Zachary Cartwright [00:00:03]:
So why do all us government agencies recommend that humans don't drink raw milk? Welcome to The Drip, where we keep your mind hydrated with some science, music, and a mantra. I'm your host, Zachary Cartwright, lead food scientist at AQUALAB. By adium in today's episode, I will be talking with Savana Everhart Nunn, who recently graduated with her PhD in one health sciences from Texas Tech University. Savana's dissertation focused on staphylococcus aureus as it relates to mastitis and dairy cattle in the Texas panhandle. She also helped to pioneer the start of a PhD program in one health sciences. Hi, Savana. Thank you for being on The Drip. We appreciate you being here.

Zachary Cartwright [00:00:44]:
So why is it that all us government agencies recommend that humans don't drink raw milk?

Savana Everhart Nunn, PhD [00:00:50]:
So, basically, the US government agencies recognize that there is a risk with raw milk. And generally, when we're talking about that risk, we're talking about different pathogenic microorganisms. So that could be bacteria, that could be even protozoa. There's a few viruses, but we won't get into them today. But generally, it's because of the risk of foodborne illness when drinking that raw milk. And they can make you sick up to the point of death. Even. So, the government just wants to keep people safe, and that's why they don't recommend it.

Zachary Cartwright [00:01:21]:
And when you say raw milk, are you just referring to milk that hasn't been pasteurized?

Savana Everhart Nunn, PhD [00:01:26]:
Yes. So raw milk is milk that hasn't been pasteurized. And pasteurization is a definition that we food scientists use to basically show that milk does not have pathogens that can cause harm in humans. So that means it's completely pathogen free. It doesn't necessarily mean that it's completely bacteria free.

Zachary Cartwright [00:01:44]:
That's a really good distinction to make. And when you talk about government agencies, are we talking about the FDA or the CDC or. Exactly which agencies are you referring to?

Savana Everhart Nunn, PhD [00:01:53]:
Yeah. So both the Food and Drug Administration or the FDA and the Centers for Disease Control and Prevention or the CDC, both do not recommend drinking raw milk. Additionally, there's some other agencies, such as the American Academy of Pediatrics, that doesn't recommend feeding raw milk to children. That's been a trend that I have seen here recently, especially with some of the issues that we've had with infant formula food production. So a lot of people were turning to raw milk, such as goat's milk, instead. But it's really not necessarily the best idea, especially for our kids.

Zachary Cartwright [00:02:28]:
And are there any other vulnerable populations that our listeners should be aware of that should also be especially careful not to consume raw milk, for sure.

Savana Everhart Nunn, PhD [00:02:37]:
So there is actually an acronym that we use in food science called the yopi. Yopi populations. So y stands for young, so that's children. O stands for older people. So anybody that is really over the age of 65, that's kind of when our immune systems start to decrease. P is for pregnant. And that gets really important when we talk about an organism called listeria monocytogenes. So that organism can actually cause miscarriages and abortions in human women and also make them very sick because your immune system is compromised when you're pregnant.

Savana Everhart Nunn, PhD [00:03:10]:
And then the I stands for immunocompromised. So that's anybody who is undergoing different therapies or such as chemotherapy or has some other immune compromisation illness. And so those people really need to be cognizant of their risk because they are at a higher risk for developing a foodborne illness, especially when they are drinking raw milk.

Zachary Cartwright [00:03:32]:
And you mentioned earlier some pathogenic bacteria. You just mentioned listeria. Are there any other types of pathogenic bacteria that may be in raw milk?

Savana Everhart Nunn, PhD [00:03:41]:
So we see Salmonella and E. Coli, specifically shigepoxin producing E. Coli. Those two, in addition to Listeria monocytogenes, definitely get blamed for a lot of things, but then there's other pathogens as well, such as mycobacterium tuberculosis, which causes bovine tuberculosis, Coxiella burnetti, which can cause Q fever in humans and cattle. And so all of these are actually pathogens that can infect humans and the cattle themselves. And so those pathogens are called zoonotic pathogens because they affect animals and people. Lastly, an organism that's super near and dear to my heart, Staphylococcus aureus. So this pathogen actually can cause mastitis in cattle, but it can also make humans sick due to the enterotoxins that it produces.

