Abstract
BackgroundRecent studies suggest that some of the clinical effectiveness of soy or daidzein, which is a type of isoflavone, may be attributed to a person’s ability to produce equol from daidzein. Equol, which is a metabolite of one of the major soybean isoflavones called daidzein, is produced in the gastrointestinal tract by certain intestinal microbiota where present. Habitual dietary patterns may alter the intestinal bacterial profile, and influence the metabolism of isoflavones and the production of equol. Fructooligosaccharides (FOS) have a prebiotic activity as well as being a dietary fibre. The purpose of the present study was to determine whether FOS supplementation increases equol production in equol producers and stimulates equol production in equol non-producers in Japanese postmenopausal women.MethodsA soy challenge was used to assess equol-producer status prior to the start of the study in healthy postmenopausal Japanese women. The study involved 4 separate groups in randomised crossover design. First, subjects were classified as equol producers (n = 25) or non-producers (n = 18), and then they were randomly assigned to the FOS or control group. All subjects received a daily dose of 37 mg isoflavone conjugates in the capsule (21 mg aglycone form) and either FOS (5g/day) or sucrose as control, in a randomised crossover study design. Equol -production was assessed by testing the serum and urine before and after the 2-week supplementation period.ResultsThe analyses were conducted on 34 subjects completed the study, 21 (61.8%) were classified as equol producers, and 13 (38.2%) as non-producers. Significant differences were observed in the interaction effect of time × equol state after 1 week of intervention (p = 0.006). However there were no effects after 2 weeks of intervention (p = 0.516). Finally, in both equol producers and non-producers, FOS supplementation did not affect the serum equol concentration or the urinary equol to daidzein concentration ratios.ConclusionsWe have reported that FOS intervention (5 g/day for 2 weeks) does not significantly modulate the capacity of intestinal microbiota to produce equol in postmenopausal Japanese women, in either equol producers or non-producers in this pilot study. Further larger investigations that explore the roles of specific intestinal microbiota in equol production will enable the establishment of dietary conditions that are required to enhance equol production.
Highlights
Recent studies suggest that some of the clinical effectiveness of soy or daidzein, which is a type of isoflavone, may be attributed to a person’s ability to produce equol from daidzein
Soybean isoflavones are structurally similar to oestrogen; they exhibit a weak affinity for oestrogen receptors, ERα and ERβ, eliciting mild oestrogenic-like activity in various tissues [1]
Habitual dietary patterns may influence the metabolism of isoflavone and the production of equol [16]
Summary
Recent studies suggest that some of the clinical effectiveness of soy or daidzein, which is a type of isoflavone, may be attributed to a person’s ability to produce equol from daidzein. Recent studies suggest that some of the clinical effectiveness of soy or daidzein, which is a type of isoflavone, can be attributed to a person’s ability to produce equol from daidzein via their intestinal bacteria, because its biological activities differ from those of its precursor [9]. Many studies have provided that only 25-30% of the adult population of Western countries produce equol when fed soy foods containing isoflavones [10,11,12] This is significantly lower than the reported 5060% of equol producers in adults from Asian countries [13,14,15]. Several studies comparing the habitual diets of equol producers and non-producers who consume Western diets have reported that equol producers tend to have a higher intake of carbohydrate and dietary fibre, a higher percentage of energy as carbohydrate and lower percentage of energy as fat, and intake of soy, plant protein [10,12,17]; this has not been a consistent observation
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