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Welcome to Science with Sanjula where we talk about anything global health.

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My name is Sanjula Singh, and I'm a researcher at the University of Oxford.

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Join me as I speak to world leading scientists who tackle today's biggest challenges in health care.

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Today, we're joined in the studio by Dr. Keren Papier, a senior nutritional epidemiologist at the University of Oxford.

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We're going to talk meat, veganism, alcohol and much more.

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Thank you so much for joining us today, Keren. First of all, can you please tell me what made you so interested in what we eat?

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It started really as a child I was really interested in nutrition, and I was really fortunate.

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I got to live in different countries across the world and I got to see what people ate and how different it was and how lifestyles went around food.

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I just was really interested in it. I was really fortunate during my studies, so I studied public health, nutrition, and in my first year,

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really in my first semester, I had the topic called epidemiology, which is about people and diseases and patterns.

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And I just thought, this is amazing.

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What a way to tie in interest in nutrition and people and different cultures around the world and understanding disease and patterns.

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And I just fell in love with it. And through my degrees I got to do research over the world as well.

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So I was able to go to the Philippines and investigate malnutrition in children and schistosomiasis.

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So it really unfortunate worm that children are unfortunately dealing with.

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Just from from the lifestyles, from from farming and being in the water and being there was really interesting

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because I saw that there were a lot of children who were undernourished.

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So we see malnourished as in poor nutrition, but really not getting enough.

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But a lot of the adults actually had over nutrition.

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So they were actually larger overweight or obese, but not necessarily eating what they should be eating.

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And I found that really interesting. And that led me to doing my Ph.D. from Australia, but also through Thailand and looking at yeah,

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looking at how the changing lifestyles were changing diseases and how diabetes was becoming

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an issue that hadn't been an issue previously because of all the different changes going on.

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Then how did you move to Oxford? 
So at the end of my PhD, I was of course looking for opportunities and thinking about what the next stage would be.

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And having done a lot of work in global health and really in countries that were sort of becoming either upper middle income or not quite high income,

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but seeing that some of the issues were quite similar with what's happening in high income countries,

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I thought that I could easily translate that research and wanted to see, well, what else is happening in high income countries as well?

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What happens when we eat meat, for instance? What happens when we don't eat meat?

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What does that do to our health and our long term health? What are people that are eating meat doing?

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What are their lifestyles? Are there differences between them?

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And that's evolved into projects also on what happens to people who completely omit meat.

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So what we call vegetarians, for instance.

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Well, let's dive into a vegetarian diet and maybe could you maybe explain first what is a vegetarian diet and what is a vegan diet?

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It's a great question because we know what they are not.

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So we know that vegetarians do not eat meat and do not eat fish.

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We know that vegans don't eat meat, don't eat fish, don't eat eggs, don't eat dairy.

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But what they do eat could be completely different. 
So it's even a tough one to define, so to say.

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Absolutely. And of course, what does that mean for health? Because if someone is having, say,

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vegetables and fruit and legumes and pulses and nuts and really a variety diet versus someone who might just be having white pasta,

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maybe tomato sauce soda the whole day. 
And both could be vegan diets.

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Right. That's exactly right. 
So how do you go about and do research on that?

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We're very fortunate that people are really kind and are happy to take part in research and help us answer interesting questions.

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So a lot of the research we do is through cohort studies.

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So what that means is we'll ask people to take part in a study and the people that we asked to take part,

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they might have something interesting about them.

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So in the case, for instance, of vegetarians and vegans, we really target people who are omitting meat,

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are omitting fish, are omitting dairy, or eggs and say, can you please take part in our study?

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And we've done this over the years. And for instance, we have a study that's been running since the mid 1990s called the Epic Oxford Study,

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and it's got over 65,000 people who have said, Yep, I'll take part in your study.

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So then we sent them surveys. These are questionnaires and they ask about their diet, their lifestyle habits.

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So do you smoke? Do you drink alcohol? What do you eat?

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And looking at these questions and information, we then know who's following a vegetarian diet,

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who's eating a meat diet, for instance, and we can then follow them up over time.

