Food And Nutrition (1940)

for [Music] man is a living machine he requires a supply of food for energy growth and maintenance of the body organs a typical man usually eats daily carbohydrates about 600 G fats 100 proteins 100 minerals five traces of vitamins and water 2,000 gram during digestion the simple sugars are absorbed by the walls of the intestines here they pass into the bloodstream and the portal vein carries them to the liver aided by insulin and enzymes the liver converts soluble sugars into insoluble glycogen and stores it until needed by the body some sugar is is also converted to glycogen in the various muscles of the body the fats digested in the intestines enter the lymphatics and pass through the main lymphatic duct into the jugular vein the blood carries the fats to all tissues some are stored in specialized fat cells represented here these are located in all parts of the body but they are particularly abundant under the skin stored fats are one form of Reserve energy Hogs may become fat from overeating fats excess carbohydrates and part of the excess protein may all be converted into fat people who follow their natural urges for food are likely to take in more food than the body can use the best ways to keep from getting fat are to decrease the food eaten and to increase the muscular work done working hard or for that matter merely living demands fuel the body's main fuel is sugar and as the sugar in the blood is used the liver converts its glycogen back to Sugar which enters the blood and goes to all the cells in the body to supply energy for additional work proteins and stored fats may also be drawn upon for energy but they are less readily mobilized than is the glycogen of the liver in the diet starches fats and proteins may be substituted one for the other to supply energy to obtain energy this fuel must be burned and this requ Ires oxygen whether used slowly as by the white mouse in this jar or rapidly as by the candle in this when the candle and mouse have used up 1/5 of the volume which is the total oxygen in the air within the jars the flame of life goes out in both by measuring the amount of oxygen used by this man it is possible to determine the rate of organ activity as well as the amount of heat produced this container holds pure oxygen which the man breathes as the man breathes in the tank Falls as he exhales the tank Rises oxygen is inhaled directly from the tank exhaled air due to the one-way valve is forced back through soda lme which absorbs the carbon dioxide produced in the body and permits return of unused oxygen to The Container absorption of carbon dioxide by lime can be demonstrated by exhaling through lime water insoluble calcium carbonate is formed this stylus records the amount of oxygen still remaining in the tank the low points are the ends of each inspiration we draw a line joining these low points from the slope of this line we compute the volume of oxygen used by this man in 6 minutes then we calculate what this volume would be under standard conditions of temperature and barometric pressure from the height and the weight of this man we determine his body surface warm blooded animals when resting and not recently fed use oxygen at a rate directly proportional to the body surface therefore the basil metabolism is expressed in calories produced per square meter of body surface in 24 hours the same man is now doing work against a break the stylus dro drops much faster than before indicating a more rapid consumption of oxygen performing the same calculations as before we now find that the metabolic rate is almost four times as great as when he was at rest cattle assist Man by making readily available in the form of meats and dairy products the proteins which are manufactured by plants during digestion the proteins are broken down to amino acids here we see young cells growing in tissue culture essential building stones for their growth and for the repair of all cells are the amino acids from proteins no other food will substitute for them in this important function we shall feed one of these young rats a normal diet and the other a diet too low in protein note the difference in the rate of growth after five weeks the one on the low protein diet is stunted weak and diseased in the liver the amino acid molecules not used in growth and repair are split some parts may be changed into fats and and move away to be stored in fat tissues or these parts may be changed into glycogen and stored in the liver for future use in either case ammonia is left most of this is converted into Ura which is excreted by the kidneys besides carbohydrates fats and proteins the body needs at least a dozen different minerals for example inadequate calcium in the diet may lead to many defects especially of the teeth and bones insufficient iron may result in anemia that is too few red Corpus in the blood anemia may also be caused by insufficient vitamins and proteins in the diet anemia produces great weakness total elimination of inorganic salts from the diet as in the animal at the right results in extreme weakness and early death we also need in the diet very small amounts of many organic substances called vitamins the specific defects produced by lack of these vitamins are determined by giving to experimental animals diets adequate except for one of these vitamins if for example rats receive no vitamin A growth is and the eyes become infected a deficiency of vitamin B results in Disturbed nerve control as in the case of this pigeon insufficient vitamin D results in rickets or softening of the bones as in this child in the past hunger and appetite rather than understanding have been on the whole satisfactory guides to eating when the stomach is empty there occur in it waves of severe contractions which produce the sensation of hunger an urge fixed by heredity appetite however appears to be the memory of pleasant experiences with food it is aroused by the sight of food which stimulates the optic nerves the odor of food which stimulates the AL Factory nerves and the presence of food in the mouth which stimulates the taste nerves during a meal these impulses pass to the brain which relays them to the walls of the stomach causing relaxation of the stomach and eventually stops both hunger and appetite when all men have understanding of adequate diets and also have means to secure them then hunger and appetite will guide the people of tomorrow to a healthier life not only more years but more years of happiness in achievement