In people with compromised immune systems, including those with HIV, AIDS, and several other conditions, probiotics can lead to dangerous infections If you have a medical condition, consult your healthcare provider before taking a probiotic supplement.

Probiotic supplements may cause digestive symptoms, which should subside within a few days. They may also be dangerous for people with certain medical conditions.

Science has made tremendous strides in the past two decades toward understanding the roles that probiotics play in human health and disease.

Despite widespread studies, researchers are still working on identifying all the individual microbial species that live in your gut.

Identifying them is crucial to understanding how they function in human health. For example, researchers in reported identifying nearly 2, previously unknown gut bacterial species.

This was a major step toward categorizing the microbes living in the human gut After identifying the microorganisms, the next challenge facing researchers is to associate the various species, subspecies, and strains of microbes with their effects on human health — and this is where things get tricky Though thousands of studies have assessed the health benefits of probiotics for many clinical conditions, the results often contradict each other 79 , One reason for this is that methods for processing and analyzing probiotics data are not consistent around the world.

This leads to conflicting research analyses of published data The standardization of probiotics research is challenging because the human body contains a large and diverse set of microorganisms, which varies among countries — and even among individuals in the same country.

Plus, the bacterial strains themselves are constantly evolving, as are the health and environments of their human hosts.

Probiotics researchers face the task of classifying what might be trillions of ever-changing organisms in varied and evolving environments. Scientists must standardize a mountain of sometimes conflicting evidence from thousands of studies, and then translate that evidence into clear recommendations for therapeutic probiotic use Researchers are challenged with identifying all the microbiota in the vast and changing microbiome of the human gut.

They also need to establish a system for standardizing research results to develop clear therapeutic recommendations for probiotic uses. Maintaining a healthy gut is about more than taking a probiotic supplement. Day-to-day diet and exercise are just as important, as many lifestyle factors affect your gut bacteria.

However, probiotic supplements may offer a wide range of benefits with few side effects. If so, you might want to consult the World Gastroenterology Organization Global Guidelines. It lists probiotics, conditions, and recommended dosages. Caution is always advised when starting with probiotics.

Be sure to use a reputable product, start slowly, and get good advice from a trusted healthcare practitioner. Our experts continually monitor the health and wellness space, and we update our articles when new information becomes available.

VIEW ALL HISTORY. How long does it take for probiotics to work? What to know about probiotics and gut health. Find out about the probiotic Lactobacillus helveticus, and how it might help your digestion and general health.

This article examines probiotics' effects on weight loss. Several studies suggest that they can help you lose weight and belly fat. Lactobacillus acidophilus is a probiotic bacteria found in your digestive system. Here are 9 ways that Lactobacillus acidophilus can improve your….

Yogurt is typically a healthy choice, offering benefits for heart health, weight management, and more. Here are 6 yogurt benefits for health. Probiotics can improve your health. Learn how taking probiotics can benefit weight loss, heart health, digestion, immune function and more.

A Quiz for Teens Are You a Workaholic? How Well Do You Sleep? Health Conditions Discover Plan Connect. Medically reviewed by Grant Tinsley, Ph. Share on Pinterest Stocksy. What are probiotics?

Importance of microorganisms for your gut. Impact on digestive health. Impact on weight loss. The rise of psychobiotics. Other health benefits. COVID and probiotics. Safety and side effects. Challenges facing researchers.

The bottom line. How we vet brands and products Healthline only shows you brands and products that we stand behind. Our team thoroughly researches and evaluates the recommendations we make on our site.

To establish that the product manufacturers addressed safety and efficacy standards, we: Evaluate ingredients and composition: Do they have the potential to cause harm? Fact-check all health claims: Do they align with the current body of scientific evidence?

Assess the brand: Does it operate with integrity and adhere to industry best practices? We do the research so you can find trusted products for your health and wellness. Read more about our vetting process. Was this helpful? Share on Pinterest.

A quick look at the best probiotic supplements. What are CFUs? How we chose the best probiotic supplements. A comparison of the best probiotic supplements. What are probiotics? What are the benefits of taking probiotics?

