ZOE Science & Nutrition - The truth about low carb diets, sugar spikes, and ‘multigrain’ labels | Prof. Tim Spector

Episode Date: March 27, 2025

Carbs are one of the most misunderstood aspects of nutrition. For decades, they’ve been praised, demonized, and debated. Today, low-carb diets are everywhere, but the reality is more nuanced. While over 80% of the carbs we eat come from low-quality, refined sources, the right kinds of carbs are essential for good health. In this episode, Professor Tim Spector breaks down the difference between good and bad carbs and explains why quality matters more than quantity. He explores how the rise of ultra-processed foods has led to an overconsumption of unhealthy carbohydrates, contributing to energy crashes, hunger, and long-term health issues. He also explains the benefits of fiber-rich carbs, their role in gut health, and why cutting carbs entirely may not be the best approach. The episode also answers common questions about carbs, including the best time to eat them, how to pair them for better digestion, and whether alternatives like almond flour are actually healthier. Tim also shares practical tips, such as why freezing bread might be a simple way to make it better for you. 🥑 Make smarter food choices. Become a member at zoe.com - 10% off with code PODCAST 🌱 Try our new plant based wholefood supplement - Daily 30+ Follow ZOE on Instagram. Timecodes: 00:00 Introduction 01:39 Quickfire questions 03:06 What is a carb? 07:43 Is rice healthy? 08:56 What makes sugars unhealthy? 11:49 Truth about sugar spikes 14:49 Potatoes, white rice, bread and pasta 18:44 'Big Food' industry 21:22 What is a good carb? 27:32 Effects of low carb diets 33:18 Effects on mood & energy 36:25 Tim's favourite carbs 39:48 When should you eat carbs? 41:47 Eating carbs with other foods 46:45 Should you freeze bread? 50:33 The healthiest rice 50:53 Is multigrain and wholemeal healthy? 56:20 Should you consume flour? 59:45 Easy way to improve healthy carb intake 📚Books by our ZOE Scientists The Food For Life Cookbook Every Body Should Know This by Dr Federica Amati Food For Life by Prof. Tim Spector Free resources from ZOE Live Healthier: Top 10 Tips From ZOE Science & Nutrition Gut Guide - For a Healthier Microbiome in Weeks  Mentioned in today's episode Trends in Dietary Carbohydrate, Protein, and Fat Intake and Diet Quality Among US Adults, 1999-2016, 2019, published in  Journal of the American Medical Association Carbohydrate intake for adults and children: WHO guideline, 2023, published by World Health Organization Association between changes in carbohydrate intake and long term weight changes: prospective cohort study, 2023, published in British Medical Journal Low-Carbohydrate Diet, 2023, published in National Library of Medicine  Diet Review: Ketogenic Diet for Weight Loss, published by The Nutrition Source, Harvard TH Chan School of Public Health Have feedback or a topic you'd like us to cover? Let us know here. Episode transcripts are available here.

Welcome to ZOE, Science and Nutrition, where world-leading scientists explain how their research can improve your health. Eating a low-quality carb when you're hungry is like throwing crumpled newspaper into the fire. The flames roar for a moment, but then they fade to nothing almost as quickly, leaving you in the cold. Over 80% of the carbs we eat are like that crumpled newspaper. You feel full in the moment, but hungry shortly after. Now imagine reaching for a sturdy log instead. The flame doesn't leap up in an instant. It builds slowly and stays warm throughout the night. And that's what you get with

a high quality carb, feeling full for longer. Carbs seem so simple when explained this way. But which are the good carbs? Are they better for breakfast or dinner? Can we mix them with something else to make them healthier? This complexity is confusing and celebrities peddling restrictive diets are making matters worse. Today, Professor Tim Spector sets the record straight, according to the latest research. Tim has written three books debunking diet myths, and today he'll give you the information you need to know to eat healthy carbs without restricting your diet. Tim, thank you for joining me today.

What a pleasure. So, I don't think I really need to explain the rules to you, Tim. We are, as always, going to start with our rapid-fire questions from our listeners. Are you ready to go? Hit me. All right. Are all carbohydrates bad for us? No.

Do we eat too many bad carbohydrates? Yes. Is a low carb diet a healthy choice for everyone? No. Could pairing your carb with another food make it healthier? Absolutely. Is there a time of day that's better for eating carbs? For some people. And finally, what's the most common misconception

about carbohydrates? I think most people believe that all carbs are bad and that's absolutely not true. Some of them contain fiber are the most essential foods we can eat. Well, I think that's hopefully what we're going to do today. And I'll be honest, I find the topic of carbs quite confusing. When I say the word, I was thinking about this as I was coming in this morning, I immediately think of this freshly baked loaf of bread, right? You can smell it, smells amazing, and then the delicious taste. And then unfortunately, Tim, you've ruined it for me, because I now know that it's followed by my blood sugar jumping through the roof over the next couple of hours. And at that that point suddenly I'm feeling tired and hungry or hangry as my family would say. But Tim you've also told me that carbs aren't just bread and potatoes. So what is a carb

and what is it that can make it unhealthy? Well a carb is a macronutrient. So in the old school world that we used to know, everything was divided into these three groups of proteins, fats, and carbs. And most other things we eat are mixtures of those rather than one thing. You don't actually eat a carb. You eat a plant, and that plant will have different amounts of proteins, fats and carbs in it. And within the carbs, it's going to have different types of carbs in it. And some of the foods we eat, which you say, oh, that's a carby food, like say bread, is also going to have

some protein in it and a little bit of fat in it. So we tend to massively oversimplify, but that's what we've done in the past, mainly through ignorance, and the food companies have liked it that way because it's made it very easy to sell products to us. Now, I think we need to break down carbs into what they are, which they are essentially sugars that are either very simple, moderately simple, and really complex, and long and hard to break down. The simple sugars like sucrose, your table sugar, is a very simple carbohydrate. It's a very simple sugar.

