By E.C. Robertson and F.F. Tisdall and by Dr. E.V. McCollum
Summary: Excerpts from two chapters of a 1939 compilation by the Canadian Medical Association, which admits that “the practical application of facts concerning nutrition has not kept pace with our increasing knowledge” and warns Canadian physicians that they “must increase their interest in this problem of normal nutrition, otherwise the public will seek information on this subject elsewhere.” (Advice that was, tragically, almost wholly ignored.) In the chapter “Nutrition and Resistance to Disease,” Roberston and Tisdall explain that while clinical evidence regarding nutrient deficiencies in humans can be difficult to obtain because of experimental limitations, this is not the case for animal studies, which show quite clearly the effects of even “comparatively slight” shortages in vitamins. The authors present studies showing drastic differences in resistance to disease in animals fed a diet sufficient in nutrients and those fed diets deficient in, respectively, vitamins A, B, and D; minerals; and animal protein. “These studies furnish clear-cut evidence that improper nutrition lowers the resistance of the animal to infection,” the authors state, “and also that the nutritional deficiency does not have to be so severe as to produce outstanding evidence of disease.” In the second chapter, “Better Nutrition as a Health Measure,” Dr. McCollum discusses the specific roles of vitamins A, C, and D in the body and in dental health in particular. From Nutrition in Everyday Practice, 1939. Lee Foundation for Nutritional Research reprint 115.
Excerpts from “Nutrition in Everyday Practice”[spacer height=”20px”]
Foreword: The Physician’s Responsibility for Normal Nutrition[spacer height=”20px”]
By the Canadian Medical Association
No science has made greater advances during the past twenty-five years than that of human nutrition. Before 1912 the physician’s main concern was to see that his patient received a proper supply of fats, carbohydrates, and proteins; very little was known of the importance of the minerals, and the word “vitamin” was then unknown. Now we know that of the twenty-two amino acids commonly present in protein ten are essential, and life could not exist without thirteen minerals and at least seven vitamins.
In the past the goal of the physician and public health worker has been to see that the population enjoyed average health and did not suffer from undernutrition or marked malnutrition. Recent observations on animals show that, starting with a diet already considered adequate, the feeding of additional amounts of certain food elements increases the rate of growth of the animals, maintains their youthful appearance longer, and lengthens their span of life.
Carefully conducted studies in Canada have indicated that our present dietary customs may result in many persons not receiving amounts of some of the food elements commensurate with the highest attainable level of health. Unfortunately, the practical application of facts concerning nutrition has not kept pace with our increasing knowledge. The practicing physician is so absorbed with the problem of diagnosis and treatment of disease that frequently the question of diet is more or less pushed into the background. The physicians of Canada must increase their interest in this problem of normal nutrition; otherwise the public will seek information on this subject elsewhere.
The Canadian Medical Association has long been interested in this subject, and this interest has crystallized in the formation of [its] Committee on Nutrition. With the view of presenting very briefly—and in a practical manner proved facts concerning what the normal person should eat and the reasons why, the committee obtained for the Canadian Medical Association Journal a series of short, practical, authoritative articles on normal nutrition, which appeared regularly for eighteen months. This was done in the belief that the physician could apply these facts with benefit to every patient who consults him for any cause.
It is hoped that the efforts of the committee will result in a more general application of our present knowledge of normal nutrition by the physician in his everyday practice. This, combined with an increased interest of the lay public in the subject of nutrition and a desire on their part to obtain authoritative information free from fads and fallacies, will result in a higher level of health for the Canadian people.
[Excerpt, chapter XIII, pages 62–66:][spacer height=”20px”]Nutrition and Resistance to Disease[spacer height=”20px”]
By Elizabeth Chant Robertson and Frederick F. Tisdall, Department of Pediatrics, University of Toronto, Toronto, Ontario
Nearly a hundred years ago, Graves wrote, “Want of a sufficiency or food of an unwholesome or an improper character predisposes the human frame to disease by its debilitating effect on the system.”
It is interesting to note that some physicians in the past recognized and emphasized the role of nutrition in the maintenance of health and resistance against infection. No one now questions the role of proper nutrition in resistance against disease. From a clinical standpoint, possibly most of us think of it in terms of undernutrition rather than of malnutrition. The difficulty of obtaining clinical evidence of the effect of minor nutritional deficiencies is obvious. The story is entirely different, however, in regard to animal laboratory experiments, where all conditions can be adequately controlled.
