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The Effects of Probiotics/Synbiotics on Glucose and Lipid Metabolism in Women with Gestational Diabetes Mellitus: A Meta-Analysis of Randomized Controlled Trials.
Mu, J, Guo, X, Zhou, Y, Cao, G
Nutrients. 2023;15(6)
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Women with gestational diabetes mellitus (GDM) are at an increased risk of complications during pregnancy and type 2 diabetes, pancreatic cancer, and heart disease after pregnancy. There is some controversy over the research surrounding current treatments of GDM and as such new treatment strategies are being researched and developed. Amongst these is the possibility of using probiotics and synbiotics to alleviate the driving factors of GDM, however the research is inconclusive as some studies have shown a benefit whereas others have not. This meta-analysis of 11 randomised control trials (RCTs) containing 779 participants aimed to determine the effect of probiotic/synbiotics on sugar and lipid levels in the blood. The results showed that amongst 8 of the RCTs, Lactobacillus was the most researched probiotic gut bacteria, with 6 species researched. In addition, Bifidobacterium bifidum and Streptococcus thermophilus were also used as a probiotic. 3 RCTs looked at synbiotics including 5 Lactobacillus species and 3 Bifidobacterium species. Supplementation with probiotics/synbiotics significantly improved blood sugar levels, measures of insulin resistance, and total cholesterol in pregnant women with GDM. Other blood lipids such as triglycerides, high density lipoprotein, low density lipoprotein, weight at the end of the trial, and weight gain during pregnancy were unaffected by supplementation. It was concluded that probiotics/synbiotics are of benefit to women with GDM especially if they contain L. acidophilus and B. bifidum. However, there may be more research required to better inform GDM management. This study could be used by healthcare professionals to understand that the gut microbiota may have a pivotal role in GDM. More research is required before this forms part of a regular management strategy.
Abstract
BACKGROUND Gestational diabetes mellitus (GDM) is prevalent with lasting health implications for the mother and offspring. Medical therapy is the foundation of GDM management, for achieving optimal glycemic control often requires treatment with insulin or metformin. Gut dysbiosis is a feature of GDM pregnancies, therefore, dietary manipulation of the gut microbiota may offer a new avenue for management. Probiotics are a relatively new intervention, which can reduce the mother's blood sugar levels and, furthermore, adjust glucose and lipid metabolism in both mother and offspring. OBJECTIVE The aim of this systematic review and meta-analysis is to explore the effect of probiotics/synbiotics on glucose and lipid metabolism in women with GDM. METHODS A systematic search of the literature was conducted using the electronic databases Cochrane Library, Web of Science, PubMed, and EBOSCO, published between 1 January 2012 and 1 November 2022. A total of 11 randomized controlled clinical trials (RCTs) were analyzed. The indicators included fasting plasma glucose (FPG), fasting serum insulin (FSI), the homoeostatic model assessment for insulin resistance (HOMA-IR), quantitative insulin sensitivity check index (QUICKI), total cholesterol (TC), HDL cholesterol, LDL cholesterol and triglycerides (TG), the mean weight at end of trial, and gestational weight gain (GWG). RESULTS Compared with the placebo, probiotics/synbiotics were associated with a statistically significant improvement in FPG (MD = -2.33, 95% CI = -4.27, -0.40, p = 0.02), FSI (MD = -2.47 95% CI = -3.82, -1.12, p = 0.0003), HOMA-IR (MD = -0.40, 95% CI = -0.74, -0.06, p = 0.02), and TC (MD = -6.59, 95% CI = -12.23,--0.95, p = 0.02), while other factors had no significant difference. The subgroup analysis revealed that the kind of supplement led to heterogeneity for FPG and FSI, while heterogeneity was not found for others. CONCLUSION Probiotics/synbiotics could control glucose and lipid metabolism in pregnant women with GDM. There was a significant improvement in FPG, FSI, HOMA-IR, and TC. The use of specific probiotic supplementation may be a promising prevention and therapeutic strategy for GDM. However, due to the heterogeneity among existing studies, further studies are warranted to address the limitations of existing evidence and better inform the management of GDM.
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Effects of probiotics administration on lactose intolerance in adulthood: A meta-analysis.
