an Interview with Danny Grannick

Today we are talking about oral health, and why am I talking about oral health? Because our oral microbiome and oral health directly impacts what’s going on in the rest of your body. This is easily seen during pregnancy. As an obstetrician, I would see it often that women would develop cavities for the first time when they got pregnant. I know that happened to me. Or they get gingivitis, swollen gums, or different diseases of the mouth. 

A lot of times that’s connected with nausea and vomiting in the first trimester of pregnancy and things like that. We’ve always been so reactionary in the past with just trying to manage the symptoms and treat the symptoms, but not really understanding, why is this happening. It turns out that it has a lot more to do with the bacteria living in your mouth, and the westernized diet that we call the SAD diet, the Standard American Diet, which is very high in processed sugars, grains, and things like that. 

My Guest in This Post is Danny Grannick 

Danny started an oral microbiome company called Bristle. They will test your oral microbiome and tell you if you have the wrong bacteria living in your mouth. I’m really excited about this because I see patients with hormonal issues, thyroid issues, chronic fatigue issues, and they inevitably have gut issues. Oftentimes, what’s living in our gut and in our intestines in our stomach, is impacting our health systemically. What impacts the bacteria in our gut affects the bacterial in our mouth. It’s all connected.

I’m so excited about the future of medicine because we’re finally getting to the root cause of issues and it’s microscopic. It’s tiny little microbes that you cannot see, but they are running the show. When you can get your microbiome in balance, then you can live in harmony with the bacteria, viruses, fungi, and everything that’s living in you. They actually keep you in harmony and balance.

On this podcast, we are going to talk about…

  • How your oral health is impacted by your oral microbiome.

  • What is the actual cause of cavities?

  • How our diets affect our oral health.

  • One thing that you can do to improve your oral microbiome.

  • Oral health during pregnancy and how it can impact our children’s oral health later in life.

About Danny Grannick

Danny Grannick is the CEO and co-founder of Bristle. He received his BA in biochemistry from the University of San Diego. After receiving his degree, Danny moved into a variety of commercial roles at Illumina where he focused on bringing genomic tent technologies and applications to existing and emerging markets. Danny was then recruited by Oxford Nanopore to lead sales and business development for Northern Carroll, California in strategic accounts. His passion is in bridging the gap between innovation and implementation. He has really pivoted and is going in a new direction.

Get more content by listening to the full interview on The Functional Gynecologist Podcast

Welcome Danny to the Functional Gynecologist

Danny: Thank you, it’s great to be here.

Tabatha: I’m really excited about this conversation because oral health affects women’s systemic health so much, and so many doctors don’t realize the impact. I love that you guys are bringing this to the masses so that we can start to understand this a little more. 

Tell me How Did You Even Get Into This?

Our whole team’s background is in the genomics industry. My own background was originally in biochemistry. I was doing a lot of research in the lab and found myself a lot more fascinated by the applications of my research than the experiments themselves. That was a bit of a wake-up call. It was just a really exciting time in the industry, sequencing was starting to be applied in some really incredible clinical areas like oncology and noninvasive prenatal testing. There are some really exciting advancements there. For us, it was really fortunate that the technology had advanced to the point where it was becoming cheaper to access. Coincidentally, Brian, one of our co-founders has had some issues with cavities his entire life. It was the combination of those two experiences that highlighted oral health as this relatively unmet area in healthcare. We knew we could take our genomics research and apply it to oral health.

Can You Tell Us About Bristle’s Oral Microbiome Test?

So let’s jump right into it then. Tell us about Bristle’s Oral Microbiome Testing. What are you testing in layman’s terms?

Danny: First let’s talk about what a microbiome is. A microbiome, in general, is a makeup of bacteria, fungi, and viruses that are related to a specific environment. There’s a lot of familiarity around the gut microbiome and the bacteria that live inside of our gut that help with the digestive process. We also have skin microbiomes. These are the bacteria that help protect and clean our skin. Women have a vaginal microbiome that is related to vaginal health. Just like all those areas, we have an ecosystem and microbiome that lives in our mouths and our saliva.

Just like every other microbiome, there are some microbes that live in there that are really beneficial to our health, help us fight off disease, and break down foods. There are some microbes that are harmful, disease-causing, or pathogenic. They can produce harmful byproducts that lead to infection and diseases like cavities, gum disease, and bad breath.

