Clinical connections: Smoking and the liver

Associate Professor Paul Gow

Associate Professor Paul Gow is a Melbourne based gastroenterologist and hepatologist and is currently working in private practice. He spent more than two decades as a liver transplant physician at the Victorian Liver Transplant Unit based at the Austin Hospital. He has clinical interest and expertise in all aspects of liver disease and has published more than 200 peer reviewed journal articles and a liver health education book entitled "Liver Better Life." He is an Associate Professor at the University of Melbourne and has an ongoing appointment with the Gastroenterology unit at the Austin Hospital.  

• Cancer Council: Hepatitis B and liver cancer fact sheet
• Cancer Council: Caring for your health Preventing hepatitis B-related liver cancer flip-chart
• Smoking and liver diseases: an updated review of pathogenesis, progression, and therapeutic implications
• Cigarette smoking and liver diseases
• Liver Better Life: The evidence-based diet and lifestyle guide to liver health and longevity
• Tobacco in Australia Facts and Issues
• Associate Professior Paul Gow : LinkedIn
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• My QuitBuddy App
• Cancer Council Victoria

[00:00:00] Paulette: This Quit Insights clinical series podcast is recorded on Wurundjeri Woi Wurrung Country. We acknowledge the traditional custodians and pay our respects to elders past and present, and we extend that respect to those on the lands where you're listening today. This podcast is intended for health professionals and is for educational and informational purposes only. The content discussed does not constitute medical, legal or professional advice and should not replace your own clinical judgment. Welcome. I'm Paulette Trevena and this is the Quit Insights clinical Series podcast for health professionals. Each of our episodes bring you in-depth information and insights from professionals who are experts in their field. Our guest today is Associate Professor Paul Gow, who is a Melbourne based gastroenterologist and hepatologist, and is currently working in private practice. Paul has spent more than two decades as a liver transplant physician at the Victorian Liver Transplant Unit based at the Austin Hospital. He has clinical interests and expertise in all aspects of liver disease, and has published more than 200 peer reviewed journal articles, as well as a liver health education book entitled "Liver Better Life". Paul is an associate professor at the University of Melbourne and has an ongoing appointment with the Gastroenterology unit at the Austin Hospital. Welcome, Paul, and thanks for being our podcast guest today. 

[00:01:27] Paul: Good morning Paulette. Thanks for the invitation. Thank you. 

[00:01:29] Paulette: Great. So in this episode, we'll be exploring the clinical connections between smoking and the liver. Liver health is often discussed in relation to alcohol, hepatitis, metabolic health, and other risk factors, while the potential impact of smoking may receive less attention. We know a lot about the impact of smoking on the lungs, but what about an organ we hear less about in the context of smoking - the liver? So, Paul, can you give us an overview of the liver, where it is and what does it do? 

[00:01:57] Paul: Yeah, it lives under your ribs, on the right hand side at the top of your tummy, so it's under the ribs so that your ribs can protect it from injury. And it's big. It's about 2L or 2L in volume. So the size of a two litre bottle of milk. So it's quite large and it really does your body chemistry. So for example, after you've had breakfast, there's, you know, thousands of different chemicals in your yoghurt and muesli breakfast or toast and Vegemite, whatever you're having, there's thousands of different biological chemicals and your liver is sorting them. So it's keeping the good stuff, putting it into the right packages and storing it away and getting rid of the bad stuff. The liver makes your blood clotting factors for example, and it makes chemicals to help you absorb food. So it's really doing all of your body chemistry. It's what it's doing. 

[00:02:49] Paulette: Right. Okay. They describe it as a powerhouse. 

[00:02:51] Paul: It is a powerhouse. It's really interesting. Yeah. 

[00:02:53] Paulette: Great. So first of all, how does smoking affect the liver? 