Savana Everhart Nunn, PhD [00:04:25]:
So it produces these toxins, and then when they are drunk by a person, that person actually gets sick from the toxin. And there's quite a few toxins that Staphylococcus aureus produces, but it doesn't necessarily mean that every bacteria produces those toxins. But it's just kind of, in my opinion, you're sort of playing russian roulette when you're drinking raw milk, because you just don't necessarily know when some of these organisms are going to be in your milk and when they're not going to be. And so there's plenty of other bacteria, there's even some protozoa as well. That can be in our milk. But those are kind of the things that I thought of off the top of my head that can cause some significant illnesses.

Zachary Cartwright [00:05:04]:
And to remove those bacteria, of course, we pasteurize. And how effective is that at removing these microorganisms?

Savana Everhart Nunn, PhD [00:05:12]:
So that's basically the whole point of pasteurization, is to ensure that there are no pathogens in the food that we're drinking. And so in this case, it would be milk. And so it's extremely effective at removing these harmful bacteria. The only time it wouldn't necessarily be effective is if it was done incorrectly or if, for example, an organism like Staphylococcus aureus that can produce enterotoxins if a significant enough level of enterotoxin was already produced. Unfortunately, that doesn't end up getting degraded. The enterotoxin itself isn't degraded by that high heat. And so if it's there, then you would have a problem, but if not, it's extremely safe.

Zachary Cartwright [00:05:55]:
I understand there's different methods or different approaches to pasteurize. There's low temp, long time, and even ultra high temperature. How do different producers, how did they decide which of these methods to use?

Savana Everhart Nunn, PhD [00:06:06]:
So htst or high temp, short time? That's the most common method used in the United States, actually. If anybody is a little bit of a food engineering nerd, super, super fascinating. It was always one of my favorite things that we talked about in food engineering, because you have these plates that are up against each other, and it's a really interesting process. If you want to learn more, there's other resources online, but that's the most commonly used method in the United States. So it's 161 degrees fahrenheit for 15 seconds at minimum. And then usually that because of the technology, most people that are using these are larger dairy operations that can afford this equipment because it is kind of expensive. Another type that we do see used in the United States and a lot of smaller producers use is LTLT. So low temp, long time, and that's 145 degrees fahrenheit for 30 minutes.

Savana Everhart Nunn, PhD [00:07:02]:
And you don't have to have these specialized plates that are up against each other. A lot of times, it's kind of heated. Another name for it is actually vat or batch pasteurization. So we'll heat it in a big pot for that period of time. And then the last one that you had just mentioned was ultra high temperature pasteurization. So that's 280 degrees fahrenheit for two to 5 seconds at minimum. We see a lot of this. If you notice your heavy cream in the grocery store or a couple of the organic milk producers use this process, you might see a significantly longer shelf life.

Savana Everhart Nunn, PhD [00:07:34]:
So about three more months from the time you buy in the grocery store, which is a little bit different from our HTST pasteurization. If you notice when you go to buy milk in the grocery stores, usually it's about two to three weeks out for the best by date. And so this UHT processing, or ultra high temperature processing allows for a longer shelf life of milk. And it's generally thought that it's killing some of the spores that are creating spoilage. And that's kind of why there's a longer shelf life with these milks. This is a little bit more commonly used in Europe as well, but that's just kind of a couple different types of pasteurization, and it does change the taste of the milk too. So if you ever want to play around and do some sensory science, you're more than welcome to try HTST versus UHT milk and see what you think differences are there.

