The Effect of Supplementation with Saccharomyces boulardii in Women with Polycystic Ovary Syndrome: A Double-blind, Randomized Controlled Trial

Abstract

Objective:

Polycystic ovary syndrome (PCOS) is a prevalent endocrine disorder that affects women during their reproductive age, which may cause infertility. Probiotics may be effective in PCOS by affecting the gut microbiota. We aimed to evaluate the effect of probiotic supplementation on metabolic parameters and androgen levels in women with PCOS.

Methods:

This double-blind, randomized clinical trial was performed on 84 patients aged 18–45 years with PCOS. Participants were randomly assigned to two groups and received probiotics (Saccharomyces boulardii) or a matched placebo for 3 months. Anthropometric parameters, including body mass index (BMI), waist circumference, and abdominal circumference, were assessed at baseline and after 12 weeks for all patients. Fasting blood samples were collected before and after the intervention to assess fasting blood sugar (FBS), dehydroepiandrosterone sulfate (DHEA-S), and testosterone levels.

Finding:

Probiotic supplementation significantly decreased testosterone hormone level (P = 0.0029) and DHEA-S level (P = 0.0031) compared to the placebo group. The reduction in the BMI and FBS parameters in the intervention group was significant within the group, but the between-groups difference was not significant. Also, intragroup analysis in the placebo group revealed no significant differences in BMI, FBS, testosterone, or DHEA-S levels before and after the intervention.

Conclusion:

Overall, probiotic supplementation of S. boulardii in PCOS women did not affect weight, BMI, or FBS but reduced testosterone and DHEA-S levels. Therefore, S. boulardii probiotics might be beneficial in the management of PCOS patients.

INTRODUCTION

Polycystic ovary syndrome (PCOS) is recognized as a complex endocrine-metabolic disorder affecting women during reproductive age, with a global prevalence estimated between 5% and 10%.[1,2,3] This syndrome results from interactions among hormonal, metabolic, genetic, and environmental factors and is considered a major contributor to ovulatory dysfunction and female infertility. In addition to reproductive complications, psychological disturbances are also frequently observed in affected individuals.[2,3]

PCOS is commonly associated with hypersecretion of luteinizing hormone, an elevated luteinizing hormone/follicle-stimulating hormone ratio, and ovarian theca cell hyperactivity, which collectively contribute to excess androgen production. Biochemically, elevated serum testosterone, decreased plasma sex hormone-binding globulin (SHBG), and elevated inflammatory biomarkers, including C-reactive protein (CRP), are frequently observed in affected women.[4,5] These hormonal imbalances are strongly associated with clinical manifestations including hirsutism, acne, androgenic alopecia, and menstrual irregularities.[6,7,8] In addition to reproductive dysfunction, PCOS is increasingly recognized as a metabolic disorder. Insulin resistance is considered a central feature of the syndrome and is observed in a significant proportion of patients, independent of body mass index (BMI). This metabolic dysfunction contributes to hyperinsulinemia, which in turn exacerbates ovarian androgen production and disrupts normal follicular development.[6,7,8,9]

The Rotterdam guideline is the most widely accepted framework for diagnosing PCOS. According to this definition, diagnosis is confirmed when at least two of the following manifestations are identified: ovulatory dysfunction or absent ovulation, biochemical or clinical evidence of androgen excess, and ultrasonographic findings consistent with polycystic ovarian morphology.[10]

Current management strategies include lifestyle modification, dietary regulation, weight reduction, and physical activity.[11] Pharmacological treatments such as metformin are widely used, although their overall long-term efficacy remains variable.[12] Combined oral contraceptives, including formulations containing cyproterone acetate and ethinyl estradiol, are commonly prescribed for symptom control, particularly in patients with hyperandrogenic manifestations.[13]

