Recap: Why nuts make you healthier | Professor Sarah Berry
08:47 Share

Hello and welcome to Zoe Recap, where each week we find the best bits from one of our podcast episodes to help you improve your health. Today we're discussing nuts. If you've heard that nuts are bad for you because they're full of fat, then you're in for a surprise. Professor Sarah Berry has led large-scale human studies to uncover how nuts affect our health, and she's here to tell us the healthiest ways to incorporate them into your diet.

But first, a discovery that'll help when you're reading the nutrition information on the back of a nut packet: appearances can be deceiving.

I think the elephant in the room is really weight. If nuts are high in calories, won't they contribute to weight gain? So this is where I think it gets really interesting. And obviously I'm biased because this has been the focus of my research with nuts, which is their food matrix. So what makes the humble nut even more special is their structure. And this is what I call the food matrix. Could you explain why?

a bit more what the food matrix is. Yeah, so we're not talking about Keanu Reeves here, Jonathan. We're talking about the food structure and really simply put, it just refers to the structure of a food. So I think a really good way to illustrate this is using almonds. And let's say you had a packet of whole almonds and a packet of ground almonds. According to the back of pack labelling information, they're not nutritionally identical, but actually how they behave in our body is really different.

Nuts consist of millions of tiny cells and these have cell walls, which we've already mentioned is the fiber. And they have a really important structural role. And within these cell walls are tiny fat globules. Now, if I very, very finely grind the nuts, I break down the cell walls and the fat bursts out. But when you eat whole nuts, the matrix, so the structure of these cell walls,

cell walls remains intact. So the fat is remaining within the cell walls and it's therefore not easily digestible. And so research has shown that about 30% fewer calories are absorbed from these whole nuts compared to what's predicted based on the ingredients listed on the back of

pack labelling. And Jonathan, from the studies that I've done where we collect poo after people have eaten whole nuts, you actually see these whole big nut particles. And if you slice through them, which fortunately my researchers do rather than I do, and then put them under a microscope, you can actually see these hundreds of in

of intact cells still within these chewed nut particles that we've collected from the poop. And you can see within those all of these fat globules, which is why it has 30% less calories that are being absorbed.

And Sarah, is this true of any plant that we eat? Or is this because like most plants, we cook for ages first? Or is there something special and magical about nuts? How do we understand that? This is true of nearly all nuts. So we've looked at this with lots of different types of nuts. And we find consistently that the back-of-pack labeling information would overestimate the calorie amount by about 30%. The impact of the

The cell wall structure within other plants varies depending on the plant. So for example, in more carbohydrate rich foods such as oats, you will still get full absorption of all of the nutrients. So you will still absorb all of the calories, but you will change the rate at which you absorb them. So you will lower your blood sugar response, which is beneficial if you're having really large oats versus having really finely ground oats. Got it.

So if I'm eating, I don't know, lentils, for example, which are quite a high fiber food, I know, but they do have lots of carbohydrate. It's not the same as nuts. I am probably going to end up extracting all of that, but it's just going to take a while. But, you know, I'm going to get to it, including my bacteria. They're going to get their way through. Whereas these nuts,

It's sort of really unusual. Basically, we're sort of struggling to get all the calories out before actually it's coming out the other end. Yeah, absolutely. And we've done what we call mastication studies, Jonathan, where these are even more glamorous than the poo studies that we do. These studies involve people chewing nuts.

And at the point at which they're about to swallow, they spit them out. We collect them and we analyze them. We analyze them for how much fat is released at that point. And what's interesting is at the point at which you're about to swallow an almond, the amount of fat that's released...

from the chewing action bursting the cells is only about 10% at that point. And this is because the cells of almonds, and it's the same with other nuts, are so, so tiny. They're 35 micrometers, which is tiny. Yet the point at which you swallow nuts is normally around nearly one millimeter particle size. And so that's why so much is entering your stomach and your intestine intact.

And so that explains why actually, you know, the amount of calories you actually consume might be much less than sort of on the packet. Presumably that does mean the more that you process nuts, the more that the fat will be released and the more energy you'll be able to absorb. Yeah, and this is another really interesting area of research is looking at the effect of consuming whole nuts versus nut butters and really finely ground nut powders. And what we know is if you commercially consume

grind the nuts to break all of the cell walls and release all of the fat, then a lot more of that fat is accessible and therefore you do absorb a large proportion of the calories. However, using the kind of techniques that you might use at home to grind nuts

or to make your own nut butters, you're unlikely to be able to grind the nut to an extent that you break all of the cell walls. So you're still likely to actually have a nut that has a lot lower energy density, so lower calorie amount that's absorbed compared to if it was fully ground.

So I guess one question follows from this. You know, you might think it's a good idea that your body isn't absorbing all the fat. But on the other hand, does it mean that all these other nutrients that you were talking about, like, you know, vitamin E and whatever else are also not going to be absorbed as much? Yeah, that's right. And I've actually published research showing that the vitamin E in the blood after eating whole almonds is lots lower than the vitamin E after eating industrially ground almonds where all of the cell walls are broken down.

And Sarah, I remember you telling me something really extraordinary that there's a study about how many calories different individuals extract from the same nuts and sort of showing this huge variation. Yeah, absolutely. So there was a study carried out a number of years ago by David Baer in the US where they fed individuals nuts over a period of time, collected their poo and had a look how much energy was excreted

from consuming nuts. And what this meant in real terms is that for some people, a 30 gram portion of almonds resulted in them eating about 56 calories. And yet for other people, eating a 30 gram portion of almonds resulted in them eating about 168 calories. So that's a huge difference. And if you extract that over a week, that's about 750 calorie difference. So Jonathan, I think all

all of this taken together goes some way to explain why, despite what a lot of people fear, research has shown that nuts simply do not cause you to put on weight. And whilst the nutritional makeup of each nut varies slightly, broadly speaking, one nut is not necessarily better than another. And

any type of nut, as long as they're not coated in chocolate, salt or sugar, will make a really great addition to anyone's diet. That having different types of nuts is great because whilst nearly all nuts contain fantastic combination of healthy fats and these magic polyphenols, they do also differ slightly in some of their other attributes. So having mixed nuts is great. And my other top tip is to actually try substituting your normal snacks for

for nuts. We know that about 20% of our energy intake comes from snacks. If you can change your typical snacks to nuts, you'll really see big improvements in your health. That's it for this week's recap. If you're listening to this, you're already on your way to living healthier through better nutrition. And at Zoe, we're doing everything we can to help you on your way. So we've developed Daily 30, a delicious dietary supplement to add to your meals.

Because we're Zoe, we ran a clinical trial testing Daily 30. The results were staggering. It's selling out in the UK and we're working hard to bring it to the US as soon as possible. Sign up to the waitlist at zoe.com slash daily30.