[00:02:57] Paul: You're going to think of a human as a sort of biological organism. And when I think about what's good for our liver health and what's bad for our liver health, I think about the environment we've evolved in. And smoking was not one of the environmental agents that we evolved with. So smoking is noxious to our body in all parts, and we're inhaling hundreds of different chemicals. And those chemicals cause inflammation in the body. And that inflammation affects your liver by causing deposition of fat in the liver, which is damaging, and also to cause scarring of the liver, which is damaging. And scarring is the mechanism by which your liver ends up with cirrhosis. So smoking is damaging by altering your metabolism. And that metabolism therefore causes excess liver fat, which is bad for your liver and potentially scarring, which can potentially lead on to cirrhosis. 

[00:03:47] Paulette: Right. Do we know anything about vaping and its effect on the liver at this stage? 

[00:03:52] Paul: Yeah. Look, the data we have about smoking and liver health is very good. We've got really good black and white data about what it's doing and the way it's doing it. But because vaping is a relatively new entity, the scientific data we have about human health and vaping is and liver health is at the minute pretty poor. The small amount of data that we do have about vaping is that mechanistically it looks like it's bad, just like smoking is bad. But the data is not as granular as it is with smoking and liver health. 

[00:04:22] Paulette: Right. Okay. Most people who smoke know about lung damage, but do they realise that smoking affects their liver, do you think? 

[00:04:29] Paul: I doubt it. I think the public health message about smoking and lung health, cardiovascular health, lung cancer has been really well promoted. And I think it's everyone understands that link, but the link with liver health is less clearly understood and perceived. So fatty liver disease, for example, which is excess fat within the liver, which is present in four out of ten Australians, so 40% of the population. Smoking is a risk factor for that. So no, I don't think the population is aware that the significance of the relationship between their liver tests, their liver health and smoking. 

[00:05:07] Paulette: Yes. For sure. And how does the liver respond to injury? 

[00:05:11] Paul: That's a really important question because the vast majority of people with liver disease have no symptoms. So we're fortunately all born with enormous amounts of spare liver reserve. So you can get quite a lot of liver injury and still have no symptoms. And the vast majority of people who have liver disease in Australia have zero symptoms. But the liver response to injury in a variety of different ways. The first is excess fat. And that excess fat is deposited within liver cells. And that's called fatty liver disease. It's exacerbated by smoking and that's asymptomatic. There's no symptoms associated with it. And by itself it's relatively benign, having excess fat. But excess liver fat is a marker of your general metabolic health. So the excess liver fat can be measured in blood tests. And those blood tests not only tell you about this liver function test, they not only tell you about your liver health, but they're also a marker of your general metabolic health. So your liver tests can, if they're abnormal, will mean that you're at increased risk, not just of liver damage, but of cardiovascular disease, dementia, cancers, diabetes, all of those things that really kill western people. So the commonest mechanism by which smoking affects the liver is excess liver fat. But there's two other really important effects. And the second is scarring and the liver's response to long term damage from anything, whether that be viral hepatitis, smoking, alcohol, metabolic syndrome, all of those things. The liver's response to long term injury is scarring. Scarring causes no symptoms. But if scarring progresses, then you end up with cirrhosis. Cirrhosis really means just a lot of scarring, and that is exacerbated by smoking. And the third important endpoint is cancer. And any sort of long term liver injury or insult increases the risk of liver cancer. I think people would probably recognize that alcohol can increase the risk of cirrhosis and also of liver cancer, but smoking can do the same things. So it increases the risk of cirrhosis, and it also increases the risk of liver cancer. 

[00:07:17] Paulette: Right. Okay. So is liver damage in people who smoke mostly picked up in the late stages of disease? 

[00:07:23] Paul: I would think it's mostly picked up in the early stages of the disease, Paulette surprisingly. So, again, most people with liver damage have no symptoms. And I would define that as relatively early in the course of the condition. They haven't got cancer. They haven't got cirrhosis. So the majority of people have got excess liver fat, for example, fatty liver disease or some liver scarring. And so those people have got no symptoms. And that would be the vast majority of people with smoking related liver disease are picked up relatively early on in the course of their liver illness. 

[00:07:54] Paulette: Okay. Right. So we know that the liver has an amazing capacity for recovery. Is liver damage reversible if patients stop smoking? 