Recent evidence highlights the important role of gut microbiota in regulating metabolism, immune responses, and endocrine function.[14,15] Dysbiosis has been implicated in the pathogenesis of PCOS through mechanisms such as chronic inflammation, impaired intestinal permeability, and altered metabolic homeostasis.[15] Probiotics may improve metabolic and hormonal disturbances by enhancing insulin sensitivity, modulating lipid metabolism, strengthening gut barrier function, and reducing systemic inflammation.[14,15] Although several studies have investigated bacterial probiotics in PCOS, probiotic yeast strains, particularly Saccharomyces boulardii, have received limited attention in reproductive and metabolic disorders. This probiotic yeast has demonstrated anti-inflammatory and gut-protective effects and has shown beneficial metabolic effects in obesity and diabetes models.[16,17] However, clinical evidence regarding its efficacy in PCOS remains unknown. Therefore, the present trial aimed to evaluate the S. boulardii effects on hormonal and metabolic factors in women diagnosed with PCOS.

METHODS

Trial design and participants

This investigation was a randomized, double-blind, clinical trial that was conducted on women aged 18–45 years old with PCOS in Al-Zahra Hospital, Tabriz, Iran. The study was performed between October 2018 and May 2019 for 8 months. Eligible participants were randomized in a 1:1 ratio to the probiotic or placebo group through an online random block allocation system (block sizes of 4 and 6). The sequentially numbered, opaque sealed envelopes process was used for concealment allocation. A total of 91 participants were randomized to two groups: intervention group (n = 46) received 2 probiotics capsules daily (equal to 500 mg or 2 × 10¹⁰ CFU) and the placebo group (n = 45) received a matching placebo daily for 12 weeks.[18,19,20,21,22] Patient’s adherence to the study intervention was assessed through capsule count and telephone follow-up.

Specifications of the probiotic

The S. boulardii probiotic capsules used in this trial were manufactured under the brand name DAILYEAST^@ by Zist-Takhmir Pharmaceutical Company of Iran. According to the manufacturer’s recommendation, this product should be stored at temperatures below 25°C and away from moisture.

Blinding

The probiotic and placebo were provided to patients in identical, coded packaging. The placebo capsule was identical in appearance, color, and consistency to the probiotic capsule. Neither the participants nor the clinical staff were aware of the group assignments.

Inclusion and exclusion criteria

Females between the ages of 18 and 45 who were diagnosed with PCOS entered the study. PCOS diagnosis was based on the presence of 2 of 3 characteristics: (a) anovulation or oligo-ovulation, (b) clinical or biochemical manifestations of androgen excess, including hirsutism, male-patterned hair loss, acne, increased free testosterone levels, and (c) confirmed PCOS based on the ultrasound results.

All individuals were given standard treatment (oral contraceptive containing cyproterone acetate and ethinyl estradiol), besides a probiotic or a placebo.

The study’s exclusion criteria were heart failure, liver impairment, diabetes mellitus, thyroid disorders, hypertension, Cushing syndrome, chronic kidney disease, autoimmune diseases, malignancy, history of thrombosis, hyperprolactinemia, cigarette smoking, pregnancy, breastfeeding, and co-administration of other probiotics and antibiotics.

Ethical considerations

Ethical clearance for this investigation was granted by the Ethics Committee of Tabriz University of Medical Sciences in Tabriz, Iran (ID: IR.TBZMED.REC.1397.599). The trial was also formally registered in the clinical trial registry platform (IRCT 20180404039187N3). The present study was conducted based on the Declaration of Helsinki. Prior to enrollment, written informed consent was obtained from every participant.

Study outcomes

The primary outcomes were the change in the dehydroepiandrosterone sulfate (DHEA-S) and testosterone plasma levels during the study period between the two groups. Secondary outcomes include change in the BMI and fasting blood sugar (FBS) during 3 months.

Blood sampling timing

Fasting blood specimens were obtained in the morning following an overnight fast of at least 8 h. To reduce hormonal variability, sample collection was scheduled during the early follicular stage of the menstrual cycle, specifically between days 2 and 5.