The Actual Cause of Cavities

A cavity is an easy example. There is a subset of bacteria that can reside in the oral cavity. Those bacteria consume carbohydrates or sugars, and they produce acid. If we have a lot of these bacteria present, or if we eat a high amount of sugar then those bacteria multiply and produce a lot of acids. The acid erodes the enamel and our teeth, eventually leading to tooth decay. That decay is exactly what your dentist is picking up in the X-ray when you go in for your appointment. That’s when you find out that you have a cavity.

Tabatha: I think that’s going to be surprising to some listeners that there are bacteria causing cavities. When you go to the dentist that’s not really talked about because we haven’t really understood what bacteria should be living in there necessarily, and what to do about the bad bacteria. So I love all this work that you’re doing. I think it’s so important. There’s been this huge push over the last 20 years to sterilize your mouth, to the point where you’re using mouthwash that burns and feels like it must be doing something? Is that the right answer?

Is Bacteria Killing Mouthwash the Answer?

Danny: I think it’s not the right answer. Just like every other part of our body, we want to maintain homeostasis, we want to maximize the good organisms and we want to eliminate what’s bad. There are a lot of different ways to do this. The idea around mouthwashes is an example of what has become a pattern in the way that we address disease and the way that we go about healthcare. It’s a reactive prescriptive approach. Instead, we need to address the root cause of the disease. Most forms of mouthwash are antimicrobial. While it may be effective in eradicating the disease-causing bacteria, it’s also wiping out everything that is beneficial to your health. When you wipe out everything, it’s great because you’re getting rid of the bad bacteria, but you’re also giving those harmful microbes a chance to potentially expand into new places because you don’t have those protective bacteria anymore. I think the oral care industry is particularly behind in developing new ways to really promote the growth of beneficial bacteria and selectively eradicate the harmful ones. We’ve been relying on the same kinds of products for decades.

Bacteria killing mouthwash is not the answer to a better oral microbiome

Tabatha: It’s the exact same mentality in the health care system. We just give antibiotics for everything, we wipe out your microbiome and, and we hope that the right stuff will grow back. Inevitably, it really doesn’t, because we’re not eating the right stuff. We’re not making the right choices. We’re not supporting that beneficial bacteria.

Is There a Link Between What’s Going on in Your Mouth and What’s Going on In Your Gut?

There were actually two studies that came out in the last month that produced some really exciting things. It’s a remnant of, of our health care system to think of our bodies as these completely distinct and independent components. Everything is really interconnected and dependent on each other. If you have issues in one part of your body, it’s not just isolated to that single part, it’s probably manifesting as other symptoms or conditions in other places.

Two studies came out, the first study connected distinct shifts in the oral microbiome with patients that were diagnosed with IBS and IBD and periodontal disease. The other study that came out connected the bacteria in your oral microbiome to some pathogenic microbes in the small intestine. These both show that there’s a linkage between oral disease or shifts in the oral microbiome and systemic diseases in other parts of the body.

Tabatha: I see that all the time. I have patients with bacteria showing up in their stool test that should never ever get there. It’s starting in the mouth, in the stomach, somehow not getting killed off, and it’s making its way all the way to the gut and out.

Danny: One of the most exciting discoveries in the past couple of years was the presence of the bacteria that causes gum disease in the brains of Alzheimer’s patients. They were able to find connections between proteins that those bacteria produce in the onset of Alzheimer’s. Three companies have formed around creating therapeutics targeting that protein. There’s this incredible connection. All of our systems are connected.

Tabatha: Wow, that is so crazy. You think of having elevated blood sugar as increasing your risk of Alzheimer’s and dementia, but just that there’s a connection between the bacteria that cause gum disease and alzheimers disease. It all makes so much sense. I feel like they’re running the show and we’re just inhabiting the body. But really, they own it, and they’re in control. It’s so important to make sure you have the right stuff living in all of your microbiomes. I heard this statistic, there’s more bacterial DNA in our bodies than human DNA. So really, they are running this show.

What are the most common patterns you’re seeing in oral microbiome testing associated with health or with disease? Are there good bacteria that we’re striving for, and certain ones that we know we need to kill off?

What Are The Good Bacteria That You Want And How Can We Encourage More?


We’ve identified a series of really beneficial bacteria that are present in the mouths of individuals that were diagnosed by a dentist as having a healthy mouth. We’re continuing to investigate behavioral changes and specific products that that people can use to increase the abundance of those bacteria. On the flip side, we’ve identified distinct bacteria that are associated with the onset of periodontal disease and cavities. Again, there are some very simple behavioral changes.

