The truth about oats with Prof. Sarah Berry

Oatmeal has long been considered a heart-healthy breakfast, but is it really as good for us as we think? In recent years, some nutrition experts have warned that oats can cause blood sugar spikes, so what’s the truth?

Sarah also unpacks the hidden side of oats: Are pesticides a concern? Is oat milk as healthy as it claims? And how does food pairing change their impact on blood sugar?

Finally, she shares the ultimate guide to choosing the healthiest oats—and for those who prefer alternatives, she’s got delicious, nutrient-packed swaps to try.

If you love oatmeal (or are skeptical about it), this episode is packed with evidence-based insights to help you make the best choice for your health.

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Transcript

Jonathan Wolf: All right, Sarah. Well, as you know, we always like to start with a quick-fire round of questions from our listeners. Are you ready to go? 

Sarah Berry: I am. It's my worst part, Jonathan. I hate having only yes, no.  But I'm always game for it. 

Jonathan Wolf: It's going to be fine. Are oats bad for us? 

Sarah Berry: No. 

Jonathan Wolf: Are all oats good for us? 

Sarah Berry: No. 

Jonathan Wolf: Are the heart healthy labels on oat products lying to us? 

Sarah Berry: Sometimes. 

Jonathan Wolf: Is oat milk as healthy as some people think? 

Sarah Berry: No. 

Jonathan Wolf: Is there a healthy way to enjoy oats? 

Sarah Berry: Absolutely. 

Jonathan Wolf: And so then finally, what's the biggest misconception when it comes to oats? 

Sarah Berry: I think the biggest misconception is that all oats are bad for us. 

Jonathan Wolf: So I used to eat oatmeal for breakfast every morning, Sarah, or porridge as my Scottish grandmother would call it.

In fact, that oatmeal porridge was a regular winter breakfast for me whenever I stayed with her and then long into adulthood, but I haven't actually eaten any oats for breakfast for about the last five years.

But just a few minutes ago, you and I both ate a bowl of oatmeal, and during this episode, you're going to explain what's going on, and we're both going to discover in real time how this meal has been affecting our blood sugar.

And that's because both of us put on a blood sugar sensor yesterday, so I'm very excited to see the results and hopefully settle the controversy around oats once and for all. 

But before we start to look at what's going on, can you just start with what are oats? And what happened to them before they arrived in my bowl?

Sarah Berry: So oats are a type of seed or a whole grain that comes from the oat grass and this is called the Avena sativa plant. And I hope I pronounced that correctly. 

They're very much like a wheat kind of plant and the seed is encapsulated within this hull, which is like the kind of shell. And what happens is, that is removed because you wouldn't be able to eat that shell, and what you're left behind is the oat grain or the oat seed. 

That consists of this outer bran layer, which is slightly brown orangey, which is what you sometimes see in your oat flakes. You see a little specks, don't you, of this kind of brown and orange and that's from this outer skin. 

Then within that outer skin is the main part of the oat, which we call the endosperm. It's within that endosperm that contains all of the starch, so all of the carbohydrate, as well as some fiber, and as well as some protein. 

Then in the outer layer, that skin, we often call it the bran, that contains a lot of fiber. So an oat seed typically contains about 60 to 70% carbohydrates. It contains about 10% of protein, which is quite high for a whole grain. And it contains a very special type of fiber called beta glucan. 

It also contains lots of vitamins, particularly B vitamins. It contains lots of minerals, so magnesium, zinc, iron, manganese, and it contains some bioactives, which we call polyphenols, and it contains a particular type of bioactive.

Jonathan Wolf: So it sounds a little bit like it's a bit like wheat or something that I'm familiar with. It's growing on the grass and it's sort of the seed and then it has all these different things inside it. 

Sarah Berry: Yeah, absolutely. So a little bit like wheat, and what happens is that it is then processed in different ways to form different types of oats that we would commonly recognize.

So the kind of main seed that we're left with that's edible is actually called a groat. This is the seed that has that bran skin on and then that kind of starchy endosperm. These are typically then cut using steel into what we call steel cut oats, these are groats that are literally cut about two or three times, so they're quite chunky. 

These are the least processed oats and they take quite a long time to cook. So they might take about 30 minutes, for example, on a hob to cook, but you can eat those as porridge. 

Then what you can do as well is actually roll the groat, so you roll that oat grain and that's what gives you the rolled oats. So typically they're steamed or cooked a little bit before, so that they're soft enough to roll. And then when you roll them out, that's what a rolled oat essentially is, just a rolled groat. 

Jonathan Wolf: And Sarah, when you say rolled, do you mean somehow squashed between two big rollers or something so that it goes flat and thin? Is that what that means? 

Sarah Berry: You know, really heavy, not the kind of thing you could do with a rolling pin, I don't imagine at home. I mean, I've never tried it, but yeah, you know, using industrial techniques to roll it at high pressure so that it becomes this flat rolled oat. 

Jonathan Wolf: Got it. So it's flattened and you said it's also cooked a little bit through this process to allow that to happen.  

Sarah Berry: So most rolled oats will be steamed a little bit to soften them a little bit so that they can then be rolled. 

Then there's another kind of oatmeal or porridge that we can also commonly buy in our supermarkets, which is the instant oats. Essentially these are the rolled oats that have been pre-cooked so that they're very quick and easy for us to cook. 

