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Join Gail Cresci, PhD, RD, as she discusses the link between diet and many medical conditions, the composition of the gut microbiome and ways to maintain a healthy balance, the role of inflammation, and much more.

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Understanding the Role of Diet on Medical Conditions and the Gut Microbiome

Podcast Transcript

Scott Steele: Butts & Guts, a Cleveland Clinic podcast exploring your digestive and surgical health from end to end.

Welcome to another episode of Butts & Guts. I'm your host, Scott Steele, the chairman of the Department of Colorectal Surgery here at the Cleveland Clinic in beautiful Cleveland, Ohio, and we're very pleased to have Dr. Gail Cresci here. Gail is the director of nutrition research in the Center for Human Nutrition. She's also the nutrition thread director for the Cleveland Clinic Lerner College of Medicine. Gail, welcome to Butts & Guts.

Gail Cresci: Thank you. My pleasure.

Scott Steele: We always like to start off with all of our guests by just give us a little bit of background about yourself, where you're from, where'd you train, how did it come to the point that you're here at the Cleveland Clinic?

Gail Cresci: Well, I'm originally from Cleveland, but after undergraduate, I joined military, and I did my training there to become a dietician. Then I served on active duty for six years, and my last duty assignment was in Georgia. I got out of the military there, and I went on faculty at the Medical College of Georgia where I worked in Department of Surgery as a nutrition support dietitian and educating residents, faculty. Then while I was there, my last couple of years, I got my PhD in biochemistry and molecular biology. At the same time I was finishing, I was being recruited to come here to Cleveland Clinic by the nutrition department to help lead nutrition research for Center for Human Nutrition, so I came here in 2010.

Scott Steele: I have to ask this, former military myself, were you at Eisenhower?

Gail Cresci: I was. Yeah.

Scott Steele: Fantastic. Well, we're glad that you're here at the Cleveland Clinic. Let's start real broad. Can you explain the relationship between diet and medical conditions?

Gail Cresci: Well, it's really interesting that more and more of that data is starting to come out, and we're now learning more about how just what we eat and how it affects chronic diseases. So many different aspects, like with inflammation, with... my area of research is looking at the gut microbiome. We know how diet is one of those environmental factors that really influences gut microbiome. In response to that, there's alterations in metabolic byproducts, which are now being linked with cardiovascular disease, diabetes, liver failure. That's one small aspect of how diet is being linked, but we know excessive amounts of simple sugars can contribute to longterm insulin resistance. It really depends on what medical condition you're talking about.

Scott Steele: We'll delve in a little of that a little bit later. But I have patients all the time that say, "I eat this food, and it really sets me off." Obviously, I'm a colorectal surgeon, so they might be talking about their bowels being constipated, or diarrhea, or it's just belly pain or bloating. This isn't what we're really talking about here though. What we're really talking about is diet and medical condition. Can diet be used as a way to help manage a medical condition or cause a medical condition on the other hand?

Gail Cresci: That's what research is now coming out and showing both of those. For instance, it could be that diet is linked with causing different medical conditions, not directly, but indirectly. If you think about obesity, so if you're overeating, and over time, you become obese, we know that obesity is linked with many other chronic medical conditions such as the diabetes, heart disease. Then by losing weight, and diet is one mechanism to help lose weight, there's reversal of some of that pathology. That's a way that diet is linked with causing it and then also with helping manage that condition.

Scott Steele: Yeah. One of the things that you said that's fascinating to me is you talked about inflammation and that potentially some of the foods that we eat can cause inflammation. What is this link?

Gail Cresci: That's another interesting factor. There's a lot of misconceptions out there. That's why it is challenging with nutrition as a means to manage medical conditions because if you go on to the Internet and you do a Google search, you can see like, "Oh, this is an inflammatory food," but there's no proof of that. There's no hardcore research to evaluate that. But as I mentioned, indirectly, there's ways that diet can be pro-inflammatory. That's more, again, along the lines of, where I'm most familiar with is regulating through the gut microbiome, and so shifts in the microbiome can lead to more pro-inflammatory, so when more pathogenic bacteria or opportunistic bacteria are there, then they're more apt to secrete more pro-inflammatory factors, and our body's a mechanism to regulate that is decreased, and so then this low grade inflammation can proceed.

Scott Steele: Gail, for the listeners out there that don't understand or really aren't familiar with this concept of microbiome, can you talk a little bit about that?

Gail Cresci: Yeah, so what I'm referring to are the trillions of bacteria that we know reside within our intestinal track. We've now for over a decade know that these bacteria are beneficial to us, the host, and they help not only metabolize some of the food like fiber that we can as the host digest. These bacteria have the metabolic machinery to digest and ferment these fibers, and in response to that, they generate beneficial byproducts that we know are anti-inflammatory and also immune modulatory. That's just one factor. We know that when, as an example, diet is not optimal, so let's say your diet's not rich in these fibers that the bacteria likes to eat, then if it's high in fat, high in sugar, the bacteria will shift in their composition to a less desirable composition. Then these bacteria take over, and instead of producing those beneficial metabolic byproducts, they produce things that aren't beneficial. That's where the inflammation can start to erupt.