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So people are very kind to also allow us to access their records, their NHS records.

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So National Health Service. So if someone's gone to hospital or had a cancer or passed away, we can see what's happened.

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So we can see did someone follow a vegetarian diet, say, in 2000?

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And then we could see over time we might ask them again repeatedly, Oh, what was your diet five years later?

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What was your diet ten years later? And we can use this information to look at diet over time with different health outcomes.

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So then what we're doing is really comparing. We see people who, say, developed ischaemic heart disease.

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So for instance, heart disease, what's different to the people who developed heart disease compared to those who didn't develop heart disease?

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Were they eating a different way? Did they smoke? Did they not smoke?

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What was their weight, for instance? So then we can compare and see.

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Right. Are the vegetarians and vegans having more or less of different disease outcomes, for instance, to people who are eating meat?

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You just some very interesting points. I'm just going to kind of pinpoint those.

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First of all, biomarkers.

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What are those?
The biomarkers, unlike, for instance, with a questionnaire where you're asking questions maybe on a survey or in paper,

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biomarkers are actual measures of what's happening in the body.

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So, for instance, blood biomarkers is something that we might use a fair bit in in nutrition.

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We have different types of biomarkers. So we have what's called recovery biomarkers that are trying to reflect absolute intake.

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So, for instance, energy, how much energy did somebody consume?

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Now, this is great because it's very, very precise.

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In theory, you should be able to find out how much energy someone ate.

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But it's very expensive; you have to take it to a lab to process it.

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It's not always the most feasible thing to do.

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So we do have some other biomarkers in nutrition, but they need to be used in combination with dietary surveys.

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So for instance, you might want to know if somebody had fruit and vegetable intake.

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So you might ask them to tell you in a questionnaire.

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We can have a biomarker that tells you, well, what, someone's vitamin C in their blood right now.

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Now, that's helpful because you can try to compare them. And you can imagine that if I looked at your vitamin C in your blood,

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that doesn't require you having to remember if you ate fruits or vegetables yesterday.

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So it does get rid of that. But it's not always perfect because when I measure the biomarker might change completely.

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So you might change during the day between days.

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Also, your metabolism, your personality, the things that are about you

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for instance, your body size, how you metabolise that might affect it.

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So if you think of something like vitamin D, for instance, if we look at intake,

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that information is not really good because most of our vitamin D actually comes from the sun.

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So something like a biomarker might actually tell you that, whereas an intake might be a bit tricky.

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But of course, your body size, whether you smoke all these different factors, might affect the levels in your blood.

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Do you think in the future there may be more biomarkers that are going to adequately reflect our long term intake?

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Or do you think that something that may just not be possible for diet? 
I think it's hard to have sort of a one stop shop.

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I think the best we can do in research is really look at the evidence coming from different sources

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and seeing how it lines up and really try to understand why is this telling us something different.

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So for instance, with the vitamin D example, it makes sense that because it comes from the sun that looking at our intake might not be enough.

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So this area is developing and we have a lot of really clever techniques now to measure all these different types of biomarkers,

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and that is super informative and super helpful and it's a really exciting space.

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So that area is still developing,

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but I still think that it's best to do it in combination with the different types of data that are available, not the sort of the one solution.

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All right. So we need cohort studies. We need very good questionnaires.

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We need biomarkers. What else do we need? 
Well, genetics is an area that's of interest.

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It's been particularly useful for some areas, maybe not for all aspects of nutrition, but it depends how you define nutrition.

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So for instance, something like alcohol could be called a dietary factor, but it's really also a lifestyle factor.

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We also have trials. So trials don't work for all aspects of nutrition because of course some diseases take so long to develop.

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Some things trials are quite useful for nutrition. For some things, genetics might be.

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For others, observational study biomarkers. So it's really this kind of mixed bag of where we're getting our evidence from.

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If you open up pretty much any magazine these days in the UK or anywhere in the world,

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you'll see a very large headline saying "this is a superfood, you should eat this" or "this is really bad for you".

