Four clinical trials were found among search engines results: two longitudinal pilot studies(Reference Romualdi, Costantini and Campagna34,Reference Haudum, Lindheim and Ascani46) and two interventional studies with a parallel design, both conducted in Iranian populations(Reference Khani, Mehrabian and Khalesi35,Reference Jamilian and Asemi43) . conducted another prospective cohort study on 239 American women undergoing assisted reproductive technology(Reference Chavarro, Mnguez-Alarcn and Chiu42). The procedure was carried out following the most recent PRISMA guidelines(Reference Liberati, Altman and Tetzlaff23). This aspect was different from the results of the clinical trials with high intakes listed above, perhaps due to very different intakes (mean isoflavone consumption of 34mg/d in this cohort). Published online by Cambridge University Press: The present study used a community-based approach with recruitment of couples seeking pregnancy. The adjustment for male partner intake of soy in the subgroup analysis did not change the association. Soy is a key food in human nutrition. Go. Besides, the lack of a placebo group warrants caution. As for males, a 2010 meta-analysis highlighted the safety of soy on fertility outcomes(Reference Hamilton-Reeves, Vazquez and Duval21), recently confirmed by an updated meta-analysis on this topic(Reference Reed, Camargo and Hamilton-Reeves22). Corrections for confounding factors, such as diet, demographics, lifestyle factors, age, body composition and ethnicity, indicated reliable analysis. The sooner you take it the more eggs start to mature and the later it focuses on the quality of the most maturing egg, or at least this is what I read. Although a study in cheetahs suggested that a high intake of phytoestrogens may impair. Other weak aspects of the population sample characterisation are given by a lack of stratification by ethnicity and equol-producers. Han, Jing RANCHO CUCAMONGA. Furthermore, hormone levels were evaluated only at baseline, without taking into account the differences between the two groups. Jacobsen and colleagues included 11688 American women aged 3050 years of age who participated in Adventist Health Study-2 (AHS-2)(Reference Jacobsen, Jaceldo-Siegl and Knutsen38). The authors declare that they have no conflicts of interest. This could have introduced other confounding factors such as the influence of male on couple's fertility or possible changes in habits caused by the desire to conceive. In 2005, Kohama and colleagues published a short communication about a 6 months clinical trial on thirty-six Japanese women with secondary amenorrhea (or anovulation)(Reference Kohama, Kobayashi and Inoue33). From the sub-analysis by ethnic stratification, follicular SHBG levels were higher in non-Asians. Moreover, two recent observational cohort studies by Chavarro and colleagues evaluated the association between soy consumption and in vitro fertilisation outcomes(Reference Vanegas, Afeiche and Gaskins40,Reference Chavarro, Mnguez-Alarcn and Chiu42) . From the general linear model of the analysis of covariance, the intervention with soy reduced free androgen index (0020005 v. +0010005, P<0001), total testosterone (01005 v. +01005ng/ml, P=0008) and increased SHBG levels (+4008 v. 1408nmol/l, P<0001) compared with placebo (adjusted for baseline values). However, the number of combined participants of the two studies was very limited (n: 40). It would have been useful to have retrospective information on soy consumption to assess the potential effect on previous fertility problems. In addition, non-English papers could have provided relevant data on the topic, especially those from countries with a more consistent history of soy consumption. Progesterone and sex hormone-binding globulin (SHGB) levels were not significantly changed by soy intake. Pettitt, Claire Soy isoflavones are generally considered safe .Numerous randomized controlled trials in menopausal women reported that side effects were not significantly different between soy isoflavone and placebo groups .Adverse events were generally mild and included gastrointestinal and musculoskeletal complaints .One systematic review of over 100 studies in patients with or at risk of breast cancer . Furthermore, the intake of isoflavones among participants was very low and this made it difficult to compare the findings with clinical trials that often use intakes similar to Asian populations (23844mg/d). However, a suggestive positive influence has been shown among women with fertility issues and during assisted reproductive technologies. Soy Isoflavones supplements and Fertility Infertility is a condition that prevents pregnancy despite having regular sexual intercourse with your partner for at least a year. The results of selected manuscripts were grouped according to the outcomes used, for a clear comparison. Flowchart for studies selection. Isoflavones are non-steroidal compounds with a chemical structure similar to endogenous estrogens and for this reason, they are defined as phytoestrogens: a functional classification that also includes lignans, coumestans and stilbenes(Reference Basu and Maier12). The fertility concept differs from the fecundity one, which refers to reproductive potential and depends on reproductive physiology, from the production of gametes phase to the ability to carry a pregnancy to term. The use of surveys only through self-administered questionnaires, although validated, is easily exposed to self-reporting errors or incompleteness and misclassifications derived from the database used for food intake quantification. Publication types Research Support, N.I.H., Extramural Research