extra vitamin D needed in pregnancy, lactation, and childhood.
In general, it should be remembered that foods are our best sources of vitamins, and if the diet is well balanced there is little need of using artificially prepared products. All of the vitamin concentrates that are available today should be carefully used, and only upon the advice of a physician.