Probiotics: The Complete Guide You've Been Waiting For

There's a lot of talk about probiotics these days. Are they really as good as they're made out to be? Are there any side effects that we should be aware of? Do they actually work? As an integrative gastroenterologist, I get asked a LOT of questions about probiotics. And so allow me to break it down for you.

But what are probiotics, exactly? Probiotics are live microorganisms that are taken for the purpose of conferring a health benefit. Things that affect probiotic function include our genetics, diet, and gut microbiome; there are also a variety of factors that can influence the function of the probiotic1 as well. These include the genetic composition of the organism and its gene expression and growth phase. Some of the ways it is thought that probiotics might help2 include inhibiting certain bacteria from sticking to the gut lining; beefing up the protective lining of the gut; influencing the immune system; releasing certain chemicals or metabolites; and regulating the nervous system of the gut and the whole body.

In addition to the gut microbiome, there is also a vaginal microbiome; Lactobacilli are the most dominant organisms in the vagina. We have seen taking certain probiotics that set up shop in the vaginal tract can be an important method of maintaining normal health in this region, and they can also prevent or treat certain infections6. Additionally, giving vaginal lactobacillus was found to be important in preventing recurrence of bacterial vaginosis7. Certainly, there is a lot of fascinating research with regards to probiotics and the role they play in women's health.

We know that there are over 100 trillion microorganisms making up the ecosystem of the gut. We also know that this ecosystem modulates the immune system, as 70 percent of our immune system is located in the gut. A recent review suggested that if probiotics were selected appropriately, there could be "potent" effects on the immune system8. Another article suggested that live probiotics or their metabolites (products that they make) could work with different immune cells and help them regulate the immune system and responses; they further suggested that probiotics could help maintain balance in the gut microbiome and modulate inflammation9.

In my practice as an integrative gastroenterologist, I often call on probiotics when people have diarrheal illnesses to help keep the balance in the gut microbiome. Certainly, there are considerations regarding which probiotic and how much to give depending on the diarrheal condition itself and what is going on with your health at the time, so I would certainly make sure you discuss the choice of probiotic with your health care provider.

Taking probiotics, in the appropriate circumstance, can certainly be a gut-supportive measure. Not only can they potentially help with diarrhea, but they can also help with constipation. A review and meta-analysis suggested that Bifidobacterium lactis could improve whole gut transit time11, stool frequency, and even stool consistency; however, we should note that the authors called for better randomized controlled trials before making any highly specific recommendations. The American Journal of Gastroenterology suggested that probiotics are effective treatments in irritable bowel syndrome (IBS)12 but also noted that the exact species and strains are not clear.

Many of you already know that antibiotics are sometimes prescribed for acne, but what you might not know is that probiotics might help with acne, too. An interesting study demonstrated that probiotics could be a therapeutic option for acne vulgaris by way of their anti-inflammatory effect. The study concluded that they could be a useful measure to include in treatment plans13. A fascinating review in the journal Frontiers in Microbiology this year described the gut-skin axis14 and how the gut microbiome communicates with the skin and is a regulator of this axis. If anyone was wondering whether or not the saying "All disease begins in the gut" was really true, this recent article certainly supports it.

This connection between the gut and the skin isn't just true for acne; it also applies to eczema. In children, L. rhamnosus has shown some efficacy in reducing signs and symptoms of eczema15, which is a very common inflammatory skin condition. One study suggested that L. rhamnosus HN001 might be especially beneficial in preventing eczema in children16. That said, a September 2018 systematic review suggested that Lactobacillus rhamnosus GG was not effective in reducing eczema17, and the authors of the study refuted the guidelines that suggest using probiotics to reduce the risk of eczema—unless specific strains are able to be indicated18.

Probiotics are also important for maintaining optimal brain health and function. One study demonstrated this when mice were given probiotics and researchers observed changes in the gut microbiome and changes in the brain19. We know that the blood-brain barrier can become dysfunctional, and when this happens there could be consequences such as neurological and neuropsychiatric conditions. In a recent article, scientists suggested that approaches that are targeted against leaky gut and dysfunction of the blood-brain barrier, such as probiotics containing Bifidobacteria and Lactobacilli20, should be considered as possible therapeutic intervention21.

Maybe even more fascinating than brain health, probiotics also have the potential to influence aging and longevity. While more research is certainly needed, we know that equilibrium and resilience of the gut microbiome is very important when considering health and aging in general. Scientists have discovered that five bacterial mutants can promote longevity by increasing the secretion of a polysaccharide22 called colanic acid. Colanic acid regulates a few things such as how the mitochondria (the energy powerhouses of our cells) work. Changes in the mitochondria can be induced by colanic acid and as a result of this have been linked to greater longevity23. Wouldn't it be awesome if one day we could create special probiotics that were made for our individual gut microbiomes that could promote healthy aging?

And remember, probiotics don't always have to be pills. Probiotic foods are a great source of improving the diversity of your gut microbiome. What foods are probiotics? Miso, kombucha, kefir, sauerkraut, pickles, kimchi, and natto are all great places to start. It takes a variety of strategies to create a robust ecosystem in your gut. Probiotics are certainly one of the key tools you have at your disposal.