We are inundated by advertisements telling us that probiotics — beneficial bacteria marketed in the form of pills, beverages, breakfast cereals, and countless other products — are the answer to everything from weight loss to digestive discomfort.

In fact, the global probiotics market is set to be valued at a staggering $7 billion by 2025. Does this industry have a place in medicine? The short answer is: We don’t know. There are so many questions about our microbiome and probiotics still unanswered by modern medicine.

To understand probiotics, we must go to the source: the microbiome. Your gut is inhabited by 40 trillion bacteria, viruses, fungi, and protozoans that collectively make your microbiome. Together, these organisms play a vital role in metabolism, gut wellness, and immune health.

With the help of the Human Microbiome Project, researchers have examined the relationship between our microbiome and anxiety, depression, mood disorders, obesity, cancer, diabetes, and chronic pulmonary diseases. However, this research is still in its infancy, and there are still many unanswered questions. Something physicians can agree on is that this diversity of organisms is necessary to keep the gut functioning well.

So, can we establish diversity by introducing probiotics into your gut? Depending on the quality and quantity of the organisms they contain, probiotic products can potentially modify good and bad bacteria populations, break down toxins made by bad bacteria, improve gut immune function, affect absorption of foods, and modify pain perception.

While the clinical trials behind probiotics have exploded over the years with improvements in technology, these studies are small and yield conflicting results. What makes the situation more complicated, explains Drexel gastroenterologist Neilanjan Nandi, is that one’s innate microbiota determines response to probiotics. In other words, one probiotic can have different effects in different individuals.

The American Journal of Gastroenterology synthesized all the studies on probiotics and identified certain medical situations where specific probiotics can play a role. This includes diarrhea after taking antibiotics, certain situations in ulcerative colitis, and mental confusion associated with liver failure. In all these cases, probiotic therapy is added to other treatments and always with the physician’s input.

Currently, there are two ways to add probiotics: supplements or food products.

The supplement industry is enormous and unregulated by the Food and Drug Administration. These formulations’ content can vary widely, so they may not confer promised benefits. The main issue is that probiotic supplements contain a few organisms, but we know that the key to a healthy microbiome is diversity.

Food products, in contrast, offer a wide variety of organisms. Fermented foods such as yogurt, pickles, kefir, and tempeh get the most attention for containing probiotics. What you may not know, however, is that fruits and vegetables also can be a good source of beneficial bacteria.

Researchers in Colorado who studied the surfaces of vegetables noticed a high diversity with as many as 161 different families of bacteria. Sprouts, spinach, and tomatoes took the lead. Most of this bacteria are harmless and beneficial. For this reason, physicians such as Nandi counsel their patients to follow a diet high in fresh produce to promote a diverse microbiota.

Unfortunately, our diets are high in sugars, fats, refined grains, and processed foods. Nandi explains that this highly processed diet actually causes a dramatic decrease in microbial diversity, and that this happens in two ways.

One, the high amounts of simple sugars lead to a boom in sugar-loving bacteria, which alters microbiome species composition. Two, processed foods contain emulsifying additives that are introduced to low-fat formulations to impart better taste, texture, and overall experience. Researchers in Georgia have replicated both changes in mice and found a sizable decrease in microbial diversity.

A recent study published in Nature explains that these alterations in gut microbiome lead to low-grade inflammation in the gut and such metabolic disorders as obesity and diabetes.

If the goal is to grow a healthy intestinal microbiome, favor food over supplements, and turn to a diet rich in fruits and vegetables and low in sugary, processed foods. “Let food be your medicine,” Nandi urges patients.

Keerthi Shah is board certified in internal medicine and a gastroenterology fellow at Temple University Hospital. Follow her on Twitter @DigestDoc and Instagram @digestivedoc.