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The Effect of Grapes and Grape Products on Urinary Acidity

(From the Fruit Products Laboratory, University of California, College of Agriculture, Berkeley)

Sixteen experiments with men subjects on basal diet and on the same basal supplemented by fresh grapes, fresh natural grape juice, detartrated grape juice, natural grape juice concentrate, concentrate-tartrate mixture, Thompson seedless and Muscat seeded raisins are reported. The following results were observed when the grapes or grape products were added to the basal ration.

1. An increase in the pH of the urine occurred, ranging from 0.8 to 1.2 pH units.

2. A decrease in the ammonia excreted and a corresponding decrease in the total acidity was noted.

3. There was an increase of the alkaline reserve above the normal for each subject, the alkaline reserve being estimated by the plasma CO₂ combining power determined from the acid and ammonia content of the urine and calculated by the method of Fitz and Van Slyke.

4. A correlation between the alkalinity of the ash and the physiological reaction was apparent. Grapes and grape products with the greater alkalinity of ash were associated with a more basic body reaction.

5. An increase occurred in organic acids excreted. This may be explained by the presence in the urine of some incompletely oxidized tartaric acid.

6. Approximately 94 per cent of the ingested organic acids appeared to be oxidized.

These results are applicable to grapes and grape products of the varieties and types investigated.

The writer wishes to express his appreciation of the interest and thoughtful consideration of Professor W. V. Cruess, upon whose suggestion this study was initiated. The friendly advice of P. F. Nichols of this laboratory has been of great assistance. The full cooperation of the men taking a part in the diets is acknowledged with pleasure.