Zachary Cartwright [00:08:24]:
When I look into this more, and I see why people might want to consume raw milk, a lot of proponents for it argue that it contains beneficial enzymes and more nutrients that are destroyed during the pasteurization process. How would you respond to these people?

Savana Everhart Nunn, PhD [00:08:41]:
I would say, and this is kind of what the other us government agencies argue as well, is that there's really negligible degradation. So a lot of people are really wanting those beneficial enzymes and sometimes nutrients, and in my opinion, the benefits of having those potentially negligible, and that's kind of what these studies are coming out as, is that the difference in nutritional value and the beneficial enzymes that are there in pasteurized milk versus raw milk are pretty negligible when you actually look and go down to the science of it. There was a study that did say that it degrades the heat of pasteurization, degrades vitamin C, but milk is not really seen as a big source of vitamin C for humans anyway. So there's other ways that you can get those beneficial enzymes and nutrients from other food groups and that you're not drinking this pretty highly risky product. And so I would just say the benefits are negligible of drinking raw milk and the risks far outweigh it, in my personal opinion.

Zachary Cartwright [00:09:44]:
And I understand you recently finished graduate school and I was wondering how your research in grad school relates to this topic and expands the body of knowledge around it.

Savana Everhart Nunn, PhD [00:09:54]:
Sure. So my dissertation was more so looking at the animal health side of things. So I kind of mentioned, I studied staphylococcus aureus. It causes mastitis and dairy cattle. And so the way it kind of got into projects, specifically was there was a farm that was local to my university, and they were having some severe issues with mastitis in cattle. Staphylococcus aureus is actually one of the most common pathogens in the United States that causes mastitis, which is inflammation of the cow's udder. And it can cause a lot of health issues for the cow, but it can also cause a lot of quality issues for the milk and a lot of headaches for the farmers that are producing the milk. And so I ended up going at it from a more animal health side of things and really just trying to understand what's going on in our cattle population, specifically in the Texas panhandle.

Savana Everhart Nunn, PhD [00:10:47]:
There hadn't been a lot of research done in that specific area, and Texas is actually currently the fourth highest producing milk producer in the whole United States, and that number is actually on the rise. We've had a lot of dairies move into the panhandle area specifically. And so I kind of started to look at what was going on specifically within this dairy farm, kind of as a pilot study to hopefully show that we do need more literature and more studies done in the panhandle at large. And so in addition to that, I did some work with antimicrobial resistance of staphylococcus aureus. So if you've ever heard of MRSA or methicillin resistant staphylococcus aureus, we hear that a lot people, and that's really important to both human and animal health, because we have to have these antimicrobials to be able to treat Staphylococcus aureus infections. And it's actually a really unique pathogen because it has a lot of ways to mitigate antimicrobials. And so I ended up finding that the panhandle, at least in the pathogens that we were studying, there was a lot of penicillin resistance, which we haven't seen as much in us livestock populations, specifically in dairy cattle. I didn't end up finding any methylcillin resistance, which was great, but we did see a lot of penicillin resistance, which was more on par with what the Staphylococcus aureus genes that are in human populations look like.

Savana Everhart Nunn, PhD [00:12:10]:
And then I also screened for enterotoxins, and I did end up signing an enterotoxin in one of our strains. But it was really interesting because that specific strain we think actually originated in humans. And so it was interesting for me, kind of this concept of one health, which we'll talk about a little bit later, but basically one health is how humans, animals in the environment, and their health all interrelate to each other. And so with my research, I kind of was able to see, you know, we've got this transfer of organisms that we thought were in humans and thought this strain originated in humans. But here we're finding it in cows. And so in dairy specifically, it's really interesting because you have humans working with these dairy cattle directly using their hands, which can be a way to transmit staphylococcus aureus. About a third of the United States actually has staphylococcus aureus just living symbiotically on their bodies. And so we kind of see this transfer with these animals as well.