So the groats, that are then steel cut, will probably take about on average 30 minutes to cook on the hob. The rolled oats that have only had a little bit of steaming before in order to roll them would probably take about 20 minutes or so to cook on the hob. And then the instant ones have been pre-cooked, rolled, and therefore they can take just a couple of minutes or five minutes to cook on the hob. 

Jonathan Wolf: That's interesting because when I grew up, my grandmother made me this oatmeal often, but she definitely boiled it on the stove with milk. I remember that very well. It's part of the process, as a child, you associate it then with the food that's afterwards. 

When I grew up, I switched to this oatmeal porridge in a packet that I could just rip open, put in a bowl, put in the microwave, and you could eat the whole thing in a couple of minutes.

And so you're saying it's the same oats in those two examples, but in the second one it's sort of being pre-cooked and chopped up more than in the first one, it seemed to me. 

Sarah Berry: So you have some kind of instant oats that are literally the rolled oats that just have been pre cooked and then you've got this kind of super quick, instant oats that are the kind of ones that often you find in the sachets, often are more finely ground, so it increases the surface area, so it's even more quick for us to cook. 

Often those also have added ingredients like golden syrup or sugar or, or other things added to them as well. 

You can also go even one step further, Jonathan, to produce what's called oat flour. And that is literally, again, just the oats really, really finely ground into a flour.

You can also produce something called oat bran. So you've probably heard of oat bran. It's often added back into cereals or added in as an ingredient or a thickener. And the oat bran is just the brown outer skin from oats. So it's very rich in fiber. 

So they're the key forms that are used. So we've got the steel cut groats, so the steel cut oats. We've got the rolled oats. We've got the instant pre-cooked rolled oats. Then we've got these super, super instant oats. Then you've got the flours. You've got the whole oat flour, and then you've also got the oat bran.

And these all, because of the way they're processed. Impact our health slightly differently. 

Jonathan Wolf: And I think our little experiment over the last 24 hours is going to help to explain that. So I know I am doing the experiment in my body right now.

But before I think you're ready to start, let me measure myself and start to explain it, I want to come to the biggest question that our listeners had. Over and over, the biggest question was, are oats really good for our hearts, like the heart-healthy labels that they're seen on all sorts of foods? 

Sarah Berry: So I think it depends on the type of oats. And as I say, with every podcast we do, I always say, it depends and it's more nuanced.

But overall, I think the overall body of evidence shows that most oats, not all oats, are certainly good for heart health because of the properties that they have in lowering our cholesterol, controlling our blood glucose, and some other beneficial effects as well.

Jonathan Wolf: So I think now you said we're allowed to check our blood sugar, Sarah, but you also said that we're both supposed to check how we're feeling right now. Is that right? 

Sarah Berry: Yeah. So we will check our blood sugar so we can see. But also what we can change, how we feel in this 30 minutes, how full we feel, our alertness levels, our mood, our energy levels, et cetera, and really importantly, our hunger levels. 

So I guess the thing to ask you is how hungry do you feel? 

Jonathan Wolf: Well, interestingly, I hadn't thought about it until just now. And actually, I feel like I've got a little bit of a headache, so I'm really interested to see what happens when I go and check my blood sugar. Because that instant oats breakfast is not what I normally have for breakfast anymore, and of course I also ate later than I normally would. 

How about you, how do you feel? 

Sarah Berry: I feel great, but mine was a very balanced plate as we'll dive into. So I feel really full, which is nice because often if I choose the wrong type of breakfast, I can feel hungry very quickly after. 

Jonathan Wolf: Well, I'm definitely not hungry now. Let's go and see what happens with our blood sugar. 

We're going to scan mine and show you what I've got, Sarah. Here we go. Wow. Can you see that? 

Sarah Berry: So Jonathan's has just gone up to 10.7. I can't believe that. Well, I can believe it, but I'm quite surprised. And mine's gone up to 8.4. 

So this is higher for me than what my blood sugar was yesterday.

Jonathan Wolf: So, Sarah, I just had 10.7 and my number, you know, when we scanned it 20 minutes ago was around six. What does any of that mean? What's going on? 

Sarah Berry: So what's happening is the carbohydrate from the oats is being processed and broken down into glucose molecules and the glucose molecules are now passing through your bloodstream and this is what we're detecting from the glucose monitor that you're wearing on your arm. 

So you're seeing this increase in circulating glucose from the carbohydrates that are in those oats, and this increases within 5 to 10 minutes after eating any carbohydrate-rich meals. Typically it peaks around 30 minutes so it'll be interesting to see what it looks like in about 10 or 15 minutes.

Jonathan Wolf: It seems to me that that number has shot through the roof in the last 20 minutes when I ate this instant oats. 

In fact, I have worn these before. I don't think I've managed to get above 10 with anything I eat in the last three or four years. I definitely did used to go above 10 before I started at ZOE.

So that's a pretty impressive spike I've achieved, isn't it? 

Sarah Berry: Yeah, that's quite a big increase in blood sugar levels. Now, an increase in blood sugar after a carbohydrate-rich meal is a normal physiological response. But once it starts to get really high, quite often it can impact how you're feeling in the moment.