Scott Steele: Should I be taking antibiotics ever, or do I avoid those, or how does that work?

Gail Cresci: Oh, my gosh. If you can ever avoid an antibiotic, you should because even just one course of antibiotics can cause disruption in your gut microbiome. Most people, if they're absolutely healthy, their microbiome will rebound and not have a lasting effect; however, there are those people, and I've had several patients myself, that may have just had one prophylactic dose of antibiotic for a dental procedure, and they just had a really bad reaction. They obviously were more susceptible and had Clostridium difficile, a pathogenic bacteria overgrowth, and having to have the negative side effects.

Scott Steele: I just want to be clear here on the podcast, obviously, we've had some other healthcare providers. We're not saying to avoid antibiotics altogether. We're saying if you don't have to have them, just to go out and take them, that can have some downward consequences that you need to be aware of, but if antibiotics are needed for you, then you should make sure that you go ahead and take them as your doctor recommends. But let's switch that now and talk a little bit about probiotics. Well, I mean, they're all the rage. I've seen probiotics as in they're a cure for everything or they don't work at all. You can go into any health food store, and you can see probiotics. You can turn on the television and see this type of brand of yogurt and that with activated cultures. What are probiotics, and what role do they play in all of this? Are they something that are good for you, or is it individualized, or how does this all come together?

Gail Cresci: Probiotics, by definition, are live active cultures that have shown to have proven some beneficial effect. The concern with that is that industry takes over in marketing, and so a lot of products like you're referring to in the grocery store, in the health food stores are using the language of probiotic, but they're not a true probiotic. In order to be a probiotic, there's strict definitions, and they should be a strain of bacteria that's isolated from a human. They should be able to survive the upper part of our intestinal track, not be destroyed by gastric acid and bile, and they should be able to reach our distal gut, our colon, and be able to colonize the intestine, secrete some beneficial byproduct, and then of course, they need to be safe for use, and then lastly, need to have clinically validated beneficial effects. Most probiotics on the market do not meet that criteria.

We also know that, and this really complicates it, is that the gut microbiome is different across the life cycle. There's also this discrepancy in data where you look at probiotics being used in children for antibiotic-associated diarrhea and shown a beneficial effect, but if you use that same strain in a geriatric population, we don't see any benefit. But we know now that the gut microbiome of infants is totally different from that of geriatric, so it makes sense that it may not be the right strain for the other population. That's where research is going and leading us.

But for the general consumer, I think what's really important is to make sure you're looking at a product that has a strain. The manufacturers don't have to put the strain on the product, but if there is a strain specificity to that product, the manufacturer will put the strain on there. If you see a strain listed on a product, then that's probably a good product because the manufacturer's making sure that you know that. Then you should only use that probiotic for what it's been demonstrated to have a beneficial effect.

For example, you can go in the grocery store and find a yogurt that may be labeled to help with immunity and then another yogurt that's labeled to help with bowel regularity because there are those, and they're strain-specific. But taking the immunity-based yogurt and trying to help your bowel irregularity, it's not going to work because, again, that strain specificity. That's where a lot of people get confused, and they say, "Just take a yogurt." Most yogurts are not probiotics because the starter culture to make yogurt is not probiotic. Yogurt's a good food. It's got lot of beneficial effects, but it does not necessarily have that probiotic effect.

Scott Steele: Something near and dear, I guess, to my heart as a colorectal surgeon, and speaking of this microbiome and diet, there's a lot of fad diets out there. Some of them use colon cleanses and things like that. Obviously, I would think that that may have a role or an impact on the microbiome. Can you speak to any one of these without getting into diet specific, but just kind of how this all fits together with these diets?

Gail Cresci: Yeah. It frightens me to hear about the colon cleanses because you're doing something that you really don't want to do is eliminate your entire microbiome and then not properly replace it back. When we do that in a medical way, like for instance, to do fecal microbiotic transplant for Clostridium difficile infection... but to just do it just because, "Oh, I want to be healthy and... " that's probably a very bad thing to do. It's better to just eat the foods that we know help to maintain a good healthy blend of bacteria in your gut. Those are down to the basics, just eating regular non-processed food, rich in fruits and vegetables, rich in different types of fibers. That's really what the gut microbiome wants to be fed.

Scott Steele: We're going to switch gears. One of the hats that you wear as I said in your introduction was your role at the Cleveland Clinic Lerner College of Medicine. I think that's very interesting because nutrition education in and of itself is widely variable in medical education training. Can you talk a little bit about the importance and the benefits of integrating nutrition education in a medical school training?