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What do you think about that when you read such statements? One - we're popular.

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Everyone loves nutrition. Everybody eats all the time.

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It's not a drug. It's not a for instance, smoking, for instance, food affects everyone from the day they are born to the day you die.

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You're going to be eating. So people have a vested interest. It's going to catch headlines.

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But then for somebody on the other end, reading the headline,

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I guess a few things that would be amazing if people could consider is please don't hate the scientists right away.

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Often the things we put out are not exactly what's being picked up in the headline.

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And I think it's good to have like a toolkit of what do you do if you do read this headline that just says something,

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you know, "butter is good", "butter is bad". What do you do?

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Yeah. And I think that some things to sort of keep in mind are really what was the question?

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What were they asking? So, for instance, if they're asking, is butter good or bad,

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what are they comparing it to? Are they comparing eating butter versus just eating sugar all day?

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Because in that case, butter might look a little bit better than if you're comparing butter to maybe whole grains and different oils, for instance.

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So what's the actual question? Are you comparing something that makes sense?

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It needs to sort of be plausible. And when we're thinking about that, things that can actually maybe lead to something.

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So having more of this might lead to more of that, it's really does it make sense?

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Is it biologically plausible? Is this something that could have just been an artefact?

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We look at really large numbers. So sometimes you find things that you weren't looking for.

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So to think about what was the question at hand to think about, does it make sense?

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What does the evidence say overall? 
I am going to ask you to give a mini lecture on what you think,

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given all the current evidence out there, is the best diet for any person living on the planet right now.

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I think anybody who's got any sort of aunt or grandmother in their corner would have probably grown up with hearing.

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"it's all about balance", and "don't have too much of those, don't have too much of that".

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And I really think there's some really good advice there.

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In the end of the day, that it's really about staying within some form of balance.

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We have some good evidence around plant based foods so that consuming more fruits and vegetables and beans and legumes and

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maybe trying to limit the amount of red and processed meat that were eating every day that it seems to be health promoting.

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And this might be from various types of diets,

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but these are the components that we know more about and that our guidelines are supporting. In terms of what we eat in our diet

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it's so cultural and it's so personal and specific.

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And for instance, when I was doing my research in the Philippines, rice was so important and it was really sort of the central meal of the day,

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whereas in other parts of the world, maybe bread is the centre of the meal.

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So what goes into your meal is going to be so dependent on what you like, what makes you feel good,

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what you can afford, what you know how to cook, what you enjoy, what maybe you've been handed down from your family.

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But I think also when we're thinking about diet, we do know that we have more evidence for consuming more plant based foods.

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But it's not just about our health. There's other aspects.

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So besides maybe religion and culture and also preference, taste time what

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you know how to make- environment.

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We have good evidence that reducing our red and processed meat, it is helpful and it does help reduce impact on the environment.

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So I think when we think about our diet, there's so much to think about.

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But in the end of the day, it's what's going to fit in with your lifestyle and you might be someone who doesn't consume meat at all.

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So what you're eating in the day might be completely different.

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And we've learned from looking at vegetarians and vegans, for instance, in our cohort in Epic Oxford,

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that it's not just about removing the steak from the plate and putting tofu on there, but the whole day is different.

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More vegetables, more grains, more cereal. Everything changes throughout the day.

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So to answer your question, I think the day could be completely different within those sort of boundaries and guidelines

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and really also thinking about not just health but our environment and other things that are

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important to us and trying to limit some of the things that we think could be worth limiting,

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like salt and sugar and saturated fat. 
But what can you tell us about alcohol?

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Because some people would say, well, one glass of wine per day is actually good for you.

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Other people, they would say you should not drink at all.

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Other people may say, well, maybe a moderate amount of alcohol is actually good for your mental health, for example.

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Is there any evidence on that or what is the evidence like?

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Alcohol is so interesting.

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Again, it's both could be considered diet, but it can also be considered lifestyle and and living in the UK seeing how embedded,

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makes you think about well what happens if someone who's never having alcohol? They're probably going to be different,

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right? What does that say about them? It's probably not random if you're not having alcohol, especially somewhere like the UK.

