Updated 26th April 2023

Why eating nuts makes you healthier, according to science

There's no shortage of variety when it comes to the mighty yet humble nut — or the ways we like to eat them.

Dried, chopped, made into a butter, or roasted over an open fire, these little guys provide the nutrients our brains and bodies need in surprisingly high quantities.

From industrial farming to indigenous hand-harvesting, the story of nuts is, well … nuts!

In today’s short episode of ZOE Science & Nutrition, Jonathan and Sarah ask: If nuts are so full of fat, can they really be good for us?

If you want to uncover the right foods for your body, head to joinzoe.com/podcast and get 10% off your personalized nutrition program.

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Episode transcripts are available here.

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[00:00:00] Jonathan Wolf: Hello and welcome to ZOE Shorts, the bite-sized podcast where we discuss one topic around science and nutrition. I'm Jonathan Wolf, and today I'm joined by Dr. Sarah Berry, and today's subject is nuts. 

[00:00:17] Dr. Sarah Berry: And Jonathan, this is a subject I love. I've done loads of interventional human studies measuring the effects of eating nuts on people's health.  

[00:00:26] Jonathan Wolf: Well, the good news is we had lots of listeners worried that nuts are full of fat. And therefore are bad for you?  

[00:00:33] Dr. Sarah Berry: Well, I hope that they'll be very surprised by what we're about to discuss then. 

[00:00:37] Jonathan Wolf: Good. Let's go nuts! Sorry about that. 

[00:00:44] Dr. Sarah Berry: Right. So it's important before we get into the nutritional value of nuts to point out that there are lots of different ways of consuming that. On average, our consumption of nuts and seeds in the UK is about six grams per day, which doesn't sound like lots, but that's because we have a lot of [00:01:00] people that don't consume nuts at all, and that also includes nut butters. To put that in perspective, one portion of nuts is around 30 grams, and that's roughly a small handful of nuts.  

[00:01:10] Jonathan Wolf: So six grams is just a couple of nuts a day then, Sarah.  

[00:01:15] Dr. Sarah Berry: Yeah, that's right, Jonathan.  

[00:01:16] Jonathan Wolf: Which is a shame because I know they're packed full of nutrients. Uh, I've heard Tim describe the nut as a tree egg, uh, and Sarah, you know how much you like the nutrients in eggs. 

[00:01:26] Dr. Sarah Berry: Yeah. And mixed nuts contain so many great nutrients. They contain fiber, they contain vitamin E, magnesium, selenium. Nuts are also very high in fat, but they're particularly high in monounsaturated fats, which we know are the healthy type of fats.  

[00:01:45] Jonathan Wolf: So Sarah, let's get into the nuts and bolts of things, shall we? 

[00:01:49] Dr. Sarah Berry: Oh my gosh. 

[00:01:50] Jonathan Wolf: I've got, I've got loads more of these today. It's, it's a great one. Um, how do nuts affect our health then, in particular? I've read that nuts might be good for our hearts?

[00:01:58] Dr. Sarah Berry: Yeah, nuts do [00:02:00] lots of great things that help our heart health. So in particular, nuts can decrease our bad LDL cholesterol and they can also decrease our blood triglyceride concentrations. And this means that nuts might help to lower the risk of both heart disease and stroke. Now, In addition, nuts also contain bioactives, and these are tiny molecules that have lots of really special roles to play in the body. For example, some have antioxidant and anti-inflammatory properties, and a great example is polyphenols. And these are thought to protect your cells from damage that is caused by free radicals and polyphenol chemicals from nuts can help to reduce bad cholesterol from being oxidized, which happens when LDL cholesterol reacts with free radicals. This is great because we. Oxidized LDL cholesterol can build up in the walls of your arteries. It can cause them to become thicker and stiffen, reducing just how much blood can get through these arteries, which can lead to atherosclerosis, which is the first step towards heart disease and strokes. And [00:03:00] there are lots of different studies that have measured this, and there are several different ones that have found that people who eat various types of nuts see a drop in the levels of these oxidized bad LDL by up to about 30%.  

[00:03:12] Jonathan Wolf: So now on top of that, there's also, um, impact on inflammation, isn't there? Um, and inflammation is something that we're very interested in at ZOE because of the way that it seems to be linked to sort of almost every long-term disease that scientists are investigating. That just comes up over and over again on, these podcasts, and elsewhere. My understanding, looking at some of the research there is that there are also studies where people whose diets were supplemented with nuts saw a real decrease in inflammation, what they call inflammatory markers in those papers.  

