Intake of a fermented soymilk beverage containing moderate levels of isoflavone aglycones enhances bioavailability of isoflavones in healthy premenopausal Japanese women: a double-blind, placebo-controlled, single-dose, crossover trial

Abstract

This study aimed to investigate the bioavailability of serum isoflavones after the intake of soymilk fermented by Lactobacillus casei strain Shirota containing 32.5% isoflavone aglycones (FSM) or placebo soymilk containing no isoflavone aglycones (SM). In a double-blind, placebo-controlled, single-dose, crossover trial, 7 healthy premenopausal Japanese women (mean age: 35.3 ± 11.0) consumed FSM or SM on day 1 and crossed over to the other soymilk after a 6-day washout period. Serum isoflavones in blood samples collected at 0, 1, 2, 3, 4, and 5 hr after intake were analyzed by liquid chromatography coupled with tandem mass spectrometry. The area under the curve (AUC) values for the serum concentrations of genistein and total isoflavones were significantly higher, by about 1.4-fold, up to 5 hr after FSM intake compared with SM intake (each p<0.05), and that of daidzein tended to be higher after FSM intake. In addition, AUC analysis of total isoflavones for individual subjects revealed that 5 out of 7 subjects had higher AUC values after FSM intake compared with SM intake and that the 2 remaining subjects had similar AUC values. These 2 subjects had higher AUC values after SM intake (mean, 2,502 ± 348) than those of the other subjects (mean, 1,158 ± 269). These results indicate that the bioavailability of isoflavones, especially genistein, is enhanced after the intake of FSM containing 32.5% isoflavone aglycones compared with intake of SM containing no isoflavone aglycones and that the enhancement is observed in healthy premenopausal Japanese women whose isoflavone absorption capacity is low after SM intake.

Fermentation of soybean meal improves isoflavone metabolism after soy biscuit consumption by adults

“…The fermentation, which increases the aglycone content of biscuits up to 97% (supporting information, Table S1), improved isoflavone absorption and metabolism in human intestine. In general, it is reported that isoflavone aglycones are absorbed in greater amounts than glycoside forms, and thus soy foods rich in aglycones, such as FSBM biscuits, show higher absorption of isoflavones than soy foods rich in glycosides, such as SBM biscuits . Isoflavone aglycones have lower molecular weight and higher lipophilicity when compared to glycosides due to the absence of a sugar moiety in their chemical structures, which facilitates their absorption by enterocytes.…”

“…Isoflavone aglycones have lower molecular weight and higher lipophilicity when compared to glycosides due to the absence of a sugar moiety in their chemical structures, which facilitates their absorption by enterocytes. Glycoside forms need to be hydrolyzed to aglycones by intestinal enzymes and/or gut microbiota in order to be absorbed, which also may explain differences between absorption of aglycones and glycosides …”

“…This result may be explained by the faster absorption of isoflavone aglycones than glycoside forms. Thus, soy foods rich in aglycones, such as FSBM biscuits, show faster absorption rates of isoflavones than soy foods rich in glycosides, such as SBM biscuits . Kano et al .…”

Soy and Health Update: Evaluation of the Clinical and Epidemiologic Literature

“…The three isoflavones genistein, daidzein and glycitein and their respective glycosides account for approximately 50%, 40% and 10%, respectively, of the total isoflavone content of soybeans [68]. There is disagreement over whether isoflavone form affects total absorption; some studies show that in comparison to the glycoside, aglycone isoflavones are absorbed faster and to a greater extent [74,75,76] whereas other studies show aglycones are absorbed more quickly but total absorption is the same or even less [77,78,79]. In this document isoflavone amounts are expressed in aglycone equivalent weights.…”

New Insights Regarding the Potential Health Benefits of Isoflavones

“…They can be classified into fermented (tofu, okara, yuba, fresh greed soybeans, whole dry soybeans, soy nuts, whole-fat soy flour, soy sprouts, soymilk and soymilk products) and nonfermented (tempeh, natto, miso, fermented tofu and soymilk products and soy sauces) products [46]. Epidemiological studies among the Japanese population suggest that fermented soybean products have better effects than nonfermented soy products, probably because of a higher bioavailability of isoflavone aglycones [47].…”