It means it only has a few bonds, easily broken down and used by your body as energy. Then you've got the starches, which are slightly more complex storage forms of sugar, which are joined together by bonds, which can be broken down by other enzymes in your body. Every plant has these starches and we're designed to do them. They break it down into simple sugars, which are then released. It just takes a little bit longer. designed to do them. So they break it down into simple sugars, which are then released, just takes a little bit longer. And then you've got the really complicated long sugars all joined together with lots of tight bonds that are called fibers. And these are sometimes

really impossible to break down in the body and only by the gut microbes sometimes rather than ourselves and they pass through the body. So you've got this complexity all the way from simple to very long and complex with very different effects on the body. So most people think of carbs as only the sugary end ones. They forget a lot of the healthy carbs are these complicated fibers at the other end. So they throw the baby out with the bath wards, say, I'm not having any carbs, it's all rubbish, they're all deadly.

Well, that's not true. And could you give me some examples of what those like simple and starchy carbs are? Well, a simple carb is like table sugar, it's like honey, maple syrup, these things here. There's nothing, it's just you and the sugar, right? Coca-Cola, because it's got added sugars to it. So the sodas, they're having essentially table sugar or fructose, high fructose corn syrup,

which is the sugars extracted from corn, which is virtually identical to table sugar, just a slightly different ratio. Again, a really simple sugar. These ones give you that instant taste in the mouth. An example of a starch, which is like this middle grade, is when you might eat a cheese biscuit or cracker. You put it in your mouth and it's savory. You don't taste any sugar.

If you keep it in your mouth, your enzymes in your saliva and it's savory. You don't taste any sugar. If you keep it in your mouth, your enzymes in your saliva will break it down. That starch will become into these simple sugars. And after it's been in your mouth about 30 seconds, it will turn sweet. Let me get that straight. You're saying that I might have this cracker, like it's not a sugar,

but within 30 seconds of being in my mouth, actually just like the saliva in my mouth, actually just like the saliva in my mouth has broken that down and turned it into sugar. Richard Lyle That's right, yes. And the same thing is, if you're having some white rice, or you're having a pasta, or having a potato, they're all starchy carbs, which are transformed fairly rapidly into sugars, but they're not sugar when they start. So it takes a little bit of work for our body to break them down. But often that's done really just with our saliva in the early stages of digestion.

It doesn't take that much. This is one of the things that most shocked me when I started doing Zoe with you, Tim, because I'd always thought of rice as being this really healthy thing that you had with sushi and that was so healthy or you had it with some sort of Asian meal and this was like much better than the food that I'd grown up with. And so I was completely shocked by this story that actually basically it turned into sugar almost immediately. Is that really what happens? Yes, unfortunately it is. What you think is the more synthetic rices like these so-called parboiled rices or the Uncle Ben's style rice actually happens slightly slower because it's

pre-cooked. It's been cooked in two stages. But most rice, particularly the sticky rices, are really sugars. And that's why in Japan you get these, most of their candies are made out of these sticky rice and it is known for its sweetness. So yes, white rice is a fantastic example of a very starchy food that converts very quickly into sugar, gives you a sugar spike in your blood and will have those consequences. And we used to think it was healthy, I agree. And, you know, before I got into this, that's exactly what I thought as well.

And Tim, could you explain a little bit what makes it unhealthy? So you've described the way that, you know, either you're just literally eating something with sugar in it, or you're eating one of these starches and you're saying it turns into sugar fast. What goes on that makes that then unhealthy for us? It's the way we react to the sugar rather than necessarily the sugar itself, which is bad because our ancestors were seeking out honey and other things with great relish. So when you have a

sugary drink or a soda or a bowl of rice, white bread, you will see after about 30 minutes a sugar spike in your blood. So your blood glucose levels will be going up very fast and you can see these in these glucose monitors that anyone who's done ZOE will know about. It varies in people how long and how high those sugar spikes are, but that then triggers production of insulin by the body to drive it down. And this is actually causing effort to the body. So there's a metabolic effort in doing this.

And if this is repeated a lot of the time, it's, I mean, some people find it hard to keep these spikes down. They're very sensitive. We found this in the Zoe study, if you remember, a few years ago now, tenfold differences between people like you and I in how we respond to a standard meal of a cookie or a muffin or whatever it is. Everyone's very different, but the people who suffer get these really big sugar spikes that causes metabolic problems that is working the body really hard all the time.

And we think this causes low level inflammation and goes on to lead to metabolic disturbances, increased risk of diabetes and all kinds of other consequences, as well as short-term ones, which we also showed, it can make you hungrier. So, that's the sort of catch 22 here is, yeah, okay, you have your little sugary snack to relieve hunger. What does it do? It gives you a sugar spike, maybe you get a dip after it.

You're even hungrier, so you're eating more during the rest of the day. So, long-term and short-term consequences of having sort of free sugars everywhere without real food to in a way to help mop it up. Every time I hear this story always slightly blows my mind Tim. It's this idea that like eating the food now might actually make me more food later. You know it's exact opposite of how I was brought up and I was thinking about this with my my wife you know this morning who has this very strong view that absolutely, my daughter mustn't leave the house

without having had a good breakfast, even when she's not very hungry. Cause I will, how could she possibly go to school if she's not hungry? And I think about this idea that obviously you don't want anyone to go to school hungry, but there is this weird thing that eating the wrong food as you're describing might actually make me hungry again

in two hours time. And is this real science? Because it sounds crazy. Yeah, it sounds very weird. And it's against everything we've been taught by our parents. But it's absolutely true. And we've shown this in our Zoe studies quite consistently that people who have these big spikes and the dips afterwards, three hours later, they're consistently hungrier than people that don't. And they will consistently overeat, you know, by about 10 to 20 percent over the day compared to people who aren't having those sugar spikes.

So it's now well known in the scientific literature, and it's one of the big dangers of, you know, not worrying about sugars. You've mentioned, I think, a lot of metabolic diseases and inflammation. How does this tie into this epidemic of obesity that we've seen over the last sort of 40, 50 years? Is this important or not really? I think it is very important because as we shifted away from fats to carbs and sugars

and starches in particular, and this was standard government health advice, we've been seeing increase in obesity, in heart disease and all those consequences. Many studies have linked obesity to intake of these starchy carbohydrates and free sugars. So some of this is due to, say, sugary drinks, beverages, sodas, et cetera, which can account for about a quarter of our sugar intakes. A quarter of our sugar intake can be from these sugar, sweetened beverages. Yeah, I mean sometimes more.

