MICROBIAL AND DIETARY FACTORS ASSOCIATED WITH THE EQUOL AND 8-PRENYLNARINGENIN PRODUCER PHENOTYPES

Abstract

The importance of the gut microbiota in the phyto-oestrogen bioavailability and bioactivity has been convincingly demonstrated in vitro and in vivo. Equol, a microbial metabolite of the soy isoflavone daidzein, is more bioactive than its precursor, and has been hypothesized as a clue to the effectiveness of soy and its isoflavones. Analogously, the weakly oestrogenic hop prenylflavonoid isoxanthohumol can be demethylated to the very potent phyto-oestrogen 8-prenylnaringenin (8-PN). However, these bioactivations are characterised by large inter-individual variation. The question why these phyto-oestrogen-bioactivating microbial populations colonised only 30-50% of the population, remains unanswered. Therefore, microbial and dietary factors associated with the ability to produce equol or 8-PN were studied in a dietary intervention trial with 150 healthy menopausal women. After a 4-d washout, subjects delivered urine and faecal samples. Next, they started a 5-d treatment with either soymilk, soy germ or hop extract and collected on the last day 24-h urine samples. A validated food-frequency questionnaire was used to estimate the usual fat (total fat, saturated, mono and polyunsaturated fatty acid), fibre, alcohol, caffeine, and theobromine intakes. Based on the urinary excretion profiles subjects were phenotyped as poor, moderate and strong equol or 8-PN producers. The equol production correlated negatively with Clostridium coccoides - Eubacterium rectale counts and positively with the abundance of sulphate-reducing bacteria. Recent antibiotic therapy seemed to affect the 8-PN production negatively. Furthermore, strong equol producers reported higher poly-unsaturated fatty acid and alcohol intakes, whereas strong 8-PN producers consumed less alcohol and more theobromine.