How to choose the best probiotic supplement for you. Do you need a probiotic supplement? When to talk with a doctor. Frequently asked questions.

What is the most effective form of probiotic? What is the most effective probiotic supplement? Is it OK to take a probiotic every day? What probiotic do gynecologists recommend? The bottom line.

How we reviewed this article: Sources. Healthline has strict sourcing guidelines and relies on peer-reviewed studies, academic research institutions, and medical associations.

We avoid using tertiary references. You can learn more about how we ensure our content is accurate and current by reading our editorial policy.

Jan 23, Written By Ellen Landes, MS, RDN, CPT, Jillian Kubala MS, RD. Jan 11, Medically Reviewed By Imashi Fernando, MS, RDN, CDCES. Share this article. Read this next. By Anne Danahy, MS, RDN. By Mary Jane Brown, PhD, RD UK. After speaking with their pediatrician, consider one of these 7… READ MORE.

How Do You Use Lactobacillus bulgaricus? For example, there's no evidence to suggest that probiotics can help treat eczema.

But for most people, probiotics appear to be safe. If you want to try them, and you have a healthy immune system, they shouldn't cause any unpleasant side effects. If you're considering trying probiotics, there are a few issues you need to be aware of.

Probiotics are generally classed as food rather than medicine, which means they don't go through the rigorous testing medicines do. Because of the way probiotics are regulated, we can't always be sure that:. There are many different types of probiotics that may have different effects on the body, and little is known about which types are best.

Therefore, many scientists believe that your gut bacteria are important in determining body weight 41 , While more research is needed, some probiotic strains appear to aid weight loss Nevertheless, researchers advise caution in rushing to this conclusion, noting that there are still many unknowns.

These unknowns include 44 :. In one study, people with central obesity, which is characterized by excess belly fat , took the probiotic Lactobacillus gasseri daily.

Participants lost an average of approximately 8. Evidence also suggests that Lactobacillus rhamnosus and Bifidobacterium lactis can aid weight loss and help prevent obesity — though more research is needed Though more research is necessary, some evidence suggests that certain probiotic strains can aid weight loss.

In the past decade, research has shown that the gut and brain are connected in a system called the gut-brain axis. Some research shows that certain microbes in the gut can affect your brain via this axis in both health and disease.

Which microbes these are and how they interact with the brain is the subject of much current research Some researchers suggest that, for some people, supplementing with certain strains of probiotics may be preferable to taking psychotropic drugs to cope with the mental stress, loneliness, and grief accompanying the current COVID pandemic In addition to their potential effects on weight loss, digestion, and neurological disorders, probiotics may improve heart health, immune function, and symptoms of depression and anxiety.

Some researchers propose that improving the gut microbiome via probiotic supplementation and diet may be a strategy to fight and treat an infection with the novel coronavirus SARS-CoV This infection can cause COVID, which stands for coronavirus disease This is believed to be the main cause of deteriorating health and even death Also, people with COVID have reported gastrointestinal symptoms, such as diarrhea, nausea, vomiting, abdominal pain, and loss of appetite Some researchers theorize that probiotics could help prevent the coronavirus by blocking the angiotensin-converting enzyme ACE receptor where the SARS-CoV-2 pathogen enters the body to invade gastrointestinal cells Imbalances of the intestinal flora are known to be related to lung diseases and respiratory tract infections.

Researchers suggest that correcting those imbalances may promote optimum lung health, which might help guard against pathogens like SARS-CoV-2 68 , Other research suggests that probiotic supplementation may promote antiviral activity in general to improve immune, pulmonary, and anti-inflammatory response that might help clear the SARS-CoV-2 infection 70 , All these hypotheses are at the theoretical stage.

Researchers say further studies are needed to confirm them. One study advises caution, suggesting that not all probiotic strains will exert the same effects. It questions whether probiotic supplementation can alter the content of the gut microbiome enough to combat COVID Some current research proposes that improving the gut microbiome through probiotic supplementation and diet may help treat the SARS-CoV-2 infection that causes COVID Research is preliminary, and much more data and clinical trials are needed.