Savana Everhart Nunn, PhD [00:13:11]:
And we also know that these animals can transmit this pathogen specifically to humans, too, and it can also be harbored in the environment. And so that was kind of just an eye opening experience for me, just to kind of see the way that kind of genetically, these organisms are working with each other in the environment to you.

Zachary Cartwright [00:13:28]:
And as you started to move into your research project, what were some of the largest challenges that you had to overcome in order to finish your projects and finish your degree?

Savana Everhart Nunn, PhD [00:13:38]:
I think for me, we've heard a lot of these discussions on mental health in graduate school. And I think for me, in my opinion, sometimes I was my own worst enemy, and I definitely struggled with my mental health a little bit through graduate school, both just in wanting to be this high performer. And then you've got things that don't work out or don't work in your favor. And I kind of had to realize that, you know, life isn't going to be perfect grad school and your research isn't always going to be perfect and sort of just push through those things. I had a really great therapist in grad school, and if you're in grad school, I would highly recommend having one just because it is a really challenging part of your life. You're asked to do a lot of things and manage a lot of things. And for me, I was asked, and I was so, so thankful, and I had a really great experience with my advisor and some of the administration at my university. But you're still, you know, pushing yourself to the middle of May.

Savana Everhart Nunn, PhD [00:14:36]:
You're working really hard hours sometimes. You're learning a lot of new information that sometimes is really scary. I know for me, one of my big things that I was really nervous about, but actually ended up really loving, was learning some of the bioinformatics on how to deal with whole genome sequencing and microbiome research. And I was really kind of nervous to use the computer and sort of jump into that. But I actually, that ended up being one of my favorite parts of learning in grad school. And so I'm really thankful that I did it, but that was definitely a challenge overall, is just pushing through and not being scared to take some risks. Yeah.

Zachary Cartwright [00:15:12]:
And part of what this podcast is for is for people to listen to and understand how other scientists deal with their stress and coping mechanisms. And I think it's really helpful to understand that. Yes, it's helpful sometimes to go see a therapist or to have some way to balance your life in the lab. And for me, it was becoming a dj and using yoga to get past that. And part of every episode we're going to hear from our listeners like you to see what your recommendations on. At the end of this episode, I will recommend a mantra, a saying that you can say to yourself to help build some positive energy. And I'm wondering if you used any type of mantra or quote or anything that really helped inspire you to keep you going while you were in grad school.

Savana Everhart Nunn, PhD [00:15:53]:
So I had two. One, I don't even remember how I ended up figuring out about this specific quote, but I was watching something on tv, and it was, I can do hard things. And this woman was just repeating, I can do hard things, I can do hard things. I can do hard things. And that was towards the end of my PhD, when I was writing my dissertation and sort of learning a lot of this bindramatic where, and was so, so nervous about it. And I would just have to sit in my office at my computer just telling myself, like, I can do hard things, I can do hard things. And that really helped me just push through that part at the end. The second one, I don't know if there's any listeners who are fans of Ted Lasso, but my advisor and I both are.

Savana Everhart Nunn, PhD [00:16:35]:
And especially this last season, that came out at a really good time for me as I was finishing up my research and my dissertation, but the coach, Ted Lasso, always tells his teammates or his players on his team to believe, and he's got a big sign for that. And my advisor always used to tell me that because he and I were both fans of the show. And so I kind of had that back in the back of my mind throughout all of the things. It's just like, believe in yourself, believe in the way that you conduct research and your training. And so that's why what also helped me through, too, is just having the faith of my advisor as well.

Zachary Cartwright [00:17:10]:
That's definitely needed. And I think having that relationship with your advisor is maybe one of the most important things in grad school. For anybody who's looking to go to grad school, make sure that it's a good fit. I wanted to come back to one health briefly and just understand, again, what is one health? Is this a new program at your university? And I understand that you helped to pioneer this program. So I was just hoping that you could talk a little bit about that program and what it entails.