Ahn, SI, Kim, MS, Park, DG, Han, BK, Kim, YJ
Journal of dairy science. 2023;106(7):4489-4501
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Milk and dairy products are good sources of protein, calcium and other nutrients. However, many people experience lactose intolerance due to their digestive tract's inability to digest lactose, resulting in symptoms such as flatulence, abdominal pain and diarrhoea. Oral administration of certain friendly live microorganisms or probiotics can help digest lactose more efficiently as they have greater β-galactosidase (β-gal) activity. β-galactosidase is an enzyme responsible for the digestion of lactose in the dairy products. A total of twelve studies were included in this meta-analysis. The results of this meta-analysis showed an improvement in the symptoms of lactose intolerance in adult patients, following probiotic administration. Probiotic administration was also found to enhance the digestion of lactose and calcium absorption in adult patients. Healthcare professionals can use the results of this study to understand the potential benefits of oral supplementation of probiotics for adult lactose intolerance patients. However, further studies are needed to understand the relationship between calcium absorption and lactose digestion after probiotic administration.
Abstract
This meta-analysis aimed to investigate the effect of probiotic administration on adults with lactose intolerance. Twelve studies were identified from databases such as PubMed, Cochrane Library, and Web of Knowledge based on the inclusion and exclusion criteria. The effect size was estimated using the standardized mean difference (SMD), and Cochrane's Q test was used to evaluate the statistical heterogeneity of the effect size. Moderator analysis, including meta-ANOVA and meta-regression, were performed to determine the cause of heterogeneity in the effect size using a mixed-effect model. Egger's linear regression test was conducted to evaluate publication bias. The results showed that probiotic administration alleviated the symptoms of lactose intolerance, including abdominal pain, diarrhea, and flatulence. Among them, the area under the curve (AUC) showed the greatest decrease following probiotic administration (SMD, -4.96; 95% confidence interval, -6.92 to -3.00). In the meta-ANOVA test, abdominal pain and total symptoms decreased with monostrain probiotic administration. This combination was also effective for flatulence. The dosage of probiotics or lactose was significantly associated with a reduction in the total symptom score, and the linear regression models between the dosage and SMD were found to be Y = 2.3342 × dosage - 25.0400 (R2 = 79.68%) and Y = 0.2345 × dosage - 7.6618 (R2 = 34.03%), respectively. Publication bias was detected for most items. However, even after effect size correction, the probiotic administration effect for all items remained valid. The administration of probiotics was effective at improving adult lactose intolerance, and it is expected that the results of this study could help improve the nutritional status of adults by increasing their consumption of milk and dairy products in the future.
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Are probiotics, prebiotics, and synbiotics beneficial in primary thyroid diseases? A systematic review with meta-analysis.
Zawadzka, K, Kałuzińska, K, Świerz, MJ, Sawiec, Z, Antonowicz, E, Leończyk-Spórna, M, Abadi, AK, Trofimiuk-Müldner, M, Bała, MM
Annals of agricultural and environmental medicine : AAEM. 2023;30(2):217-223
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Irregularities in intestinal microbial composition are thought to be correlated with thyroid dysfunction. Supplementation of prebiotics, probiotics and synbiotics are gaining momentum in recent times in improving health in general. This systematic review of randomised controlled trials was conducted to summarise the up-to-date evidence on the therapeutic potential of prebiotics, probiotics and synbiotics in the treatment of thyroid disease. The meta-analysis did not show beneficial effects on thyroid hormone balance, BMI or levothyroxine dosage reduction. Supplementation with Lactobacillus and Bifidobacterium resulted in improvement in constipation and a statistically non-significant reduction in thyroid-stimulating hormone in adult participants with hypothyroidism. Further robust long-term studies are required to evaluate the efficacy of prebiotics, probiotics and synbiotics in thyroid disease treatment as the availability of the number of studies included in this systematic review was limited. However, healthcare professionals can use the review to understand the current evidence in this area and the correlation between gut microbial alterations and thyroid disease.
