The truth about low carb diets, sugar spikes, and ‘multigrain’ labels with Prof. Tim Spector

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.

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.

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Transcript

Jonathan Wolf: Tim, thank you for joining me today. 

Tim Spector: What a pleasure. 

Jonathan Wolf: 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? 

Tim Spector: Hit me.

Jonathan Wolf: All right. Are all carbohydrates bad for us? 

Tim Spector: No. 

Jonathan Wolf: Do we eat too many bad carbohydrates?

Tim Spector: Yes. 

Jonathan Wolf: Is a low-carb diet a healthy choice for everyone? 

Tim Spector: No. 

Jonathan Wolf: Could pairing your carb with another food make it healthier? 

Tim Spector: Absolutely. 

Jonathan Wolf: Is there a time of day that's better for eating carbs? 

Tim Spector: For some people. 

Jonathan Wolf: And finally, what's the most common misconception about carbohydrates? 

Tim Spector: I think most people believe that all carbs are bad, and that's absolutely not true. Some of them that contain fiber are the most essential foods we can eat. 

Jonathan Wolf: 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. 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 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? 

Tim Spector: 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.

Most of the 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. Within the carbs, it's going to have different types of carbs in it. 

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. 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 to sell products to us.

Now I think we need to break down carbs into what they are, which are essentially sugars that are either very simple, moderately simple, really complex and long, and hard to break down.

So the simple sugars like sucrose, you know, your table sugar is a very simple, it's very simple sugar. It means it only has a few bonds, and is 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 that can be broken down by other enzymes in your body. And every plant has these starches and we're designed to do them. So they break it down into simple sugars which are then released, it just takes a little bit longer. 

Then you've got the really complicated long sugars, all joined together with lots of tight bonds that are called fibers. 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. 

Most people think of carbs as only the sort of sugary end ones. They forget that a lot of the healthy carbs are these complicated fibers at the other end. 

So they throw the baby out with the bathwater and say, I'm not having any carbs, it's all rubbish, they're all deadly. Well, that's not true. 

Jonathan Wolf: And could you give me some examples of what those like simple and starchy carbs are?

Tim Spector: Well, a simple carb is like table sugar, it's like, honey, maple syrup, these things, 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. So 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, the enzymes in your saliva will break it down into these simple sugars. And after it's been in your mouth for about 30 seconds, it will turn sweet. 

Jonathan Wolf: Let me get that straight. You're saying that I might have this cracker, it's not a sugar, but within 30 seconds of being in my mouth, actually, just the saliva in my mouth has broken that down and turned it into sugar.

Tim Spector: That's right, yes. And the same thing is if you're having some white rice, or you're having pasta, or you're having a potato. They're all starchy carbs that 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.

Often that's done really just with our saliva in the early stages of digestion. It doesn't take that much. 

Jonathan Wolf: 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.

So I was completely shocked by this story that actually basically it turned into sugar almost immediately. Is that really what happens? 

Tim Spector: 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. That's why in Japan, most of their candies are made out of the 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 we'll have those consequences.

We used to think it was healthy, I agree. And before I got into this, that's exactly what I thought as well. 

Jonathan Wolf: Tim, could you explain a little bit what makes it unhealthy? So you've described the way that 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? 

Tim Spector: It's the way we react to the sugar, rather than necessarily the sugar itself, which is bad. Because, you know, our ancestors were seeking out honey and other things with great relish. 

When you have a sugary drink, a soda, a bowl of rice, or 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. That then triggers the 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. 

If this is repeated a lot of the time, some people find it hard to keep these spikes down. They're very sensitive, and we found this in the ZOE study, if you remember, a few years ago now, tenfold differences between people like you and me in how we respond to a standard meal of a cookie, or a muffin, or whatever it is.

So everyone's very different, but the people who suffer with it, get these really big sugar spikes, that cause 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. Okay, you have your little sugary snack to relieve hunger. What does it do? Gives you a sugar spike. Maybe you get a dip after it, and you're even hungrier, so you're eating more during the rest of the day.

So long-term and short-term consequences of having free sugars everywhere without real food to, in a way, help mop it up. 

Jonathan Wolf: Every time I hear this story, it always slightly blows my mind, Tim. It's this idea that eating the food now might actually make me eat more food later. It's the exact opposite of how I was brought up.

I was thinking about this with 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. 

How could she possibly go to school if she's 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.

