Updated 14th March 2023

Can you reverse damage from a bad diet?

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    A recent study claims that eating a hot dog reduces life expectancy by 38 minutes, and eating salmon could extend it by 70 minutes. At face value, this data implies you can eat your way to immortality.

    Taken with a pinch of salt, it suggests you can offset the harm from poor dietary choices. But does food really work this way?

    In today’s short episode of ZOE Science and Nutrition, Jonathan and Sarah ask: Can you reverse the effects of a bad diet? 

    Follow ZOE on Instagram.

    If you want to uncover the right foods for your body, head to joinzoe.com/podcast and get 10% off your personalized nutrition program.


    [00:00:00] Jonathan Wolf: Hello, and welcome to ZOE shorts. The bite-size podcast, where we discuss one topic around science and nutrition. I'm Jonathan Wolf. And as always, I'm joined by Dr Sarah Barry today, we're asking, can you reverse the damage from a bad diet?  

    [00:00:18] Sarah Berry: So Jonathan, everyone wants to live a long and healthy life and we know that a lifetime of healthy food choices can increase your life expectancy, but some research has attempted to assign a set amount of time to certain foods that could help hack your diet and prolong your life. 

    [00:00:33] Jonathan Wolf: Well, that sounds very cool. So you're saying there is a definitive list of how to get rid of all those terrible dietary choices in the past. And I will be able to figure out exactly how many years I would live longer as a result. It sounds a bit too good to be true.  

    [00:00:47] Sarah Berry: It does. And whilst I'm actually really skeptical of this kind of approach to defining the healthfulness of our diet, based on just single foods, given that our diet is so much more complex than this, some of the data produced could help people make smarter choices when it comes to their diet. 

    [00:01:03] Jonathan Wolf: Sounds brilliant. Let's dive into it. So first of all, Sarah, this idea that some foods can extend your life expectancy goes back millennia. We did a bit of research and the ancient Greeks wrote about the life-extending power of Ambrosia, which I've yet to try, but I'm definitely up for. Apparently, explorers in the 16th century spent their lives searching for the fountain of youth. We're no longer praying to the gods or searching the world for magical water sources, but we are still obsessed with finding foods with these mythical properties that will extend our lives. So does science support any of this magical thinking that we've been going after for thousands of years? 

    [00:01:43] Sarah Berry: No, simply, as disappointing as it is there's just no silver bullet. When it comes to our diet, our diet's far more complex than single foods. It's a combination of, you know, many different foods, each of which has thousands of chemicals in each food, which interact with the other foods and other chemicals in the meal to modulate their health effects. 

    Plus we have to consider our dietary habits such as the timing that we eat, our food, the order that we eat, our meals, how much sleep or exercise we've had and so forth. Because all of this can also modulate the health impact of any given food on our body. 

    However, Jonathan, having said this. There is some interesting research that was published by Michigan University that analyzed almost 6,000 foods found in the diet of typical Americans and compared how healthy or unhealthy they were using the idea of how much time they added or removed from our life expectancy. 

    [00:02:36] Jonathan Wolf: I like the idea of that. It is very simple. So let's start maybe with bad news. Sarah, what's the biggest offender in terms of shaving those precious moments off of my life.  

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    [00:02:47] Sarah Berry: So if we look at some of the individual items that they reported on the study found that due to its high content to process meat and sodium, which is a measure of salt, in the food that a standard hot dog takes an entire 36 minutes off your life expectancy. So imagine that in the context of someone consuming a hot dog maybe every other day. 

    [00:03:09] Jonathan Wolf: 36 minutes, that doesn't sound good. Bad for all the professional hot dog eating contestants who are listening to this podcast for the rest of us, what other foods are considered to be the most harmful to my lifespan.  

    [00:03:22] Sarah Berry: Well, I don't think many of these will come as a surprise. So it's mainly other highly processed foods like bacon, pizza cheeseburgers, which will also take several minutes from your life expectancy with every serving. So every portion of these that you have. 

    [00:03:37] Jonathan Wolf: Okay. So, that doesn't sound good, but it can't all be bad. You mentioned that they'd also looked at some foods that were on the other end of the spectrum and can add to my life expectancy. So what can I eat and add minutes to how long I'm going to live.  

    [00:03:51] Sarah Berry: Yeah. So the foods that add to your lifespan include seafood, which can range from anywhere between 10 minutes to 70 minutes. Depending on the type of seafood that you're having. And this is largely due to these healthy omega3 fats that are found here in some fish. 

    Nut butter, actually ranked high as well, largely due to the healthy fats, protein and fibre, and what may surprise some people is, really interestingly, the researchers found that there was no association between the food scores and the calorie amount in each of the food. 

    And this adds just more strength to this whole argument that we must focus on food quality and not calories. When we consider the health effects of foods.  

    [00:04:33] Jonathan Wolf: Got it. So what you're saying is that if I eat a certain fish every hour I can live forever. Sarah, is that right? 

    [00:04:40] Sarah Berry: No, the diet's far more complicated than that. 

    [00:04:43] Jonathan Wolf: We may have found a small flaw in this research approach, but given that we can, we rarely in fact eat single ingredients or foods in a meal. 

