Normal urine is slightly acid, froths when shaken but the foam soon disappears when at rest The normal quantity is 40 to 50 ounces in 24 hours. On standing, a cloud of mucus is deposited, derived from the surface lining of the bladder and urinary passages. The specific gravity is in proportion to its concentration. This can be determined by gently dropping a urinometer into the fluid. This instrument is a glass tube usually about 51/4 inches long, weighted at the large end with quicksilver. When it drops into distilled water it sinks so that the zero mark lines with the surface of the water. Normally it should register from 12 to 25 points denser than zerothat is, the stem should risethough it may rise, in the opinion of such a distinguished physiologist as Starling, as high as 1.040 and as low as 1.002 (from 2 to 40 points above 0) depending frequently upon such incidental factors as the drinking of a large or small amount of water.
In Chittenden’s observations on 9 athletic students and on 8 soldiers, referred to elsewhere, the average daily output of urine through a period of about 5 months was for the students 1,215 cubic centimeters (about 41.6 ounces), with an average specific gravity of 1.020, and for the soldiers 1,042 cubic centimeters with specific gravity of 1.023.
In concentrated urine, often associated with constipation, a deposit of urates occurs on cooling. This dissolves when the urine is warmed. Under certain circumstances urine is turbid as it is passed, but in this the turbidity generally consists of earthy phosphates, a salt of phosphoric acid, and is not cleared up by heating.
The color of the urine varies with its density or concentration. Dense urine in health is a condition to avoid. After severe sweating the amount of water excreted by the kidneys is small and the urine has a deeper color. After copious drafts of liquid the color may be very pale, indicating desirable dilution, with increase of quantity .1
Normal urine is generally mildly acid as indicated by litmus paper which is turned pink. This is due to the acid end products of food broken down in the digestive tract, notably proteins, fully described elsewhere.
One of the striking facts about urine is that when we eat a meal rich in proteids, on the theory that meat, eggs, cheese, etc. are needed to maintain health, nearly all of the distinctive element, nitrogen, soon appears in the urine, which also increases its acidity under these conditions. This fact is set out in great detail and with much emphasis in the Nutrition of Man, by Chittenden, Director of the Sheffield Scientific School, of Yale. It is also beautifully developed in the following important and instructive little table by Folin, of Harvard, quoted by Chittenden, which is based on two kinds of diet for the same healthy man, one rich in protein and the other a week later, a diet with little protein:
Commenting on this table Chittenden points out the marked difference in the percentage of urea-nitrogen in the two casesabout 26 per cent. A similar difference is seen in the uric-acid nitrogen, and the great difference in the extent of protein broken down in the two dates, an excretion of 16.80 grams against 3.6 grams. The creatin, not being an end product of food (a result of the breaking down process), but a tissue product, re-mains about the same. Elsewhere he says no other form of food can take the place of proteid (same as protein as used by other authors). A certain amount of such food is needed to make good the loss of tissue material broken down in the various functions of the body. But we must be ever mindful of the fact that proteid does not undergo complete change in the body to simple gaseous products like the non-nitrogenous foods, but that there are left behind solid, non-combustible products which are not easily disposed of. As Curtis puts it, “the combustion of proteid within the organism yields a solid ash which must be raked down by the liver and thrown out by the kidneys. Now when this task gets to be over-laborious, the laborers are likely to go on a strike. The grate then is not properly raked; clinkers form, and slowly the smothered fire grows dull and dies.”
Referring to similar facts brought out by experiments of his own Kellogg says a study of his results will show at once the enormous amount of extra work put on the kidneys by a high protein diet. For instances the total quantity of urine eliminated by persons taking an ordinary high protein diet is 43 per cent greater than the amount required by the low protein diet without meat. The acidity is more than double. The total nitrogen excreted is increased nearly 150 per cent. The urea is increased in the same proportion while the ammonia, which is the result of putrefaction in the colon, is increased to nearly 3% times normal. These facts, he says, show beyond any room for doubt that a high protein diet, or even the ordinary mixed diet, such as Folin was considering, comprising an excess of protein, compels the kidneys to do an enormous amount of extra and harmful work in order to remove from the blood the excessive amount of poisonous waste thrown into it.
The reader here should carefully note the sequence set forth by Chittenden, Folin, Curtis and Kellogg. A diet rich in protein (food rich in nitrogen) means a urine as relatively rich in nitrogen, and this nitrogen is a waste product of protein that must be handled by the liver and kidneys. Elsewhere we learned that it comes from putrefiable food that is closely associated with putrefaction in the intestinal tract. So that the excessive use of food rich. in nitrogen (Iargely from animal sources) not only greatly increases the labor of the kidneys and liver but is apt to set up a state of disease in the intestinal tract that may speedily lead to chronic invalidism of the most serious character.
See end of Chapter XXIX for table showing the relative value of different foods.
The reader should note in the table of foods referred to above that protein is found in nearly all the foods mentioned, even in strawberries, the exceptions being sugar and corn starch, pure carbohydrates. The foods called nitrogenous are those that have a high percentage of nitrogen, such as meat, cheese, fish, dried beans, chicken, eggs, etc. So that when authorities speak of a low protein diet they mean the selection of food that is relatively weak in protein. All the foods listed also contain fat except sugar and corn starch. Fats yield more heat per pound than carbohydrates because they have a larger percentage of carbon-oxygen for their combustion, by which is meant physiological combustion. In other words, says Chittenden, it is not a direct combination of oxygen with the carbon and hydrogen of foodstuffs, or tissue elements, that takes place in the body, but rather a gradual, progressive decomposition of complex organic compounds into simpler products; made possible by the agency of the oxygen from the lungs circulating in the blood.* The increase of oxygen required in the breaking down of fats in the small intestine makes them harder to digest than the carbohydrates, a difficulty greatly increased in weak digestions by the incorporation of excessive fats in carbohydrate foods, such as pie crust, fried potatoes, “short” biscuit, and other so called palatable foods.
