There’s tons of hype around probiotics right now—different colored bottles and names fill the shelves at your local Walmart or Target. Probiotics are advertised everywhere—chances are you’ve seen a targeted ad naming some brand as “the ultimate probiotic.” So it’s easy to wonder what all the fuss is about, and also if you need to or should be taking them. Probiotic supplements have been marketed for targeting many areas like women's overall and vaginal health, sleep, digestive health, weight and appetite regulation, immunity, and even for improving your mood. It can seem pretty challenging to choose and you may be left wondering if they’ll really help. We’re here to clarify things, so let’s get to the “guts” of probiotics (we know, corny! But all puns aside, let’s chat probiotics). There are easily 30 trillion—maybe as many as 400 trillion—micro-organisms living in your gut, some of them beneficial. (Perspective: There are ten times more microbes in your gut than there are cells in your body. Mind. Blown.) Probiotics are supplements designed to improve that microbiome, made with strains of live “friendly” bacteria meant to cause a host of benefits. And they may well be a way to boost gut health for some people. But the science examining the benefits of taking probiotic supplements is still inconclusive, and for some people, probiotic supplements can cause problems. Despite grocery store and pharmacy shelves being filled with probiotics, prebiotics and now, even postbiotics (the stuff beneficial bacteria make), the jury’s still out on whether taking a probiotic can improve your health.

There isn’t yet enough evidence for scientists to conclusively say that probiotic supplements, functional foods like probiotic juices and bars, or even eating foods like yogurt, will improve your gut health. There also isn’t enough evidence showing that a diverse crowd of gut bacteria is healthier, nor is there enough evidence indicating that low diversity makes you unhealthy.

Science still can’t confirm that probiotics can improve other aspects of health, either. Even though there are known connections between mental and physical health and the gut, what’s not known is whether a probiotic supplement can help. For example, research shows that people with excess weight and obesity are more likely to have lower microbial diversity, which is associated with low-grade inflammation. Probiotics, prebiotics, and synbiotics (the combination of probiotics and prebiotics in one pill or product) may help treat obesity, but researchers say it’s still early and more work needs to be done. If it is possible that a probiotic can help people achieve a healthy weight, a doctor should guide the treatment instead of taking a DIY over-the-counter approach.

Next, there is a lot of science arguing how much of the bacteria in a probiotic even make it to your gut alive. The journey from the mouth to the colon is quite acidic, which poses a threat to live bacteria. When you see labels that proclaim having high CFU (colony forming units), it's not that more is better for your health, but that higher CFUs provide more of a chance that some of the bacteria is actually making it to your gut alive.

The “making it to your gut alive” part is problematic, too: There’s no guarantee that the probiotic bacteria will make it to the right part of your body—the large intestine, where the majority of your gut microbes live. In fact, one complication of taking probiotics is that it can lead to a condition called SIBO, or small intestinal bacterial overgrowth. Not fun.

Finally, not all probiotics are created equal. Probiotics are considered a dietary supplement, and unlike medications, dietary supplements don’t need to be approved by the FDA. (In fact, no probiotic is.) This means that manufacturers can sell probiotics simply with “claims” of safety and effectiveness. While there is some evidence that probiotics can improve health, what type and how much is still unclear.

All this scientific uncertainty may pop your probiotic bubble. (Give it time!) But most research about gut health is being done to understand the microbes in the gut and their role rather than on the impact probiotics can have. And when it comes to gut health, science shows the food you eat can have a beneficial impact.

First, let’s be clear about what kind of food we’re talking about: We don’t mean quart-size containers of yogurt every day. It’s true there are multiple foods that are nutrient-dense and rich in both probiotics and prebiotics. (Prebiotics are food for the probiotics.) However, getting probiotics from food sources alone can be a challenge. Fermented and cultured foods that inherently contain probiotics—kimchi, sauerkraut, yogurt, kefir, cultured buttermilk, miso, kombucha, and others—are natural products, so the bacteria count in them varies. So it’s hard to say how much you need.

Manufacturers of functional foods (food products designed to deliver health benefits, like probiotic juices, bars, or yogurt with designer strains) aren’t required to show a specific dose of a probiotic, so most of them don't. Again, the bacteria count varies, consumers typically don’t know the details, and it’s hard to say how much you need. There isn’t enough evidence to support claims that these really do improve your health.

So here’s what works: Eating plants. Basically, what’s good for you is good for your gut. Plants—including fruit, vegetables, and whole grains—provide prebiotics or food for the bacteria that are already residing in your microbiome. Remember that “eat the rainbow” veggie campaign? (No. Not Skittles.) Eating a wide variety of fruits and vegetables isn’t just about vitamins and minerals. People who ate 30 plants or more per week had more diverse gut bacteria than people who ate ten plants or fewer in a week, according to a study of the American Gut Project, a citizen science project started by researchers at the University of California-San Diego. (So, about that fruit and veggie rainbow: check out our articles on How to eat for a healthy gut and How fiber supports weight care for more info.)

At Found, our position is that the science around probiotic supplements is so new and inconclusive, we encourage eating a variety of whole foods to support gut health—a method of gut care that science backs. But if you still want to explore it, please consult your healthcare provider before starting any new supplement or medication routine, including probiotics, as they can do more harm than good to some people.