You know, so particularly more in children. So we thought we were sorting out your child's a bit hungry or thirsty, give them something, but actually you're just making it worse by giving them these high sugar intakes. And also sensitizing children to even more sweet tastes and seeking out even more unhealthy foods. So I think part of this is the massive amounts of soda beverages we've been having that are sugar sweetened. The other is this real push by governments and health people and the food industry towards starchy foods rather than fats or fiber. And so what are, if I was thinking about this on my plate, you know, you've mentioned white

rice and you've mentioned these sort of sugary drinks, what are the other big sources of these sort of unhealthy starchy carbs that someone listening might be putting on their plate? Well, we're surrounded by them really. You know, most of snack foods are starchy carbs, your potato chips, Doritos, your Pringles. Most of the breads that we're having are highly starch rich and very poor in fiber. These are the staples really. Most people are eating potatoes, rice, bread every single day. You only have to ask a family doctor and say when you've got your patients with pre diabetes or diabetes what's their diet it's nearly

all potatoes rice and toast which they've been told was good because it's low-fat. I think it's interesting because I think I was definitely brought up with a view well that sounds really happy. I mean a potato after all is sort of like a plant and it's taken out of the soil. You feel like you're doing something really good. I mean, I used to eat quite a lot of boiled potatoes and I didn't even really like them very much, but I felt, well, that's really healthy. And what you're saying is I could have eaten something really delicious that tasted sweet

as I was eating it, because I'd have got the same effect, which is it's been turned into sugar in my stomach in just a few minutes anyway. Exactly. So it's all about how quickly is that carbohydrate dissolved in your body? How quickly does it go? So there are even differences between types of potato. So you've got the worst, which is your... Do you like mashed potato, Jonathan? There was the artificial one, Smash, which was powdered. That was the ultimate in the quick fix. Is that right? You sort of get it instantaneously because it's been completely powdered.

Yeah, there's nothing for you to break down. It's all done for you. So then you've got normal mashed potato, then you've got boiled potatoes, then you obviously got fried ones, which are also easy. And probably the best ones are a small jacket potato where you're actually eating the skin. and then at least you're getting some fiber there, it's slightly harder to break it down. But they're all on a continuum, and generally the idea that potatoes are a healthy food, for most people that's not true. I mean, they're a very good source of nutrition, but in the modern world, I think we're probably eating too much of them. We're too reliant on those, you know, bread, potatoes and white rice. And to some extent, pasta, although pasta has some other advantages,

it's got more fiber in it. It's got more protein compared to rice. And why are we eating so much of these sorts of carbs? Is it just because they're the things that we like the taste of? I think it's a combination that they're comfort foods for many of us. I mean, white rice has a sort of health halo to it. And you look at every health cookbook generally, particularly vegetarian and vegan ones, they've got beautiful pictures of steaming white rice that look very tempting. And I think it comes from that.

You were saying earlier, the smell of crusty bread when you go into a restaurant and the first thing they serve you. I mean, it is irresistible for most of us. Just knowing that it should be more of a treat than a staple, I think, is really important. Or you pick the right ones, you fussy about which ones you're going to have and when. Because I'm not saying you should never have these foods. I'm just saying that if you're having them on a regular basis and you're susceptible, because not everyone is as susceptible, then it's a problem. So everyone

should know about it. And I think I've heard you talk a little bit about the role the food industry might have played in this. Yes, they're very keen to push these products because you can make them very cheaply. You can create powders so that they can be added to things. Ready meals are instantly made with carbohydrates that store forever, that you can add preservatives to and that keep you coming back for more.

So what they like is the fact that the more you eat, the hungrier you get and the more you want them. And there are examples in these carbohydrate snacks. My favorite is always Pringles, but you can cut the name out if you're worrying about being sued. No, no, go on. What was Pringles claim? Well, they claim they're a potato snack, but actually it's made up of about four different

plant extracts with rice and tapioca. Basically, they take the cheapest products they can use, the dregs of that, they dry it all up, and then they stick them back together, they glue them back together to look like a potato. And then they slice it up in these nice ways. And the average one has about 30 ingredients. If you look at the back of pack, which are flavorings, colorings, glues, emulsifiers to stick it together.

And Tim, I seem to remember something like, once you pop, you just can't stop. Is that, am I thinking right? That's right and if anyone's done this a test it is very hard to just have one of them and they've been created with these addictive properties but they're combining the carb with salt and some fats as well. So they know that that combination produces this bliss point. So very often when we're talking about, you know, how carbs are used in big food, it's in combination with these other ingredients to give them that perfect bliss point where your brain just

lights up with dopamine and you know, you go, ah, you know, isn't that nice? And it's a short hit, but you know, it doesn't last. That's crazy. So you get the hit, you feel that nice? And it's a short hit, but it doesn't last. That's crazy. So you get the hit, you feel good, then it falls away fast, and therefore you need the next pringle and the next pringle in order to keep it going. And then you've finished the whole tube and that's it.

Yeah, and you feel sick. That's amazing. So it's even faster than the description you were giving with the potatoes and the bread, where I'm getting this big blood sugar spike, it feels really good as I'm eating it, and then two to three hours later, I'm really hungry and I'm having to go back again.

Absolutely, yes. Now I feel like you've done nothing but tell us how awful carbs are so far, Tim. Some carbs, some carbs, Jonathan. Well, that's where I wanted to go, because I know that your very highly cited research has helped reveal the connection between the food that we eat, our gut health,

and like our overall wellbeing. How do we feel? And I know that within that, you've also talked about how carbs can be good. So could you help us to understand now what is a good carb and why do we need it? Well, a good carb is something that has important nutrients without the downsides of too much free sugar that causes these problems. So that is slightly harder to digest, but is full of the things that plants give you. Because remember, all carbs come from plants, not just cans or containers. So we're talking primarily about those that contain fibers and polyphenols. Now we've talked a lot about fiber and polyphenols, and basically the less processed that food

is, the more it's going to contain those two key elements which we think are really important for our health. And can you remind us just quickly what they are and above all why they're good for our health? So polyphenols used to be called antioxidants and they are these thousands of chemicals that you find in plants, natural defense chemicals, that when you eat the relatively unprocessed plant, you'll be getting the benefit of them, which will go through if it's not immediately digested into your gut and your microbes will benefit from it.