So it might be that you have a slight headache or you might feel that your heart is racing a little bit. Also, about two to four hours after having quite a big peak like that, you might get a dip in blood glucose. 

We found from our own ZOE research that the dip can drive increased hunger, increased food intake. It can give you poor energy, poor alertness. 

What we also know is if you were eating every day, all of your meals to cause that kind of peak, the over sustained period of time, we know that that's linked to some unfavorable long term health effects, like an increased risk of obesity, type two diabetes, and cardiovascular disease.

So I would not recommend, based on that, you having instant porridge on its own with water for every meal of the day. Absolutely. 

Jonathan Wolf: Or even every breakfast, right? 

Sarah Berry: No, because you're likely as well to just not feel great for the rest of the day because it sets you up on that kind of roller coaster where you're having the big peak, you're having this dip.

It's driving you then to go and have a quick fix to get your blood sugar back up. You're then eating more at your next meal and you'll probably feel less energetic, less alert. So, yeah, I wouldn't advise that. 

Jonathan Wolf: Now, Sarah, you didn't eat exactly the same thing as me, did you? You added all those other ingredients onto these instant oats. Do you want to scan your blood sugar and let us know what's going on there?

Sarah Berry: I do. So Jonathan, mine's gone up to 8.4, which for me is actually quite high. 

Jonathan Wolf: Why is your number not the same as my number, Sarah? 

Sarah Berry: So I added nut seeds, dried berries, and some nut butter, and they contain extra fiber, extra protein, and extra fat. And we know that fiber, fat, and protein impact the rate at which our stomach empties.

They impact also the rate at which blood glucose is then absorbed from the bloodstream, and also some hormones like insulin, which obviously also impact how we metabolize the blood sugar. 

So by adding and layering on this extra fat protein and fiber, it modulates how quickly we absorb the glucose. So it modulates this rise in blood sugar.

Jonathan Wolf: Sarah, when you say modulates, what does that mean? 

Sarah Berry: So it modifies, it changes. So in the case of these particular ingredients and these particular nutrients, it's reducing. So it's slowing down the rate at which it’s entering the bloodstream, but also changing the rate at which it's also being absorbed later on.

Jonathan Wolf: Now, I know what we have with our meal is one part, but also it's true that we don't all respond the same, right, as we eat these meals. And you already showed that my baseline blood sugar was higher than yours. 

So even with your pairing, Sarah, and the fact that your blood sugar control is better than mine, isn't it? When we've done these ZOE tests, it turns out that my blood sugar control is really quite poor. My memory is that yours is fairly good. 

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Sarah Berry: Yeah, mine is a little bit better than yours, yes. And it's surprising actually, even though I paired it with the fiber, the fat, and the protein, that it's still gone up that high.

Jonathan Wolf: I remember the first time that I ever did this test with ZOE with my blood sugar sensor, this was the thing that blew my mind. Because I sort of thought these are oats, right? They're really healthy for you. And yet I was having this response, which was sort of as fast as when I just drank a sugary drink.

It seems to me that what you're seeing there, Sarah, is even when you've mixed in those other things, that this instant oats is, it feels like it's almost like you're having sugar with your yogurt. What's going on there? 

Sarah Berry: Yeah. And it's all to do with the magic of the food matrix that we often talk about here at ZOE, which basically is the structure of the food. 

So the structure of what we ate yesterday was different to the structure of what we ate today. And it's interesting because there's actually been lots and lots of clinical trials as well that have had a look at whether what we're seeing between us today actually plays out when you recruit lots of different people and ask them one day to eat one type of porridge.

So for example, there was a clinical trial where they asked people to eat one day, these steel cut oats, another day, the rolled oats, another day, instant oats, and another day, really heavily processed oats that are used often in breakfast cereals like Cheerios.

What they found, similar to what we've observed today, is that the less processed, the lower the blood sugar response. So, the steel cut oats cause the lowest increase in blood sugar after eating, the rolled oats that we had yesterday, called only a moderate increase, but as it became more processed up to the level of the oats that we had today, you got a bigger increase. 

It's because of changing the structure, changing the rate at which the stomach empties, the rate at which they're absorbed, that you see these differences.

We've done a study at King's actually, where we fed people whole rolled oats and people were fed oat flour, which is essentially pretty much what we ate in this last experiment. And they see that the whole large oats stick around in the stomach for longer. So they see this lower increase in circulating blood glucose or blood sugar.

They see that the whole rolled oats stay in the stomach for quite a bit of time compared to the powders. So the oats that we had this morning are really quickly entering our bloodstream. 

Jonathan Wolf: So actually, Sarah, what's going on now? 

The way I'm thinking a bit now, I'm sort of imagining piranhas in the Amazon and so when I eat, they're ripping apart the food. And it's a bit similar to, I fall in the Amazon river and the piranhas are on you. Clearly if you're small, they can rip you apart really, really fast, right? Whereas if it's some enormous thing, it's going to take a long time.

That's sort of the analogy I'm reaching for with the difference between the oats that are all pre-cooked and powdered, that basically, if my body is, these piranhas getting off into the bloodstream, then it does it almost immediately. But these whole oats, it's slow and takes a long time to be able to break apart the carbohydrates.

Is that… you're looking at me. I think this may not be my best. 

Sarah Berry: I think that's a crazy metaphor.

