Absorption, distribution, metabolism, and excretion of isoflavonoids after soy intake

Abstract

Soy is the major source of dietary exposure to isoflavonoids (IFLs). Accumulating evidence supports a role for soy and IFLs in the protection against many chronic diseases including cancer. After soy intake we found a biphasic IFL appearance pattern in plasma as well as in urine that we suggest to be due to IFL absorption in the small intestine (ca. 10%) during the first 2 h after intake and IFL absorption in the large intestine (ca. 90%) 4–6 h after intake. While each IFL disappears from the circulation at different times excellent correlations between urinary and circulating IFL values were discovered and algorithms to convert urinary excretion values into circulating levels were established. We suggest the term ‘apparent bioavailability’ when using urinary data to describe IFL exposure. The IFL bioavailability was found to be influenced by gut bacteria, oral antibiotic treatment (OABX), and an individual’s age and health status. While daidzein (DE) and genistein start to be absorbed minutes after intake, equol (EQ) appears in plasma only after a minimum of 8 h following soy intake owing to the required transit time of DE to the colon where the conversion of DE to EQ takes place by intestinal microbiota. We have also shown that the apparent IFL bioavailability is higher in children than adults, higher in healthy versus non-healthy individuals, and decreased in children but increased in adults during OABX. Finally, we propose to use a urinary EQ/DE ratio of 0.018 with a DE threshold to identify EQ producers. With this cutoff definition we observed that EQ production is inconsistent over time in 5–30% of both premenopausal and postmenopausal women.

Non-digestible stachyose promotes bioavailability of genistein through inhibiting intestinal degradation and first-pass metabolism of genistein in mice

“…Urine is favored as a reliable biomarker to assess genistein bioavailability because of its high secretion level compared to plasma or the other body fluids, and therefore urine was used to extrapolate systemic exposure of genistein metabolism in this work [20]. As shown in Figure 2(e), the co-treatment of stachyose at 250 and 500 mg/kg·bw remarkably caused the 32.2% and 42.7% increases in 12-h cumulative uninary excretion of total genistein and its metabolites including sulfated (GEN-7-S) and glucuronidated (GEN-4’-G and GEN-7-G), and hydrogenated (DH-GEN) metabolites of mice in comparison with single genistein treatment, respectively ( p <0.05).…”

Nutrimetabolomics: An Integrative Action for Metabolomic Analyses in Human Nutritional Studies

“…The latter is an emerging field and for only few compounds/compound classes has the metabolic activity of the gut microbiota been assessed as an important contributor to metabolite transformation and urinary metabolite profiles. The production of equol from daidzein as a lead in soy and soy products is the paradigm, with only around 30–40% of the European population able to produce equol (that carries likely the relevant bioactivity) in their guts.…”

A Review of Natural Stimulant and Non‐stimulant Thermogenic Agents

“…For example, isoflavone daidzein may be metabolized in the intestine to equol, a metabolite that has greater estrogenic activity than daidzein. Studies that measure urinary equol excretion after soy consumption indicate that only about 33% of individuals from Western populations metabolize daidzein to equol (Zheng et al , 2013; Franke et al , 2014). Thus, individual differences in the metabolism of isoflavones could be decisive in use of those compounds as thermogenic food supplements.…”