Statistical analysis

Statistical analyses were carried out using Statistical analyses were carried out using STATA, Release 17 (StataCorp LLC, College Station, TX, USA). Numerical data are expressed as mean values accompanied by standard deviations (SDs), while categorical data are reported as frequencies and percentages. Between-group comparisons for continuous variables at baseline and post-intervention were performed using either the independent samples t-test or the Mann–Whitney U test, depending on data distribution. Differences in categorical variables were evaluated using the Chi-square test. In addition, analysis of covariance (ANCOVA) was conducted for the comparison of the means of two groups after intervention and adjustment of potential confounders. A probability value below 0.05 was considered indicative of statistical significance.

RESULTS

In this study, 84 patients met the eligibility criteria for analysis. Figure 1 presents the study’s CONSORT flowchart. The mean ± SD ages of the probiotic group and placebo group were 31.86 ± 6.4 and 33.43 ± 5.85 years old, respectively.

Figure 1.

CONSORT flow diagram of the study

The initial demographic and clinical features of participants assigned to the probiotic and placebo arms are summarized in Table 1. Significant between-group differences were identified for the BMI and FBS levels at baseline; therefore, the ANCOVA was performed, and data were reported as adjusted marginal means. The intragroup changes of BMI, FBS, testosterone, and DHEAS at baseline and the 3^rd month are summarized in Table 2.

Table 1.

Baseline characteristics of the patients in the probiotic and placebo groups

Characteristic		Placebo group (n=42)		Probiotic group (n=42)		P
Age (years)		33.43±5.85		31.86±6.4		0.55
BMI (kg/m2)		25.9±5.6		29.1±6.7		0.022
FBS (mg/dL)		84.8±6		87.2±5		0.053
Testosterone (ng/dL)		0.46±0.3		0.43±0.2		0.705
DHEA-S (μg/dL)		208.7±68.1		211.5±83.9		0.870

Significance P-value is P<0.05. The statistical methods used: independent t-test or Mann–Whitney U-test. BMI=Body mass index, FBS=Fasting blood sugar, DHEA-S=Dehydroepiandrosterone sulfate

Table 2.

Mean±standard deviation of intragroup changes of body mass index, fasting blood sugar, testosterone, and dehydroepiandrosterone sulfate at baseline and after three months

Variable		Placebo group (n=42)				P		Probiotic group (n=42)				P
		Baseline		Third month				Baseline		Third month
BMI (kg/m2)		25.9±5.6		26.1±5.7		0.68		29.1±6.7		28.5±6.4		<0.001
FBS (mg/dL)		84.8±6		82.5±6.7		0.073		87.2±5		84.7±4.9		<0.001
Testosterone (ng/dL)		0.46±0.3		0.43±0.2		0.68		0.43±0.2		0.29±0.2		0.003
DHEA-S (µg/dL)		208.7±68.1		198.8±50.4		0.25		211.5±83.9		175.9±79.5		0.003

Significance P-value is P<0.05. The statistical methods used: independent t-test or Mann–Whitney U-test. BMI=Body mass index, FBS=Fasting blood sugar, DHEA-S=Dehydroepiandrosterone sulfate

The mean ± SD for BMI (kg/m²) of the probiotic group was decreased significantly from 29.1 ± 6.7 to 28.5 ± 6.4 after 12 weeks of supplementation with probiotics (P < 0.001). Furthermore, the results showed no significant decrease in the mean ± SD for BMI in the placebo group (P = 0.68).

The mean ± SD of FBS in the probiotic group was 87.5 ± 2 mg/dl before the intervention which was decreased to 84.7 ± 4.9 after 12 weeks of probiotic use. This reduction in FBS values was statistically significant (P < 0.001). In the placebo group, the mean ± SD of FBS (mg/dl) decreased from 84.6 ± 8 to 82.5 ± 6.7 after 12 weeks; however, this change was not significant (P = 0.073).