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Maybe you're sick, maybe religious purposes, maybe for some different reason you're not having alcohol.

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So it's good to keep in mind when we're thinking about alcohol that comparing anything,

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any intake to someone who never drinks, the never drinkers are a little bit different.

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They're not at random. There's probably something a bit special about them. Now in terms of the research about

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what we know about consuming alcohol in different health outcomes when it comes to cancer,

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more alcohol, pretty much more of many cancers.

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So if you think about it, it makes sense through the mouth, the pharynx, this sort of area really through the GI.

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that all going down to the liver, of course, right,

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your breast, colorectal cancer, there are several cancers that more alcohol, more risk of these cancers.

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So not drinking at all would mean the lowest risk of those cancers?

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That's right. So it's really sort of this dose response where more alcohol is more of these cancers. With cardiovascular disease risk

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there have been a bit of a mixed bag in the literature.

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So we used to see, and we still see, this situation where some studies show what's called a j-shaped association,

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which means that no alcohol looked like it had it looked worse than some alcohol.

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Exactly. Actually, one or two glasses per wine is a for example. Exactly.

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Now why that's happening. So again, if you keep in mind, if we're comparing to people who have no alcohol, they might be different.

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So again, are they people who had an illness who are no longer drinking because of their illness?

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It might not be the best comparison group. So more and more we're moving towards, instead of comparing it to non-drinkers,

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to maybe people who drink a little bit because they might be a little bit more or less outstanding than the non-drinkers.

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In terms of the evidence we do have, it's mostly observational.

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Now, if you're trying to report alcohol, that is really tricky because it can come with judgement.

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Also, if you're trying to remember if it's wine versus if it's beer, if, if you're say out,

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you might not really know the differences or maybe you're having a drink that mix with them all together.

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Now also, okay, let's say you remembered in your report and you put it in the survey and you know the amount and you're okay with all that.

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The type of drink might just depend.

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So people who are drinking beer might not be the same as people who are drinking wine and champagne in terms of maybe your ethnicity,

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in terms of how much you can handle having different alcohol types or if you're a man versus a woman.

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So there's trickiness around reporting how much we're consuming, what we're consuming,

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the types we're consuming, who's drinking the different types of drink.

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So all these factors muddle up a little bit when you're trying to then look at alcohol, which makes it so tricky.

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So these associations we were seeing with cardiovascular disease risk,

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we didn't know if to take them at face value or if this is really what's happening.

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And more recently, we've been able to have some genetic evidence with regards to alcohol.

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And in East Asians particularly is is a really interesting group to look at because they have a genetic variant.

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So it means that they have something different about their genetic predisposition to how they metabolise alcohol and they don't do it as quickly,

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which means that they're probably not going to feel very good if they drink too much.

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So having this genetic predisposition to metabolising alcohol slowly is sort

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of a predictor of the fact that you're probably not going to drink very much. So using that evidence, using genetic evidence,

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there's been research showing that when you don't look at the observational, so when you're not looking at people self-reporting in questionnaires,

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but rather looking with the genetic evidence, this j-shaped association not as clear.

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So, for instance,

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if some of the observational evidence showed that there might be this sort of protective effect of some alcohol for heart disease and for stroke,

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some of the genetic evidence isn't actually showing this and is actually showing that more alcohol, more stroke.

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What about red or processed meat? How far are we in figuring out how bad that actually is for you?

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Because I think there are some people who still don't believe that eating meat is bad for you.

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And they may use, I don't know, personal arguments that they just like eating meat, for example,

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or they'll say that people have been eating meat for centuries now.

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How do you feel about that? 
Great question. Something that takes up a lot of my thoughts during the day, I'll be honest with you.

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Processed meat and red meat. Not the same thing. 
Can you please explain what is the difference?

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By definition, processed meat should be something that has enhanced shelf life.

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It's been cooked or smoked or cured. It's had something added to it preserved.

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So like bacon that's been cured, for instance. So it's something a little bit different about it.

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Things have been added to it. A lot of salt has been added to it potentially, right?