So the large rolled oats when they enter your stomach, there's less surface area for the enzymes to get to is one of the things. They also form bigger clumps inside the stomach, so there's even less overall surface area for the enzymes. And it's the enzymes that break the starch, which is the carbohydrate. 

Jonathan Wolf: So I think you said enzymes and I thought piranhas, but can you, is that not the right way to think about this?

Sarah Berry: It is a good enough analogy. So enzymes are like kind of chemicals, I guess you could say, that break down bonds. They break our food down. 

So when we have a carbohydrate, starch is a complex carbohydrate. You have these enzymes, these chemicals that need to break it down to very simple carbohydrates, because it's only the simple carbohydrates that we can actually absorb into our blood or that we can use for energy, et cetera.

So the starch that's in the oat seed needs to be broken down by these chemical enzymes into the simple sugar, which is glucose. And so the bigger the surface area, the more the enzymes, I guess, can kind of attack using your analogy to break it down into glucose. 

Jonathan Wolf: And my stomach is full of these enzymes?

Sarah Berry: So you have some enzymes in your mouth that start to break down some of the bonds in the carbohydrates. You have some in your stomach and you have a lot there as it passes through your intestines. It passes through your small intestine from where it's then absorbed as these very simple sugars, what we call glucose, into the bloodstream. 

Jonathan Wolf: So I'd love to talk a minute about what might be starting to happen now inside my blood because I feel like I'm going to check again, but I'm certainly hoping that it's not going to continue to spike because that seems quite scary. 

Let's see what's going on.

Sarah Berry: So what should be happening now, Jonathan, is most of those oats have been emptied from the stomach. Most of it has passed through the small intestine. And most of it, the enzymes would have broken down. Most of it has come into the blood.

But you'll also be releasing hormones such as insulin that then, in simple terms, remove the sugar from the blood so that you should start to be having a reduction in the levels.

Jonathan Wolf: So my number is down to 10.1. So you can just sort of see there's a little graph there that it's starting to dip down. So this is now my body pulling the sugar out of my blood?

Sarah Berry: Yeah. In simple terms, it's the insulin, which is a hormone that's released when you eat carbohydrate-rich meals that then controls the level of sugar in your blood and deposits in the different places that it needs to go. Whether it needs to go to the muscle or whether it needs to go to the liver, et cetera.

Jonathan Wolf: So I'd love to finish talking about the experiment about the sort of the personalization aspect of this. 

You've explained that the different ways in which we grind up these oats have this profound difference. And you've also said that when you wrap it with other sort of healthier foods, which you were describing, and the fats that sort of can slow down the absorption.

Why is it, though, that I am having just a stronger response than you for the same foods?

What's going on there and what does that mean about how I should think about what I eat? 

Sarah Berry: So you're firstly having a strong response cause we're not eating exactly the same. And you're having a meal that is essentially a very available carbohydrate, that is broken down very quickly into glucose, which is what we're measuring when we talk about blood sugar.

But also we're all very individual in terms of our biology, in terms of also, how we're living our lives, that all impacts our blood sugar responses. So we know from our own ZOE research that how much we slept last night can impact our blood sugar response. 

So if you've had a bad night's sleep compared to me, you're likely to have a higher blood sugar response. Your stress levels can impact. At the time of day that you're having it, you can impact it. As well as what you typically eat can impact it. 

In addition to that, we know that biological differences, so age, sex, menopause status, genetics, and so many other factors related to who you are biologically versus who I am.

And this is what we've been looking at over the last seven years at ZOE, trying to disentangle all of this so that we can give people the best advice in terms of what to eat best for their health. 

But I think it's also important to say, Jonathan, that, you know, we often talk at ZOE, about the importance of blood glucose, but also recognizing that it's one piece of a huge puzzle in terms of how a food impacts our health. 

So while some of the oats yesterday that you ate caused a blood sugar peak, there are other benefits to oats beyond the blood sugar. So I would say that, yes, for you, it's not the best breakfast because you're going to feel pretty rubbish having that massive peak as you said now with your headache.

But I would say that there are other benefits that we need to consider that make it perhaps a healthier choice than white bread and honey. 

Jonathan Wolf: So I'd love to transition to that, because I think we talked a lot about the blood sugar because we've had the fun of this experiment, but you're telling me it's not the only thing that matters when we think about the health of oats.

So could you talk about what else to think about? 

Sarah Berry: So I'd love to take a step back and first look at, is there evidence to show in populations that eating oats are even healthy for us. 

There's some fantastic data that's come from what we call the epidemiological studies, which are studies in large populations where they've followed people for a long period of time, and looked at, depending on whether people are oat eaters or not oat eaters, whether that affects their risk of disease.

In one such study where they followed more than 500,000 individuals over many years, they found that people who were oat eaters versus those who didn't eat any oats actually had lower rates of type two diabetes by about 15% and lower all cause mortality, which basically means risk of dying, and that was by about 20%.

Now, obviously, there's lots of other things that might explain some of this. People who eat oats tend to just smoke less, et cetera, but you can actually adjust for that in the analysis. You can never fully disentangle it. So it's not kind of the strongest evidence to pull on, but that gives us an idea that there's something going on there, that there's something about eating oats that might be beneficial for our health.

So the next thing we need to look at is clinical trials and also, is there a mechanism? Is there some kind of rationale why we might be seeing this? 

