Bioavailability of isoflavone phytoestrogens in postmenopausal women consuming soya milk fermented with probiotic bifidobacteria

Abstract

We investigated the effects of consuming an isoflavone aglycone-enriched soya milk containing viable bifidobacteria on urinary isoflavone excretion and percentage recovery. Sixteen postmenopausal women were randomly divided into two groups to consume either fermented or non-fermented soya milk. Each group participated in a double-blind, crossover study with three 14 d supplementation periods, separated by a 14 d washout. Subjects ingested three daily dosages of isoflavone via the soya milk and collected four 24 h pooled urine specimens per supplementation period. Soya milks were prepared with soya protein isolate and soya germ, followed by fermentation with bifidobacteria. Isoflavone levels were quantified using HPLC. Non-fermented soya milks at 20, 40 and 80 mg isoflavone/200 ml contained 10 %, 9 % and 7 % aglycone, respectively, with their fermented counterparts containing 69 %, 57 % and 36 % aglycone (P,0·001). A trend to a greater percentage urinary recovery of daidzein and glycitein was observed among women consuming fermented soya milk at a dosage of 40 mg isoflavone (P¼ 0·13). A distinct linear dose response for the fermented soya milk group (R 2 ¼ 0·9993) compared with the non-fermented group (R 2 ¼ 0·8865) suggested less interindividual variation in isoflavone absorption. However, total urinary isoflavone excretion was similar for both groups (P.0·05), with urinary isoflavone recovery at approximately 31 %. Increasing the isoflavone dosage correlated positively with its urinary excretion, but urinary percentage recovery of isoflavone was inversely related to dosage level. Hence, a modest dosage ranging from 20 to 30 mg/d may provide the most bioavailable source of isoflavone, regardless of whether it is via an aglycone-rich fermented soya milk or a glucoside-rich soya milk.Isoflavone: Bifidobacteria: Soya milk: Bioavailability: Postmenopausal women Diminishing levels of oestrogen caused by ovarian failure, inadequate to maintain oestrogen-dependent tissues, are associated with higher rates of chronic disease in postmenopausal women. Phytoestrogens, a group of non-steroidal plant-derived compounds, are structurally similar to oestrogen and thus able to exert weak oestrogenic effects (Mayr et al. 1992;Markiewicz et al. 1993). Specifically, isoflavone phytoestrogens found abundantly in soyabeans are bioactive di-phenolic structures able to bind to oestrogen receptor sites (Setchell & Cassidy, 1999). Isoflavones behave in a similar manner to selective oestrogen-receptor modulators, acting as oestrogen agonists and antagonists in different tissues (Brzezinski & Debi, 1999). Hence, isoflavones have been associated with the prevention of hormone-dependent disorders based on epidemiological (Lee et al. 1991;Setchell, 1995;Cassidy, 1996) and small-scale human clinical studies (Anderson et al. 1995;Kurzer, 2000). Soyabeans contain three types of isoflavone, each type being present in four chemical forms. Aglycone structures of daidzein, genistein and glycitein are those forms with an oestrogen-like configuration ...

A randomized, double-blind, placebo-controlled, clinical trial on probiotic soy milk and soy milk: effects on epigenetics and oxidative stress in patients with type II diabetes

“…Scientists believe that using soy foods like soymilk with probiotic can improve the protective effect of either one of them because: (1) Soymilk can act as a substrate for probiotics; therefore, it increases epigenetic effects of probiotics, and (2) probiotic changes isoflavones to other active metabolites and increases their absorption through a change in the intestinal environment (Teh et al 2010;Tsangalis et al 2005;Zielinska et al 2014). Lactobacillus plantarum A7, a strain of probiotic, is also known to change the expression of many genes and has antioxidant effects, but there are no clear evidences of the mechanism of these effects (Citar et al 2014;Li et al 2014).…”

Urinary excretion of equol by postmenopausal women consuming soymilk fermented by probiotic bifidobacteria

“…Subjects ingested three daily doses of daidzein. Four 24-h pooled urine specimens were collected per supplementation period (baseline, days 4, 13 and 14) and processed as per (Tsangalis et al, 2005). Each participant consumed a restricted selfselected diet and provided a weighed food record.…”

“…Soymilk from each batch was analysed for daidzein and its glucosides using high-performance liquid chromatography (HPLC) (Tsangalis et al, 2005). Fermented soymilk contained approximately 10 8 viable cells of BB12 per millilitre.…”

“…Three FS and NFS containing 20 (SPI/SG20), 40 (SPI/SG40) or 80 (SPI/SG80) mg isoflavone/200 ml were manufactured and packaged as described earlier (Tsangalis et al, 2005). Soymilk from each batch was analysed for daidzein and its glucosides using high-performance liquid chromatography (HPLC) (Tsangalis et al, 2005).…”

“…Fermented soymilk contained approximately 10 8 viable cells of BB12 per millilitre. Urinary equol was extracted and analysed using a method involving b-glucuronidase/sulphatase deconjugation, previously used to quantify urinary daidzein (Tsangalis et al, 2005). However, HPLC conditions for equol were as per Xu et al, (1994), with the ultraviolet-visible detector set at 282 nm.…”