Gail Cresci: Yeah, we just had paper come out. That's so exciting because we're looking at these chronic diseases that are just rising in our society, and so future physicians need to be able to talk to their patient about diet because we're learning diet is a way to help manage many of these conditions, yet the medical school curriculum is lagging with proper training of physicians in how to talk about diet with their patients. There is some component of nutrition in medical school curriculum, but it's not linked with diet. Students learn about biochemical pathways. They learn about carbohydrate metabolism, protein metabolism, fatty acids, but they don't really get that link back that that's really what you're eating every day. It starts with your diet. Your diet's high in fat. This pathway's going to be more predominant versus another.

There's that whole aspect bringing that back to, well, what is diet? Then there's the aspect of, well, how do you talk to your patient about diet, and how do you know what is the right thing to advise your patient to eat? How are those different guidelines, how are they developed? Where's the literature that supports them into... so for future physicians to understand where dietary guidelines come from, what they are, how to talk to your patient... I have a good example. My mom, she'd probably be mad I'm telling this story today, but she told me the other day... she's elderly and has diabetes, or she was telling me she met with her primary care. My mom brought it up that her hemoglobin A1C was high. She said to the doctor, "What do you think about that? What should I do?" and the doctor said, "Eat less carbohydrates."

Well, what is a carbohydrate? What foods have carbohydrate? How much has less? What's the appropriate amount? None of that was discussed. It was just ended with "eat less carbohydrate." This is where the conversation needs to get a little bit richer, and then physicians need to know, you're limited with time that you can spend with your patient to go into this depth of information, who can you refer your patient to to continue that conversation with a dietician and then really support that patient interaction to go and work with the dietician. Patients really listen to their doctors. They look at their doctors as like their parent. They totally put their trust in them, so for the physician to understand the importance and to really support it and encourage it for the patient I think is also something that we talk about in the curriculum.

Scott Steele: What steps do you feel are currently being taken at medical schools that emphasize this nutrition training?

Gail Cresci: Each school is different on their approach because each school has a different dynamic on how their curriculum is set up, how it's developed, who the faculty is to teach at the particular school. Here at Lerner College, we have a five-year program, and so while we have standard courses that are organ-based driven, we also have threads. Threads are considered important enough topics throughout the whole course of medical school that they get their own topic area, and that content is weaved throughout the five years such as like immunology, physiology.

Well, just recently in the last two years, nutrition has become a thread, and so it was recognized by the steering committee that nutrition was so important that it needs to be included, were pertinent in all aspects of medical curriculum. Other schools don't have that kind of set up. They may have a standalone course in nutrition, but being able to integrate that and weave it so that it is an important component of other aspects of medical school and what the physicians are learning is really important.

Scott Steele: You have ultimate control over all of the nutrition education in the US or the world. What would be the goal or ideal scenario for nutrition education integration?

Gail Cresci: I think getting enough adequate time. That's always an issue. Then also being able to make sure that it's interdisciplinary. That's one of the things that we're doing here is that it's not just physicians. It's actually more, the dieticians are educating the students, but there is an interdisciplinary approach to it because that's how medical care is and that it's in all years of the medical school.

A lot of the schools, it's just in the first two years, but it's really becomes important when they're doing the clinical clerkships and they're actually working with the patients and seeing the patients. We've started to do that here. I've started a two-week elective, clinical nutrition elective, and the students are actually able to work with our nutrition staff and side by side with them and learning about the patient care with the nutrition focus, of course. I think that's important that it continues throughout all four years of, or five, of the medical school.

Scott Steele: Well, that's exciting stuff and we always like to wind up with our quick hitters with our guests. What's your favorite food being a dietician?

Gail Cresci: Vegetables. I'm not kidding. I love any type of vegetable.

Scott Steele: Are there any specific bad foods out there that we need to avoid?

Gail Cresci: Well, as a dietician, you're never supposed to say that food's a bad food, just all in moderation. But I think anything fried you should really try to stay away, or processed.

Scott Steele: Glad you didn't say ice cream. What's your favorite sport?

Gail Cresci: My favorite sport? Well, I do triathlon, so I like that sport.

Scott Steele: What's the last book that you've read?

Gail Cresci: I'm actually reading a book right now. It's about this woman who becomes this world-class runner. She started running later in life, and she uses running as a means to deal with their husband's cancer, et cetera. It's really exciting book.
Scott Steele: Then tell us something that you like about here in Cleveland.

Gail Cresci: Well, it's my hometown. I really love how Cleveland has this nice comradery. You just look at our sports teams, and so I like that, that nice feel of the Midwest.

Scott Steele: Well, that's awesome. For more information about Cleveland Clinic's Digestive Disease and Surgery Institute, to include nutrition, please visit That's To make an appointment with a Cleveland Clinic specialist, please call 216-444-7000. That's 216-444-7000. Gail, thanks so much for joining us on Butts & Guts.

Gail Cresci: Thank you.

Scott Steele: That wraps things up here at Cleveland Clinic. Until next time, thanks for listening to Butts & Guts.

Butts & Guts

Butts & Guts

A Cleveland Clinic podcast exploring your digestive and surgical health from end to end. You’ll learn how to have the best digestive health possible from your gall bladder to your liver and more from our host, Colorectal Surgery Chairman Scott Steele, MD.
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