Changes You Can Make to Improve Your Oral Microbiome

Dietary changes

If you eat sugar do it all at once. That all-day sucker or random candy-eating throughout the day is hurting your teeth and causing the bad bacteria to multiply. Be aware of acidic foods. Brush 30 minutes after eating or drinking acidic things like coffee, tea, soda, fruit, or fruit juice. Also drink water in between sips of coffee, soda, etc. to raise the PH of your mouth. Eat vegetables that are high in fiber. They have been shown to stimulate saliva production and neutralize acid, both of which protect teeth from decay. They also tend to be high in vitamins A and C, which aid in rebuilding tooth enamel and helping gums heal quickly from wounds, respectively. Consume higher PH vegetables such as cruciferous veggies, dark leafy greens, and cucumber. These are especially good for your teeth and gums. They also have many other health benefits.

Chew Xylitol sweetened gum after meals. (Note: if you have dogs, be very careful to keep anything sweetened with Xylitol away from them. It is extremely toxic. A small amount can cause hypoglycemia, seizures, liver failure, and death.)

Hygiene changes

There are hygiene changes that people can make to reduce the onset of bad bacteria, as well as specific oral care products that can target them. We’re starting to see a very direct correlation between the reduction of the abundance of those bacteria between good oral hygiene and poor oral hygiene. We’ve heard this mantra from our dentist of brush and floss more, but there hasn’t been a ton of evidence behind why and it’s hard to really see the results of those efforts. That’s something that we’re starting to uncover in the test. It sounds obvious, but it’s really exciting to see.

Tabatha: Obviously, if brushing more and using more microbe killers in your mouth was all that was needed, we’d have made some headway by now. Right? It seems like oral health is getting worse and worse. Are there any particular products that you would just recommend in general that women avoid or use?

Are There Any Products That You Recommend Women Avoid or Use?

It really depends on the specific makeup of bacteria in your mouth. There are certain products that are going to be more effective against certain oral microbiome profiles than others. Especially with pregnant women, it’s important to keep in mind that the dietary changes that you make during pregnancy and some other factors can increase your risk for oral disease. It doesn’t mean that you have to cut out sugar completely for the entirety of your pregnancy, but it does mean that maybe you should be a bit more mindful about the symptoms that are popping up and maybe be a bit more mindful about the cadence of hygiene that you’re using.

In terms of specific oral care products, one of the most effective oral care products that we’re really excited to continue investigating is xylitol. It’s a form of sugar that is unable to be digested by the pathogenic bacteria that cause infection and produce acid as a byproduct. When you use xylitol instead of traditional sugar, you’re tricking the bacteria into thinking that they’re getting food. They start becoming more active and burning a lot of energy, but because they can’t process the xylitol, they end up essentially starving and dying off. It’s been a very effective ingredient in a lot of chewing gums, toothpaste, and mouthwash, I would definitely recommend looking for products with that ingredient in there.

Tabatha: Oh, that’s so interesting. Okay, that’s really cool. So should everybody get their oral microbiome checked? Or is it just people that are having oral issues?

Stay on top of oral disease by getting your oral microbiome checked

Who Should Get Their Oral Microbiome Checked?

This is what we are trying to do is help people understand the distinction between dental care and oral health. Today, you get told to brush and floss, but you probably don’t do it. You get told to go to the dentist for a checkup every six months, but you probably don’t. Eventually, something pops up a worrisome symptom or a toothache and you finally go to the dentist. We use observational screenings and X-rays to look for cavities and symptoms of gum disease. If they find those symptoms, then you have to go back in for a reactive procedure. It’s an endless cycle.

Cavities and Gum Disease Are Largely Preventable

We’re trying to educate people that cavities and gum disease are largely preventable. It’s wild to think about that fact, and then also realize that they’ve been the most prevalent diseases on the planet since 1990, but they’re entirely preventable. There are a multitude of behavioral changes and product changes that people can make to greatly reduce their risk for disease. There’s been this missing connection, like what we’ve talked about between oral and overall health. Getting people those insights and highlighting some risk factors outside of how much sugar do you eat reduces your risk for oral disease. Not only that but it improves your overall health. I think everybody should get their oral microbiome tested. Everybody should be a lot more mindful of their oral health status because it means a lot more than just having a cavity.

Dr. Tabatha: I think you hit the nail on the head. Dental care is very reactionary, it’s like, let’s just keep waiting until you have the problem, and then you know, drill big hole in your tooth to “fix it. “ and fill it with something probably toxic that’s gonna get you sick in the future. That’s a whole nother podcast. Think of indigenous people in Africa and places like that. They never brushed their teeth and they never get cavities. They have white strong teeth their entire lives. Our lack of oral health really is a civilized problem that we’ve created with our food industry and our poor eating. It’s awesome that we can get a picture of what’s going on with this test and start making changes now. Don’t wait until you have periods of periodontal disease.