Abstract
INTRODUCTION AND OBJECTIVE A number of studies indicate the presence of a thyroid-gut axis and the important influence of the gut microbiota on thyroid function. As prebiotics, probiotics and synbiotics show therapeutic potential in the treatment of intestinal dysbiosis, the aim of this review is to evaluate the efficacy of their supplementation in primary thyroid diseases. REVIEW METHODS Electronic databases (Ovid MEDLINE, Embase, CENTRAL), registers of clinical trials, and grey literature up to 6 October 2022 were searched for randomised controlled trials (RCTs) meeting pre-specified inclusion criteria. The protocol was registered in PROSPERO (CRD42021235054). BRIEF DESCRIPTION OF THE STATE OF KNOWLEDGE After screening 1,721 references, two RCTs were identified, which included 136 hypothyroid participants in total. Meta-analysis of the results after eight weeks of supplementation with predominantly Lactobacillus and Bifidobacterium strains indicated a clinically and statistically nonsignificant decrease in TSH (MD -0.19 mIU/L; 95% CI -0.43 to 0.06; I2= 0%), and no effect on fT3 levels (MD 0.01 pg/mL; 95% CI-0.16 to 0.18; I2= 0%). Data from single studies indicated no significant change in the levels of fT4, thyroid auto-antibodies, BMI, levothyroxine doses, and severity of symptoms measured with validated scales. Only constipation scores showed significant improvement (MD -8.71 points in the Faecal Incontinence Questionnaire; 95% CI -15.85 to -1.57; I2= 0%). SUMMARY Low-certainty evidence from two randomised trials, suggests that routine administration of probiotics, prebiotics or synbiotics may result in little to no benefit in patients with primary hypothyroidism.
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Effects of Probiotics on Glycemic Control and Metabolic Parameters in Gestational Diabetes Mellitus: Systematic Review and Meta-Analysis.
Yefet, E, Bar, L, Izhaki, I, Iskander, R, Massalha, M, Younis, JS, Nachum, Z
Nutrients. 2023;15(7)
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The prevalence of gestational diabetes is increasing worldwide. Gestational diabetes mellitus (GDM) increases obesity and future development of type 2 diabetes in mother and child. Previous research has looked at the beneficial effects of probiotics in reducing metabolic diseases, however, these specific benefits on women with GDM are not fully understood yet. This systematic review and meta-analysis of fourteen randomised controlled trials assessed the beneficial effects of probiotics on glycemic control and metabolic parameters in women with GDM. This study separately assessed probiotic bacterial strains such as Lactobacillus acidophilus, Bifidobacterium bifidum, and Lactobacillus casei to understand their beneficial effects on metabolic parameters. This meta-analysis and systematic review suggest that probiotic supplementation could help improve glycemic control, insulin resistance and lipid levels in women diagnosed with GDM. All probiotic strains showed improvements in metabolic parameters when assessed separately. Further robust studies are required to assess the effect of probiotic supplementation on post- and pre-prandial glycemic control in women with GDM. Healthcare professionals can employ the results of this study to understand the therapeutic benefits of probiotics for improving GDM.
Abstract
OBJECTIVES To assess the effects of probiotic supplements on glycemic control and metabolic parameters in women with gestational diabetes mellitus (GDM) by performing a systematic review and meta-analysis of randomized controlled trials. The primary outcome was glycemic control, i.e., serum glucose and insulin levels. Secondary outcomes were maternal weight gain, neonatal birth weight, and lipid parameters. Weighted mean difference (WMD) was used. Cochrane's Q test of heterogeneity and I2 were used to assess heterogeneity. RESULTS Of the 843 papers retrieved, 14 (n = 854 women) met the inclusion criteria and were analyzed. When compared with placebo, women receiving probiotic supplements had significantly lower mean fasting serum glucose, fasting serum insulin, homeostatic model assessment for insulin resistance (HOMA-IR), triglycerides, total cholesterol, and VLDL levels. Decreased neonatal birth weight was witnessed in supplements containing Lactobacillus acidophilus. CONCLUSION Probiotic supplements may improve glycemic control and lipid profile and reduce neonatal birth weight in women with GDM.
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Impact of probiotics on muscle mass, muscle strength and lean mass: a systematic review and meta-analysis of randomized controlled trials.
Prokopidis, K, Giannos, P, Kirwan, R, Ispoglou, T, Galli, F, Witard, OC, Triantafyllidis, KK, Kechagias, KS, Morwani-Mangnani, J, Ticinesi, A, et al
Journal of cachexia, sarcopenia and muscle. 2023;14(1):30-44
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Sarcopenia is a progressive skeletal muscle disorder involving accelerated loss of muscle mass, strength and function. It generally occurs in older age groups but can also be seen in younger people. Multiple factors contribute to the development of the condition. Besides nutritional management strategies, probiotics have recently caught the interest of researchers. As probiotics promote metabolic building activity, aid digestion and absorption and reduce muscle breakdown by favourably managing inflammation, they present great potential for the management of sarcopenia. This systematic review and meta-analysis explored the impact of probiotic supplementation on muscle mass, total lean mass and muscle strength in human adults. The review included 24 studies, with probiotics mainly from the Bifidobacteria or Lactobacilli family. The analysis concluded that probiotic supplementation improved muscle mass in comparison to placebos. It also significantly increased overall muscle strength in 6 randomized controlled trials, which was most obvious in age groups of 50 and above. However, no changes were seen concerning total lean mass. It appeared that longer studies, of >12 weeks or more, showed better outcomes in this review. Furthermore, Bifidobacteria species seemed to exhibit more favourable effects, and the authors also noted the beneficial results were more significant in Asian populations. Further research is needed to understand more about the underlying mechanism, best probiotics strains and the specifics of different demographic groups. This article yields a concise overview of sarcopenia, the nutritional aspects of the disease and how probiotics may be beneficial in disease management, strengthened with data from the review.
