Scientific literature and the media have been inundated with research about probiotics and prebiotics and how they play a tremendous role in the digestive health of the host. What are previous research and more recent science saying about probiotics and prebiotics for organ and tissue health outside of the gastrointestinal (GI) tract? 

The Various Ways Pre- and Probiotics Benefit the Host

In previous posts, we have discussed the various functions probiotics have on human health, and the plethora of conditions these tiny microbes may help benefit from. In addition to improving IBS symptoms, probiotics may help improve the behavioral symptoms associated with inflammatory diseases, such as symptoms of fatigue, alterations in mood, and social withdrawal that is common among patients with chronic autoimmune diseases such as rheumatoid arthritis and inflammatory bowel diseases, by altering the communication between the immune system and the brain. Probiotics accompanied with fish oil during pregnancy and infancy has been shown to reduce the risk of atopic diseases such as eczema and food allergies. Probiotics, specifically from the Lactobacillus and Bifidobacterium genus, were shown to reduce liver fat and improve liver enzyme markers, a benefit for patients suffering from non-alcoholic fatty liver disease (NAFLD) and/or nonalcoholic steatohepatitis (NASH). In the case of obesity and metabolic syndrome, a review showed that prebiotic fibers and specific strains of probiotics improved the diversity of the GI microbiome, which is associated with improved insulin resistance and brown fat activation supporting patients with obesity and other metabolic syndrome parameters.

Probiotics & Respiratory Health

A recent review published in late 2019 suggested that prebiotics and probiotic intake may help prevent urinary tract and respiratory tract infections as well as their severity and duration. A double-blind randomized, placebo-controlled trial published in Nature studied the effects of probiotic supplementation in children with asthma. The researchers found that the children who received both Lactobacillus strains had much lower immunoglobulin E (IgE) levels and an increase in peak expiratory flow rates, as well as lower asthma severity scores, demonstrating the beneficial effects probiotics have on immune system health.

Probiotics & Autism Spectrum Disorder (ASD)

According to a recent randomized controlled trial in Frontiers in Neurology, the most common non-neurological manifestations in children with ASD are negative symptoms of the GI tract, such as diarrhea and constipation, and that multiple studies show the GI microbiome of children on the autism spectrum is much different than the intestinal microbiota of “neurotypical” children.

In the study, 37 children with ASD were provided 4 weeks of applied behavioral analysis (ABA) training along with 6 grams per day of probiotic supplements containing 6 strains of bacteria at 1 billion CFU per gram, and 28 other ASD children were randomly selected as controls and treated with ABA training alone. After 4 weeks, the Autism Treatment Evaluation Checklist (ASD-related symptoms) and GI scores (frequency of diarrhea) decreased more in the treated ASD group compared to the controls. 

A systematic review examining the role that prebiotics and probiotics play in autism spectrum disorder found prebiotics improved GI symptoms, and that prebiotics in combination with gluten and casein-free diet, significantly reduced anti-sociability scores. However, according to the review, there was no evidence showing statistical significance showing probiotics to alleviate GI or behavioral symptoms.

Further research is needed to elucidate whether probiotic supplementation improves the common undesired symptoms associated with ASD, but it is well-known in the science that the health of the GI tract significantly affects the health of the brain and vice versa.