There is evidence that a lack of almost any one of the thirty-two food elements essential for animal nutrition will result in a lowered resistance to infection. A number of experiments giving evidence of this nature have been reported by one of us (E.C.R.). The procedure developed was to feed animals with a measured amount of a disease-producing organism and note the number of animals that survived.
This sounds like a very simple procedure, but actually it constitutes a most difficult and time-consuming experiment. A suitable disease-producing organism had to be first obtained. After a number of trials, an organism called Salmonella muriotitis (rat typhoid) was found to be suitable for this type of study. It was comparatively harmless for the human being, but in suitable doses was found to be pathogenic for the rat and yet not so severe in its effect that it invariably killed all animals. When death occurred, it was preceded by marked diarrhea, cyanosis, and a bloody discharge from the nostrils.
Blood cultures were taken aseptically from the hearts of all the dead animals, and the organism was regularly recovered, usually in pure culture, indicating that the rats had a muriotitis septicemia when they died.
The animals were observed for twenty-eight days after the infecting dose, [at which time] the experiments were terminated; those animals that lived for this length of time constituted the survivors. When death occurred, it usually was within the first ten days. The degree of resistance was estimated by the percentage of survivors in each experiment. In every case the experimental animals were fed a diet adequate in all respects with the exception of the factor or factors being studied. Control littermates were fed the same diet with the addition of the substance under study.
In Table I is shown the effect of lack of vitamin A on resistance to infection. It is to be noted that when the diet was deficient in this vitamin, only 40 percent of the animals survived, as compared to a survival rate of 79 percent in the littermates who were fed the same diet with added vitamin A—in the form of its precursor, carotene.
Table I. Effect of Lack of Vitamin A (Carotene) on Resistance to Infection
| Vitamin A Deficient Diet | Vitamin A Deficient Diet + 0.5% Carotene Solution | |
| No. of Animals | 10 | 14 |
| No. of Survivors | 4 | 11 |
| Percentage Surviving | 40% | 79% |
In Table II it is seen that when the diet was lacking in the vitamin B complex, 20 percent of the animals survived, as compared with a survival rate of 72 percent when the diet was perfect in all respects.
Table II. Effect of Lack of Vitamin B Complex on Resistance to Infection
| Vitamin B Deficient Diet | Vitamin B Deficient Diet + 6% Yeast | |
| No. of Animals | 79 | 72 |
| No. of Survivors | 16 | 52 |
| Percentage Surviving | 20% | 72% |
Similar results were obtained—as shown in Tables III, IV and V—when the diets were lacking, respectively, in vitamin D, minerals, and animal protein. In Table V it should be noted that the first lot of animals received their protein from grain sources, while the control animals received their protein largely from milk casein. This is evidence in favor of the advisability of including in the diet each day a certain proportion of protein as animal protein, namely, meats, fish, poultry, eggs, milk, and cheese.
Table III. Effect of Lack of Vitamin D on Resistance to Infection
| Rachitogenic Diet | Rachitogenic Diet + Vitamin D | |
| No. of Animals | 375 | 364 |
| No. of Survivors | 106 | 201 |
| Percentage Surviving | 28% | 55% |
Table IV. Effect of Lack of Minerals on Resistance to Infection
| Diet Very Low in Minerals | Diet Adequate in Minerals | |
| No. of Animals | 63 | 61 |
| No. of Survivors | 34 | 53 |
| Percentage Surviving | 54% | 87% |
Table V. Effect of Lack of Animal Protein on Resistance to Infection
| Normal Diet with 17% Wheat Gluten | Normal Diet with 17% Casein | |
| No. of Animals | 40 | 41 |
| No. of Survivors | 23 | 37 |
| Percentage Surviving | 57% | 90% |
In considering the percentage of survivors in Tables I to V, no comparison should be made between the number of survivors in one table with the number of survivors in another table, because with each set of experiments it was necessary to regulate the dosage of the Salmonella muriotitis. This was necessary because there was a variation in the degree of virulence of the organism as the experiments proceeded. However, in each individual experiment, the conditions of the control animals and of the experimental animals were identical—with the exception that the diet in the experimental group was lacking in the factor or factors being studied.