Expert Review
Conflicts of interest:
None
Take Home Message:
- This was a well-conducted meta-analysis based on its methodological approach that demonstrated that Lactobacillus and Bifidobacterium probiotic supplementation may contribute to improved muscle mass in younger adults and improved muscle strength in older adults.
- Bifidobacterium probiotic supplementation was associated with enhanced muscle mass in younger adults, a potential focus for those considering probiotic supplements.
- The duration of probiotic therapy matters, with longer-term (12 weeks or more) supplementation showing improvements in muscle mass and strength..
Evidence Category:
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A: Meta-analyses, position-stands, randomized-controlled trials (RCTs)
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B: Systematic reviews including RCTs of limited number
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C: Non-randomized trials, observational studies, narrative reviews
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D: Case-reports, evidence-based clinical findings
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E: Opinion piece, other
Summary Review:
Introduction
This systematic review and meta-analysis evaluated the effect of probiotics on muscle mass, total lean mass and muscle strength in both young and older adults.
Methods
- The search encompassed PubMed, Scopus, Web of Science, and Cochrane Library databases, from inception up to June 2022; studies included spanned a period from 2013 to June 2022.
- The study adhered to Preferred Reporting Items for Systematic Reviews (PRISMA) guidelines and included the Risk-of-Bias tool to assess study quality.
- The study focused on changes in muscle mass, total lean mass, and muscle strength.
- Inclusion criteria: randomised controlled trials (RCTs) with adult participants (>18 years); interventions involving any probiotics, and a control group receiving either no treatment or a placebo.
Results
- 24 RCTs were included (709 participants), with studies conducted in Europe, USA, and Asia. Intervention durations: ranged from 3 weeks to 12 months.
- Participants included overweight, untrained healthy and resistance-trained individuals, and those with specific conditions like metabolic syndrome and frailty.
- Body composition assessments were conducted using bioelectrical impedance (BIA) and/or dual-energy X-ray absorptiometry (DXA).
- Probiotic strains employed in the included studies varied, with Lactobacillus the most common, followed by Bifidobacterium; some combined both. 5 of 24 studies also used additional strains.
- Dosages: ranged from 2 × 10^9 to 11.2 × 10^10 colony-forming units (CFU).
- 4 out of 24 studies used fermented food products like cheese and noodles as sources of probiotics.
- 22 RCTs measured muscle mass and total lean mass; 6 RCTs measured global muscle strength.
- Probiotic supplementation (≥12 weeks) moderately increased muscle mass, with a standardised mean difference (SMD) of 0.42. This significant effect (95% CI: 0.10–0.74, P=0.009) was observed only in younger Asian adults (<50 years) after Bifidobacterium supplementation, based on a meta-analysis of 10 studies.
- Probiotic supplementation (≥12 weeks) significantly increased global muscle strength in older adults (>50 years; SMD: 0.69, 95% CI: 0.33–1.06, P = 0.0002).
- Probiotic supplementation showed no significant impact on lean mass (SMD: -0.03, 95% CI: 0.19 – 0.13, P = 0.69).
Conclusion
Probiotic supplementation, especially Lactobacillus and Bifidobacterium may have a positive impact on muscle mass and global strength
Clinical practice applications:
- Consumption of probiotics, mainly Lactobacillus and Bifidobacterium may contribute to improved muscle strength in older individuals (>50y).
- Consumption of Bifidobacterium strains was associated with improved muscle mass in younger individuals (<50y) in Asian countries, in a low number of studies (k=2).
- Bifidobacterium breve B-3 was associated with an improvement in muscle mass in older overweight individuals, although a causal relationship was not established.