So they give you these really important heart benefits, anti-cancer benefits, many other ones that we're just discovering. Then the other element is the fiber. So fibers are these long string of sugars that are really hard to break into their component parts. Most of them pass as insoluble fibers throughout our body. A few can be mixed in with water. The key is these reach the lower part of our colon where our microbes feed on them and they can break them down and release all the nutrients and all the goodness from those fibers which help our immune system and make our gut microbes flourish.

And Tim, you were saying that when I was eating these like starchy foods, you know, I can start to, it hits my bloodstream in just sort of 30 minutes. Just as a contrast, if I'm eating these sort of less starchy foods with more fiber, how rapid is the process you're describing? You probably won't see any change in your blood sugar level from having a huge bowl of some fiber rich food, whether it's your spinach or your kale or your lentils, your

beans, your nuts, whatever it is, or rye bread for example. So you won't see a sugar spike Because everything's happening much slower much lower down And it's about the speed of which these these carbs are being digested so you've got sort of fast medium and slow and this is really slow and This is really what our body likes and it likes to take its time And it turns out that when you're eating these hard to digest foods, it fills you up more. So the total opposite to having those free sugars where you feel hungrier, these actually

make you feel fuller quicker. So you're less likely to eat fast, less likely to overeat. And that's part of the reason that they're helpful, as well as their impact on our gut and our general health. And just to put this in context, if you have five grams of extra fiber, which is actually just one tablespoon, one scoop of our daily 30 mixture, for example, every day, that will reduce your risk of heart disease and early death by 14%.

Five grams of extra fiber will reduce your risk of death by 14%. Correct. It's pretty mad, isn't it? I mean, that's a lot. It is. And when you think that we're supposed to be eating, you know, 30 grams of fiber, roughly each country has got its own slightly different levels. And we're generally, most Western countries are somewhere between 15 and 20 grams is what we're actually doing. Just an extra five grams can make such a really big difference to your health.

It's probably one of the most important things we can all do so easily. So I was thinking about your example between the two and I was thinking a little bit about driving the car. And, you know, when you've got sort of, you know, a teenage driver proving everything, they're like slamming on the accelerator and slamming on the brake, you know, when the lights change, just slamming on the accelerator again. And that sounds a little bit like this blood sugar spiking up and down with these starchy foods. And then I guess what I'm, I think your analogy is here is I'm eating these much more whole

grain foods, a lot more fiber. And it's sort of like I'm just steady the whole time. I'm not having to accelerate or break. And clearly if I keep doing that for 10 years, my car is going to be in much better shape than the person slamming it on and off. Is this a terrible analogy, Tim? No, I think it's pretty good actually. I think there's other things going on as well as this that are damaging your engine, but clearly your clutch is going to go pretty quickly if you're using those gears unnecessarily.

So your body is taking much more of a toll by having to deal with these glucose spikes than if you're not. That's absolutely evident. But there's also the big advantages going on in the gut microbiome of having all this food that many people are not getting in the US and the UK. Most people, I think you're describing, mainly the carbs they're eating are bad carbs. So they're like, I'm not going to eat any bread, I'm not going to eat any French fries or potatoes or rice, you know, or crackers or pizza or pasta, like I'm throwing it all

out. I'm just not going to eat it. What goes on inside them? Well, for those people who are on a really crappy diet anyway, which is most of us, they'll feel better. Okay? So that's, they'll say, well I'm not, because most of that food is going to be ultra processed food, low quality, low fiber.

So they won't be getting the sugar spikes. They will probably feel better. They've got more energy. Their mood might be lifted. But after a certain while, if they're having zero carbs, they're getting zero fiber, that's going to have some knock-on effects further down the line. So this is the problem we're facing with people who quite rightly want to change their diet and improve it and say, okay, I'm eating too many

bad carbs, let's cut them all out and let's go to say a keto or a fatty diet. They will suffer the consequences further down the road. They'll feel better initially, but if you don't look after your gut microbes, they won't look after you. This is what we see with people who are going on a fiber-free diet. Some people on a fiber-free diet, by having carbs, so as well, you can do it both ways. If you're just really a junk food diet, like I put my son on, just the McDonald's diet, there's no fiber in that, so actually you're having the similar effects. So I think

it's really important for people to be mindful about what they're doing when they're cutting one group out. Okay, they should be saying, okay, let's just cut out the really, you know, the sugars, the starches, but I'm going to keep all the other good carbs in there, then their gut microbes won't suffer, and they'll be fine. And some people I think will be saying, yeah, but I know that if you go on this keto diet, then in just a few weeks you lose all of this weight, so that must be really good for you.

What would you say to them? I'd say you will feel better if you can cope with it. Again, we've seen big differences between people on how they support a really strict keto diet. For those who don't know, a keto diet is when you're getting around 70% of your total calories as fats. So very little carbs in your diet at all, and you're using fats as a fuel source.

And many people can't do this. They feel sick, nauseated, those that can support it report feeling better for definitely for a few weeks. They will lose weight, but it's very hard to sustain it long term. And so that initial weight loss usually goes back to where it was. And so there's only a small percentage of people that can maintain it, and they're very vocal on social media. And I think you should realize they are a tiny minority.

And keto diets do have its place for people with type 2 diabetes who are trying to get off their meds, a few weeks of that can be a good route out of your medication cycle. But as a long term solution for most people, I don't recommend it. And it sounds like the key point is you're saying you need to be eating all of this stuff that supports your gut bacteria. Correct. Long term, that's what you need. That's what of this stuff that supports your gut bacteria? Correct. Long-term, that's what you need. That's what's going to keep you healthy.