The mean ± SD of testosterone hormone level (ng/dl) in the intervention group was decreased from 0.43 ± 0.2 to 0.29 ± 0.2 over 12 weeks which was statistically significant (P = 0.003). Furthermore, the mean ± SD of testosterone hormone level (ng/dl) in the placebo group was decreased from 0.46 ± 0.3 to 0.43 ± 0.2 over 12 weeks but was not statistically significant (P = 0.68).

The mean ± SD of DHEA-S level (μg/dl) in the probiotic group was decreased from 211.5 ± 83.9 to 175.9 ± 79.5 over 12 weeks which was statistically significant (P = 0.003). Also, the mean ± SD of DHEA-S level (μg/dl) in the placebo group was decreased from 208.7 ± 68.1 to 198.50 ± 8.4 over 12 weeks but was not statistically significant (P = 0.25).

As shown in Table 3, the adjusted marginal means reveal a significant difference between the two groups in testosterone levels (P = 0.003) and DHEA-S levels (P = 0.043) following the intervention.

Table 3.

Adjusted mean±standard errors of body mass index, fasting blood sugar, testosterone, and dehydroepiandrosterone sulfate in the probiotic and placebo groups

Variable		Placebo group		Probiotic group		P
BMI (kg/m2)		27.64±0.265		27.04±0.265		0.120
FBS (mg/dL)		82.9±0.873		84.3±0.873		0.267
Testosterone (ng/dL)		0.43±0.031		0.29±0.031		0.003
DHEA-S (μg/dL)		199.5±8.360		175.2±8.360		0.043

Significance P-value is P<0.05. The statistical methods used: ANCOVA test. BMI=Body mass index, FBS=Fasting blood sugar, DHEA-S=Dehydroepiandrosterone sulfate

Mild gastrointestinal adverse effects (bloating and abdominal discomfort) were reported by six participants receiving the probiotic supplement and by two individuals in the placebo group. No serious treatment-related adverse events occurred throughout the study period.

DISCUSSION

Based on the available literature, no previous randomized controlled study has specifically investigated the clinical impact of S. boulardii in women with PCOS.

This randomized clinical trial indicated that supplementation with S. boulardii for 12 weeks significantly decreased circulating testosterone and DHEA-S levels among women affected by PCOS. However, no significant between-group effects were observed for BMI or FBS, despite within-group improvements in the intervention arm.

PCOS is considered a frequently endocrine and metabolic disorder affecting women. Although both genetic and environmental causes are linked to the occurrence of PCOS, its etiology remains indistinct. In 2012, Tremellen and Pearce revealed that dysbiosis of the gut microbiota might have a key role in PCOS development.[23]

Several potential mechanisms could describe the favorable effects of probiotics in women with PCOS, including anti-inflammatory, antioxidant, and beneficial metabolic effects, regulation of sex hormones, and anti-lipopolysaccharide activities.

These effects, combined with the dysbiosis theory in PCOS pathogenesis, led to conducting studies to evaluate the therapeutic efficacy of prebiotics, probiotics, and synbiotics.

In a randomized clinical trial on 60 females with PCOS, participants were allocated to receive either a placebo or Vitamin D with a probiotic for 12 weeks. Co-administration of Vitamin D with probiotics significantly reduced total testosterone levels and hirsutism.[24] However, it cannot be determined which intervention, Vitamin D or probiotic, is responsible for these effects.

In another clinical trial by Arab et al. on 99 women with PCOS, probiotic supplementation with seven strains was associated with increased serum SHBG levels compared to placebo (+3.95 vs. −6.49, P = 0.030). Nevertheless, the intervention did not produce significant changes in either hormonal parameters or clinical manifestations.[25]

In a randomized controlled study involving 60 women diagnosed with PCOS, Karamali et al. investigated the impact of probiotic supplementation containing Bifidobacterium bifidum, Lactobacillus casei, and Lactobacillus acidophilus (each at a concentration of 2 × 10⁹ CFU/g) on hormonal status, inflammatory markers, and oxidative stress indices.[26] After 12 weeks, the probiotic-supplemented group showed a significantly higher SHBG and total plasma antioxidant capacity than the placebo group. Probiotic administration also led to a significant reduction in total plasma testosterone, serum malondialdehyde levels, and plasma high-sensitivity CRP levels compared to the placebo group.