What we know is that oats contain a very special fiber called beta glucan. And this fiber is well known to reduce circulating cholesterol levels, so to reduce total cholesterol, but also reduce LDL, which is our bad cholesterol that we know is linked to heart disease. 

There have been lots of clinical trials that have been published showing that if you add oats to a meal or the beta glucan to a meal, that you can significantly reduce people's cholesterol levels.

It needs to be about a certain dose, so we know that you need to be having about three grams of the beta glucan a day in order to lower your cholesterol. And so the FDA in the U.S. and the EFSA, the European Food Standards Agency in the U.K., actually have an approved health claim that beta glucan, this fiber that's in oats, at three grams a day can reduce your cholesterol and hence is associated with improved heart health.

And I think the evidence is quite consistent for that. 

Jonathan Wolf: If I understand it rightly, what you're saying is that it's the fiber in the oat that is giving you these health benefits. And there's some really good scientific evidence to support the health benefits. 

It's not the starchy carbohydrate that you were talking about before. It's just this thing I feel like we come back to over and over again in this podcast, you know, it's sort of the fiber and the plant part of it, as it were, that's doing this. 

Sarah Berry: Yeah, like with all food, there's often a double edged sword and there's components in foods that might be really, really great for us and there might be another component in the same food that isn't so healthy for us.

But this is why we have to look at the food. In its totality, which is what we do a lot at ZOE, rather than looking at individual components. 

So we need to look at that oat in terms of also who you are. So if you're someone that has this big blood sugar response, that's not going to be the best food for you.

For me, I have less of a blood sugar response. If I had slightly elevated cholesterol, then maybe I want to make it part of my daily routine, having some oats in there in order to reduce my cholesterol. 

Jonathan Wolf: And is the beta glucans the only thing about the oats that's contributing to that health effect?

Sarah Berry: So we think the beta glucans is one of the main elements that make oats healthy because of how it can reduce our cholesterol. 

We know, though, that in addition to how beta glucans impact our cholesterol levels, that they may also reduce our risk of type 2 diabetes. There’s quite good evidence to show that if you consume oats, you have lower risk of type two diabetes and you have better insulin control. Which might seem a little counterintuitive given the experiment that we've just done.

But the beta glucans that are in oats cause the contents of your stomach and also your intestine to be quite sticky, gel-like, and we use a term in science called viscosity. So beta glucans increase the viscosity, so the stickiness of its surroundings. 

So you know when you had your finely-ground oats today, something that you said to me is, Oh, they're really gloopy. And you said it was actually like wallpaper paste, didn't you? Because it's so sticky. That's because it's the beta glucan in the porridge causing this kind of stickiness. 

So that's what it does in the stomach, which is why it kind of slows down the gastric emptying. It also does that in your small intestine, and it lines a little bit, the surface of your small intestine. So it does slow the absorption of the sugar a little bit. 

So if you were to compare the breakfast that you had today, although it caused the big blood sugar peak, if you were then to compare it with the matched amount of sugar, you should find that the peak, although high, is actually lower because of the beta glucans.

This is where it gets a little bit interesting because you also said that the breakfast you had today was more gloopy than the breakfast you had yesterday. And that's because the more you grind down the grain, the more of the beta glucan is released. So this is where you get that double-edged sword with processing.

The way it was processed today, where it's a powder, it's causing these big peaks in glucose, but you're getting slightly more of the beta glucan. And yet what you had yesterday, you had a lower peak in blood glucose, but you might get slightly less of the beta glucan. So it's kind of balancing that out a little bit.

And this is where personalization, I think, can be really valuable. 

Jonathan Wolf: You're talking again about the impact of the beta glucan. Is there anything else in the oat that you think that's contributing to these health benefits? 

Sarah Berry: Yeah, so oats are also packed full of B vitamins, also other minerals like the iron, the magnesium, et cetera. They also have polyphenols. 

There's a particular type of polyphenol and I can't remember the name. It's very long. It begins with ‘a’, and there is some evidence that this polyphenol has beneficial impacts on blood pressure, on pathways associated with inflammation, oxidative stress, and also has some beneficial impacts on blood vessel function.

Now it's difficult to tease apart where the benefits of oats on heart health are coming from. Is it all from the beta glucans or is this polyphenol also impacting that as well? Again, I think it's kind of the whole grain and all of the different components that are having that beneficial effect. 

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Jonathan Wolf: I wanted to come onto another question that we got from our listeners a lot, which is about pesticides in oats. And I think one of the reasons I might've asked it is that we did a podcast a while ago about organic foods with professor Tim Spector, who we both know well. Oats was one of the foods that he talked about in terms of pesticides. So what's the situation and how worried do you think we should be?

Sarah Berry: So there's a particular pesticide that is used to dry out oats before harvesting so that they can be harvested more quickly. It's a chemical called glyphosate. It's also found in common pesticides that you can go and get in your DIY store, like Roundup, for example. 

What it does is it dries out the grain so you can harvest it more quickly and so you can produce it more quickly.

Now you've got to remember the grain has this outer hull, this kind of shell. So it should be a little bit protected from it. But there is some evidence that oats will still absorb some of this pesticide. Oats seem to absorb it more than some of the other whole grains like wheat, for example. And so there are small levels found in many oats.

