The Nutrition of Man

Chapter I Page

FOODS AND THEIR DIGESTION 1

TOPICS: The purpose of nutrition. The food of man. Proteid foods. Carbohydrate foods. Fats. Food as fuel. Composition of foodstuffs. Availability of foods. Food as source of energy. Various factors in the nourishment of the body. Processes of digestion. Secretion of saliva. Function of saliva. Enzymes. Reversible action of enzymes. Specificity of enzymes. Mastication. Gastric secretion. Components of gastric juice. Action of gastric juice. Muscular movements of stomach. Time foods remain in stomach. Importance of stomach digestion. Processes of the small intestine. Secretion of pancreatic juice. Chemical changes in small intestine. Destruction of proteid food. Significance of the breaking down of proteid. Change of fatty foods and carbohydrates in intestine. Digestion practically complete at end of small intestine. Putrefaction held in check. Digestion a prelude to utilization of food.

CHAPTER II

ABSORPTION, ASSIMILATION, AND THE PROCESSES OF METABOLISM 39

TOPICS: Physiological peculiarities in absorption. Chemical changes in epithelial walls of intestine. Two pathways for absorbed material. Function of the liver as a regulator of carbohydrate. Absorption of proteid products. Assimilation of food products. Anabolism. Katabolism. Metabolism. Processes of metabolism. Older views regarding oxidation. Discoveries of Lavoisier. The views of Liebig. Theory of luxus consumption. Oxidation in the body not simple combustion. Oxygen not the cause of the decompositions. Oxidation not confined to any one place. Intracellular enzymes. Living cells the guiding power in katabolism. Some intermediary products of tissue metabolism. Chemical structure of different proteids. Decomposition products of nucleoproteids. Relation to uric acid. Action of specific intracellular enzymes. Creatin and creatinin. Relation to urea. Proteid katabolism a series of progressive chemical decompositions. Intracellular enzymes as the active agents.

CHAPTER III

THE BALANCE OF NUTRITION 77

TOPICS: Body equilibrium. Nitrogen equilibrium. Carbon equilibrium. Loss of nitrogen during fasting. Influence of previous diet on loss of nitrogen in fasting. Output of carbon during fasting. Influence of pure proteid diet on output of nitrogen. Influence of fat on proteid metabolism. Effect of carbohydrate on nitrogen metabolism. Storing up of proteid by the body. Transformation of energy in the body. Respiration calorimeter. Basal energy exchange of the body. Circumstances influencing energy exchange. Effect of food on heat production. Respiratory quotient and its significance. Influence of muscle work on energy exchange. Elimination of carbon dioxide during work and with different diets. Effect of excessive muscular work on energy exchange. Oxygen consumption under different conditions. Output of matter and energy subject to great variation. Body equilibrium and approximate nitrogen balance to be expected in health.

CHAPTER IV. Source of the Energy of Muscle Work, With Some Theories of

SOURCE OF THE ENERGY OF MUSCLE WORK, WITH SOME THEORIES OF PROTEID METABOLISM 119

TOPICS: Relation of muscle work to energy exchange. Views of Liebig. Experimental evidence. Relation of nitrogen excretion to muscle work. Significance of the respiratory quotient in determining nature of the material oxidized. Fats and carbohydrates as source of energy by muscles. Utilization of proteid as a source of energy. Formation of carbohydrate from proteid. Significance of proteid metabolism. Theories of Carl Voit. Morphotic proteid. Circulating proteid. General conception of proteid metabolism on the basis of Voit’s theories. Pflüger’s views of proteid metabolism. Rapidity of elimination of food nitrogen. Methods by which nitrogen is split off from proteid. Theories of Folin. Significance of creatinin and of the percentage distribution of excreted nitrogen. Endogenous or tissue metabolism. Exogenous or intermediate metabolism. Needs of the body for proteid food possibly satisfied by quantity sufficient to meet the demands of tissue or endogenous metabolism. Bearings of Folin’s views on current theories and general facts of proteid metabolism. Large proteid reserve and voluminous exogenous metabolism probably not needed. Importance of feeding experiments in determining the true value of different views.

CHAPTER V

DIETARY HABITS AND TRUE FOOD REQUIREMENTS 153

TOPICS: Dietetic customs of mankind. Origin of dietary standards. True food requirements. Arguments based on custom and habit. Relationship between food consumption and prosperity. Erroneous ideas regarding nutrition. Commercial success and national wealth not the result of liberal dietary habits. Instinct and craving not wise guides to follow in choice and quantity of food. Physiological requirements and dietary standards not to be based on habits and cravings. Old-time views regarding temperate use of food. The sayings of Thomas Cogan. The teachings of Cornaro. Experimental results obtained by various physiologists. Work of the writer on true proteid requirements. Studies with professional men. Nitrogen equilibrium with small amounts of food. Sample dietaries. Simplicity in diet. Nitrogen requirement per kilogram of body-weight. Fuel value of the daily food. Experiments with University athletes. Nitrogen balance and food consumption. Sample dietaries. Adequacy of a simple diet.