Savana Everhart Nunn, PhD [00:17:40]:
So I kind of already mentioned one health is the intersection of environmental animals, human health, and how they're kind of all interrelated. And it doesn't necessarily have to be science. Like you hear one health as a lot of infectious disease. And for me, that's really why I'm interested in one health. But the concept's been around for a really long time, and it doesn't necessarily have to mean infectious diseases. So in our program specifically, we actually have five different pillars that students can focus on. But basically, there's all kinds of different research programs going on. I have one friend who is working on welfare of horses who actually help in equine assisted therapy.

Savana Everhart Nunn, PhD [00:18:23]:
So a lot of people have realized there's a lot of research on how equine assisted therapy can help people with physical and mental disabilities. But there's kind of a sometimes a short time that horses can work in these kinds of environments. And so she's looking at what are things that we can do to sort of help the horses longevity and being able to be in these programs and having those relationships with those people who are going to them for help. And so animal welfare is a really big part of one health. There's also other things going on in economics and some of our social sciences. So I did a lot of work in food safety communication for my master. And I think it's really important to work with our social scientists and to appreciate their work and their research because they're also doing really interesting stuff in human behavior. So I can put out all of this research about mastitis and food safety or animal health, but unless we can actually get behavior to change, we're not necessarily going to be able to do anything with that research.

Savana Everhart Nunn, PhD [00:19:24]:
And so that part of me is very strongly tied to one health, too. Youve also got computer scientists and data scientists who are running all of our analyses were trying to solve really big problems and often means really big data. And its really difficult to get a really strong training in a specific part of biology and a very specific part of computer science. And so Im really thankful for my colleagues that do more of the bioinformatics work than I can consult with and talk to you about how do we make this project better? What can we do better with statistics and this research? That's not necessarily my strong suit. In addition, there's other things like metabolic diseases. There's a lot of comparative cancer research going on in our program specifically. And so looking at things like gray horses who have a higher incidence of melanoma, but the melanoma in them isn't as necessarily serious as melanoma in humans. So there's some people looking at what that relationship looks like and what's specific about those tumors and horses that is different from melanoma that we see in humans.

Savana Everhart Nunn, PhD [00:20:30]:
And so there's just a lot of really cool research going on, and I think that there's a lot of research that fits under the one health umbrella. And so there's a lot of big picture thinking, but then there's also a lot of, like, very detailed thinking, too. And I think that's something that's really fun about it. Our program is still pretty much in its infancy, and so if you're interested in a one health program, it's the first PhD program specifically in one health sciences in the United States. There's a couple other PhD programs that aren't necessarily named one health sciences. They're doing similar research to in other universities as well. But definitely let me know or reach out to our program director. You can find all of that information out online, but it's been a really fun program to get into.

Savana Everhart Nunn, PhD [00:21:15]:
We've got a lot of international students as well. And so there's a lot of cultural differences and cultural conversations that we've gotten to have, but there's also just a lot of research interest. And so that's been really fun as well, to kind of get to know.

Zachary Cartwright [00:21:27]:
Different research, too, and looking ahead, just looking down the road, what's next for you? I mean, you have this background now in animal health and microbiology. How do you want to use that background as you start your career?

Savana Everhart Nunn, PhD [00:21:41]:
So I'm really interested in zoonoses and mainly these pathogens that are infecting animals and humans, whether that's bad for the animals or not. I really knew that I wanted to help animal health and food safety when I was younger. I knew that I wanted to work with animals and people. I originally thought that was going to be in a veterinary perspective, but then I found out about grad school and decided that was a better option for me. And so I'm really looking for something that's going to allow me to be able to work with both. And so I'm really hoping for some kind of maybe government research position, maybe policy that can really help understand some of the science, but then actually be able to make a difference. That's really important to me. But then there's industry companies that are also working in these spaces to produce better vaccines, better drugs to help control some of these things, monitoring antimicrobial resistance.