Danny: Exactly. There has been a huge shift. I was talking to another founder the other day about oral care. They mentioned that there’s a huge change in the industrial revolution in terms of the kinds of foods that we were eating both from an ingredient standpoint, a lot more sugars and carbohydrates, and also from the way we created foods, so they became a lot softer. Basically, there was this huge change in the ingredients we were using and how we were using our mouths after the industrial revolution. Suddenly, there was a huge influx of oral disease. We need to keep those kinds of things in mind and be very aware that our personal kind of lifestyle and what we’re exposed to on a daily basis is impacting our health.

Tabatha: I know it breaks my heart. I have friends whose children have gone to the operating room to take care of all of their cavities and oral issues. So much of it is diet and how we make changes to support the good bacteria.

How Can We Check Our Oral Microbiome

We make it pretty easy. You just have to go to our website. We have three different versions of the test available, it’s all the same information, but there’s an ala carte option. You can just order one test if you want a snapshot of your oral health status. We have subscription models, so you can get one every six months or every three months. We provide you direct insight into your oral health status, highlight different risk factors for cavities, gum disease, and bad breath. Then give you very personalized recommendations on what you can do to improve. In the future, we’re going to really try to create a pretty comprehensive experience. We’re working to provide telehealth and connections to dentists, oral care specialists and nutritionists. We’re also working to be able to provide the very products that we’re recommending directly to our users as well.

What’s Involved in Testing Your Microbiome?

We send you a kit. You basically spit in the tube. We recommend doing it first thing in the morning before you brush your teeth or drink anything. I usually put mine on my nightstand. You spit in the tube and shake it up a little bit. We include a little bit of a clear solution called a buffer. That helps keep your sample intact. Then you mail it back and we process it in the lab. The results are generally ready within five to 10 days of receipt. Then you just log on and get your results.

Dr. Tabatha: That is awesome. Have you noticed anything that interferes with this test? Other than like eating and drinking? I mean, do you have to not eat certain foods or have any restrictions?

Danny: No. You get the best snapshot of your oral health by doing your normal daily habits and taking your sample first thing in the morning. We don’t want anybody to make any major dietary changes before testing, because it could impact your oral microbiome results. I’d say just do your normal routine. Avoid eating or drinking at least 30 minutes before you take the test. Best case scenario, you do it first thing in the morning.

Tabatha: Okay, cool. So another area of concern is pregnancy, right?

Pregnancy and Oral Health Are Important Especially for Our Children’s Oral Health

We see significantly higher rates of periodontal disease in pregnant women. Additionally, we’ve also noticed some associations with the future outcomes of children in terms of their risk for oral disease. We think that there’s a big connection between the oral microbiome of the mother and the oral microbiome of their newborn infant. We find that babies typically have their moms’ oral microbiome.

Babies Typically Have Their Mom’s Oral Microbiome Which Can Impact Their Likelihood for Cavities in the Future.

Tabatha: I have no doubt that’s the case because moms kiss on their babies. We love all over them, when they’re brand new, and we’re kissing them on the mouth, we’re cleaning off their pacifiers and their bottles with our mouth. We’re putting our fingers in their mouth. It’s a lot of close connection. So that makes total sense to me. I’ve also seen this with pregnancy. Poor oral hygiene and bad dental health really can impact the pregnancy. It can cause preterm contractions. There’s even research that it can cause preterm labor, but going to the dentist and getting your teeth “fixed” doesn’t necessarily help, so the key is what you’re doing, right?

Danny: Yeah, I can imagine, as a pregnant woman, it’s pretty hard to get to the dentist consistently. There are a lot of conflicting priorities, things physically become a lot harder to do. Getting access to consistent and preventive oral care can be really difficult. That’s something that we’re hoping to solve. With our test, you can really get in front of the progression of oral disease. Unfortunately, I think a lot of mothers aren’t aware of the changes that are going on in their mouths until the symptoms begin to arise. We know that certain hormones increase blood flow to the gums, causing inflammation that makes you more susceptible to pathogenic bacteria. After the birth, with a newborn child there’s a lot of saliva swapping going on between mother and child. The last statistic I read showed that children with parents who had a high risk of cavities themselves are at three times higher risk for oral disease in the future. So it’s a bummer for everybody.

Tabatha: It makes so much sense, but I would love to see us get to a point where we can figure out how to maximize the beneficial bacteria in our oral microbiome so we’re breaking that cycle, and we’re not passing the bad bugs on to our kids. How amazing would that be?