That's what will keep your immune system in place that's going to fight the cancers. It's going to help you fight aging, all these things. So you need that armory there. So don't give it all up for a few weeks of feeling slightly better. And Tim, we had a lot of questions from listeners about what would happen if they gave up sugar. How would they feel and would they feel any different? Well, it all depends on where their starting point is. If they're someone who's having masses of sodas and fizzy drinks and they're having

all these really starchy ultra processedprocessed foods and they decide to cut out the starch and the sugars from their diet, that means they wouldn't be getting these very large sugar spikes. Most of them will feel much better within a week of doing that because they'll be stopping these cycle of peaks and troughs. And I did this myself, interestingly, in the early days of Zoe, we had an experiment where about 10 of us took the early Zoe muffins, and that's all we ate for 24 hours, every four hours, these highly sugary muffins, and my sugars were all over the place,

and I felt terrible. So when I stopped doing that, I felt great. So I can understand how people would feel. And Tim, I just want to confirm this. You're saying that literally you were doing this experiment where suddenly you were having much more sugar than you're used to, your blood sugar was spiking up and collapsing, and literally that same day

you felt terrible. So it wasn't like, oh, you're going to get diabetes in 10 years. It literally affected how you felt, your energy, just like everything that same day. That same day I had no energy. I felt depressed. I was trying to write a chapter for my book. I couldn't concentrate. And yeah, it was a huge shock to me. And that was the first time I made this connection between your blood sugar levels and your mental state about how it's not only your risk of obesity

and metabolic problems, but how it affects your brain. And that really brought it home to me. But also we did find some people that it didn't affect that much. Again, this personalized view of it. Some people are quite resistant to these sugar spikes, others like me and you are really quite sensitive. So we will notice these big effects, but on average, most people will. And I think that to me, doing this experiment is interesting. I think so the people who are asking this question, you know, what happens if I give up sugar? As long as you understand what sugars are now and you know that bread and potatoes are

also sugar, then it's worth doing an experiment just to see how you feel. And is this just because you've felt it yourself or is there actually like real science to support this impact on mood and energy? No, there's increasing science to show this and in fact our own Zoe science has shown that one of the early effects of people adhering to the ZoE program is mood and energy improving. We believe that is due a lot to the reduction in the sugar spikes, the effect on the brain and the mood. It's probably a combination of factors, but we think that is really important.

That's come up in all our studies, whether we're testing our prebiotic daily 30 or we're doing the zoo program, mood and energy changes are big. And that's been shown also in other small clinical studies. And do you have to give it up completely? Because I heard you mentioned not just sugar there, but also like bread and rice. I mean, do you have to give all of that up 100% in order to get the benefits you're talking about? that up 100% in order to get the benefits you're talking about? No, I don't think you'd need to do anything to such an extreme unless you're just doing an experiment for say a week for your own sake. I think everyone should be experimenting a bit more with their food to see how they react. But long term, this has got to be sustainable.

And this is very much the ZOE philosophy that we want people to be on these diets for years and find out what suits them. So I still have sugar. I still have the occasional bit of honey, potato or rice. But I try and find equivalents and swaps for my staples. So I think it's about just realizing what the worst offenders are and trying to swap for something equally tasty but healthier. I think actually this is a perfect time to switch over to listener questions. We had so many questions. I just want to pick this one out first because it seems like directly relevant, which is

Tim, what are the good carbs that you eat? Well, I eat as much as I can find. So basically, you name it, I'm trying to eat it. But I make my own sourdough bread and I make sure it's got plenty of rye in it. And if I find some nice German rye bread, that to me is a good carb because it's very hard to digest.

So it's very slow to break down that rye. I'll have pasta rather than rice. So I still occasionally have traditional wheat pasta, but increasingly switching to whole grain, whole wheat pastas, which are better for me. And then you've got all these range of grains. So things like lentils, quinoa, bulgur wheat, pearl barley, instead of rice. So they're sort of little ones that people don't often think about. I certainly didn't think about those 10

years ago. So increasingly, I'm making these swaps as I'm trying to move away from the traditional staples. And whole grains and beans, I've heard you mentioned these are sort of the go-to things replacing the rice and the potatoes and the bread. So we haven't mentioned legumes and beans, but absolutely. They're a source of fats as well. So again, what's a carb source? It gives you the energy, you break down the sugars slowly, but it's also got protein, it's also got fiber. So legumes are, yeah,

I can't get enough of those beans and lentils in every dish I'm finding. As well as the classical ones, we haven't talked about the spinach and the kale and the whatever. So there goes without saying ones, you know, we haven't talked about the spinach and the kales and the whatever. So there goes without saying, they're in there. But I think it's about the little swaps people can make to move away from the too easy to digest ones, the ones that give you those sugar spikes. I have to say the thing that I found easiest is swapping regular pasta for whole grain pasta. And I know it's really easy because my daughter had a playdate yesterday and I gave them pasta. We have whole grain pasta now in-house. I gave it to her

friend who's never had whole grain pasta before, I think, and she just ate it because it has cheese and whatever else. And she's like, delicious. So that one is so easy to make the change. And I remember being like, really, oh, that's a disgusting idea. And I think within a week, I was like, oh, it's completely normal. So I found that very easy. Whereas I think other things are obviously harder, right, to re-engineer, to eat less bread, for example, you have to really rethink the sorts of food because you can't just get us, you know, if you're just always eating a sandwich, then that doesn't really work as much. And so some things are harder and some things are easier, Tim, to change?

Definitely, yes. I mean, so you've touched on some of them. And some of these areas are new, so the foods are evolving. So you might have tried whole wheat pasta five years ago, but the new ones are actually tasting better. Similarly with the chickpea pastas or the lentil pastas, they're getting better all the time. They don't fall apart like they used to.

Another question we had so much, when is the best time of day to eat carbs? Great question. The literature tells us that it's the mornings that are the best time, that we metabolize better. So eating an identical carb meal, we have seen to have better control over it, will bring those sugar levels down quicker, digest it faster than in the evening. Now, the only caveat is those studies were generally done on young people, 20-year-olds.

