Metabolites of dietary (soya) isoflavones in human urine

Kelly, Graham; Nelson, Carolyn; Waring, Mark; Joannou, George E.; Reeder, Anthony Y.

doi:10.1016/0009-8981(93)90058-c

Cited by 279 publications

(186 citation statements)

References 32 publications

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“…The mean recovery of total isoflavonoids, expressed as a percentage of supplement dose excreted during 24 h, was 2279%, which is similar to values of 19 and 30% reported in previous studies using supplements derived from red clover (Hodgson et al, 1998;Nestel et al, 1999). Greater recovery was observed with daidzein and related compounds (55723%) compared to those of genistein (7.876.0%), and is consistent with previous findings with isoflavones derived from soy (Kelly al, 1993;Hutchins et al, 1995;Xu et al, 1995;Lu et al, 1996;Tew et al, 1996).…”

Section: Discussionsupporting

confidence: 90%

“…Equol excretion in women has been associated with a hormonal profile of reduced risk for breast cancer (Duncan et al, 2000). The relatively low prevalence for equol excretors observed in this study is comparable to rates seen in studies with isoflavones derived from soy, where 20-36% of subjects were reported to excrete equol (Kelly et al, 1993;Cassidy et al, 1994;Hutchins et al, 1995;Kirkman et al, 1995;Lampe et al, 1998;Duncan et al, 2000;Rowland et al, 2000).…”

Section: Discussionsupporting

confidence: 80%

“…A dose-dependent relationship has been reported between intake and mean excretion of isoflavonoids after 9-day treatments with four levels of soy protein (Karr et al, 1997). However, intervention studies with soy products have reported surprisingly wide, largely unexplained variation in the excretion of isoflavonoids between individuals ingesting the same dose (Kelly et al, 1993;Hutchins et al, 1995;Tew et al, 1996;Lampe et al, 1998;Slavin et al, 1998;Rowland et al, 2000). The degree of metabolic conversion of the original plant isoflavones could vary according to differences in the population of the intestinal bacteria involved in the hydrolysis, demethoxylation and reduction of isoflavones.…”

Section: Introductionmentioning

confidence: 99%

“…The variation could also arise from differences in dietary macronutrient intake, which in turn could selectively modify the growth of intestinal bacteria involved in isoflavonoid transformations, particularly in the production of equol Rowland et al, 2000) where only 20-36% of subjects can produce and excrete this metabolite (Kelly et al, 1993;Cassidy et al, 1994;Hutchins et al, 1995;Kirkman et al, 1995;Lu et al, 1996;Lampe et al, 1998;Lu & Anderson 1998;Duncan et al, 2000;Rowland et al, 2000). Macronutrient composition of the diet could affect bacterial activity by changing the intestinal pH, redox potential or transit time, or influencing the availability of substrates for the bacteria to utilise (Cummings & Macfarlane, 1991).…”

Section: Introductionmentioning

confidence: 99%

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Urinary isoflavonoid excretion is inversely associated with the ratio of protein to dietary fibre intake in young women

et al. 2004

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Objective: To examine the prevalence of excretion of urinary isoflavonoids in women and determine any relationships with accustomed macronutrient intake. Design: Volunteers in one of two 4-month studies. Study 1 was a randomised crossover study whereby subjects consumed a placebo or isoflavone supplement for 2 months and crossed over. Study 2 was a parallel design in which subjects consumed a placebo for 1 month and an isoflavone supplement for 3 months. Setting: All subjects were free-living, healthy volunteers. Subjects: A total of 25 (study 1, n ¼ 14; study 2, n ¼ 11) premenopausal women were recruited through advertisements. Interventions: Volunteers were supplemented for 2 months (study 1) or 3 months (study 2) with purified isoflavones (86 mg/ day) derived from red clover. Urinary isoflavonoids were measured during the placebo and the second month of isoflavone treatment. Macronutrient intakes were determined from weighed food records. Results: During isoflavone supplementation, the concentration of urinary total isoflavonoids increased by 15-fold (Po0.0001), with 5.4-fold variation between individuals. Multiple linear regression analysis showed that 24% of this variation could be explained by an interaction between dietary fibre and protein (P ¼ 0.047), with a highly significant inverse association between total isoflavonoid concentration and the protein to fibre ratio (r ¼ À0.51, P ¼ 0.009). Conclusions: Supplementation with purified isoflavones results in an increase in urinary isoflavonoid excretion and part of the individual variation in response is associated with an interaction between intakes of protein and dietary fibre. Whether manipulation of these macronutrients could enhance efficacy of isoflavone supplements remains to be determined.