Tim Spector: Yeah, it sounds very weird, and it's against everything we've been taught by our parents, but it's absolutely true. 

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 by about 10% to 20%,  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 not worrying about sugars. 

Jonathan Wolf: 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, or 50 years? Is this important or not really? 

Tim Spector: 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 an increase in obesity, in heart disease, and all those consequences.

Many studies have linked obesity to the intake of these starchy carbohydrates and free sugars. So, some of this is due to, say, sugary drinks, beverages, sodas, etc., which can account for about a quarter of our sugar intake. 

Jonathan Wolf: A quarter of our sugar intake can be from these sugar-sweetened beverages? 

Tim Spector: You know, so particularly more in children. We thought, 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. 

So, and also sensitizing children to even more sweet tastes and seeking out even more unhealthy foods. So I think part of it 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. 

Jonathan Wolf: 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 unhealthy starchy carbs that someone listening might be putting on their plate?

Tim Spector: Well, we're surrounded by them really.  Most of the snack foods,   starchy carbs, potato chips, Doritos, your Pringles. Most of the breads that we're having are highly starch-rich and very poor in fiber. And these are the staples really. So 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. 

Jonathan Wolf: I think it's interesting because I think I was definitely brought up with a view, that a potato after all is 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.

It tasted sweet as I was eating it, because I'd have got the same effect, which has been turned into sugar in my stomach in just a few minutes anyway. 

Tim Spector: 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, do you like mashed potato, Jonathan? There was the artificial one Smash, which was powdered, but that was the ultimate in the quick fix. 

Jonathan Wolf: Is that right? You sort of get it instantaneously because it's been completely powdered. 

Tim Spector: 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. 

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, bread, potatoes, 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.

Jonathan Wolf: 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? 

Tim Spector: 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. 

I think it comes from that, you were saying earlier, the smell of crusty bread, when you go into restaurants and the first thing they serve you, I mean, it is irresistible,  for most of us. 

Just knowing that it should be a rare, you know, more of a treat than a staple, I think is really important. Or you pick the right ones. You're 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.

Jonathan Wolf: I think I've heard you talk a little bit about the role of food industry might have played in this. 

Tim Spector: 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. 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. 

Jonathan Wolf: No, no, go on. What was Pringles’ claim? 

Tim Spector: Well, they claim they're a potato snack, but actually it's made up of about four different plant extracts with rice and tapioca. Then they're molded. 

So basically they take the cheapest products they could 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.

The average one has about 30 ingredients, if you look at the back of the pack, which are flavorings, colorings, glues, and emulsifiers to stick it together. 

Jonathan Wolf: And Tim, I seem to remember something like, once you pop, you just can't stop. Am I thinking right? 

Tim Spector: That's right. And if anyone's done 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 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 go, ah, isn't that nice.

And it's a short hit, but you know, it doesn't last. 

Jonathan Wolf: 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. 

Tim Spector: And then you've finished the whole tube and that's it. Yeah. And you feel sick. 

Jonathan Wolf: 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 and it feels really good as I'm eating it. And then two to three hours later, I'm really hungry and I have to go back again. 

Tim Spector: Absolutely, yes. 

Jonathan Wolf: Now, I feel like you've done nothing but tell us how awful carbs are so far, Tim.

Tim Spector: Some carbs. Some carbs, Jonathan. 

Jonathan Wolf: 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 our overall well-being. How do we feel? 

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? 

Tim Spector: 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.

Jonathan Wolf: And can you remind us just quickly what they are and above all why they're good for our health? 

Tim Spector: So polyphenols are used to be called antioxidants and they are these thousands of chemicals that you find in plants, natural defense chemicals.

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, and many other ones that we're just discovering. 

Then the other element is the fiber. So fibers are these long strings of sugars that are really hard to break into their component parts. And 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.

Jonathan Wolf: And Tim, you were saying that when I was eating these starchy foods, it hits my bloodstream in just sort of 30 minutes. Just as a contrast, if I'm eating these less starchy foods with more fiber, how rapid is the process you're describing? 

Tim Spector:  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 at 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, it likes to take its time.

It turns out that when you're eating these hard-to-digest foods, it fills you up more. So the total opposite of 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.

That's part of, the reason that they're helpful, as well as their impact on our gut and our general health. 

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 %, 

Jonathan Wolf: Five grams of extra fiber will reduce your risk of death by 14%. 

Tim Spector: Correct. 