When we looked at the ZOE data, we found that really this time difference pretty much disappeared after the age of 50. The advantages for young people may be less relevant because young people really, apart from possibly mood changes, aren't really going to suffer many metabolic changes from having these spikes. Whereas as you get older, where it's more important, there seems to be more individual differences. So some people might be early, you know, better in the morning, some people might in the evening. So I don't think there's a rule and I think you should follow whatever practice suits you and is likely to be sustainable. And so that's why I still have most of my carbs in the evening

because I know it doesn't affect me more than the morning and it's when I'm hungrier. So my natural body tells me to do that. So listen to your body, I think is the rule here and don't just because some studies have shown young people, you know, it is better. If you can eat in the morning, that's fine, but don't get obsessed with it. And you mentioned the ZOE data here. Is this a big data set that helps to inform what you're saying? We've looked at thousands of people's data with ZOE who've done glucose monitors, and clearly this age effect and time of day

is very different in young and old people. Next question. Does eating carbs with other foods at the same time affect blood sugar spikes? Absolutely, yes. So what we're doing, if you eat it with other foods, you're essentially wrapping the sugars in other foods that are harder to digest. So whether they're fibers that their body can't break down or it's encased in fats is really important. So that's why the importance of thinking about food in combination, thinking about what's on your plate rather than any one ingredient is really important here. So mindful eating, realizing that if

you are going to have, for example, some bread, you've got no healthy bread but you're starving, well, just have it with some cheese or try and balance these things up or take it with a handful of nuts to give you some extra fiber. These have been shown quite clearly to change the height of the sugar spikes, which will then reduce the consequences. So it's not an absolute cure-all for everything, but it will mitigate in a way that that sugar spikes. So you can start to balance it.

And do you need to sort of soak the food in that fat so you know I'm thinking because I sometimes feel like oh I've got that pasta but as long as I pour loads of olive oil over it like maybe it's gonna be like slower to to break down. Does it need to be like soaked in it or can I just have the two like one you know one mouthful and one of the other but clearly it's hitting my stomach it's not actually sort of encased. I think as long as it gets into your stomach, the stomach is like a washing machine where it churns it all up. So I'm not a big fan of people saying, well, I'm going to have my fats 10 minutes before

I have my carbs in order to get this response. I believe that generally our stomach is able to sort these things out. So if we're eating them at the same time, this should solve our problem. So I'm a bit against this obsessional eating that you have to divide your meal into 10 minute intervals, having your cheese before you have your, and then your salad, and then your potatoes. I think that's going a bit too far because for most purposes, your stomach will treat it all the same.

And does eating like a sort of refined carb with some other food, does that suddenly make it as good as eating a sort of whole grain or unrefined carb in the first place? No, you can't put sprinkle on a turd. It's still going to be a sugar and it's always going to be better to have those whole grains because you've got the original nutrients of the carbohydrate, the bran, the germ, all

these things on the casing that big food takes away, in those foods we're talking about, the good carbs, then they will still have them. And you can't replace that just with a few tablets or just a bit of cheese. I have to say my own personal experience when I was doing the first seri studies with you, Tim, was that I was wearing this blood sugar sensor and I ate a big pizza. And obviously pizza's got lots of cheese on it, right? So there's lots of fat as well as this, you know, sort of bread underneath, right, which is carb. And I think I had the biggest blood sugar spike

in the entire two weeks from this big pizza. It went off the roof, stayed high for so long, then finally collapsed later. And I know that I don't have very good blood sugar control, but it did definitely make me feel that I wasn't going to just be able to put a bit of cheese on like a piece of bread and magically not have any blood sugar spike. Is that very unusual response that I had? Well, everyone's different, but there's plenty of people like you and we all respond differently to fats and sugars as we know, but I think it's a

mistake to think that you can have unhealthy carbs, like a massive pizza base, and just smother it with all kinds of unhealthy fats, and which might mask that sugar spike. But remember the fats, this is another podcast, but at six hours, your body's still trying to get rid of those fats in your body and can cause more problems than the sugar. So let's not swap one problem for another. You know, pizzas are fine, have them every now and again, enjoy it as a treat. You know, maybe have your salad as your starter, which does help prime your blood sugar, but don't get too crazy on the extra fats. I think one of the things that this has done is just changed my mind to think about a lot of these things more like treats than as just sort of the oh you must eat this because this

is your source of energy and you need to you know if you're not eating lots of bread before you go out in the morning then you know how could you possibly function in the day. But another question that came up surprisingly often, does freezing your bread make it healthier? Great question. And this is this whole question of what's called resistant starch. So bread is a good example, but it could be the question could be also be for pasta could also be for pasta, could also be for rice. And it comes from these studies that showed that if you cook these products and then the next day you put them in the fridge, then you reheat them, that they could be healthier because in some way the starch, the sugars, have become more resistant to digestion. That's why they're called resistant

starches. And so they actually became more like fiber. About 10 years ago when I first looked at it, it was more theoretical than real. But the last few years, there've been a number of studies now showing quite consistently that you get a benefit on the amount of sugar that comes out of that food and the sugar spikes if you do this for rice, for wheat, for pastas. I was very skeptical, but now I think actually it's quite reasonable. I'm not sure that I'd always want to be cooking everything two days in advance and leave it in the fridge, but it's an extra reason to have those leftovers and do batch cooking for many people because

it will slightly improve how much goes down to your gut and how much less is released. So yeah, whether it's long term, it's a technique, I don't know. But it's quite a fun thing to think about. I am thinking about bread, which my experience always when I've frozen and taken it out afterwards is it never tastes half as good as the bread before it went in the freezer. So I can believe that it's been changed, but it seems like quite a hard hit on the taste in order to reduce your blood sugar level. Yeah. hard hit on the taste in order to reduce your blood sugar level? Yeah, no, I think bread's a tricky one.

And you may need to remember to maybe want to slice it first before you freeze it as well. But I mean, I do freeze my sourdough, interestingly. It still tastes good. Some studies have shown that actually blind tasting pasta and rice, people report it tastes better on these blind experiments. So perhaps, you know, it does change some other attributes of those foods that, but, you know, often my takeaway tastes better the next day. I mean, I think that's most people's.

