Can you reverse damage from a bad diet?
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Hello and welcome to Zoë 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 Berry. Today we're asking, can you reverse the damage from a bad diet?

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 researchers actually attempted to assign set amount of time to certain foods that could help hack your diet and prolong your life. 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. It does. And whilst I'm actually really sceptical of this kind of approach to defining the healthfulness of our diet based on just single foods, you know, given that our diet is so much more complex than this, some of the data produced could actually help people make smarter choices when it comes to their diet. Sounds brilliant. Let's dive into it.

So first of all, Sarah, this idea that some foods can extend your life expectancy actually goes back millennia. We did a bit of research and apparently 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. So 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? No, simply. You know, it's disappointing. There's just no silver bullet when it comes to our diet. Our diet is far more complex than single foods. It's a combination of many different foods, each of which have thousands of chemicals in each food, which interact with the other foods and other chemicals in the meal to really 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 actually 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.

I like the idea of that. It's very simple. So let's start maybe with the bad news, Sarah. What's the biggest offender in terms of shaving those precious moments off of my life?

Okay, so if we look at some of the individual items that they reported on, the study found that due to its high content of processed 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.

36 minutes, that doesn't sound good. Definitely 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? Well, I don't think many of these will actually 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. 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 actually add to my life expectancy. So what can I eat and actually add minutes to how long I'm going to live? Yeah, so the foods that add to your lifespan include seafood, and this 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 omega-3 fats that are found in some fish.

Nut butter is actually ranked really high as well, largely due to the healthy fats, protein and fiber. And what may surprise some people actually is that 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.

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?

No. Diet's far more complicated than this. So we may have found a small flaw in this research approach. But given that 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? Okay. So according to the researchers who undertook this analysis,

they do say, yes, you can offset. So if we take vegetable pizza as an example, vegetable pizza has a near neutral effect on the minutes lost. And this is due to the vegetable in the pizza offsetting the unfavorable effect of the salt and the fats in the pizza.

I'm pretty surprised to hear this, Sarah, and I want to listen to your own 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

Is it just too late? 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 and fruit and vegetable intake.

And sadly, this is a typical Western diet that most of us consume. So I think everyone who's been listening to this podcast for a while is not going to be surprised to hear that a typical Western diet is bad. For this sort of research, how do they define a good diet?

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 diet.

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 they then estimated how many life years we would gain if we follow this optimized diet. And an optimal diet included for more legumes, pulses, whole grains, nuts, particularly less meat and particularly less red or processed meats.

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 here? 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 prohibitive.

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 that not everyone is able to completely change their diet.

or have access to the foods or resources required for the optimum 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.

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?

Okay. So according to this research, it depends how old you are. And I'm not going to ask you in front of a big audience, how old you are, Jonathan. I'm 47, Sarah. Okay.

Okay, I've got a few years on you then, Jonathan. So, you know, according to this evidence, it depends upon when you adopt this healthy diet. And what I think is really, really positive is that actually even up to adopting this at age 60 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 levels.

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 that 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 that the benefits of the feasible diet, so this kind of midway diet, were 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.

That's a pretty strong message, right? So that suggests that it's not too late to say, you know, I can make a change to my diet, even if you might have been causing a lot of damage for many, many decades. 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 what

age you give up smoking, there is a benefit to your quality and your quantity of life. And exactly 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 what? I followed this bad diet all my life. Really, is there any point changing? I think this is really nice evidence to show that

that there can be a benefit. Now, it is like you say, evidence based on a whole 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 really encouraging for people.

I think that's fantastic. I have to admit that I'm a little skeptical 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 basically 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, you know,

a false set of confidence perhaps, and this is part of the challenge that I think we faced at Zoe over the last six years, right? Really getting down to understand what individual foods do and how this links is very hard.

I think what there is, which I think is really exciting, is a lot of these very strong randomized control trials where people look at making changes in their diets and where you can see real results in sort of their bloods and their cholesterol and things like this quite fast. 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, you know, are we going to get fixated on, you know, what could seem silly little numbers, you know, how many minutes this food gives versus that food? I think where the,

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 personalise

their diet based on their preferences to make really simple swaps. And so instead of seeing as in, oh, I must never eat a hot dog, I think it's a case of, okay, I really like hot dogs, but is there something else I really like that can be cooked in the same way or the same cost or same accessibility for me? And how much healthier is that? So it's a way of kind of ranking foods in a healthy way. And I think

This gives that more personalised approach that means there's a better chance of being able to sustain the change because you're making these simple swaps. And again, you're empowered by knowing that actually they are likely to have a favourable health effect.

And what about the question I guess I was asking about, you know, how fast can you have an impact? Because I think if I was listening to this, I may feel, you know what, I've had a terrible diet for decades. That's great, but I've got to make this profound change for years before I'm going to get any benefit. What does the science say?

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 kind of sugar dips that you can have with some of these unfavorable foods.

that sap your energy and increase your hunger. So you can see switching from some of these bad foods to good foods immediately having impacts on energy, on hunger and alertness.

You can also see favorable 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 that's happening, but it is happening immediately in that two to six hours after consuming that food. So what you're saying is even in the first day of switching diet,

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, right? And 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 impact?

Okay, I know, Jonathan, you always want a simple answer and you hate it when I say it's more complicated than that. And it depends on X, Y and Z. So apologies, 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. It depends, you know, 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 no average. But if we took, say, a typical person that's got slightly high blood pressure, slightly high blood lipids. 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. So we know from hundreds of randomized controlled 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, about six weeks to see improvements in our insulin sensitivity. So that's our glucose control and our predisposition to developing type 2 diabetes.

I think that's a pretty wonderful way to wrap this up. The firm answer then, Sarah, is absolutely you can change your diet and sort of reverse the path where you've been on and some of the damage you've done previously. Absolutely. You're never too old to change your diet.

But remember, you don't have to go to extremes. Even making small switches, small swaps can actually have a big impact on your health. So remember to try and make these changes while still focusing on ensuring that you're enjoying your food and getting pleasure from what you're eating. I think that sounds wonderful. And if you'd like to try Zoe's personalized nutrition program to really 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 joinzoe.com/podcast and as always you can get 10% off the test and the program there. I'm Jonathan Wolf and I'm Sarah Berry. Join us next week for another Zoe podcast.