To the Editor.
—Dr Avorn and colleagues1 demonstrate convincingly that ingestion of cranberry juice prevents bacteriuria in the elderly. In speculating as to the mechanism of this effect, however, they appear not to consider a very simple explanation, namely, a direct antibacterial action of hippuric acid.It is well established that eating cranberries causes relatively large amounts of hippuric acid to be excreted in the urine. As reported by Bodel et al,2 Blatherwick and Long found in 1923 that 350 g of cranberries produced 4.7 g of hippuric acid (1.34% weight/weight [w/w]), and a calculation from figures published by Bodel et al2 shows that for each liter of cranberry juice cocktail ingested (approximately 330 g of cranberries), 1.9 g of hippuric acid was excreted (mean of seven experiments), yielding 0.58% w/w. The origin of this hippuric acid is presumably the benzoic and quinic acids present in cranberries.
Hamilton-Miller JMT. Reduction of Bacteriuria and Pyuria Using Cranberry Juice. JAMA. 1994;272(8):588. doi:10.1001/jama.1994.03520080030021