Savana Everhart Nunn, PhD [00:22:39]:
There's actually a lot of things that I think are really interesting, and so hopefully I'll be able to do some of that. I'm going to be guest lecturing for my food micro class from underground in a couple weeks. And so I'm really excited to go back to NC State, which is where I did my undergrad and my masters, and actually get to lecture in the same class that I really developed a passion for food microbiology and so really excited about that. But getting to do some of the mentorship aspects as well is something I'm really looking forward to, too.

Zachary Cartwright [00:23:12]:
Yeah, I think there's something really rewarding and being able to go back to the classroom you were in and to lecture and be on the opposite side. And sometimes I get to go speak at Washington State University, where I did grad school. And it's just a fun feeling to be able to give back in that way. My final question for you is that, you know, every guest we have on, we're going to ask for a music recommendation. And I was wondering if there's a certain artist or song or genre of music that you recommend for listeners.

Savana Everhart Nunn, PhD [00:23:39]:
So I actually really love metalcore. I've loved it for a really long time. My mom was a big classic rock fan. And so I think as I got into high school and college, I sort of deviated a little bit from classic rock to metalcore. But recently I've been really into a band called Sleep Token. They have a song called Euclid that I think is just really beautiful. And so that's my recommendation right now if you like Metalcore, but even if you don't necessarily know if you like Metalcore or not, it's got really beautiful vocals. There's not a lot of screaming.

Savana Everhart Nunn, PhD [00:24:11]:
I know some people get a little bit shied away from Metalcore because of that, but I would give it a listen if you just want to try.

Zachary Cartwright [00:24:18]:
Awesome. Thank you. We'll make sure to link that song in this description for the podcast. Well, Savana, I want to thank you so much. We've been really working towards this rebrand and trying a new format, and I really appreciate you being the first guest on this show, and we look forward to maybe checking in once you have started working more in this field and seeing what you're up to, for sure.

Savana Everhart Nunn, PhD [00:24:39]:
Well, thank you for having me on.

Zachary Cartwright [00:24:42]:
Today's episode is sponsored by AQUALAB. In this episode, we discussed microbiology and food safety. Did you know that microbial growth in food is governed not by water content, but by water activity? There are minimum water activity limits for microbial growth, and AQUALAB provides the fastest and most accurate water activity devices so that manufacturers can quickly determine whether or not a product is susceptible to microbial proliferation. A link to how water activity controls microbial growth will be in the podcast description. Today's track is something I released last year with the help of my friend Christian Martinez and is called the smoke. I had the chance to play it for a crowd last November to end my set, and they seem to really like it. I hope you do, too. Let's check out the first drop together.

Savana Everhart Nunn, PhD [00:25:29]:
Buenos dias. Three, two, one.

Zachary Cartwright [00:25:33]:
Let's go. And finally, to round out this episode, I will be offering another mantra as a reminder. A mantra can be a single syllable, a word, or a phrase that you repeat to yourself to feel calm, motivate yourself, or to express something that you believe in. This episode's mantra is, I get stronger every day. I'm going to repeat this three times, and maybe you, the listener, can say it to yourself and maybe even out loud. Okay, here we go. I get stronger every day. I get stronger every day.

Zachary Cartwright [00:26:36]:
I get stronger every day. As you keep this mantra in mind, I also challenge you to think about the people you are surrounding yourself with and whether or not they're building you up. And are they building you up in a way that leaves you feeling inspired and invigorated? Thank you so much for listening to this episode. Rebranding this podcast from water and food to The Drip has been a really fun process, and I'm really happy that Savana could participate in this first episode. My name is Zachary Cartwright, and this has been the first episode of The Drip, brought to you by Aqua lab. Stay hydrated and see you next time. Get your hands up high. Pants up.

Zachary Cartwright [00:27:42]:
Let's go.

Savana Everhart Nunn, PhD [00:27:46]:
Never want the smoking. Never want the smoking. Smoking. Never want the smoking. Never want the smoke.