Chemistry of Food and Nutrition

This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1911 edition. Excerpt: ...upon the nitrogen balance, but the loss of body protein was relatively small and continued only 2 days. Landergren ' also found that it is only when the carbohy-1 Shandanavisches Archiv fiir Physiologic, 14, 112 (1903); Abstract Experiment Station Record, 14, 1099. drate of the diet is entirely replaced by fat that the comparison is so strikingly against the fat as it seemed to be in Kayser's experiment. In Landergren's experiments the condition studied was not one of approximate equilibrium, but rather of nitrogen hunger. He fed men diets of adequate fuel value but containing only about one gram of nitrogen daily, and found that by four days of such feeding the urinary nitrogen may be reduced to about 4 grams per day. In one experiment in which the daily food contained 750 grams of carbohydrates the urine of the fourth day showed 3.76 grams of nitrogen. The carbohydrate was then entirely replaced by fat, with the result that the following days' urines contained respectively 4.28, 8.86, and 9.64 grams of nitrogen. Evidently in the case of a man accustomed to feeding largely upon carbohydrates the complete replacement of carbohydrate by fat leads to a loss (or an increased loss) of body protein. But by subsequent experiments of the same series it was found that a diet containing nearly half its calories in carbohydrate, and nearly half in fat, had apparently the same protein.sparing power as one made up almost exclusively of carbohydrates. The explanation offered by Landergren is that when the diet supplies no carbohydrate, the glycogen of the body soon becomes exhausted and the carbohydrate needed to keep up the constant glucose content of the blood is obtained largely by the breaking down of proteins, which presumably yield carbohydrate...