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Which you then start thinking, right, a lot of salt, maybe blood pressure, maybe stroke and heart disease.

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But processed meat is still a little bit of a grey area because in terms of risks.

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In terms of the evidence,

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for instance, processed meat in colorectal cancer is our best evidence when it comes to what we're most confident about for processed meat,

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with higher processed meat intake, increasing risk of colorectal cancer.

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And some of the reasons we think is maybe because of the additives or what's been added to the processed meat.

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But processed meat could also be a burger.

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And if you made the burger at home by mincing it, basically that's unprocessed red meat ground up,

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whereas if you're getting it from an outlet, so a takeaway place where it's been processed differently, it comes a little bit different.

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So processed meat is different to unprocessed red meat,

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which in theory shouldn't have undergone the curing or the preservatives or the colours being added to it.

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Finding people who eat just one is a little bit tricky. So if you're studying people in the population, these are real people.

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If you're getting someone to fill in your questionnaire and say, Oh, do you eat bacon? Yes.

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Do you eat steak? No, no, no. I'm bacon only, right?

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Yeah. People tend to eat both of them. So then when we're studying it, sometimes it's tricky to pull apart.

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So some things I think are a little clearer.

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So I think if you think of maybe bacon or if you're thinking of salami, you might think of those as processed meat.

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But maybe some of the foods in the middle, maybe some of the pies and the burgers, maybe kebab, those sort of things.

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You might not know where you kind of sit. And then, of course, health implications.

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So the evidence we have is with processed meat, with colorectal cancer.

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That's our strongest evidence and probably for unprocessed red meat. With regards to heart disease,

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we think there's some good evidence there as well that consuming more red and processed meat might increase the risk of heart disease.

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And again, when we're thinking about diet or any risk factor, it needs to make sense and what could it be about it?

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And red and processed meat often have a lot of saturated fat.

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And saturated fat can increase LDL, which is your low cholesterol.

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That's considered the less favourable cholesterol,

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which has been associated with a higher risk of ischaemic heart disease or heart disease, for instance.

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So it could make sense that there's something but again

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I think it's interesting to really dive into separating out some of the different meats separately and getting

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more information from people who are eating sort of just this or just that and also how much they're eating.

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Are they eating just a rasher of bacon a day or are they eating really large amounts? because how much you eat might affect.

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So we're still figuring it out as well. There's no definite answer, but there are some very strong trends.

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Yeah. And so I would say for colorectal cancer and potentially for heart disease,

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those are the outcomes that we are more confident about with regards to red and processed meat.

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And you've mentioned salts already, but could you elaborate a little bit more on that, please?

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Salt does make our food tastes great.
And it's everywhere.

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Like, how can we eliminate salt? I think it's almost impossible.

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Yeah, it's a really interesting point and also how it's consumed.

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So, for instance, in a place like the U.K., a lot of salt would be consumed in our pre-packaged foods where,

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for instance, maybe in some other countries, a lot of salt would be from home making it.

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So you're adding it yourself so that in terms of reducing it, if you're adding it when you're cooking at home,

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it's going to be different to if it's already in our products. So here, because it's already in our products,

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it kind of needs to be at the higher level in terms of reducing the amount of salt or maybe substituting the type of salt that's being used.

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I think my last question is always what would your personal and professional advice be for young professionals?

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I would say on a personal note, to stay curious, not to be afraid of asking questions,

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to keep learning, to just keep getting better and to just keep growing.

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And on a professional level? Do what you love.

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That's not always possible.

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Sometimes people can't afford to work in jobs that allow them to do exactly what they love, but just hang on to it in your mind.

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And down the track, there might be an opportunity to be able to pursue that path.

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Or if anyone asks for ideas, you're sort of ready to go. So you do what you enjoy and it'll make everything so much better.

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It was wonderful to have you in the studio with us today, Keren. Thank you so much for joining.

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Next week, we'll be joined by Professor Sir Rory Collins,

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who is one of my mentors and who is the head of the Nuffield Department of Population Health at the University of Oxford.