Now, organic oats rarely contain this because being organic, this pesticide isn't sprayed. But occasionally you'll find some organic oats that might have tiny, tiny amounts because, you know, you're getting stuff leached from soil from neighboring fields, for example. 

There are very strict regulations about the level of glyphosate that are found in food and in oats because there has been a link with cancer. Most of the evidence, though linking it to cancer, comes from a kind of cell sort of lab experiments or from animals. 

The evidence in humans is quite weak, but there is sufficient evidence to set tolerable limits, above which we know there is potentially an increased risk of cancer. 

So there's regulations internationally, in the U.S., in the U.K., in Europe, for example, of safe, tolerable, upper limits above which there is a probable association with cancer. 

There's some carcinogens, so cancer-causing agents, that we have great confidence that cause cancer. Alcohol is one of those. So alcohol is classed as a type one carcinogen that we know is linked to an increased risk of cancer.

Glyphosate is classed as a probable carcinogen. The levels that are found in most foods are actually quite low. I think unless you are eating oats all day long, day after day, it is almost impossible to reach that safe upper limit. Now obviously it's going to vary from one farm to the next farm, and so it's difficult to kind of blanket say that they are all safe.

But I think that the levels are generally found in food based on the evidence I've seen, based on the random sampling that is published, I don't think it's something we should worry too much about at all. 

However, if you can buy organic oats, if they're affordable and accessible for you, I would recommend that you choose organic over non-organic, but if that's not accessible for you, I think you can still enjoy your porridge or oatmeal without worrying about that too much.

As scientists, we always err on the side of caution. So for example, the tolerable limit that's set for glyphosate is a very cautious limit. It's also a level at which you're very unlikely to reach through normal dietary patterns. I say unlikely, not impossible. It's also a level that is set based on feeding that these excessive levels to rats or mice, and looking at how cancer may develop.

So I think the level is already very cautious, and then I'm adding some caution to that because I think we have to be so careful with areas that we don't yet have the full evidence, and so that's why I'm being overcautious, that personally I would happily eat non organic oats. 

If I were having them every day, in every meal, and I could afford it, yes, I would choose organic. Why take even a 0.00000% risk? 

But what I wouldn't want people to do who can't afford or it's not accessible for them to have organic, I wouldn't want them to say, okay, scare them off ever having oats. 

Jonathan Wolf: Thank you. I'd like to go back to one of the questions we had in the quickfire at the beginning. Because that also came up all the time from our listeners. Is oat milk healthy? 

Sarah Berry: Oh, oat milk. We've done a whole podcast on this, Jonathan, about plant-based milk. So I don't know if you remember that. That was about two years ago. 

Can I say it depends again. So I think it's important to understand quickly what oat milk is. So oat milk typically, and every oat milk variety is different, and I know some people make it at home in a very different way. 

So oat milk, typically that we purchase in a supermarket, typically contains about 10% oats. Most of the rest of it is water. Now, what they do to those oats to stop you having a drink that's all gloopy, like the wallpaper of paste that we talked about earlier, what they do is they firstly heat up those oats and dissolve them in water, and finely, finely grind them.

They then add enzymes in to break down the starch, so to break down that carbohydrate, so to break it down into those simple glucose sugar molecules. So what that means is you've got readily accessible sugar in that oats. 

They also add other ingredients like rapeseed oil, other kinds of additives, and stabilizers, etc., to come up with this final product that's essentially mainly water with a little bit of oats that have been degraded and then some of these added ingredients. 

Now, there is evidence to show that oat milk can reduce your cholesterol because it does have the beta glucan in it. But you have to drink about two pints or a litre of this to get that required amount of beta glucan that we know can lower cholesterol.

But there's been clinical trials that have compared oat milk versus cow's milk. The oat milk, if drank around a litre a day, does significantly reduce your cholesterol, but you're unlikely to ever drink that high amount. 

Also, you've obviously got this quite accessible sugar in there, you've got these other added ingredients. If you're choosing oat milk for planetary health or for animal welfare reasons, then I think that's a great choice for you. 

If you're choosing it because you think it's healthy or healthier than cow's milk, and you're spending 10 times as much, because often these are 10 times as expensive, then I think that the better option personally is to go for cow's milk.

Jonathan Wolf: If I understand rightly, that's because you're saying it's a bit similar to the oatmeal that we just had for breakfast. It's all been smashed up. It sounds like it's already been almost semi-absorbed. So actually there's a lot of sugar in this drink. And when I drink it, it's already very sugary. So it's not quite as healthy as I had in mind.

And that's quite different from when I think about just a traditional cow's milk, which is mainly fat. 

Sarah Berry: So I think the problem a little bit with oat milk is it's sold under this kind of health halo being so good for our health. Essentially it's mainly water. So you're paying a lot for the water.

The oat that's in there has already been degraded. So remember we talked about enzymes and how these chemicals break up the starch and the carbohydrate in your stomach and in your intestine down to these simple sugars, they actually add those enzymes in so that it breaks it down already. So you've got this readily accessible carbohydrate, this very rapid sugar.

So to say now at the level at which most people will use, eat this. So for example, adding it to their tea or in cereal, which is quite low, it's not going to be unhealthy for you. 