Probiotics are generally well tolerated and considered safe for most people. However, regulations differ among probiotics, so you must be cautious when choosing a product.

As you face the large selection of probiotics now available, you may feel overwhelmed. The choice can be difficult. In the United States, probiotics are generally sold as food ingredients, drugs, or dietary supplements. While the Food and Drug Administration FDA regulates each of these in different ways, most foods and supplements do not require approval before marketing Regulations on probiotics vary greatly around the world, so ordering online from other countries is risky.

Unregulated food items, cosmetics, and supplements are easy to find abroad, but their safety is unconfirmed. Looking for companies that follow best practices, such as third-party testing, can help you find high quality supplements.

The best choice is to run your choice by your healthcare provider or ask for suggestions. They may be able to recommend products they know to be safe and effective. In the first few days of taking a probiotic supplement, you may experience side effects related to digestion, such as gas and mild abdominal discomfort In people with compromised immune systems, including those with HIV, AIDS, and several other conditions, probiotics can lead to dangerous infections If you have a medical condition, consult your healthcare provider before taking a probiotic supplement.

Probiotic supplements may cause digestive symptoms, which should subside within a few days. They may also be dangerous for people with certain medical conditions. Science has made tremendous strides in the past two decades toward understanding the roles that probiotics play in human health and disease.

Despite widespread studies, researchers are still working on identifying all the individual microbial species that live in your gut. Identifying them is crucial to understanding how they function in human health.

For example, researchers in reported identifying nearly 2, previously unknown gut bacterial species. This was a major step toward categorizing the microbes living in the human gut After identifying the microorganisms, the next challenge facing researchers is to associate the various species, subspecies, and strains of microbes with their effects on human health — and this is where things get tricky Though thousands of studies have assessed the health benefits of probiotics for many clinical conditions, the results often contradict each other 79 , One reason for this is that methods for processing and analyzing probiotics data are not consistent around the world.

This leads to conflicting research analyses of published data The standardization of probiotics research is challenging because the human body contains a large and diverse set of microorganisms, which varies among countries — and even among individuals in the same country.

Plus, the bacterial strains themselves are constantly evolving, as are the health and environments of their human hosts. Studies have shown that a healthy diet and physical activity have separate, positive benefits on our overall wellness.

Lisa Hayes, M. Skip to main content. Posted By. Family Medicine, Prenatal Care, Primary Care. Recent Posts.

Speaking of Health. Topics in this Post. What are probiotics? Where are probiotics found? Probiotics can be found in multiple forms. Bacteria-fermented foods are good sources of probiotics, including: Active-culture yogurts Cheese Kefir Kimchi Kombucha Sauerkraut Probiotics also come in pill form with a variety of different strains or types, including acidophilus, lactobacillus or formulations targeted for different health benefits, such as gastrointestinal health or women's health.

If you take even just a few minutes to scroll through the GutTok hashtag on the app, you'll see dozens and dozens of videos discussing the health issues a bad gut can cause like increased acne and inflammation, and even more of them touting the benefits of paying special attention to, and healing, your gut like a strong immune system and clear skin.

Probiotics are "beneficial bacteria that keep your gut microbiome healthy," according to Daryl Gioffre , a certified nutritionist and gut health expert. Studies show that probiotics produce substances that activate the immune system and "prevent pathogens from taking hold and creating major disease," according to Harvard Health Publishing.

Probiotics may also lower the number of colds you have in a year, the health hub notes. While probiotics can be found in several foods, Gioffre believes that "supplementation of probiotics has become necessary" because we aren't getting as many probiotics through our diets as our ancestors have in the past.

Here are the most important facts you should know about probiotics and how to get more of them in your system.

Harvard Health Publishing also recommends some dairy products like yogurt, especially Greek yogurt, and kefir. When it comes to probiotic supplements, Gioffre suggests taking different types of probiotics and ideally changing the type every three months.