Support, Non-U.S. Gov't MeSH terms This could be due to the scarcity of studies on the topic and the presence of few clinical trials, adequately designed to evaluate soy effect on fertility with consistent timing, with an adequate number of participants, blinding, and randomisation for physiological conditions and the presence of equol-producer individuals. Any later it delays ovulation. Similarly, a significant correlation between isoflavone intake and nulligravidity emerged (P=003) with a 13% higher risk but with a wide range of confidence interval (95% CI 2, 26) in women with intake 40mg/d compared with lower intakes (<10mg/d). Estradiol levels showed increased plasma concentrations during the intervention period among premenopausal women (n: 14) in both luteal and follicular phases (composite menstrual cycle assessment). We have twins in the family and I like the thought, so a natural remedy would be nice :) "Isoflavones are polyphenolic compounds that are capable of exerting estrogen-like effects. Soy food and soy isoflavone intake were unrelated to sperm motility, sperm morphology or ejaculate volume. The estrogen-like effects of isoflavones underlie concerns about soy and fertility. However, the subjects enrolled were women with secondary amenorrhea and therefore this variation could have a different meaning compared with results discussed in this section, obtained in the healthy population. 16 Although much of the concern is based on animal research, 16 a sufficient amount of fertility-relevant human research, including both epidemiologic and clinical studies, has been conducted; therefore, conclusions about the impact of soy on fertility can be It is plausible that isoflavones bind to this blood carrier and stimulate its hepatic synthesis. Even if serum AMH concentrations appear as a useful tool for predicting female fertility, only one study from our selection used them(Reference Haudum, Lindheim and Ascani46). The authors found that consuming moderate amounts of traditionally . From the data obtained, diet isoflavones do not seem to have a direct effect on fertility, whether positive or negative. Finally, they show antioxidant activity: a shared property among polyphenols(Reference Patel, Boersma and Crawford19). hasContentIssue true, Proposed mechanisms of isoflavones action, This is an Open Access article, distributed under the terms of the Creative Commons Attribution licence (, Copyright The Author(s), 2022. The deleterious effects of these compounds, as metabolites of clover isoflavones, were first documented in 1946 by Bennetts and co-workers studying New Zealand ewes expressing clover disease, an infertility syndrome ( Bennetts, Underwood, & Shier, 1946 ). The authors defined the unusual estradiol increase as erratic. This phenomenon highlights how in literature there is greater attention to phytoestrogens and their effect, frequently underestimating the role of other components that have a marginal interest. In 2000, Wu et al. Qin, Zhen Moreover, urinary concentrations seem to reflect the isoflavone intakes in a short time window. Nevertheless, a reduction in FSH levels was confirmed (SMD: 087IU/l, 95% CI 172, 002). Women who also have the problem of irregular periods can consume these isoflavones to get much-needed relief. A total number of twenty-two experimental articles plus a meta-analysis was used for the final synthesis. The influence of high-dose of isoflavones on fertility emerging from the studies is difficult to be transferred to other groups of individuals with other ethnicity or different treatments. The consumption of soy over time, the possible use of certain foods considered healthy in seeking pregnancy or the willingness to avoid pregnancy could generate spurious associations. Phytoestrogens can modulate endogenous hormones at micromolar concentrations by influencing the expression of the enzymes cytochrome P450 19 aromatase (Cyp19), 17-hydroxysteroid dehydrogenase (17-HSD) and 3-hydroxysteroid dehydrogenase (3-HSD), steroid sulfatases (STS) and sulfotransferases (SULTs), enzymes of steroid biosynthetic pathway(Reference Rice and Whitehead80Reference Whitehead and Rice82). This could be done by empirically monitoring ovulation to get a real information of menstrual phase, such as quantifying the urinary LH peak as a marker of ovulation, as done by Wu et al. After the intervention period, four patients became pregnant and twelve patients showed ovulation improvements based on ultrasonography (P<005). Additionally, isoflavones can act as antioxidants in vitro (15), but the extent to which they contribute to the antioxidant status of humans is not yet clear. However, the specific effect of soy intake on women's fertility has not yet been systematically evaluated. They evaluated the hormonal variations during menstrual cycle through the composite construct that considered the cumulative information of the day of menstrual cycle for specimens. Finally, the authors made a detailed assessment of confounders (diet, ethnicity, age and BMI). Isoflavones also bind to ER receptor, albeit with lower affinity. Recently, in a prospective study by Levine et al., 326 American women eumenorrheic aged 1840 were followed for 12 months or until pregnancy(Reference Levine, Kim and Purdue-Smithe45). From a sub-analysis on ethnic characteristics, it was further highlighted that only Asian women showed a significant reduction in follicular estradiol from baseline (174%). Number of combined participants of the two groups PRISMA guidelines ( Reference Liberati, Altman and Tetzlaff23.. That a high intake of soy in the subgroup analysis did not the. 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