In contrast, Shoaei et al.’s study did not support the supplementation with probiotics capsules containing seven bacteria in women with PCOS (n = 72).[27] Although probiotic supplementation decreased FBS, insulin resistance score, and serum insulin levels, the observed difference did not reach statistical significance.

The difference between the findings of studies might be due to the use of different strains with different doses and the clinical conditions of the included participants. To date, no clinical trials have investigated probiotic yeast in the context of PCOS. To determine the most effective genera of microbial organisms in improving the condition of PCOS patients, using different types of probiotic products is of great importance.

Everard et al. revealed that 4-week administration of S. boulardii led to reductions in hepatic steatosis, fat mass, and low-grade inflammation in mice with obesity and diabetes (type II).[16]

In a randomized clinical trial on 25 obese patients, S. boulardii use for 60 days significantly decreased body weight, BMI, fat mass, insulin concentration, serum uric acid, and HOMA index from baseline.[28] However, these changes were not significantly different when compared with the placebo arm. Furthermore, the results were not analyzed based on different subgroups, including gender or women with PCOS.

Importantly, most previous research has focused on bacterial probiotic strains, whereas evidence regarding probiotic yeast, particularly S. boulardii, remains extremely limited.[29,30] This strain has been more extensively studied in gastrointestinal disorders and metabolic conditions, where it has revealed anti-inflammatory effects, improvements in gut barrier function, and metabolic benefits in animal models. Preclinical evidence suggests that S. boulardii may reduce adiposity, hepatic fat accumulation, and systemic inflammation in models of obesity and type 2 diabetes.[16,17]

As mentioned above, limited evidence in human studies indicates potential benefits on body weight, insulin resistance, and metabolic markers; however, no published studies have specifically examined the impact of S. boulardii in females diagnosed with PCOS.[28]

In this investigation, supplementation with S. boulardii did not result in significant alterations in BMI or glycemic indices; however, a marked decline in androgen concentrations was observed after the intervention. This finding may suggest a possible modulatory effect of this probiotic on steroid hormone regulation, potentially mediated through gut microbiota–host endocrine interactions.

The absence of significant effects on weight and glucose metabolism may be explained by the relatively short intervention period, limited sample size, or the possibility that S. boulardii exerts stronger effects on hormonal pathways than on metabolic outcomes in this population.

All participants received identical oral contraceptive therapy as standard care, making full removal ethically impossible. However, because both groups received identical oral contraceptive treatment, its effects were balanced between groups.

Our study has several limitations. Due to time and cost limitations, we did not investigate probiotic supplementation effects on the ovulation or fertility of women. Inflammatory biomarkers such as CRP were not investigated in our study, and it is suggested to be investigated in future studies. The sample size and follow-up period were limited. Furthermore, the 12-week intervention period may be insufficient to detect full metabolic changes, particularly in weight-related outcomes. Hence, the results should be interpreted cautiously.

CONCLUSION

S. boulardii supplementation in women with PCOS for 12 weeks reduced testosterone and DHEA-S levels without significant effects on weight, BMI, or FBS. Therefore, S. boulardii probiotics might improve PCOS symptoms and be considered as adjuvant therapy. Further large-scale trials are necessary to validate our trial results.

Authors’ contributions

FP: writing – original draft. EK: writing – original draft. KH: writing – review and editing. NSO: study implementation, data collection. PS: study design – randomization-data analysis. HM: writing – original draft. ES: conceptualization, writing – review, and editing, supervision.

Data availability

The data that support the findings of this study are available from the corresponding author upon reasonable request.

Conflicts of interest

There are no conflicts of interest.

Funding Statement

This research is supported by Tabriz University of Medical Science under grant number 60408.