Jonathan Wolf: I mean, it's pretty mad, isn't it? 

Tim Spector: It is. And when you think that we're supposed to be eating 30 grams of fiber roughly, each country has its own slightly different levels. 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. 

Jonathan Wolf: So I was thinking about your example between the two. And I was thinking a little bit about driving the car and when you've got a teenage driver proving everything, they're slamming on the accelerator and slamming on the brake when the lights change, just slamming on the accelerator again.

That sounds a little bit like this blood sugar spiking up and down with these starchy foods and then I guess what I think your analogy is here is, I'm eating these much more whole grain foods, a lot more fiber and 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? 

Tim Spector: No, I think it's pretty good, actually. I think there are other things going on, as well as this, that are damaging your engine. 

Clearly, your clutch is gonna 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 U.S. and the U.K. 

Jonathan Wolf: 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, 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? 

Tim Spector: Well, for those people who are on a really crappy diet anyway, which is most of us, they'll feel better, okay? 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 that they've got more energy, and 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. And 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. I put my son on just the McDonald's diet, there's no fiber in that. So they actually, you're having 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, they should be saying, okay, let's just cut out 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. 

Jonathan Wolf: 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?

Tim Spector: 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.

Many people can't do this. They feel sick, nauseated, they can't. Those that can support it report feeling better for a definitely for a few weeks. They will lose weight, but it's very hard to sustain it long term so that initial weight loss usually goes back to where it was. 

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. Keto diets do have their 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.

Jonathan Wolf: 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. 

Tim Spector: 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 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. 

Jonathan Wolf: 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? 

Tim Spector: Well, it all depends on where their starting point is.

If there's someone who's having masses of sodas and fizzy drinks, and they're having all these really starchy ultra-processed foods and they decided 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 the cycle of peaks and troughs. 

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 sugar was 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. 

Jonathan Wolf: And Tim, I just want to confirm this. You're saying that literally doing this experiment, 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 everything that same day? 

Tim Spector: That same day, I had no energy. I felt depressed. I was trying to write a chapter for my book, but I couldn't concentrate.

It was a huge shock to me. That was the first time I made this connection between your blood sugar levels and your mental state. How it's not only your risk of obesity and metabolic problems but how it affects your brain and that really brought home to me.

But 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. 

I think that to me, doing this experiment is interesting. I think, so the people who are asking this question,  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. 

Jonathan Wolf: Is this just because you felt it yourself or is there actually real science to support this impact on mood and energy? 

Tim Spector: No, there's increasing science to show this and in fact, our own ZOE sciences 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.

So that's come up in all our studies, whether we're testing our prebiotic daily 30 or we're doing the ZOE program, mood and energy changes are big. And that's been shown also in other small clinical studies. 

Jonathan Wolf: And you have to give it up completely? Because I heard you mention not just sugar there, but also bread and rice.

I mean, you have to give all of that up 100% in order to get the benefits you're talking about. 

Tim Spector: No, I don't think you 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. There's a 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 you know, 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.

Jonathan Wolf: I think actually this is a perfect time to switch over to listen to questions. We had so many questions, but I just want to pick this one out first because it seems directly relevant, which is Tim, what are the good carbs that you eat?

Tim Spector: Well I eat as much as I can find so basically you name it, I'm trying to eat it.

But you know I make my own sourdough bread and I make sure it's got plenty of rye in it. 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 little ones that people don't often think about. I certainly didn't think about those 10 years ago. 

Increasingly I'm making these swaps as I'm trying to move away from the traditional staples.

Jonathan Wolf: And whole grains and beans, I've heard you mention, these are sort of the go-to things replacing the rice and the potatoes and the bread. 

Tim Spector: Yes, 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  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 kales and the whatever. So it 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.

Jonathan Wolf: I have to say the thing that I found easiest is swapping regular pasta for whole-grain pasta. 

I know it's really easy because my daughter had a play date yesterday and I gave them pasta. We have whole grain pasta now in-house. 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. 

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 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. 

Tim Spector: 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, you know, they're getting better all the time. They don't fall apart like they used to. 

Jonathan Wolf: Another question we had so much, when is the best time of day to eat carbs?

Tim Spector: 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 seem to have better control over it. We'll bring those sugar levels down quicker, and 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. 

So 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 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.

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 just because some studies have shown in young people it is better if you can eat in the morning, that's fine, but don't get obsessed with it.

