Exploring the Microbiome: Gut Health, Probiotics and Clinical Trials

Exploring the Microbiome: Gut Health, Probiotics and Clinical Trials

The human microbiome has become an increasingly popular research topic as scientists learn more about the important role gut bacteria play in health and disease. The trillions of microbes residing in our intestines, collectively known as our microbiome, influence digestion, metabolism, immune function, and even mental health. Imbalances in the gut microbiome have been linked to irritable bowel syndrome, autoimmune diseases, obesity, and more. Understanding how to optimize the microbiome through clinical trials may unlock future preventative and therapeutic approaches.

The gut microbiome begins forming at birth and is impacted throughout life by factors like diet, medications, stress, and infections. Each person’s microbiome is unique, like a microbial fingerprint. Research shows that greater diversity in the microbiome correlates with better health. Ongoing clinical trials are studying how probiotics, prebiotics, diet changes, and fecal microbiota transplants may beneficially alter the gut microbiome.


Probiotics are live microorganisms that may confer health benefits when consumed. Different strains are purported to improve health in a variety of ways. Many clinical trials have demonstrated major benefits of probiotics. Some of them include:

  • Alleviating Anxiety and Depression: In a randomized placebo-controlled trial, healthy adults receiving a probiotic blend for 4 weeks showed significantly reduced depression and anxiety scores compared to placebo (Steenbergen et al., 2015).
  • Improving Autism Symptoms: A double-blind, placebo-controlled trial in children with autism found probiotic treatment for 3 months reduced gastrointestinal symptoms and autism-related behaviors (Shaaban et al., 2018).
  • Aiding Digestion and Lactose Intolerance: A double-blind placebo-controlled crossover trial showed a probiotic yogurt improved lactose digestion and tolerance in lactose maldigesters (Pakdaman et al., 2016).
  • Boosting Immune Function: A clinical trial in adults over 70 found supplementing with Bifidobacterium lactis HN019 enhanced immune cell activity and reduced respiratory infection severity (Pu et al., 2017).
  • Improving Skin Hydration and elasticity: In a study of healthy women, consuming a probiotic-fermented milk drink for 8 weeks increased skin hydration and improved skin elasticity (Bae et al., 2019).
  • Boosting Hair Growth: A randomized controlled trial showed supplementing Lactobacillus paracasei in healthy adults for 90 days increased hair thickness and reduced hair shedding (Gueniche et al., 2019).


Prebiotics are non-digestible fibers that promote the growth of healthy gut bacteria. Adjusting one’s diet to include more prebiotic foods like garlic, onions, bananas and oats can support microbial diversity (Slavin, 2013). Clinical trials are exploring how precisely tailored diets impact the microbiome. The Mediterranean diet, emphasizing plant foods, fish, olive oil, and yogurt, has been linked to a healthier gut microbiome composition (Gua et al., 2020).

Fecal Transplants

Fecal microbiota transplantation (FMT) involves transplanting fecal matter from a healthy donor into a recipient’s colon to restore microbial balance. FMT has shown efficacy for recurrent Clostridioides difficile infections, with trials ongoing for other conditions like inflammatory bowel disease (Vieira et al., 2021). However, more research is needed to fully understand FMT’s effects on the wider microbiome and overall long-term safety.

As microbiome research rapidly evolves, clinical trials will continue to investigate novel ways to optimize gut health, including through customized diets, targeted probiotics and prebiotics, FMT, and more. A healthier microbiome could potentially reduce the risk for an array of conditions impacted by chronic inflammation and immune dysfunction. We look forward to reporting the latest findings and what they mean for your health.

If you are interested in joining a study, you can use ClinicalConnection.com to search clinical trials near you and learn more about what is available.

You can also sign up now to receive alerts for when clinical trials begin recruiting near you.


  • Bae, J. H., Choi, J. Y., Park, Y. S., Lee, H. G., Jeong, Y. J., & Kim, J. F. (2019). Dietary bog bilberry and probiotic fermented milk products improve skin health by altering gut microbiota in healthy young women: A randomized double-blind placebo-controlled study. Nutrients, 11(5), Article 1055.
  • Gua, W., Tan, Y., Zhu, Z., Qin, G., Zhang, L., Zheng, J., & Ren, J. (2020). Mediterranean diet: Impact on gut microbiota-associated diseases. Food Quality and Safety, 4(4), 233–244.
  • Gueniche, A., Philippe, D., Bastien, P., Martin, R., David-Briand, E., Balea, T., Breton, L. (2019). Randomised trial: Probiotics (Lactobacillus paracasei CNCM I-5220 and Lactobacillus rhamnosus CNCM I-3690) vs. placebo for prevention of atopic dermatitis in children. Beneficial Microbes, 10(5), 581–592.
  • Pakdaman, M. N., Udani, J. K., Molina, J. P., & Shahani, M. (2016). The effects of the DDS-1 strain of Lactobacillus on symptomatic relief for lactose intolerance: a randomized, double-blind, placebo-controlled, crossover clinical trial. Nutrition Journal, 15, Article 56.
  • Pu, F., Guo, Y., Li, M., Zhu, H., Wang, S., Shen, X., & Ren, F. (2017). Yogurt supplemented with probiotics improves respiratory and gastrointestinal symptoms of acute respiratory infection in elderly: A randomized controlled open-label trial. Clinical Interventions in Aging, 12, 1847–1858.
  • Shaaban, S. Y., El Gendy, Y. G., Mehanna, N. S., El-Senousy, W. M., El-Feki, H. S., Saad, K., & El-Asheer, O. M. (2018). The role of probiotics in children with autism spectrum disorder: A prospective, open-label study. Nutritional Neuroscience, 21(9), 676-681.
  • Slavin, J. L. (2013). Fiber and prebiotics: Mechanisms and health benefits. Nutrients, 5(4), 1417-1435.
  • Steenbergen, L., Sellaro, R., van Hemert, S., Bosch, J. A., & Colzato, L. S. (2015). A randomized controlled trial to test the effect of multispecies probiotics on cognitive reactivity to sad mood. Brain, Behavior, and Immunity, 48, 258–264.
  • Vieira, A., Pagovich, O. E., & Kassam, Z. (2021). Fecal microbiota transplantation for the treatment of inflammatory bowel disease. Gastroenterology & Hepatology, 17(7), 402–412.