Soy isoflavones and their relationship with microflora: beneficial effects on human health in equol producers

The bioavailability of soy isoflavones depends on the composition of the microflora for each subject. Bacteria act on different isoflavones with increased or reduced absorption and cause biotransformation of these compounds into metabolites with higher biological activity. S-equol is the most important metabolite and only 25–65 % of the population have the microflora that produces this compound. The presence of equol-producing bacteria in soy product consumers means that the consumption of such products for prolonged periods leads to lower cardiovascular risk, reduced incidence of prostate and breast cancer, and greater relief from symptoms related to the menopause such as hot flushes and osteoporosis

Viability of probiotic bacteria and concentrations of organic acids in commercial yoghurts during refrigerated storage

Yoghurts (four varieties), prepared using Streptococcus thermophilus and Lactobacttlus delbrueckii ssp. bulgaricus and containing three probiotic strains, Bifidobacterium animalis Bb-12, L. acidophilus La-5 and L. rhamnosus GG, were examined for viability over a month of refrigerated storage. At 1, 7, 14, 21 and 28 days of refrigerated storage, the yoghurts contained stable viable populations of B. animalis Bb-12, L. acidophilus La-5 and L. rhamnosus GG, with no significant changes between intervals (P > 0.05), populations remaining at 8.0 to 8.7 logjo viable cells/mL for the projected shelf life. Decreases in pH between storage intervals appeared to reduce the viable populations of probiotic bacteria in each yoghurt (P > 0.05). Low pH levels (≤ pH 4.0) were due to lactic and acetic acids and acids derived from fruit juice flavourings. The concentration of lactic acid was significantly greater than acetic acid in each yoghurt (P > 0.05).link_to_subscribed_fulltex

Biotransformation of isoflavones by bifidobacteria in fermented soymilk supplemented with D-glucose and L-cysteine

Soymilk prepared using soy-protein isolate supplemented with D-glucose and L-cysteine was fermented with 4 strains of Bifidobacterium. Enumeration of bifidobacteria and quantification of isoflavones using HPLC were performed at 0, 12, 24, 36 and 48 h of incubation. Supplementation did not significantly enhance (p > 0.05) the growth of bifidobacteria between 0 and 12 h, but did after 12 h. The increase in concentration of isoflavone aglycones and equol was significantly lower (p < 0.05) in supplemented soymilk after 24 h when compared to plain soymilk. Supplementation increased the concentration of aglycones by 0.796 mg/100 mL in soymilk fermented with B. animalis between 12 and 24 h, and the population by 1.27 log10 CFU/mL (p < 0.05).link_to_subscribed_fulltex

Effect of high pressure treatment on viability of Lactobacillus delbrueckii ssp. bulgaricus, Streptococcus thermophilus and L. acidophilus and the pH of fermented milk

The effect of high pressure (HP) treatment at 480 mPa on viable populations of Lactobacillus delbrueckii ssp. bulgaricus, Streptococcus thermophilus, and L. acidophilus was studied in reconstituted skim milk. Reductions in viable population were directly related to the HP processing time. L. delbrueckii ssp. bulgaricus, showed the greatest sensitivity to HP treatment, whereas S. thermophilus showed the greatest resistance to HP treatment. All organisms showed a significant recovery in their viability after one week of refrigerated storage. High pressure treatment caused the pH level of fermented milk to increase by 0.49 to 1.01 units. The greatest increase in pH after HP treatment occurred in milk fermented by L. delbrueckii ssp. bulgaricus.link_to_subscribed_fulltex

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

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 14d 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/200ml contained 10%, 9% and 7% aglycone, respectively, with their fermented counterparts containing 69%, 57% and 36 % aglycone (P0.05), 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. © The Authors 2005.link_to_subscribed_fulltex

Enzymic transformation of isoflavone phytoestrogens in soymilk by β-glucosidase-producing bifidobacteria

Five strains of bifidobacteria were screened for β-glucosidase activity using p-nitrophenyl-β-D-glucopyranoside as the substrate, and selected strains were used to ferment soymilk. Enumeration of viable bifidobacteria and quantification of isoflavones using HPLC were performed at 0, 12, 24, 36, and 48 h of incubation. Four strains produced β-glucosidase. B. pseudolongum and B. longum-a displayed the best growth in soymilk, with an increase of 1.3 log10 CFU/mL after 12 h. B. animalis, B. longum-a, and B. pseudolongum caused hydrolysis of isoflavone malonyl-, acetyl- and β-glucosides to form aglycones, and transformed daidzein to equol in soymilk. Fermentation of soymilk with Bifidobacterium sp. resulted in a significant increase (p < 0.05) in the concentration of aglycones.link_to_subscribed_fulltex

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

Objective: To study the effects of consuming isoflavone aglycone-enriched soymilk fermented by bifidobacteria on urinary excretion of equol with respect to fermentation, daidzein dose, supplementation duration and background diet. Design: Double-blind crossover pilot study comprising three 14-day supplementation periods separated by a washout. Setting: Victoria University, Melbourne, Australia. Subjects: Sixteen postmenopausal women. Intervention: Subjects randomized into two groups consuming either fermented (FS) or non-fermented soymilk (NFS), ingested three daily dosages of daidzein via soymilk and collected pooled urine specimens. Daidzein and equol were quantified using high-performance liquid chromatography. Results: After 14-days supplementation six women (38%) excreted equol (>1 μmol equol/day), including four from the FS group, two of whom were classified as non-producers at day 4. Bifidobacteria ingestion, composition of daidzein and its glucosides, and carbohydrate intake appeared to influence equol formation among equol producers. Conclusions: Pilot-study group mean urinary equol excretion results provided insufficient evidence (P>0.05) that FS consumption instigates equol production in women predetermined as non-producers. Sponsorship: Australian Research Council's Strategic Partnership with Industry (Sanitarium Health Food Company) for Research and Training.link_to_subscribed_fulltex

Development of an isoflavone aglycone-enriched soymilk using soy germ, soy protein isolate and bifidobacteria

Soymilks comprising soy protein isolate (SPI) and soy germ (SG) at ratios of 9:1 (SPI/SG9:1), 6:4 (SPI/SG6:4) and 3:7 (SPI/SG3:7) were fermented with Bifidobacterium animalis Bb-12. Enumeration of microbial populations, pH measurements and quantification of isoflavones were performed at 12 and 24 h incubation and at 1, 7 and 14 day refrigerated storage. Isoflavone concentrations were 3, 7 and 12 times higher in SPI/SG9:1, SPI/SG6:4 and SPI/SG3:7 than soymilk made from SPI and microbial populations increased, respectively, by 1.2, 1.3 and 0.9 log10 CFU/mL after 24 h. Hydrolysis of isoflavone glucosides increased the concentration of aglycones from 0.819 to 5.645 mg/100 mL (47% of total isoflavone) in SPI/SG9:1 after 24 h (P0.05). © 2004 Elsevier Ltd. All rights reserved.link_to_subscribed_fulltex