- Probiotics may enhance muscle mass or strength by enhancing protein digestion and amino acid absorption for muscle synthesis and function.
- Considering an individual’s goals, a practitioner could consider probiotic supplementation as a complementary intervention when aiming to enhance muscle mass or strength .
Considerations for future research:
- Future research could focus on pinpointing which specific probiotic strains are most effective for muscle strength or muscle mass to tailor more precise interventions.
- Most studies did not exceed 12 weeks, highlighting the need for long-term research on probiotics sustained muscle impact.
- Future research could investigate the effects of probiotics across diverse demographic groups including different ages, sexes, and ethnic backgrounds to understand the impact in different populations.
- Delving deeper into the mechanisms by which probiotics influence muscle health could lead to targeted probiotic therapies that address specific physiological pathways.
- Finally, future research could explore how probiotics can be combined with other interventions, such as exercise or nutritional modifications, to synergistically improve muscle health and function.
Abstract
Probiotics have shown potential to counteract sarcopenia, although the extent to which they can influence domains of sarcopenia such as muscle mass and strength in humans is unclear. The aim of this systematic review and meta-analysis was to explore the impact of probiotic supplementation on muscle mass, total lean mass and muscle strength in human adults. A literature search of randomized controlled trials (RCTs) was conducted through PubMed, Scopus, Web of Science and Cochrane Library from inception until June 2022. Eligible RCTs compared the effect of probiotic supplementation versus placebo on muscle and total lean mass and global muscle strength (composite score of all muscle strength outcomes) in adults (>18 years). To evaluate the differences between groups, a meta-analysis was conducted using the random effects inverse-variance model by utilizing standardized mean differences. Twenty-four studies were included in the systematic review and meta-analysis exploring the effects of probiotics on muscle mass, total lean mass and global muscle strength. Our main analysis (k = 10) revealed that muscle mass was improved following probiotics compared with placebo (SMD: 0.42, 95% CI: 0.10-0.74, I2 = 57%, P = 0.009), although no changes were revealed in relation to total lean mass (k = 12; SMD: -0.03, 95% CI: -0.19 - 0.13, I2 = 0%, P = 0.69). Interestingly, a significant increase in global muscle strength was also observed among six RCTs (SMD: 0.69, 95% CI: 0.33-1.06, I2 = 64%, P = 0.0002). Probiotic supplementation enhances both muscle mass and global muscle strength; however, no beneficial effects were observed in total lean mass. Investigating the physiological mechanisms underpinning different ageing groups and elucidating appropriate probiotic strains for optimal gains in muscle mass and strength are warranted.
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Effect of Fructooligosaccharides Supplementation on the Gut Microbiota in Human: A Systematic Review and Meta-Analysis.
Dou, Y, Yu, X, Luo, Y, Chen, B, Ma, D, Zhu, J
Nutrients. 2022;14(16)
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Fructooligosaccharide is a prebiotic fibre that undergoes fermentation in the gut, due to which it can cause gas and bloat. Additionally, this prebiotic fibre ferments to produce short-chain fatty acids, which are beneficial for the body. This systematic review and meta-analysis included eight randomised controlled trials investigating the effects of fructooligosaccharide on gut microbial composition. Short-term supplementation with fructooligosaccharide altered the gut’s microbial composition without causing any adverse effects. Bifidobacterium spp. levels were elevated in those who consumed fructooligosaccharide supplements than those who did not. Supplementation with fructooligosaccharide did not significantly change harmful bacteria such as Bacteroides and Enterobacteriaceae levels. In addition, a higher dosage of 7.5–15 g/d of fructooligosaccharide supplementation for a period of more than four weeks was found to be beneficial. Healthcare professionals can use these results to understand better how fructooligosaccharide modulates beneficial gut bacteria such as Bifidobacterium spp. However, there is a need for more robust studies since the number of currently available studies is limited, and the exact health implications of fructooligosaccharide supplementation need to be evaluated further.