CHAPTER VI. Further Experiments and Observations Bearing on True Food

FURTHER EXPERIMENTS AND OBSERVATIONS BEARING ON TRUE FOOD REQUIREMENTS 191

TOPICS: Dietary experiments with a detail of soldiers from the United States Army. General character of the army ration. Samples of the daily dietary adopted. Rate of nitrogen metabolism attained. Effect on body-weight. Nitrogen balance with lowered proteid consumption. Influence of low proteid on muscular strength of soldiers and athletes. Effect on fatigue. Effect on physical endurance. Fisher’s experiments on endurance. Dangers of underfeeding. Dietary observations on fruitarians. Observations on Japanese. Recent dietary changes in Japanese army and navy. Observations of Dr. Hunt on resistance of low proteid animals to poisons. Conclusions.

CHAPTER VII

THE EFFECT OF LOW PROTEID DIET ON HIGH PROTEID ANIMALS 229

TOPICS: A wide variety of foods quite consistent with temperance in diet. Safety of low proteid standards considered. Arguments based on the alleged effects of low proteid diet on high proteid animals. Experiments of Immanuel Munk with dogs. Experiments of Rosenheim. Experiments of Jägerroos. Comments on the above experiments. The experiments of Watson and Hunter on rats. The writer’s experiments with dogs. Details of the results obtained with six dogs. Comparison of the results with those of previous investigators. Effect of a purely vegetable diet on dogs. Different nutritive value of specific proteids considered. Possible influence of difference in chemical constitution of individual proteids. Effect of low proteid diet on the absorption and utilization of food materials in the intestine of dogs. General conclusions from the results of experiments with animals.

CHAPTER VIII

PRACTICAL APPLICATIONS WITH SOME ADDITIONAL DATA 266

TOPICS: Proper application of the results of scientific research helpful to mankind. Dietary habits should be brought into conformity with the true needs of the body. The peculiar position of proteid foods emphasized. The evil effects of overeating. What the new dietary standards really involve. The actual amounts of foodstuffs required. Relation of nutritive value to cost of foods. The advantages of simplicity in diet. A sample dietary for a man of 70 kilograms body-weight. A new method of indicating food values. Moderation in the daily dietary leads toward vegetable foods. The experiments of Dr. Neumann. The value of fruits as food. The merits of animal and vegetable proteids considered in relation to the bacterial processes in the intestine. A notable case of simplicity in diet. Intelligent modification of diet to the temporary needs of the body. Diet in summer and winter contrasted. Value of greater protection to the kidneys. Conclusion.

INDEX 303

LIST OF ILLUSTRATIONS

FACING PAGE

Photograph of one of the athletes 190

Photograph of soldiers taken at the close of the experiment 194

Photograph of soldiers taken at the close of the experiment 195

Photograph of Fritz at the close of the experiment 200

Photographs of the dogs experimented with

Subject No. 5 August 19, 1905 248 Subject No. 5 November 18, 1905 248 Subject No. 5 April 24, 1906 248 Subject No. 5 June 27, 1906 248

Subject No. 3 August 19, 1905 251 Subject No. 3 November 18, 1905 251 Subject No. 3 April 24, 1906 251 Subject No. 3 June 27, 1906 251

Subject No. 13 January 2, 1906 252 Subject No. 13 February 27,1906 252 Subject No. 13 April 24, 1906 252 Subject No. 13 June 19, 1906 252

Subject No. 15 January 2, 1906 252 Subject No. 15 February 27, 1906 252 Subject No. 15 April 24, 1906 253 Subject No. 15 June 19, 1906 252

Subject No. 20 January 2, 1906 252 Subject No. 20 February 27, 1906 252 Subject No. 20 April 24, 1906 252 Subject No. 20 June 19, 1906 252

Subject No. 17 January 2, 1906 256 Subject No. 17 February 27, 1906 256 Subject No. 17 April 24, 1906 252 Subject No. 17 June 27, 1906 252

THE NUTRITION OF MAN

CHAPTER I. Foods and Their Digestion

FOODS AND THEIR DIGESTION

TOPICS: The purpose of nutrition. The food of man. Proteid foods. Carbohydrate foods. Fats. Food as fuel. Composition of foodstuffs. Availability of foods. Food as source of energy. Various factors in the nourishment of the body. Processes of digestion. Secretion of saliva. Function of saliva. Enzymes. Reversible action of enzymes. Specificity of enzymes. Mastication. Gastric secretion. Components of gastric juice. Action of gastric juice. Muscular movements of stomach. Time foods remain in stomach. Importance of stomach digestion. Processes of the small intestine. Secretion of pancreatic juice. Chemical changes in small intestine. Destruction of proteid food. Significance of the breaking down of proteid. Change of fatty foods and carbohydrates in intestine. Digestion practically complete at end of small intestine. Putrefaction held in check. Digestion a prelude to utilization of food.

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