I think the pasta I definitely have often reheated and very happy with. It was the bread somehow, I do feel the bread out of a freezer. Even on a blind taste, I think I could tell the difference. Yeah, it may depend on the quality of the breads, but extremely high-fiber ones, it's probably fine. But the other ones, yeah, I agree, they don't taste as good to me either. Well, I've definitely never baked my own sourdough bread

at home, Tim, so I'm not in your league, but I aspire to it. I think you already touched on this question actually, which is about other starches. So what are the other sort of starchy foods other than bread that this could help with? The ones that have been tested are things like rice and pasta. And it's a good thing really to if you do batch cooking, particularly if you are still keen on rice, and we're not particularly keen on white rice at Zoe, but realize that some people are, the reheated version will perhaps give you 30% less of a sugar spike compared to the fresh one.

And it probably works for most of these types of foods that are staples. But in general, interesting black rice, wild rice isn't much better, brown rice isn't much better than white rice. That's a common misconception. It really doesn't have that much fiber in it, or that much extra protein. So by all means, go stick with white rice if you like it, but just maybe cut down the quantities and how often you have it. Do you know someone who's confused about carbs? Maybe they struggle with an afternoon slump

and they don't know why. Why not share this episode with them right now and equip them with expert advice on what foods could fuel them better? I'm sure they'll thank you. Tim, if a food item has a multi-grain label, does that mean it's a healthy carb? Sadly not, no. That's disappointing. It is. They mean nothing. It's just a marketing technique. There are only a few terms that have an illegal requirement for manufacturers to contain things. These are whole wheat and whole grain, which are used differently in the US and the UK

and Europe. Those ones mean that you do have to have the grain intact, that they can't have stripped away the germ and the bran, and that you know you're getting something that's higher in fiber. Percentages vary, so they're always trying to get away with as little as possible because it's more expensive to do this and it doesn't have a long shelf life, things like this that big food doesn't like. But multi-grain, multi-cereal means absolutely nothing. So usually they've got a few sesame seeds on top and you think that bread looks healthy, but actually it's not.

And this goes across all foods. So ignore those signs really. Look at the back of the pack, look to see how much fiber is actually in it, how many grams of fiber and it's per hundred so it's percentage fiber you'll be getting when you look at the the back of those labels. And so what's the number that you would be looking at for fiber that would help to tell you this has moved to being like a good carb instead of one of these sort of refined bad carbs you've been talking about today? If you're getting like five grams of fiber per hundred grams, so sort of five percent,

that's sort of a minimum to be looking at. But again, it's complicated because some foods you need to be looking at the ratio of the fiber to the starches. And Bread is a good example of that. You can have a reasonable amount of fiber, but if you've got 10 times as much sugars in it, it's not going to work. So I think it's not as straightforward as that. So start by looking at the fiber, but also say, well, look at the carbohydrate total. you know a good a good bread will be something like a ratio of only four or five to one of carbs to fibre. But most common breads are about 20 to one.

Got it. So mainly like breads, rice, potatoes, they can have a lot less than that five grams that you're talking about. Yes, much less. So if I am looking for a bread, you're saying like multi-grain just means they might've dropped a couple of other grains on top of it. So what is it that I am looking for

to try and make me know that it is like a higher quality bread? Yeah, so multi-grain, multi-cereals, stone ground mean nothing. They can just add 1% of it in that form and that's enough. Which is completely shocking. Yes, it's ridiculous. There's no real good regulations in the US or in Europe about things like bread.

But what you can look for is in the US whole wheat means it has to legally contain the whole, the kernel, the bran, the germ of that wheat husk in that product. And there's a certain minimum amount they have to have in it. And the UK's generally called whole meal. And apart from that, really, it's the Wild West. And you know, the key is to look on the back of the pack and see what the amount of fiber is and the amount of carbs are. So if it has those other parts that you mentioned, that's going to be healthier for me? Generally, yes. If you've got the whole part of the cereal in it, then it will be much healthier for you. They don't have to have any additives to it because what they're doing

is when they're in these cereals, generally, they're stripping away all the good stuff and they have to then put it back in as chemical vitamins. And so that will be called, you said whole meal or? So in the UK the term is whole meal, has a legal requirement and in the US whole wheat. And everything else really is just marketing and they can contain just small amounts of that and the basic product is unhealthy. And this was very interesting. And I've gone through this big journey

because anyone who goes to the supermarket, surrounded by these labels and healthy looking things with seeds and multisides and stone ground this and whatever. And sadly, it's all pretty meaningless. So Tim, if you are buying bread in the supermarket, how do you choose a good bread? I generally disregard the labels, look on the back of pack, go for the one with the fewest ingredients and the highest ratio of fibres to carbohydrates. Brilliant.

Thank you. And that takes me on to another question from people who obviously are making things at home because we had a lot of questions about flour and lots of questions about whether alternative flours, we had quinoa flour, chickpea flour, almond flour amongst others, is that better than the traditional wheat flour which I remember growing up from my grandmother would use to bake something with? It depends. It sort of depends what you're using it for. Some of these ones will contain different ratios so you might get more protein for example if you're you're taking some from a legume like a chickpea

so it depends what you're trying to achieve in reversing it. So I don't think we should move away from wheat flour necessarily, but you want to be picking ones that are the whole flour. So these are the ones where you don't want it to be ultra-refined. So it's more the amount of refinement that is important here. How much of that whole plant is still in that food. But I think increasingly using a diversity of different flowers is fine. But the more refined it is, the more chopped up it is, the least beneficial it's going to be for your health. And I think that's in general. So the cruder, more unrefined,

all of these are, I think, the better. So you definitely prefer that I was using not like the white flour that I grew up with, but like whole wheat flour or wholemeal flour that has like all of the grain of that wheat in it, even if is that what you're saying? Yes, that's right. So that might be better than some of these refined alternative flowers that, you know, still worth experimenting with for different purposes. But, you know, there's been this big anti-gluten campaign and that's why sort of wheat got a bad name. But I think we should be focusing on, again, the quality of those ones and going for the ones that do have the higher fiber, higher protein counts within them and then go for taste and what you fancy eating. But I don't think we should give it all up just because of a particular worry about glutens in 1% of the population.