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Section: Discussionsupporting

confidence: 90%

Section: Discussionsupporting

confidence: 80%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Urinary isoflavonoid excretion is inversely associated with the ratio of protein to dietary fibre intake in young women

et al. 2004

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“…The similar change in dietary isoflavone intake and urinary isoflavone excretion according to diet indicated a high compliance with the study protocol during both diet periods. Previous studies have demonstrated the validity of urinary isoflavone excretion from single-urine samples as a compliance measure of regular soy consumption in a variety of populations (Kelly et al, 1993;Karr et al, 1997;Maskarinec et al, 1998;Maskarinec et al, 2003). Although a soy intake calendar was completed by most men, the completion rate declined in the second study period, which questions its usefulness as a dietary compliance measure in longer studies.…”

Section: Discussionmentioning

confidence: 99%

Serum prostate-specific antigen but not testosterone levels decrease in a randomized soy intervention among men

et al. 2006

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Background: Low prostate cancer incidence and high soy intake in Asian countries suggest a possible protective effect of soy foods against prostate cancer. The goal of this pilot study was to evaluate the feasibility of a randomized, crossover soy trial among men and to investigate the effects of daily soy intake on serum prostate-specific antigen (PSA) and testosterone levels. Methods: We randomized 24 men to a high or a low soy diet for 3 months. After a 1-month washout period, the men crossed over to the other treatment. During the high soy diet, the men consumed two daily soy servings; during the low soy diet, they maintained their usual diet. During the entire study each man donated four blood samples and five overnight urine samples. Dietary compliance was assessed by soy calendars, 24-h dietary recalls, and urinary isoflavone excretion measured by highpressure liquid chromatography with photodiode array detection. Blood samples were analyzed for serum testosterone and PSA by radioimmunoassay. When necessary, variables were log transformed. Two sample t-tests compared the two groups before each study period. Mixed models incorporating the repeated measurements were used to evaluate the effect of the soy diet on urinary isoflavone excretion and serum analytes. Results: Twenty-three men aged 58.777.2 years completed the study. The compliance with the study regimen was high according to self-reported soy food intake and urinary isoflavone excretion. No significant between-group and within-group differences were detected. During the high soy diet, dietary isoflavone intake and urinary isoflavone excretion increased significantly as compared to the low soy diet. A 14% decline in serum PSA levels (P ¼ 0.10), but no change in testosterone (P ¼ 0.70), was observed during the high soy diet in contrast to the low soy diet. Conclusion: The high adherence as shown by three measures of compliance in this pilot trial demonstrated the feasibility of an intervention based on soy foods among free-living men.

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Isoflavones, lignans and stilbenes - origins, metabolism and potential importance to human health

Cassidy

Hanley

Lamuela‐Raventós

2000

J. Sci. Food Agric.

260

148

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Interest in the physiological role of the bioactive compounds present in plants has increased dramatically over the last decade. Of particular interest in relation to human health are the class of compounds known as the phytoestrogens, which embody several groups of non‐steroidal oestrogens including isoflavones, lignans and stilbenes that are widely distributed within the plant kingdom. These compounds have a wide range of hormonal and non‐hormonal activities in animals or in vitro and these suggest plausible mechanisms for potential health effects of diets rich in these compounds in humans. In addition, experimental and epidemiological data are available to support the concept that phytoestrogen‐rich diets exert physiological effects, and preliminary human studies suggest a potential role for dietary phytoestrogens in affecting hormone‐dependent disease rates. © 2000 Society of Chemical Industry

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Metabolites of dietary (soya) isoflavones in human urine

Cited by 279 publications

References 32 publications

Urinary isoflavonoid excretion is inversely associated with the ratio of protein to dietary fibre intake in young women

Urinary isoflavonoid excretion is inversely associated with the ratio of protein to dietary fibre intake in young women

Serum prostate-specific antigen but not testosterone levels decrease in a randomized soy intervention among men

Isoflavones, lignans and stilbenes - origins, metabolism and potential importance to human health

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