[00:08:02] Paul: Yes. So I think that's a good news story. So two interesting things about the way your liver works is we're all born with enormous spare reserves, as I said before. And you know, the reason we've got a lot of liver reserve is your liver sits between your gut, which is really the external environment and the rest of your body. So your over the millennia, you know, millions of years of evolution, the liver's been exposed to lots of toxins, and intermittently, our ancestors would have eaten a plant and the liver gets sick from it. And so instead of that person dying, you know, evolution has recognised this and has put in a whole lot of spare reserve so that we don't die from moderate liver injury. So there's a lot of spare capacity. And the second thing is that there's enormous potential for recovery from injury. So whatever the insult that is causing your liver disease, whether it's your metabolic health, alcohol excess, viral hepatitis, or smoking, you stop the insult and the vast majority of the insult your liver just resolves. So even if you've got scarring, for example, the scarring can disappear with time if you get rid of the insult. 

[00:09:12] Paulette: That is good news. So how does smoking and/or vaping interact with other liver risk factors such as alcohol use, obesity, hepatitis, and other or existing liver diseases? 

[00:09:24] Paul: It's a co-factor. So I think people are well informed about risk factors for cardiovascular disease. They know blood pressure, cholesterol, family history, smoking. People would know that. But I don't think people know the risk factors for liver disease. And that is metabolic syndrome or being overweight, alcohol excess, viral hepatitis (hepatitis B or hepatitis C), and smoking. And so these risk factors work off each other, for example. So if you drink too much and are a smoker, then your risk of developing liver fat, liver scarring or liver cancer is markedly increased. And if you've got a third factor for say, on top of that, you've got viral hepatitis, then again, these risk factors are all working off each other. So they sort of an exponential effect of the additional risk factors. 

[00:10:15] Paulette: Right. Okay. And what are the symptoms of liver damage then? 

[00:10:20] Paul: It is surprising that, again, if I've said that 40% of Australians have liver disease, maybe less than 1% of those have symptoms. So because your liver has got such enormous spare reserve, people really develop no symptoms from their liver disease until they have liver failure. And with liver failure, people get swollen ankles, jaundice, they get fluid retention so their legs or tummy get swollen. But early on in the course of the illness. Before you develop liver failure, people have no symptoms. They might feel more tired than normal. They might have some very vague upper tummy, right sided discomfort, but really otherwise nothing. So I think the important thing is get your liver function tests done. When you see your local doctor, get them done. And it's also I think it's useful to have a look at them yourself and see whether they're in the normal range. And if they're not, ask your general practitioner why they might not be because there'll be an answer to that question. And it's almost certainly an answer that you can reverse. You know the reason why your liver tests are abnormal. 

[00:11:22] Paulette: Right. Okay. Take those results seriously. 

[00:11:25] Paul: Yeah. I think they're correct. They're a warning about your future health. So if you've got abnormal liver tests, it's telling you about your liver health today. And that's got implications for your liver health in the the decades ahead of you. 

[00:11:36] Paulette: Yes. For sure. How do you think health professionals can support the message regarding smoking and liver damage, similar to awareness of smoking and lung damage? 

[00:11:43] Paul: Yeah, I think for health professionals, it's mainly awareness that smoking is not just a risk factor for cardiovascular disease and lung disease, but it's also an independent risk factor for liver disease. And it's an independent, reversible risk factor for liver disease. So again, if you're seeing somebody who's got, for example, fatty liver disease, discussing with them that one of the variables that is contributing to the liver injury (smoking) and reducing their smoking or stopping their smoking will improve their liver health. 

[00:12:14] Paulette: Excellent. Thank you so much to our guest, Associate Professor Paul Gow, for sharing your knowledge and insights on this topic. 

[00:12:21] Paul: Thanks, Paulette. 

[00:12:21] Paulette: We invite listeners to visit the Quit Center website at quitcentre.org.au for more information and resources for health professionals. And thank you for listening today. Please listen in for future episodes of our Quit Insights Clinical Series podcast. 

This podcast is intended for health professionals and is for educational and informational purposes only. The content discussed does not constitute medical, legal, or professional advice and should not replace your own clinical judgment.