If the reader is interested in not having his urine heavily charged with nitrogen with its promise of trouble in the kidneys, blood vessels, heart, stomach, gall bladder, appendix and joints he should note that there is a rich store of carbohydrates to choose from which, with the proper addition of food fats, will supply the body with the heat and energy required. If now is added about 60 grams a day of proteid food, as estimated by Chittenden, for a man weighing 154 pounds, a balanced ration can easily be calculated. What this will be can be gathered below from the rations given in detail of eight university athletes, all trained men, who for a period of five months, thrived on carefully calculated and recorded rations, of which we give a sample, the pound avoirdupois equalling 453.6 grams of the metric system, which is here used; so that 9 grams of nitrogen (not nitrogenous food) a day means slightly over 1/50th of a pound, or a little over 1/3 of an ounce.
Breakfast: Orange 60 grams, oatmeal 207 grams, roll, 46 grams, butter 14 grams, coffee 150 grams, cream 150 grams, sugar 35 grams.
Lunch: Boiled potato 150 grams, boiled onions 145 grams, macaroni 130 grams, fried rice 138 grams, syrup 48 grams, ice cream 160 grams, cake 26 grams.
Dinner: Celery soup 150 grams, spinach 100 grams, mashed potato 100 grams, bread 19 grams, coffee 100 grams, cream 50 grams, sugar 7 grams, strawberry short-cake 169 grams.
Total nitrogen content of the day’s food equal to a little over 9 grams. The average for the last two of the five months amounted to 8.81 grams of excreted metabolized (utilized) nitrogen per man, corresponding to 55 grams of proteid matter.
The evidence of the nitrogen actually required to keep the body in a high state of efficiency as supplied by the experiment with the college athletes, was enlarged by extended experiments with a detachment of twenty men from the army. They had been used to a diet of which the following is a sample:
Breakfast: Beefsteak 222 grams, gravy 68 grams, fried potatoes 234 grams, onions 34 grams, bread 144 grams, coffee 679 grams, sugar 18 grams.
Dinner: Beef 171 grams, boiled potatoes 350 grams, onions 55 grams, bread 234 grams, coffee 916 grams, sugar 27 grams.
Supper: Corn beef 195 grams, potatoes 170 grams, onions 21 grams, bread 158 grams, jelly 107 grams, coffee 450 grams, sugar 21 grams.
For a period of six months these men were kept on a diet of which the following is a sample:
Breakfast: Soft oatmeal 150 grams, milk 100 grams, sugar 30 grams, bread 30 grams, butter 10 grams, one cup of coffee, with milk and sugar, 350 grams.
Dinner: Baked macaroni with a little cheese 200 grams, stewed tomato 200 grams, bread 50 grams, tapioca peach pudding 150 grams, cup of coffee 350 grams.
Supper: Fried bacon 20 grams, French fried potato 100 grams, bread 75 grams, jam 75 grams, cup of tea 350 grams.
Total nitrogen content of the day, a little over 7 grams (7.282) . The result of the five months’ experiment is shown in the following table of 13 men for the two dates five months apart.
Five of the men, says Chittenden, practically retained their weight or made a slight gain. Coffman, Loewenthal, Sliney and Cohen lost somewhat but the amount was very small and it occurred during the first few weeks after which their weight remained practically stationary. Fritz and Oakman lost somewhat but this likewise occurred during the early weeks. Bates was the only one who underwent any marked loss of weight. He, however, was quite stout and the work in the gymnasium, with the change in diet, brought about a desirable loss of body weight. With one exception, all the men were plainly having more proteid food than was necessary to maintain the normal nitrogen equilibrium of the body, the excess nitrogen balance in most cases being fairly large. Fifteen strength tests were made with each man during the six months’ period. Without exception all the men made a phenomenal gain in strength although they were for five months restricted to a daily diet of only one-third to one-half the amount of proteid food they had been accustomed to.
Fothergill says it is wonderful how the craving for meat dies down in a man when he has once begun to realize that meat is not good for him. One may still think of the “fleshpots of Egypt” and yet feel the sight of a solid joint positively repugnant and offensive.’
Chittenden’s tests upon himself as to the amount of protein (mostly food from animal sources) he needed to maintain the highest body efficiency are very interesting. Although Veit and Atwater had maintained (and had their conclusions generally accepted) that an adult for medium work requires from 116 to 120 grams, Chittenden as a result of his extended investigations reduced his protein intake to 34 grams (1 1/6 ounces). Two years later Chittenden stated in a personal com munication to Kellogg 2 that his daily intake of protein was but 31 grams (a little less than 1 ounce). On this ration his strength and vigor were well maintained, his health improved, his weight remained steady at 125.4 pounds (former weight 143 pounds) with clear light-colored urine, while he was able to get rid of some physical discomforts which were evidently the result of an excessive protein intake. F. G. Benedict 1 after experiments with students for approximately ten months was led to abandon his earlier view and confirm Chittenden.
It will be noted that the total amount of protein Chittenden allowed himself was about 1 1/4 ounces daily, which is equivalent to about 4 ounces of lean meat or 6% ounces of roast beef, if nothing else containing protein were eaten, as practically all the foods except sugar and starch contain protein. Commenting on the practice he had adopted for himself he said, “It is difficult to accept the assumption that’ Custom affords any indication of the food requirements of the body. To the physiologist there is a lack of any scientific evidence that carries conviction.”
The average man, says Folin, with ordinary habits of diet consumes more food from animal sources than the body can possibly use. The excess is not stored because the need of nitrogen is so small that an excess is always present in food not rich in that element.