Abstract
Background: Numerous studies have investigated the effects of the supplementation of fructooligosaccharides (FOS) on the number of bacteria in the gut that are good for health, but the results have been inconsistent. Additionally, due to its high fermentability, supplementation of FOS may be associated with adverse gastrointestinal symptoms such as bloating and flatulence. Therefore, we assessed the effects of FOS interventions on the composition of gut microbiota and gastrointestinal symptoms in a systematic review and meta-analysis. Design: All randomized controlled trials published before 10 July 2022 that investigated the effects of FOS supplementation on the human gut microbiota composition and gastrointestinal symptoms and met the selection criteria were included in this study. Using fixed or random-effects models, the means and standard deviations of the differences between the two groups before and after the intervention were combined into weighted mean differences using 95% confidence intervals (CIs). Results: Eight studies containing 213 FOS supplements and 175 controls remained in this meta-analysis. Bifidobacterium spp. counts significantly increased during FOS ingestion (0.579, 95% CI: 0.444-0.714) in comparison with that of the control group. Subgroup analysis showed greater variation in Bifidobacterium spp. in adults (0.861, 95% CI: 0.614-1.108) than in infants (0.458, 95% CI: 0.297-0.619). The increase in Bifidobacterium spp. counts were greater in the group with an intervention duration greater than 4 weeks (0.841, 95% CI: 0.436-1.247) than an intervention time less than or equal to four weeks (0.532, 95% CI: 0.370-0.694), and in the group with intervention doses > 5 g (1.116, 95% CI: 0.685-1.546) the counts were higher than those with doses ≤ 5 g (0.521, 95% CI: 0.379-0.663). No differences in effect were found between FOS intervention and comparators in regard to the abundance of other prespecified bacteria or adverse gastrointestinal symptoms. Conclusions: This is the first meta-analysis to explore the effect of FOS on gut microbiota and to evaluate the adverse effects of FOS intake on the gastrointestinal tract. FOS supplementation could increase the number of colonic Bifidobacterium spp. while higher dose (7.5-15 g/d) and longer duration (>4 weeks) showed more distinct effects and was well tolerated.
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Association between physical activity and changes in intestinal microbiota composition: A systematic review.
Aya, V, Flórez, A, Perez, L, Ramírez, JD
PloS one. 2021;16(2):e0247039
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The human gut flora or microbiota is made up of many different microorganisms, including bacteria, fungi, and viruses. Researchers still find it difficult to clearly define what constitutes a healthy gut flora. This is made more challenging by the fact that the array of microorganisms in the gut are influenced by multiple internal and external factors. Such as diet, sleep, circadian rhythm, age, and physical activity, and they also change with disease. This review sought to gather the current evidence on how physical activity (external factor) impacts the microbial make-up of the gut in healthy humans and the conferred metabolic benefits on the human host. The review included 17 studies with the findings from athletes and exercise intervention programs. Whereby some research demonstrates a consistent beneficial relationship between a favourable microbiota composition and exercise, the authors felt unable to draw a firm conclusion due to the complexity of the microbial system and other influencing factors. The authors called for further, larger scaled studies, that should distinguish between different types of exercise (i.e. endurance and high-intensity training) and age groups, as well as incorporating more information on the subject's diet and lifestyle factors. Of clinical relevance could be the potential of physical activity as a modulator gut microbiome composition.
Abstract
INTRODUCTION The intestinal microbiota comprises bacteria, fungi, archaea, protists, helminths and viruses that symbiotically inhabit the digestive system. To date, research has provided limited data on the possible association between an active lifestyle and a healthy composition of human microbiota. This review was aimed to summarize the results of human studies comparing the microbiome of healthy individuals with different physical activity amounts. METHODS We searched Medline/Ovid, NIH/PubMed, and Academic Search Complete between August-October 2020. Inclusion criteria comprised: (a) cross-sectional studies focused on comparing gut microbiome among subjects with different physical activity levels; (b) studies describing human gut microbiome responses to any type of exercise stimulus; (c) studies containing healthy adult women and men. We excluded studies containing diet modifications, probiotic or prebiotic consumption, as well as studies focused on diabetes, hypertension, cancer, hormonal dysfunction. Methodological quality and risk of bias for each study were assessed using the Risk Of Bias In Non-randomized Studies-of Interventions tool. The results from cross-sectional and longitudinal studies are shown independently. RESULTS A total of 17 articles were eligible for inclusion: ten cross-sectional and seven longitudinal studies. Main outcomes vary significantly according to physical activity amounts in longitudinal studies. We identified discrete changes in diversity indexes and relative abundance of certain bacteria in active people. CONCLUSION As literature in this field is rapidly growing, it is important that studies incorporate diverse methods to evaluate other aspects related to active lifestyles such as sleep and dietary patterns. Exploration of other groups such as viruses, archaea and parasites may lead to a better understanding of gut microbiota adaptation to physical activity and sports and its potentially beneficial effects on host metabolism and endurance.