Jonathan Wolf: And you mentioned the ZOE data here. Is this a big data set that helps to inform what you're saying? 

Tim Spector: 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. 

Jonathan Wolf: Next question. Does eating carbs with other foods at the same time affect blood sugar spikes?

Tim Spector: Absolutely, yes. So 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 a body can't break down or it's encased in fats,  is really important. 

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, you can have it with some cheese or try and balance these things up so that. 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 sugar spike. So you can start to balance it. 

 Jonathan Wolf: And do you need to soak the food in that fat?

So, 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,  maybe it's just going to be slower to break down.  

Does it need to be soaked in it? Or can I just have the two,  one, you know, one mouthful and one of the other, but clearly it's hitting my stomach, it's not actually, sort of, encased.

Tim Spector: 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 and then your salad, and then your stomach will treat it all the same. 

Jonathan Wolf: Does eating a refined carb with some other food suddenly make it as good as eating a whole grain or unrefined carb in the first place? 

Tim Spector: 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, you know, the brown, the germ, all these things on the casing that big food takes away.

In those foods we were 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. 

Jonathan Wolf: I have to say my own personal experience when I was doing the first study 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 bread underneath, right, which is a carb. 

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. 

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 a very unusual response that I had? 

Tim Spector:  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 which might mask that sugar spike.

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. Yeah, pizzas are fine, have them every now and again, enjoy it as a treat, and maybe have your salad as your starter,  which does help prime your blood sugar, but don't get too crazy on the extra fats.

Jonathan Wolf: 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 if you're not eating lots of bread before you go out in the morning, then how could you possibly function in the day.

But another question that came up surprisingly often, does freezing your bread make it healthier? 

Tim Spector: Great question. And this is this whole question of what's called resistant starch. 

So bread is a good example, but the question 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 in the last few years, there have 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 sort of an extra reason to have those leftovers and do batch cooking for many people because it will slightly improve how much it goes down to your gut and how much less is released. 

So whether long term, it's a technique I don't know, but it's quite a fun thing to think about. 

Jonathan Wolf: 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 a little. 

Tim Spector: Bread's a tricky one and, I mean, maybe you 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 in these blind experiments. So perhaps it does change some other attributes of those foods.

But you know, often my takeaway tastes better the next day. I mean, I think that's [true for] most people.

Jonathan Wolf: The pasta I definitely have often reheated and very happy with. It was the bread, somehow I do feel the bread in a freezer, even on blind taste, I think I could tell the difference. 

Tim Spector: Yeah, it may depend on the quality of the breads, but, you know, extremely high-fiber ones, it's probably fine. But the other ones, I agree, they don't taste as good to me either.

Jonathan Wolf: 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 starchy foods other than bread that this could help with? 

Tim Spector: The ones that have been tested are things like rice and pasta. It's a good thing really 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 the fresh one. It probably works for most of these types of foods that are staples.

But in general, interestingly black rice, wild rice isn't much better. Brown rice isn't much better than white rice. That's a common misconception. 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.

Jonathan Wolf: Tim, if a food item has a multi-grain label, does that mean it's a healthy carb? 

Tim Spector: Sadly not. No.  

Jonathan Wolf: That's disappointing. 

Tim Spector: It is. They mean nothing., it's just a marketing technique. There are only a few terms that have any legal requirement for manufacturers to contain things. These are whole wheat and whole grain, which are used differently in the U.S., the U.K., and Europe. 

So those ones mean that you do have to have the grain intact, that they can't have stripped away the germ, the bran, and 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 multigrain, 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. 

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 back of those labels.

Jonathan Wolf: 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 a good carb instead of one of these sort of refined bad carbs you've been talking about today? 

Tim Spector: If you're getting 5 grams of fiber per 100 grams, so sort of 5%, that's 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's 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, it's not as straightforward as that.

So start by looking at the fiber, but also say, well, look at the carbohydrate total. And a good bread will be something like a ratio of only 4 or 5 to 1 of carbs to fiber. But most common breads are about 20. 

Jonathan Wolf: Got it. So mainly breads, rice, potatoes are going to have a lot less than that five grams that you're talking about.

Tim Spector: Yes, much less. 

Jonathan Wolf: If I am looking for a bread, you're saying multi-grain just means they might have 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 a higher quality bread? 

Tim Spector: Yeah. So multi-grain, multi-cereal, stone ground means nothing.

They can have 1% of it in that form and that's enough. 