So you're not saying therefore that in general people should give up all wheat. You're saying, if I think I understand rightly, it's like the refinement of that where you throw away a lot of the comments and you're just getting left with sort of the starchy sugary bit, which is the white flour, which I have to say I love in my croissant panne au chocolat. It does taste nice, but you're saying it tastes nice because it's really sugary. Yes, exactly. That's right. You're just getting that flavor bomb of sugar. Whereas, if you're making pancakes, do you ever make pancakes?

Yes. So if you swapped for buckwheat flour or spelt, you'd be getting much less of the sugar, more of the fiber. So in many instances, there are swaps people can make that you can, but generally you're swapping for something that is a higher density, more protein. And does it, can it still taste nice? The buckwheat pancake? Definitely can. Yes, I love them. All right, we'll put the link to that in the show notes, because I'm going to give that a try. That is just about within my culinary capability is a pancake. That's sort of the limit, Tim. So my kids expect pancakes from me from time to time at the weekend. I'd like to finish with a final question, which I loved because it was so straightforward. Julie wrote into us and said, if I want to improve my carb intake tomorrow, what's the easiest way to start?

Well, it depends what you're calling a carb. We're going back to our original question. So if you want to improve your good carb intake, which means the ones towards the more fiber elements, it would be to swap your more starchy, more sugary carbs for the ones that have more fiber in it. And we've been discussing a lot of these and it's simple swap. So go with the staples. Look at your staples of your, can you change your bread for something that's healthier? Can you change your pasta to a whole wheat pasta? Can you change your white rice to a quinoa, a pearl barley, something that's really high in fiber and high in protein. So it's looking at those ones that make up the majority of what we're eating, plus reducing

those carb snacks. So instead of your savory snacks, your Doritos, your Pringles, you have some nuts and seeds instead. That's, if you want a simple starter, that's what I would do. And I think the staples are the ones that are the main ones. So for most people, changing their bread is probably the hardest thing they can do. So try and focus on that and find a loaf that's

healthier that you enjoy. Thank you, Tim. I think that's really clear. It's been a bit of a whistle stop tour across a lot of ground today. I'm hoping we've answered a lot of questions for our listeners. I'm going to try and do a quick summary maybe just of the highlights that I took away from today. So I think I start with your blood sugar spikes. Like if you

suddenly started spiking your blood sugar, it could actually affect your mood and energy in one day, which is really amazing because I was brought up with this idea that, you know, how you feel and what you're eating have nothing to do with each other. And so I think that is really remarkable. And it's been one of, I think, really eye opening idea that you could have that impact that fast. I also am thinking about the Pringles design so that once you pop you just can't stop and that this is real and you're describing the ways in which you could see what's going on in your blood sugar that is actually happening to create this craving and make you want to continue. I think you then shocked, you know, definitely some of our listeners by saying

that, you know, rice basically gets turned into sugar almost immediately and isn't healthy despite all the ways that I think both of us were brought up to believe that it was and that actually, you know, potatoes and bread are very similar. They're sort of high starchy food. They're getting turned into sugar very fast inside your body. But don't therefore be scared of carbs and suddenly say, well, I'm just not going to have any carbs. I'm just going to eat lots of fat and protein. Because you said it's essential because it is all coming from plants and it's the food that feeds our gut microbes, those bacteria.

And you shared, I think the most amazing statistic, you said, if I was to add five grams more fiber into my diet, I would reduce my risk of death by 14%. So it's a very small amount of fiber, like one teaspoon or something, and like this huge impact on death compared to anything else we talk about. So that is remarkable. And then I think you switched a whole bunch of tips.

Freeze your bread, put your pasta or your rice in the fridge, and then take it out again and suddenly it's going to have lower sugar spikes. Re-examine what you're buying from the supermarket. You talked about breads and said like a lot of the labels are just tricks. This is sort of big food, taking advantage of you. There's incredibly little regulation around the world, whether you're listening to this

in the US or the UK, Europe, wherever. What you're looking for is this sort of whole wheat or whole meal that has the whole kernel, back to this idea of it being like the whole grain rather than just a bit that's refined. And if you see something like multigrain, which I always thought was that's great, I've got all of these grains, actually you're just being tricked.

So for you, you're saying really, you need to turn the bread over, look at what's on the back and you're looking for as few ingredients as possible and you're looking for the amount of fiber. And in general, I think you said, you know, fiber is above five grams in any of these foods. It's starting to be meaningful. That's like an easy indicator of this being a sort of a good carb rather than than a bad carb. And the ratio. Yeah. And the ratio.

The ratio is you've got to look at the carbs because sometimes you can have fiber, but put in so much sugar in there that it makes it so it's that ratio of the total carbs to total fibre. Got it. Because you say we might have five grams of fibre, but it's got tons of like 80 grams of carbohydrate and some sugar, it's still not going to be good for you. Got it. So you've got to watch out again for how they play with this. And then finally, you said, Jonathan, try swapping out those pancakes, stop using the refined white flour and in fact try something different from wheat. Try a buckwheat flour or a spelt pancake and I promise to try this

and I will report back. Fantastic. Tim, thank you so much. I appreciate it and I am sure we will continue the journey. Thank you. And that's why more than 100,000 members trust Zoe each day to help them make the smartest food choices. Combining our world-leading science with your Zoe test results, Zoe's your daily companion to better health for life. So how does it work? Zoe membership starts with at-home testing to understand your unique body. Then Zoe's app is your health coach

using weekly check-ins and daily guidance to help you shift your food choices to steadily improve your health. I rely on Zoe's advice every day, and truly it has transformed how I feel. Will you give Zoe a try? The first step is easy. Take our free quiz to find out what Zoe membership could do for you. Simply go to zoe.com slash podcast, where as a podcast listener, you'll get 10% off.

As always, I'm your host, Jonathan Wolff. Zoey's Science and Nutrition is produced by Julie Pinero, Sam Durham and Richard Willen. The Zoey's Science and Nutrition podcast is not medical advice, and if you have any medical concerns, please consult your doctor. See you next time.