Prebiotics + Probiotics: Do They Really Work for Gut Health?

Prebiotics and probiotics have been trending for a while now, but lately they’re getting even more attention — and showing up in more and more products, from packaged foods (pizza crust!) to topical skin-care products. It’s no surprise consumers are interested: As scientists learn more about the trillions of bacteria that inhabit our bodies and the role they play in our health, some have touted beneficial bugs as a cure-all for digestive distress and other health problems.

But there are still many unknowns among researchers, and a lot of questions and confusion among the rest of us about what prebiotics and probiotics are, and what exactly they can and can’t do, says Bill Rawls, M.D., medical director of Vital Plan. Here, he answers some of the questions he hears most often.

What’s the difference between prebiotics and probiotics?

“Prebiotics are types of fiber, such as inulin, that are known to promote the growth of healthy microflora in the gut,” Dr. Rawls says. In other words, prebiotics feed the good bacteria already living in your gut, which allows them to multiply, thrive, and better do their job of keeping you healthy.

Probiotics, on the other hand, are actual strains of friendly bacteria or yeast that populate your gut. Ideally, probiotics maintain or restore a healthy balance of microflora, either by keeping bad bacteria in check or giving a hand to the good bacteria so they can function and flourish.

What are the best sources of both?

For prebiotics, the best sources are vegetables, hands down, Dr. Rawls says. Certain veggies such as sunchokes, mushrooms, garlic, artichokes, dandelion leaves, onions, and chicory contain high amounts of inulin, but you needn’t be overly selective.

“More than anything else, eating a range of vegetables will cultivate the growth of normal bacteria,” Dr. Rawls says. “Because it’s not just about feeding the good bacteria: All vegetable fiber helps ensure normal digestion and that you’re evacuating the gut properly and regularly, which prevents the buildup of harmful bacteria.”

As for probiotics, fermented foods such as sauerkraut, kimchi, kombucha, kefir, and yogurt are naturally rich sources of live and active cultures (as well as digestive enzymes, which may be equally important for normal digestion). “Humans have eaten lots of different kinds of fermented foods throughout our history, for many thousands of years,” says Dr. Rawls. “That’s where the original idea for probiotic supplements came from.”

Research also suggests real-food sources of probiotics may be more effective than probiotic supplements at maintaining a diverse and healthy gut microbiome, the collection of microbes that inhabit your digestive tract. That could be due to the bacteria themselves, or the fact that the foods also contain a plethora of other healthy nutrients, including prebiotics, Dr. Rawls says.

Can prebiotics and probiotics improve digestive symptoms?

Prebiotics do contribute to a happy, symptom-free gut in the sense that they serve as fuel for the good microbes that help keep the digestive process humming. So while on their own they don’t do much, you absolutely need prebiotics for gut microbiome support and healthy digestion. Natural foods are by far the best source — supplements aren’t necessary if you’re eating a healthy, balanced, and veggie-rich diet.

As for probiotics’ ability to improve digestive symptoms, the answer is possibly. Probiotic capsules seem to help most when they’re used short-term for acute GI upset (diarrhea, stomach cramps) from eating contaminated food, like a batch of chicken salad that sat out for too long, for example, Dr. Rawls says. They may also help protect your microflora while taking antibiotics, which kill off good bacteria along with the bad, or if you contract C. difficile, a dangerous bacterial infection that causes diarrhea and inflammation of the gut.

“Most probiotic supplements contain bacterial strains of lactobacilli or bifidobacteria, or a favorable yeast called saccharomyces boulardii,” Dr. Rawls says. “Those are the ones that seem to show the most benefit.”

As for other digestive conditions, it’s hit or miss, he says. “The gut contains 20,000-plus strains of bacteria, and bacterial counts in the trillions. A probiotic supplement may be just a drop in the bucket, so getting an effect can be really hard.”

Further complicating things is that the mix of bacteria in people’s guts varies widely — in fact, it’s probably unique to you, like a fingerprint. What’s more, your microbiome can change based on your diet or lifestyle, or due to illness, so what might work for one person with a certain condition or symptom might not won’t work for another, Dr. Rawls says.

In addition, while different brands may use the same species of bacteria (lactobacillus, for example), they usually contain slightly different strains. So unless human studies on that one specific strain or bacteria blend shows a benefit on your particular health concern, it’s difficult to know for sure whether it will help you.

For all those reasons, published research is also mixed. Some is promising; for example, one meta-analysis of 15 studies published in the World Journal of Gastroenterology reported that probiotic supplements reduced pain and symptom severity in those with irritable bowel syndrome compared with placebo.

But other research, especially in healthy adults, shows little benefit from taking probiotics. And in fact, it may even introduce new symptoms: One small study of 30 subjects, published in the journal Clinical and Translational Gastroenterology, showed that taking a lot of probiotics can result in symptoms like brain fog and bloating in those using them for GI complaints.

Still, many experts tend to agree that the supplements, when taken in moderate doses, pose little risk. “I think it’s fine if someone wants to try taking probiotics; the potential for harm is low,” Dr. Rawls says. “Some people — maybe 15 to 20 percent of folks – may even gain benefit from them long-term.”

The newest trend in probiotics is customized formulations that are said to be based on your unique microbiome needs. Companies develop them after testing your stool sample for different microbes, and then selecting probiotics they say you lack in your gut. “While it may be a step in the right direction, the science and technology have a long way to go before this is a viable option,” says Dr. Rawls.

If you want to try supplements, he suggests taking them daily for at least three months and keeping a journal to see if you notice any improvements. If you won’t remember to take them daily, however, don’t even bother. Because the strains of bacteria in supplements are not the same ones already living in your gut, it takes a few days for them to populate and build up in your gut, and then you must continue to deliver them via supplements to maintain any activity.

What are some alternatives to probiotics for microbiome balance?

Step one is eating a mostly plant-based diet that includes plenty of fermented foods. Getting plenty of sleep and exercise and keeping stress in check are also key, as too little sleep and activity and too much angst contribute to overgrowth of bad bacteria.

Beyond that, Dr. Rawls says herbs and botanicals are more reliably effective and beneficial than probiotic supplements in the long-term. A few to key ones to reach for:

• Chlorella, a type of green algae, is thought to be one of the most nutrient-dense foods available. It contains chlorella growth factor (CGF), a complex of proteins, vitamins, and sugars that works with fiber in the GI tract to promote the growth of healthy intestinal flora. It also contains chlorophyll, a potent antioxidant that binds to toxins and helps remove them from the body. “Chlorella is known for detoxification, but I’ve found that it does wonders for promoting normal GI function,” Dr. Rawls says.
• Berberine, a compound found in several bitter herbs and other plants that’s well known for helping to balance the gut microflora. It’s been used for centuries to address intestinal disorders and digestive problems. “Berberine works very nicely because it stays predominantly in the GI tract, isn’t absorbed, and it’s active against gut pathogens,” Dr. Rawls says. That helps tip the scales toward healthy bacteria, keeping the bad guys from taking over.
• Andrographis is likewise known to help support a healthy microbiome, plus it offers immune system-supporting capabilities. Native to India, andrographis can help promote good bacteria in the gut for better total balance, Dr. Rawls says.

The bottom line: Keeping your gut microbiome balanced is vital for maintaining healthy digestion, promoting sleep and immune strength, and more – and natural approaches are the best way to achieve that balance, says Dr. Rawls. Feel free to give probiotic supplements a try if you like, but be sure to track your progress to make sure it’s worth the money. And know that supplementing with the right herbs and botanicals, along with eating plenty of natural sources of both prebiotics and probiotics, will likely deliver the results you seek much more quickly.