Ten healthy volunteers were fed (1) a control diet for 10 days, (2) the same control diet for 3 additional days and a brussels sprouts and cabbage‐containing diet for the next 7 days, and (3) the control diet for the 10 subsequent days. Antipyrine and phenacetin were administered orally before breakfast on days 7 and 10, respectively, of each dietary regimen. During the test diet period the mean plasma half‐life of antipyrine decreased 13% and the mean metabolic clearance rate increased 11%. While small, these changes were statistically significant, indicating a stimulatory effect of cabbage and brussels sprouts on antipyrine metabolism. The values returned to control levels during the second control diet period. During the test diet period the mean plasma concentration of phenacetin was decreased by 34% to 67% at each time interval from 0.5 to 7 hr after phenacetin administration, and the mean plasma concentration of total (conjugated plus unconjugated) N‐acetyl‐p‐aminophenol (APAP), phenacetin's major metabolite, was increased from 0.5 to 3 hr after phenacetin administration. The concentrations of phenacetin and APAP returned toward control values during the second control diet period. The mean plasma half‐life of phenacetin was not influenced by the dietary changes. These results suggest that the test diet enhanced the metabolism of phenacetin in the gastrointestinal tract and/or during its first pass through the liver. Feeding the test diet increased the mean ratio of conjugated APAP to unconjugated APAP observed in plasma at each time interval from 0.5 to 7 hr after phenacetin administration, suggesting that the diet enhanced the conjugation of APAP.

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