There are two main types of probiotic supplements that Gioffre recommends: spore-based and terrain-based. And the reason is that the digestive system is a harsh terrain. When you take this probiotic supplement, it's got to go down through the acid in your stomach," he says. Once a spore-based probiotic reaches your gut, its shell opens up and attaches to the gut wall to strengthen the microbiome.

Another advantage of spore-based probiotics is that they "can actually get rid of some of the inflammatory bacteria that reside in the gut," he says.

Terrain-based probiotics have their benefits as well because they typically have "a lot more of the healthy probiotics that a spore-based probiotic won't have," Gioffre says.

Northern Europeans consume a lot of these beneficial microorganisms, called probiotics from pro and biota , meaning "for life" , because of their tradition of eating foods fermented with bacteria, such as yogurt. Probiotic-laced beverages are also big business in Japan.

Some digestive disease specialists are recommending probiotic supplements for disorders that frustrate conventional medicine, such as irritable bowel syndrome. Since the mids, clinical studies suggest that probiotic therapy can help treat several gastrointestinal ills, delay the development of allergies in children, and treat and prevent vaginal and urinary infections in women.

To continue reading this article, you must log in. Subscribe to Harvard Health Online for immediate access to health news and information from Harvard Medical School. Already a member? Login ». As a service to our readers, Harvard Health Publishing provides access to our library of archived content.

Please note the date of last review or update on all articles. No content on this site, regardless of date, should ever be used as a substitute for direct medical advice from your doctor or other qualified clinician.

Thanks for visiting. Don't miss your FREE gift. The Best Diets for Cognitive Fitness , is yours absolutely FREE when you sign up to receive Health Alerts from Harvard Medical School. Sign up to get tips for living a healthy lifestyle, with ways to fight inflammation and improve cognitive health , plus the latest advances in preventative medicine, diet and exercise , pain relief, blood pressure and cholesterol management, and more.

Get helpful tips and guidance for everything from fighting inflammation to finding the best diets for weight loss from exercises to build a stronger core to advice on treating cataracts. PLUS, the latest news on medical advances and breakthroughs from Harvard Medical School experts.

Sign up now and get a FREE copy of the Best Diets for Cognitive Fitness. Stay on top of latest health news from Harvard Medical School.

Recent Blog Articles. Flowers, chocolates, organ donation — are you in? What is a tongue-tie? What parents need to know. Another advantage of spore-based probiotics is that they "can actually get rid of some of the inflammatory bacteria that reside in the gut," he says.

Terrain-based probiotics have their benefits as well because they typically have "a lot more of the healthy probiotics that a spore-based probiotic won't have," Gioffre says. The downside is that they struggle to survive while passing through the body on the way to your gut.

Yet, there are some important factors to consider when adding probiotic supplements to your diet like how often you should take them and possible side effects. And it really depends on the amount of bacteria in the probiotic for a conventional [terrain-based] strain.

When it comes to dosage, he says taking supplements with around 30 billion CFUs daily is a good rule of thumb.

But there is currently no recommended daily intake for probiotics, according to Harvard Health Publishing. The potential side effects of probiotics are also theoretical.

One hypothesis is "if someone has an immune system weakened by illness or medication, that person could get sick from probiotics," wrote Harvard Health Publishing. Additionally, people who plan to purchase probiotic supplements should proceed with caution as dietary supplements aren't closely regulated by the Food and Drug Administration.

Want to land your dream job in ? Take CNBC's new online course How to Ace Your Job Interview to learn what hiring managers are really looking for, body language techniques, what to say and not to say, and the best way to talk about pay. Skip Navigation.

Related Stories. Health and Wellness The 4 best changes you can make to your diet for a healthy brain. Health and Wellness Fiber is one of the most important, overlooked nutrients, doctor says.

Health and Wellness Not everyone needs to take multivitamins, doctor says—focus on this instead. Health and Wellness Don't waste money on biotin, collagen and more tips about supplements.

Health and Wellness Melatonin vs. magnesium: Which supplement is better for sleep? Colorful pills and capsules on green background.