    So can I offset the bad foods with the good foods and make sure that my life expectancy is still as high at the end as at the beginning? 

    [00:05:01] Sarah Berry: Okay. So according to the researchers who undertook this analysis, they do say yes, you can offset. So if we take a vegetable pizza, as an example, vegetable pizza has a near neutral effect on the minutes lost. 

    And this is due to the vegetables on the pizza. Offsetting the unfavourable effect of the salt and the fats in the pizza. 

    [00:05:20] Jonathan Wolf: I'm pretty surprised to hear this, Sarah and I, I want to listen to your views shortly. So imagine I have eaten a lifetime of these life expectancy-reducing foods, and I think this was a good description of the first half of my life. is there a way to reverse the negative impact of this bad diet? Or is it just too late?  

    [00:05:36] Sarah Berry: So I think it's firstly important that we look at what we mean by a bad diet outside of these individual foods that we've just talked about. And overall, when we talk about a bad diet, we're talking about a diet that contains high amounts of processed foods, red meats, high sugar foods, low pulse, fruit and vegetable intake. And sadly, this is a typical Western diet that most of us consume.  

    [00:06:00] Jonathan Wolf: So I think everyone who's been listening to these podcasts for a while is not gonna be surprised to hear that a typical Western diet is bad for this sort of research. How do they define a good diet?  

    [00:06:10] Sarah Berry: So there was another really interesting research study, which took a slightly different approach to the one that we've just discussed, which was looking at these. Individual foods. And what they did is they looked at the whole diet and we know that it's really important to consider a whole dietary approach rather than demonizing individual foods or putting individual foods on a pedestal. And they devised something called an optimized diet. And this is based on research from thousands of studies, which then estimated how many life years we would gain if we followed an Optimized diet. 

    An optimal diet included more legumes, pulses, whole grains, and nuts, particularly less meat and particularly less red or processed meat.  

    [00:06:50] Jonathan Wolf: So we've got this researcher saying here is this sort of generic, optimal diet. We have to eat that completely. And we've also described the bad Western diet. Most people aren't going to be doing either of these two things. Is there a middle ground?  

    [00:07:03] Sarah Berry: Yeah. So I think you're right. That it's all very well telling someone to follow an optimal diet, but it's often actually really prohibited to people based on cost, taste and cultural preferences. So what I like about this research is that the researchers also calculated what would happen if people followed a diet, which was halfway between the typical Western diet and the optimal diet, and they called this the ‘feasibility approach diet’. 

    And this takes into account. Like I said, the fact everyone is able to completely change their diet or have access to the foods or resources required for the optimal diet. So it's great that we have a third option here for a pretty decent diet, and that's still significantly better than the Western diet. 

    [00:07:43] Jonathan Wolf: So let's say I've lived the majority of my life eating the typical Western diet. And I decide, you know, I wake up one morning and I'm like, you know what? I need to make a change. I want to embrace this sort of optimal diet from these researchers. Will that be enough to undo the damage that I've done to my body over the last 45 years?  

    [00:08:02] Sarah Berry: Okay. So according to this research, it depends on how old you are, and I'm not gonna ask you, in front of a big audience, how old you are, Jonathan. 

    [00:08:10] Jonathan Wolf: So I'm 47, Sarah.  

    [00:08:12] Sarah Berry: Okay. I've got a few years on you then, Jonathan. So, according to this evidence, it depends upon when you adopt this healthy diet. And what I think is really, really positive is that even up to adopting this age 60 or, or 80, there's an improvement. So if you swap to an optimum diet, you can significantly improve your life expectancy at a whole range of ages. 

    So for example, if you switch from a Western to an optimal diet at the age of 20, you could gain a whole extra 10 years. And even those who switched at the age of 60 would see an increase in their life expectancy on average, by about eight years. 

    I think what's important to note is the benefits of the feasible diet. So this kind of midway diet was also substantial. So we had a gain of about seven years. If you adopted it at 20 years of age and nearly five years if you adopted it at 60 years of age,   

    [00:09:00] Jonathan Wolf: That's a pretty strong message. Right? So that suggests that it's not too late to say, you know, I could make a change to my diet, even if you might have been causing a lot of damage for many, many decades. 

    [00:09:13] Sarah Berry: Yeah. And I think this applies across many areas of our lifestyle. If we think about exercise, if we think about smoking, there's really clear evidence at whatever age you take up exercise or whatever age you give up smoking, there is a benefit to your quality and your quantity of life, and the same we see with diet. 

    And so for people who are listening, that might be 40, 50, 60, 70, and think, well, do you know, I followed. Bad diet all my life, Is there any point changing? 

    I think this is nice evidence to show that there can be a benefit. Now it is like you say evidence based on different types of research. 

    It isn't what we would consider the strongest evidence from these randomized controlled trials. But I still think it's pretty robust and I think it's encouraging for people.  

    [00:10:02] Jonathan Wolf: I think that's fantastic. I have to admit that I'm, I'm a little sceptical about the first set of research that we talked about, where they were measuring the lifespan of individual foods because ultimately they're having to draw this from people recording on a piece of paper every few years, what they remember eating and then looking what happens over 70 or 80 years. 