It's more people buying it because they think it's going to be really healthy. I think that's where I would just say a little bit of caution. If you like it, environmental health, planetary health, if you like the taste, if you can afford it, fine, go with it. 

And just a reminder as well, yes, if you've got high cholesterol, then it might be a better alternative as well. But to have any benefits, you're going to need to be drinking quite a lot. And then you've got to weigh up the potential effect that the readily accessible sugar might have.

Jonathan Wolf: Thank you so much, Sarah. I think this is all incredibly clear and helpful.

A lot of it's been actionable already, but I'd love to maybe finish with helping any of our listeners to understand, okay, I would like to have oats as part of my diet. How do I figure out how to eat it in a way where I can get the benefits that you're describing but avoid the terrible downsides that, for example, you've made me experience today. 

So maybe start with, what would the ultimate healthy oatmeal recipe look like? 

Sarah Berry: Okay, so the ultimate healthy oatmeal recipe would firstly include steel cut oats as the foundation. Or proper old-fashioned large rolled oats that haven't been pre-cooked. Either of those, but steel cut oats would be their preference. 

Then it would include adding something in. So as though we're all about adding stuff in, not taking it away. So adding in something that's got additional protein, additional fat, healthy fats, and potentially additional fiber. So just like I did this morning, depending on your preferences, that could be adding in yogurt.

So you could add in, Greek yogurt, kefir, you could add in nuts, seeds, some dried berries, although they're quite high in sugar, they've also got a great amount of fiber as well. You could add in some of the nut butters that are out there. I mean, that's a great way of packing in fiber, protein, healthy fats.

Jonathan Wolf: And if I want to think about cooking this, what's the best way to do it? 

I know quite a few friends of mine who say I really like this soaking it overnight. Is that good? Does that suddenly make it back like this instant oats? 

How should I think about that, versus obviously, one of the big disadvantages and there's a reason why we all switch to microwave, isn't it, which is that cooking it in the morning takes time, but also you've got a pan and it's become all gluey. 

Sarah Berry: So I don't actually know if there's been any studies looking at the health effects of overnight oats versus the kind of traditional way we cook in a pan or in a microwave. 

I'd be interested actually to know if there has been that research. So I can't tell you which is better in terms of overnight soaked oats or traditionally cooked. 

What we do know, it's a kind of rule of thumb, the longer it's taking to cook them, the better it is for your health. So if your porridge or your oatmeal is taking less than say 20 or 15 minutes to cook, it's likely it's going to be of a structure, therefore that isn't quite as good for us as if it was like the steel cut oats that take, we know, 20 minutes or more to cook.

Jonathan Wolf: If I took some of those oats you've told me are good, like the steel cut or sort of those jumbo rolled ones, and I did do the overnight oats. Would you be worried that now that it isn't going to be good for me anymore? Or are you saying actually you feel that that would be okay as part of my diet?

Sarah Berry: Based on what I know, I would say that doing the overnight oats would still be good for you. So I would say that it's the type of oats that are important rather than the way that you're cooking them. 

So if you're taking the still cut oats, the jumbo rolled oats and either cooking them in on the hob or you can cook them in the microwave or leaving them overnight as these soaked overnight oats, then based on my knowledge, I would say that they're all going to give you some health benefits.

But it's adding that extra protein and fat on top of them that I think will really balance out the oats as a really good balanced meal that will leave you feeling fuller for longer, balance out your energy, alertness, et cetera. 

And you are about to yawn, and that's probably because you are now an hour, probably, post us having the oats earlier, and I'd be quite surprised not to start to see a bit of a dip. And this is because you didn't have that balance, Jonathan. 

Jonathan Wolf: So I imagine a lot of listeners are saying, I really want to make sure I pick the right oatmeal, the right oats tomorrow. Can you help them, when they're looking on the label, I guess partly what is good, but also what the sort of things to look out for that would make you realize it wasn't.

Sarah Berry: So look to see if it's steel cut. These are a lot more difficult to find in the U.K. in your typical supermarkets than they are in the U.S., but you should be able to find them in many of the whole food stores, or some of the smaller retailers. 

If you can't find them, go for the rolled oats. Some people might not like the steel cut ones either because they are slightly chunkier. Go for the rolled oats. Make sure you look at the backpack labeling to also look at how long it says they're going to take to cook. The longer they're going to take to cook, we believe that they're likely to be more healthy for us.

Also check they haven't got loads of added ingredients. So some of the kind of individual sachets that you can get that you can cook, as well as having the oats, and therefore the benefits of the oats, also unfortunately have lots of other stuff added in like added sugar, added flavors, etc. 

Jonathan Wolf: And Sarah, how many ingredients should there be in a packet of oats?

Sarah Berry: There should be one. 

Jonathan Wolf: That's easy. 

Sarah Berry: Oats. So just look for that. The breakfast we had earlier, as well as having the oats, it also had that oat flour as well. And it had lots of other ingredients. 

Jonathan Wolf: I think that's really clear. We also had a lot of questions about whether oats are gluten free. 

Sarah Berry: So oats are gluten free. The only thing to watch out for is some manufacturers will say that the oats are processed in a factory that might also process ingredients that do contain gluten, so not all will give a gluten free guarantee, but oats per se are gluten free. 

Jonathan Wolf: And then final question, if you're like me and your blood sugar control is really poor, you've listened to all of this and you're like, well, I'm not going to make this something I'm having every day in my diet because I'm very conscious about that impact that I've seen with oats compared to quite a lot of other foods.