In the experiments the conditions were naturally quite severe, in that the deficiencies produced were very marked. One might say that deficiencies of this degree would rarely, if ever, be encountered under Canadian dietary conditions. Further studies were therefore made in which the degree of the deficiency in the diet was comparatively slight. The results obtained in one set of experiments are given in Table VI. It is seen that with this lesser degree of deficiency there is still a marked difference in the resistance of the two groups of animals against disease.
Table VI. Effect of Partial Lack of Vitamin B Complex on Resistance to Infection
| Partial Vitamin B Deficient Diet | Same Diet + Vitamin B | |
| No. of Animals | 30 | 38 |
| No. of Survivors | 6 | 33 |
| Percentage Surviving | 20% | 87% |
These studies with animals furnish clear-cut evidence that improper nutrition lowers the resistance of the animal to infection and also that the nutritional deficiency does not have to be so severe as to produce outstanding evidence of disease. With this laboratory evidence in mind—that a nutritional deficiency will result in a lowered resistance to infection—how are we to feed our sick patients?
If the illness is an acute one of short duration, that is, simply a matter of three or four days, then this question is not urgent. However, it is obvious that if the patient is suffering from any disease that lasts more than a week or so, special attention must be given to his nutrition as a whole.
Strange as it may seem, this is frequently neglected. Recent work has indicated that the presence of any infection increases the need of the body for many of the food elements. To give only three examples: it has been shown that the amounts of vitamin A and vitamin C in the blood are markedly lowered by infection, and there is evidence of an increased need for vitamin B1 [during infection].
The physician’s duty to his patients, however, should not stop with just the treatment of the acute or chronic illness. When the patient presents himself with even some minor infection, our interest should be aroused as to why the infection developed. Was it the result simply of a focus that could have been removed or treated, or have the patient’s habits been such that he is not enjoying the highest level of resistance?
Probably the most important of these habits are his habits of nutrition. The remarkable adaptability of the body is such that a person may have a nutritional deficiency for many years before it clearly evidences itself. In the interval, however, the patient will not be enjoying the highest possible level of health and resistance against infection.
One should not expect that infections can be completely prevented by dietary means. This, of course, is impossible, and with many diseases there is no evidence that nutrition has any effect on the susceptibility of the patient to the disease. However, from clinical observations there is no question that with proper nutrition the patient’s resistance to disease is maintained at a high level and that he will “throw off” or recover from his infection more often and more quickly than the one who is malnourished.
One cannot lay down any rules as to the nutritional treatment of a patient during illness. However, when the patient has recovered and if there is no specific contraindication, his food should include each day: a pint to a pint-and-a-half of milk for children or one-half pint for the adult, some meat, one egg daily, two liberal helpings of vegetables other than potatoes, some raw fruit or vegetables, and, during the winter months, some source of vitamin D. If this is done, you will be assisting your patients to reach that goal that we all desire, namely, optimum resistance against infection and optimum health.
[Excerpt, pages 69–71:][spacer height=”20px”]Better Nutrition as a Health Measure[spacer height=”20px”]
By Dr. E.V. McCollum
Turning to the vitamins, we find eminent medical opinion supporting the view that many people do not get enough of several of them because their diets are not well chosen. I can mention only the most important practical applications.
Vitamin A is closely associated with the health of the mucous membranes lining the respiratory, gastrointestinal, and urinary tracts. Healthy mucous membranes are an effective barrier against the entrance of bacteria, and as a general health measure, it pays to take a diet abundant in this vitamin. It is provided by all green and yellow vegetables [in the form of its precursor, carotene] and by milk, butter, liver, kidney, fish, etc., but not by white vegetables such as potatoes, white turnips, and white cereal products. It is very abundant in fish liver oils.
A striking relation exists between deficiency of vitamin A and the functioning of the eye. There is a pigment called visual purple in the retina of the eye that is made, in part, of vitamin A. When we become depleted of this substance, vision is impaired. This condition is widely prevalent among people who subsist on poor diets.
Many people, especially children and pregnant and lactating women, are not getting enough of vitamin B1, which is necessary for the health of the nervous system. The prevalence of neuritis, poor appetite, and smooth, bald tongue point to deficiency of this vitamin.