Danny: Yeah, exactly! We can do that by taking some preventive steps early on during pregnancy. It’s a huge impact without having to do too much extra. This reminds me of another statistic that I came across the other day. There’s also a placental microbiome and there are a couple of research studies that showed that the oral microbiome is more similar to the placental microbiome in a mother than it is to the gut microbiome. So there is there’s a very clear connection there as well.

Tabatha: Yeah, I guess that makes a lot of sense, the oral microbiome can very easily get into the bloodstream, just by any little nick from your toothbrush and biting your tongue, things like that. That will definitely go straight to the uterus and placenta. This is really amazing. Things are going to be really different now that we understand what’s running the show and how we can influence that.

I’m thinking about moms and their oral bacteria when they’re pregnant. I remember being so sick that all I could keep down was saltine crackers which are basically sugar. Your body is waiting to digest and absorb and I’m feeding the wrong bacteria in my mouth. This means, I’m increasing my risk of cavities and disease because I’m just trying not to throw up and feel sick, right? If women could focus on getting some fiber in and eating more raw stuff that you have to chew on and things like that would that help?

What Feeds the Good Bacteria in our Mouth?

We’re still trying to figure out a lot of that information, because, again, oral health has been such an overlooked area. We’ve been so focused on these 10 or 12, bacteria that cause periodontal disease or cavities. There hasn’t been a ton of attention given to the beneficial microbes. Stay away from carbohydrates and sugars, making sure you’re getting a lot of fiber, these are things that we know improve digestive and oral health in general. As a company, we’re working to investigate exactly what those connections are with specific microbes. Another complication during pregnancy is sickness. Obviously, during vomiting, you’re introducing a lot of acids back into your mouth. That contributes not only to tooth decay but it can lower the pH in your saliva. That’s very good for bad bacteria as well.

Tabatha: Right! I have no doubt that those bad bacteria are making their way to your stomach and wreaking havoc in your stomach and making your nausea worse. So then you’re stuck in that vicious cycle again. I love the idea of doing probiotics for your mouth, doing probiotics for your gut and really supporting those good bacteria by eating whole real foods that weren’t made in a factory. Quit eating out of boxes and bags, everybody.

This has been so good. Where can my readers get your test, Danny?

If you go to, and there’s a button in the right-hand corner. You can click it and it’ll take you right to the product page. I would also highly recommend going through our blog, there’s tons of really good information on there. A lot of it really hasn’t been disseminated to the public. We really work to find the best research to educate our users. Once you get the test, you will continually be updated with new information. Even if you just get the snapshot, you’ll get an email every now and again, letting you know what new features we’ve added, or what new discoveries we’ve made. On top of that, every new user that takes our tests contributes to the creation of this really exciting data and helps accelerate the discoveries that we’re making. The more pregnant women that we can get to be tested, the more discoveries that we can make that will help us connect the oral microbiome and oral health to pregnancy.

Tabatha: Awesome! Well, thank you for being such a pioneer! This is amazing! It’s the future. I hope everybody does the test because the more data you can get, the more that we can understand and really make some headway in this issue. Thank you so much!

Danny: Thanks for having me.

To Wrap it Up

Awesome. I hope you thought that was a really cool interview. I love just hearing all of the amazing new things that are coming out in science. Unfortunately, most doctors aren’t aware of this. When I was stuck in that broken medical system, working as an OB-GYN. I was in survival mode. I was focused on trying to get a couple of hours of sleep, and taking care of my patients was priority number one. There was no time to be reading new research and studies and articles. We had one or two journals that we would read. Those are very much directed by the broken medical system that’s driven by big pharma. Unfortunately, the information that we’re even given as physicians is biased, it’s one-sided.

Don’t be mad at your doctor. They don’t know any better. They’re trying to do their best. They’re trying to help you, just like I was, so it’s important to keep doing your own research and keep listening to new people. Educate yourself by listening to podcasts, watching Docu series, reading blogs and articles. Don’t give up searching for answers because we need to figure out the whys. Why don’t you feel well? Why are your hormones imbalanced? Why isn’t your thyroid working? Why are you getting cavities? Why are you so tired during the day that you don’t even want to participate in life?

If you keep asking why. You’ll find the answers and the answers are coming from the amazing research that these people are doing in the labs and understanding our microbiomes. I would really love it if you would support Danny and his company Bristle in this effort to help us understand how the oral microbiome affects the rest of our bodies.

If you want to find out more about what is driving your health, the best way to do that is to get your gut microbiome tested and get testing that is really going to look at the underlying causes, not a diagnosis. I can help you with all of this, just schedule an appointment with me. I am here for you.