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Probiotics: The Complete Guide You've Been Waiting For

Marvin Singh, M.D.
October 12, 2018
Marvin Singh, M.D.
Integrative Gastroenterologist
By Marvin Singh, M.D.
Integrative Gastroenterologist
Marvin Singh, M.D. is an integrative gastroenterologist in San Diego, California. He is trained and board certified in internal medicine and gastroenterology/hepatology.
Image by Tatjana Zlatkovic
October 12, 2018

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.

The benefits of probiotics.

Generally speaking, there is a ton of literature supporting the use of probiotics for a wide variety of issues and conditions. If you enter "probiotics" in the search bar of PubMed, you get almost 20,000 search items, so you know that it's definitely a highly studied area of interest.

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.

Probiotics for women.

A 2013 study suggested that if pregnant women ate a probiotic yogurt 3(instead of regular yogurt) for nine weeks, there may be a benefit in preventing the development of insulin resistance. In older women, a more recent study this summer demonstrated that supplementation with Lactobacillus reuteri could be one method of preventing age-related bone loss4 and osteoporosis. In obese women who were postmenopausal, another recent study demonstrated that a broad-spectrum probiotic improved cardiometabolic parameters and leaky gut. The authors even suggested that probiotics could be used to prevent and treat cardiovascular disease5.

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.

Probiotics for immunity.

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.

Probiotics for diarrhea.

Another very common condition that probiotics can help with is diarrhea. The Journal of Clinical Gastroenterology published an article in 2015 stating that Lactobacillus rhamnosus GG and Saccharomyces boulardii can support a reduction in duration of diarrhea. Additionally, there is robust evidence that probiotics are beneficial in the treatment of gastroenteritis. There is also evidence that probiotics could be beneficial in antibiotic-associated diarrhea10.

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.

Probiotics for constipation.

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.

Probiotics for acne.

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.

Probiotics for eczema.

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 and brain health.

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.

Probiotics for longevity.

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?

Probiotics for animals.

Are humans the only animals that can benefit from probiotics? That's a great question—and the answer is no! In fact, certain probiotics have been successful in treating gastroenteritis, inflammatory bowel disease, and allergies in dogs and cats. It turns out that gut health is important for our pets24 just as it is for us. Probiotics have also been shown to expedite treatment and stabilization of the gut microbiome25 in dogs with infectious diarrhea. It seems that some of the key concepts that we need to keep in mind as humans should also be considered pertinent for our pets. This means not just giving your pet a probiotic but also feeding it a healthy and balanced diet.

Now, before you go out to the store or start filling your online shopping cart with bottles and bottles probiotics, let's just pause for one second. We've talked a lot about the benefits of probiotics. However, one of the underlying themes is that there may not be a great consensus on which probiotic to use for which condition in which person. Meaning, what is good for you might not be good for someone else. It may be important to understand what the status of your gut microbiome is before actually picking a probiotic.

For this reason, some people may find that probiotics make them feel unwell. You might get diarrhea, constipation, bloating, abdominal pain, stomach upset, stomach cramps, among other symptoms depending on what probiotic you choose at a particular time. Don't get discouraged if you are trying probiotics empirically (without any test results to help guide you) and they don't work like a charm. If you get some of the side effects, you should probably consult your health care provider and consider changing to another probiotic (or perhaps none at all for a period of time).

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.

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Marvin Singh, M.D. author page.
Marvin Singh, M.D.
Integrative Gastroenterologist

Marvin Singh, M.D is an Integrative Gastroenterologist in San Diego, California, and a Member of the Board and Diplomate of the American Board of Integrative Medicine. He is also trained and board certified in Internal Medicine and Gastroenterology/Hepatology. A graduate of Virginia Commonwealth University School of Medicine, Singh completed his residency training in Internal Medicine at the University of Michigan Health System followed by fellowship training in Gastroenterology at Scripps Clinic Torrey Pines. Singh was trained by Andrew Weil, M.D., a pioneer in the field of integrative medicine, at the Andrew Weil Center for Integrative Medicine.

Singh is currently the Director of Integrative Gastroenterology at the Susan Samueli Integrative Health Institute at UC Irvine. He is also currently a voluntary Assistant Clinical Professor at UCSD in the Department of Family Medicine and Public Health; prior to this, he has been a Clinical Assistant Professor at UCLA and an Assistant Professor of Medicine at Johns Hopkins University. Singh is a member of the American Academy of Anti-Aging Medicine, American College of Lifestyle Medicine, and many other societies. He is actively involved in the American Gastroenterological Association. He is one of the editors of the textbook of Integrative Gastroenterology, 2nd edition (a Weil Series text) and has written several book chapters and articles.

He is dedicated to guiding his clients toward optimal wellness every step of the way, using the most cutting edge technologies to design highly personalized precision based protocols. Towards this end, he founded Precisione Clinic and wrote the book Rescue Your Health to bring the best in preventive medicine to his clients.