ScopePlant polyphenols are widespread in the American diet, yet estimated intake is uncertain. We examine the application of the Polyphenol Explorer® (PED) database to quantify polyphenol and ellagitannin (ET) intake of men with prostate cancer and tested the implementation of diets restricted in polyphenols or ETs.Methods and resultsTwenty‐four men enrolled in a 4‐week trial were randomized to usual, low‐polyphenol or low‐ET diet. Estimated polyphenol and ET intakes were calculated from 3‐day diet records utilizing the PED. Urine and plasma metabolites were quantified by UPLC‐MS. Adherence to the restricted diets was 95% for the low polyphenol and 98% for low‐ET diet. In the usual diet, estimated dietary polyphenol intake was 1568 ± 939 mg/day, with coffee/tea beverages (1112 ± 1028 mg/day) being the largest contributors and estimated dietary ET intake was 12 ± 13 mg/day. The low‐polyphenol and low‐ET groups resulted in a reduction of total polyphenols by 45% and 85%, respectively, and omission of dietary ETs. UPLC analysis of urinary host and microbial metabolites reflect ET intake.ConclusionPED is a useful database for assessing exposure to polyphenols. Diets restricted in total polyphenol or ET intake are feasible and UPLC assessment of ET metabolites is reflective of dietary intake.