Jonathan Wolf: Which is completely shocking. 

Tim Spector: Yes, it's ridiculous. There are no real good regulations in the U.S. or in Europe about things like bread. 

But what you can look for is in the U.S., whole wheat means it has to legally contain the whole,  the kernel, the bran, the germ of that wheat husk in that product.

There's a certain minimum amount they have to have in it and the U.K. is generally called wholemeal. And apart from that, really, it's the wild west and 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.

Jonathan Wolf: So, if it has those other parts that you mentioned, that's going to be healthier for me? 

Tim Spector: 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.

Jonathan Wolf: And so that will be called, you said, whole meal or 

Tim Spector: So in the U.K., the term whole meal has a legal requirement and in the U.S. 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 a supermarket surrounded by these labels and healthy-looking things with seeds and multisides and stone ground, this and whatever, but sadly it's all pretty meaningless.

Jonathan Wolf: So Tim, if you are buying bread in the supermarket, how do you choose a good bread? 

Tim Spector: I generally disregard the labels, look on the back of the pack, and go for the one with the fewest ingredients and the highest ratio of fibers to carbohydrates. 

Jonathan Wolf: 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 alternative flours. 

We had quinoa flour, chickpea flour, almond flour, amongst others, is that better than the traditional wheat flour which, you know, I remember growing up from, you know, my grandmother would use to bake something with? 

Tim Spector: It depends. It sort of depends on 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 taking some from a legume, like a chickpea.

So it depends what you're trying to achieve in reversing it. 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. 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. I think that that's in general. 

So the cruder, more unrefined, all of these are, I think, the better.

Jonathan Wolf: So you definitely prefer that I was using not the white flour that I grew up with, but whole wheat flour or wholemeal flour that has all of the grain of that wheat in it.

Tim Spector: Yes, that's right. So that might be better than some of these refined alternative flours. Still worth experimenting with for different purposes.

But 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. 

Jonathan Wolf: So you're not saying therefore that in general people should give up all wheat. 

You're saying if I understand rightly, it's the refinement of that where you throw away a lot of the components, you're just getting left with the starchy sugary bit, which is the white flour. Which I have to say I love in my croissant, pain au chocolat. 

It does taste nice, but you're saying it tastes nice because it's really sugary.

Tim Spector: 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? 

Jonathan Wolf: Yes. 

Tim Spector: 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, but generally, you're swapping for something that is,  higher density, more protein.

Jonathan Wolf: And can it still taste nice, the buckwheat pancake?

Tim Spector:  Definitely can, yes, I love them. 

Jonathan Wolf: 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. Julius wrote in to us and said, if I want to improve my carb intake tomorrow, what's the easiest way to start? 

Tim Spector: Well, it depends what you're calling a carb. So we get 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 them. 

We've been discussing a lot of these and it's simple swaps. So go with the staples, look at your staples. 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, 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 to. The simple starter, that's what I would do. And I think it's the staples, 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.

Jonathan Wolf: Thank you, Tim. I think that's really clear. It's been a bit of a whistle-stop tour across like 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 summary, maybe just of the highlights that I took away from today. 

So I think I start with your blood sugar spikes, 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 how you feel and what you're eating have nothing to do with each other.

So I think that is really remarkable. And it's been one of, I think, really eye-opening ideas that you could have that impact that fast.

I also am thinking about the Pringles, designed 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 definitely some of our listeners by saying that 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. 

That actually potatoes and bread are very similar. They 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 that's a very small amount of fiber, it's like one teaspoon or something. And this huge impact on death compared to everything else we talk about. So that is remarkable. 

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 a lower sugar spikes. 

Re-examine what you're buying from the supermarket. You talked about breads and said that 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 listen to this in the U.S. or the U.K., Europe, or wherever. 

What you're looking for is a 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. 

If you see something like multi-grain, 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. 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, an easy indicator of this being a sort of a good carb, rather than Than a bad carb. 

Tim Spector: And the ratio. The ratio is you've got to look at the carbs. Because sometimes you can have fiber, but they've put in so much sugar in there, so it's that ratio of the total carbs to total fiber.

Jonathan Wolf: Got it. Because you're saying it might have five grams of fiber, but it's got 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 played 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. 

Tim Spector: Fantastic. 

Jonathan Wolf: Tim, thank you so much. I appreciate it. And I am sure we will continue the journey. 

Tim Spector: Thank you.