Are there any alternatives to oats that you feel are still going to give a lot of those health benefits? 

Sarah Berry: Yeah, it says lots of options. We have loads of ideas also on our Instagram page at ZOE with different alternatives as well. We've actually done a whole article on our blog on different alternatives for oats for breakfast.

One great idea, it's really simple, is chia seeds. Soak them overnight in either a yogurt or milk of your preference. And then in the morning you can layer on whatever you want, just like we did with the oats day. You can layer on nut butters, seeds, berries, et cetera. 

Jonathan Wolf: And the chia seed is also something that's really good for me.

Sarah Berry: Absolutely. Packed with fiber, loads of great health benefits from chia seeds. So you'll get all the benefits and you won't get the downside of the blood sugar peaks that you have. 

Jonathan Wolf: Amazing. So I think my takeaway, actually, my takeaway from this episode overall is I'm definitely going to try some oats in my diet again. 

Because my takeaway from this experiment is that if I was having these steel cut oats, you know, as a part of a meal, right, so not just this massive bowl of steel cut oats, which I know is still going to cause me a problem, but actually if it's a part mixed in you have done with a lot of the things I tend to eat, then actually I don't think it's going to cause the sort of problem. 

And even my experiment myself yesterday with the classic oatmeal on the stove, I was struck that it was a lot less of a spike than I'd expected because I was used to what we've tried this morning. 

On the other hand, I'm not about to start saying, oh, I should have oats every morning. I think I'm also struck, Sarah, that even with your good blood sugar control, and even with all the things that you put on top of that oatmeal this morning, you actually managed to get pretty amazing amount of blood sugar response, which does show that when it is sort of smashed up, it does get into your blood really fast.

So this thing that you often talk to me about, how much the complexity of the food, your famous food matrix, how much that really affects your blood sugar is amazing. 

Sarah Berry: Yeah, and you know, I've learned something from doing this experiment as well because I stopped eating porridge probably about 30 years ago because I would feel so hungry within an hour or so and I'd feel quite rubbish as well within an hour or so. 

It was really interesting yesterday when I had the porridge that was this old-fashioned porridge, you know, the rolled oat porridge and had all of these other bits added to it, actually, how good I felt and how full I felt for longer.

So I've now, through doing this experiment, gained an extra breakfast in my breakfast repertoire. But I won't be having these ground oats for sure. 

Jonathan Wolf: That does seem to be the takeaway. And in fact, talking about takeaway, I'm going to try and do a quick summary. 

My biggest takeaway today is that instant oats are not our friend. I have spent most of this podcast with a headache, which is not usual. And I managed to spike my blood sugar up to 11, which is remarkable. 

My learning is there's this huge difference between the types of oat. And so, instant at one end is almost just like eating sugar. But then I can go to rolled, which is much better, and steel cut, which is the best.

So if I'm going to go out and buy this from the supermarket, I'd like to try and get steel cut oats if I can. And the next best is this large pre-rolled oats. 

That if I look on the back of the package, I want the thing that says the longest cooking time. That is also telling me that this is much more like the original food. I want that to be one ingredient, oats. 

I've also learned that there's really strong scientific evidence to say that oats can support your health. And you said there was a study of I think half a million people and that the people who are eating oats had a lower risk of dying, which I like. So I like the idea of putting a little bit of oats into my diet.

You said there's a lot of good things in the food. And as always, we should be careful of people who say there's just one ingredient that causes the health. And so you're saying the beta glucan is part of it, but probably not all of it. 

We have to be really careful because you need to eat, I think you said three grams of that a day to get the benefit.

I think my other big takeaway was that oat milk is not in fact as healthy as I had thought it was, because you need to drink two pints of oat milk a day to get that benefit that you talk about. And actually the oat milk itself is very processed. So it's been chopped down, it's been broken down with these chemicals.

You said there are good reasons you might want to do it for environmental reasons or animal welfare reasons, but actually in terms of health, you're not saying it's bad, but you're not saying it's actually better than cow's milk. 

And then finally, we talked about pesticides. And I think your takeaway was you were not personally very worried about it. If you can afford it, yes, you would go and choose the organic oats because of the way that it tends to be higher in these pesticides than most other grains. 

But if you couldn't afford it, that wouldn't be for you a reason not to take out. 

Sarah Berry: Correct.

Jonathan Wolf: Brilliant. Well, I really enjoyed that, particularly the fact that now I'm finished and I can now eat some other food that will hopefully balance me out.

I really enjoyed this thing, being made science made real. And I hope a few listeners also enjoyed seeing one of the world's leading nutritional scientists actually talk us through a real live experiment here on the podcast. 

Sarah Berry: I loved it. And Jonathan, I'd love to invite you to come to my lab for one of our next podcasts so we can actually do some of the experiments that we've talked about before. You'll have to be the guinea pig. 

It's not going to be as easy as just eating porridge though. We'll be taking blood, looking at your poo, looking at your spit, all sorts. 

Jonathan Wolf: The things I do for ZOE. Sarah, it'd be a pleasure. 

Sarah Berry: Great. I'm going to hold you to that. 

Jonathan Wolf: Yeah. I'll be there. Thank you.