Nutritional physiology / by Percy Goldthwait Stiles.

  • Stiles, Percy Goldthwait, 1875-1936.
Date:
1931
Catalogue details

Licence: In copyright

Credit: Nutritional physiology / by Percy Goldthwait Stiles. Source: Wellcome Collection.

    179/330 (page 165)
    What is the principal non-nitrogenous compound produced from the amino-acids? There seems to be no doubt that it is dextrose. Evidence in support ot this belief has been derived from the study of diabetes. Whether this condition is experimentally induced or devel- ops spontaneously, it is found that, if the case is one of full severity, sugar excretion goes on even when no carbohy- drate is fed, and, indeed, throughout long periods of fast- ing. This sugar might be assumed to have come from the fat of the body, but it can be more surely attributed to the protein which is being decomposed. The following con- sideration shows this: the nitrogen and the sugar in the urine of the fasting diabetic patient maintain, in many cases, a singularly constant ratio; 1 gram of nitrogen is ac- companied by 3.6 grams of dextrose. They rise and fall to- gether. This seems to prove that the two must have a common source, which can only be protein. Again, the feeding of amino-acids to the diabetic increases his loss of sugar; the feeding of fat does not have this effect. A simple calculation shows that 100 grams of protein fed may give rise within the body to about 58 grams of sugar. The seriousness of diabetes will now be better appreciated than has been possible up to this time. The organism loses not merely the support normally secured from the chief carbo- hydrates of the diet, but, in great part, that ordinarily furnished by protein food. From all this it appears that much of the protein which we eat serves only to supply the tissues with carbohydrate. The impression is likely to be that this is a roundabout and not an economical way to provide sugar, which might have been taken as such at the outset. The facts may fairly be employed to support the modern teaching that excess of protein is to be avoided, but we have already shown the necessity for allowing more than is actually to be reconstructed after the digestive dismembering. Recog- nizing as inevitable the discarding of amino-acids, we can see the desirability of having them made to furnish a simple standard food like sugar, valuable for its store of