    Right? Sarah. So trying to link this in that way to these specific numbers, I think can create a false set of confidence, perhaps and this is part of the challenge that I think we've faced at Zoe over the last six years. Right? Getting down to understanding what individual foods do and how this links is very hard. 

    I think what there is, which I think is exciting, is a lot of these very strong, randomized control trials, where people look at making changes in, in their diets and where you can see real results in sort of their bloods and their cholesterol and things like this quite fast.  

    [00:10:52] Sarah Berry: Yeah. I mean, I think I'd quite like to pick up on a few of those points, Jonathan, I think the first is around, is this kind of meaningful? 

    Is it adoptable by people? And are we gonna get fixated on what could seem silly little numbers? You know, how many minutes this food gives versus that food? I think where this is quite useful is if we look at the actual foods and from the research, there's a table published that's ranking these foods in terms of those that give life and those that take away life. 

    I think it can be used in quite an empowering way by consumers. It can allow the consumer to truly personalize their diet is based on their preferences to make really simple swaps. So instead of seeing as in, 'oh, I must never eat a hot dog'. I think it's a case of, ‘okay. I like hot dogs, but is there something else I like that can be cooked in the same way or is the same cost or same accessibility for me and how much healthier is that’? 

    So it's a way of kind of ranking foods, healthily, and I think. This gives that more personalized approach. That means there's a better chance of being able to sustain the change because you are making these simple swaps. And again, you are empowered by knowing that actually, they are likely to have a favourable health effect. 

    [00:12:07] Jonathan Wolf: And what about the question, I guess I was asking about, how fast can you have an impact? Cause I think if I was listening to this, I may feel like I've had a terrible diet for decades. That's great, but I've gotta make this profound change for years before I'm gonna get any benefit. What does the science say?  

    [00:12:23] Sarah Berry: I think that the evidence is quite clear that in some of these physical feelings you could see improvements very quickly. So we know this from studies that have been conducted and people talking anecdotally that when they switch to some of these healthier foods, they can, within the same day, feel more energy, not have these kinds of sugar dips that you can have with some of these unfavourable foods. 

    That sap your energy and increase your hunger. So you can see switching from some of these bad foods to good foods, immediately has an impact on energy, hunger and alertness. You can also see favourable effects immediately on what's going on at the level of your physiology. So in your blood, in all of these circulating factors that I talked about earlier now, unfortunately, you can only see that by doing blood tests or certain measures. 

    So you won't know that's happening, but it is happening immediately in that like two to six hours after consuming that food.  

    [00:13:18] Jonathan Wolf: So what you're saying is, even in the first day of switching diets, I'm already having an impact on the stuff that's going on inside my blood. And how long would I have to wait to be able to see something that maybe if I went to visit the doctor? 

    Maybe the doctor said you have high cholesterol or whatever these things are, your blood sugar levels are high. How long, based upon sort of real randomized control trials, would you have to wait to be able to see.  

    [00:13:41] Sarah Berry: Okay. I know Jonathan, you always want a simple answer and you hate it. When I say it's more complicated than and it depends on X, Y, and Z. 

    So I apologise but I do have to say it's more complicated and it depends on X, Y, and Z. So it depends on who you are to start with. There's huge variability. And we know from our Zoe predict studies in how individuals respond to food is hugely variable, but let's take the average person. 

    And I know we try and avoid talking about the average person because there is. Average, but if we took, say a typical person, that's got slightly high blood pressure, slightly high blood lipid. So by that, I mean, cholesterol and is slightly overweight. If we were to change their diet from a typical Western diet and we were to change it to this feasible or this optimized diet, you would see improvements pretty quickly. 

    Now, again, it depends on the outcome. We know from, you know, hundreds of randomized control trials that you can see changes in as small as two weeks in blood cholesterol to a healthy diet. We know it takes about six weeks to see improvements in blood pressure and about six weeks to see improvements in our insulin sensitivity. So that's our glucose control and our predisposition to developing type two diabetes.  

    [00:14:54] Jonathan Wolf: I think that's a pretty wonderful way to, to wrap this up the firm answer then Sarah is, you can change your diet and sort of reverse the pathway you've been on and some of the damage you've done previously. 

    [00:15:07] Sarah Berry: Absolutely. You can change your diet so that you are never too old to change diet. But remember you don't have to go to extremes, even making small switches, small swaps can have a big impact on your health. So remember to try and make these changes while still focusing on ensuring that you are enjoying your food and getting pleasure from what you're eating. 

    [00:15:28] Jonathan Wolf: I think that sounds wonderful. And if you'd like to try ZOE's personalized nutrition program. To understand actually what's the optimal diet for you, and help you through this pathway. Because as Sarah said, this is complicated, then go to join zoe.com/podcast. And as always, you can get 10% off the test and the program there. 

    I'm Jonathan Wolf. 

    [00:15:48] Sarah Berry: and I'm Sarah Berry.  

    [00:15:50] Jonathan Wolf: Join us next week for another ZOE podcast.

    This podcast was produced by Fascinate Productions.

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