Vitamin C is found in fresh, uncooked fruits and vegetables and in other raw and commercially canned foods. Deficiency causes scurvy, which is still fairly common in infants. The health of the blood vessels is dependent on an adequate supply of this substance. When the body becomes depleted in vitamin C, it is much more susceptible to injury by bacterial poisons that arise through infections than is the case when the body reserves are high. Arterial damage resembling that seen in arteriosclerosis seems to result from bacterial poisons in persons who run short of this vitamin.
Vitamin D is of outstanding interest in relation to health. Only twenty years ago, rickets, a disease of the bones, was common. The discovery of vitamin D—and its power of promoting normal bone growth—represents one of the major contributions of nutritional science to public health. Now rickets in infants and children is much less common than formerly, and when the disease does exist, it is much milder. Now almost all mothers in Europe and America know that the baby must be given cod liver oil or one of the other sources of vitamin D. The benefits to infants and children resulting from the application of this knowledge have already been incalculable, and the boon of this knowledge is a permanent possession for the future.
There are three ways in which tooth structure may be influenced by diet. The organ that forms the enamel is very dependent for its health and function on vitamin A. If a deficiency of this vitamin occurs in the infant or child whose teeth are still forming, the enamel will contain pits and fissures, which are potential food traps in which particles of carbohydrate food lodge and ferment, [resulting in] the formation of acids that dissolve away the enamel.
If the diet contains an abundance of vitamin A but not enough vitamin D, the content of phosphate in the blood will fall, as it does in rickets, to so low a level that calcium phosphate, the substance of enamel, cannot be laid down, and poor enamel will result from this deficiency. The dentin-forming organ is especially dependent on an abundance of vitamin C. If an infant or child whose teeth are forming does not get enough of this factor, the dentin of the teeth will be badly formed, and the future health of the tooth will be impaired.
Teeth of perfect structure—free from imperfections such as pits and fissures and with smooth, polished enamel surfaces—are far less likely to decay than are teeth exhibiting these imperfections. Hence the fundamental importance to the individual of having optimum nutrition during the period when the teeth are developing.
Decay of the teeth is not only a source of discomfort, as from toothache, but also an inconvenience because of the early loss of the teeth. Tooth decay is [also] a menace to [overall] health, since the dead tooth is frequently the source of an abscess from which bacteria or their poisons find their way into the bloodstream. Secondary infections in the joints, kidneys, gallbladder, and other places have not infrequently been traced to an infected tooth.
Decayed teeth have been and are the cause of much ill health. The prevention of tooth decay would constitute one of the greatest possible achievements in improving public health. If our present day knowledge of nutrition could be applied to the entire population, there is no doubt that tooth decay could be reduced to a small fraction of its present ravages.
Optimum nutrition is so important in the minds of the leaders in the field of public health that in Europe and America a great movement is under way to improve the dietaries of the peoples. Governments are now taking active measures to provide the better-class foods at lower cost. In Canada an abundance of the better-class foods are available. The great need is for the dissemination of knowledge about the selection of foods, so that the daily diet will be complete.
In summary let me emphasize that through diet we may accomplish the following:
- Improvement of the health of the mucous membranes, making them more effective as barriers against the entrance of infective agents, with consequent reduction in the incidence and severity of respiratory disease.
- Improvement in the structure of the teeth and reduction in their liability to decay and subsequent infection; relief in great measure from secondary infections of the joints, kidneys, and heart.
- Safeguarding the health of the nervous system, especially as respects neuritis and the secondary effects of nerve injury such as heart and digestive disorders and disease of the digestive tract.
- Protection of the blood vessels against injury caused by bacterial poisons acting upon them when the body’s reserves of vitamin C are low.
We do not claim to have found in adequate nutrition the panacea for all human ills. We do claim that malnutrition is widespread and of a degree of severity that is reflected in many people in ill health in one of the categories mentioned. Attention to the proper selection of foods throughout life will go far toward reducing the incidence and severity of these conditions. When the body is not functioning normally, as in malnutrition, its capacity is lowered to withstand the effects of infections, fatigue, and emotional strain.
From Nutrition in Everyday Practice, Canadian Medical Association, 1939. Excerpts reprinted as single publication, Reprint 115, by the Lee Foundation for Nutritional Research.
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