[00:03:45] Dr. Sarah Berry: Yeah, that's right Jonathan. We see lots of different types of nuts, like walnuts, almonds, and pistachios. If you eat a long period, a portion of these nuts a day, you have a reduction in many of them. Different types of inflammatory measures. We [00:04:00] also know that there's an impact of eating nuts. For people that have metabolic syndrome and type two diabetes, we know that they improve insulin sensitivity. We know that they reduce your fasting, uh, blood glucose, but interestingly, they also improve your blood vessel function.

And this is something I've looked at in my research. And I think it's important to say at this point that um, I have received a lot of funding from the Almond Board of California to research the impact of almonds on cardiovascular health. So I do always like to put any conflict of interest out there. And we ran a study where we supplemented, uh, people with nuts for six weeks compared to a control, and we found an improvement in the functioning of people's blood vessels when they had almonds. So almost like how elastic, they are. And finally, there's some evidence as well emerging that nuts might even prevent memory loss as we age. Although this is still at quite the early stages of research.  

[00:04:56] Jonathan Wolf: So it's all pretty amazing. These like tiny nuts are punching [00:05:00] well above their weight.  

[00:05:02] Dr. Sarah Berry: Oh, how many more of these jokes are we gonna have Jonathan? Okay. Jonathan, we haven't even mentioned the fiber. That's in nuts, which is another great property of nuts. Fiber simply put is the nuts cell walls. And in one 30-gram portion of peanuts, um, there's about two and a half grams of fiber. And this is in comparison to a pack of, uh, salted crisps or potato chips, which has less than one gram of fiber. And there's compelling evidence linking high fiber intake to reducing the risk of many chronic diseases. 

[00:05:37] Jonathan Wolf: And, and even death, which I'm particularly keen on. So, you know, as you increase your dosage of fiber, actually your life expectancy increases. Um, and this is rare, right? There are very few things actually where you see a really clear impact, not just on some sort of disease, but actually whether or not you're going to live longer. 

[00:05:54] Dr. Sarah Berry: Yeah. And fiber's the one nutrient that every nutritional scientist in the world agrees. We need to be getting [00:06:00] more of. You know, in the UK in the US we consume less than 20 grams. We should be getting at least 30 grams a day of fiber. So what's great is these nuts are packed, uh, fiber. And this fiber works to feed your healthy gut bacteria. 

[00:06:13] Jonathan Wolf: So Sarah, it seems pretty clear nuts have lots of benefits. They're also surprisingly well studied, um, in terms of sort of the research that you're talking about compared to a lot of the, the topics where we say, you know, there's like three studies. The whole world ever. Um, and it seems particularly clear to do with cardiovascular health. So you know, sort of heart disease and strokes. I think the elephant in the room is weight. Um, if nuts are high in calories, um, won't they contribute to weight gain?  

[00:06:38] Dr. Sarah Berry: So this is why I think it gets really interesting. And obviously, I'm biased because this has been the focus of my research with almonds, which is their food matrix. So what. The humble nut is even more special in its structure, and this is what I call the food matrix.  

[00:06:53] Jonathan Wolf: So, so Sarah, most people only know the Matrix as like a hit film 30 years ago, so could you [00:07:00] explain a bit more what the food matrix is? 

[00:07:03] Dr. Sarah Berry: Yeah, so we're not talking about Kiana Reeds here, Jonathan. We're talking about the food structure and simply put, it just refers to the structure of the food. So, um, I think a really good way to illustrate this is using almonds. Um, and let's say you had a packet of whole almonds and a packet of ground almonds according to the back of pack labeling information, they're nutritionally identical, but actually how they behave in our body is 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 remains intact. So the fat is remaining within the cell walls and it's therefore not easily digestible.

And so [00:08:00] research has shown. 30% fewer calories are absorbed from these whole nuts compared to what's predicted based on the ingredients listed on the back of pack labeling. And Jonathan, from the studies that I've done where we collect poo after people have eaten whole nuts, you see these whole big nut particles. And if you slice through them, which fortunately my researchers do rather them than I do, and then put them under a microscope, you can see these hundreds of intact cells still within these chewed nut particles that we've collected from the poo, and you can see within those, all of these fat globules, which is why it has 30% fewer calories that are being absorbed. 

[00:08:37] Jonathan Wolf: And Sarah, is this true of like any plant that we eat or is this because like most plants, you know, we cook for ages first? Or how, you know, is there something special and magical about nuts? How? How do we understand that? 

[00:08:49] Dr. Sarah Berry: 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 [00:09:00] overestimate the calorie amount by about 30%.

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

[00:09:30] Jonathan Wolf: Got it. And so if I eat, I dunno, lentils for example, which are quite a high fiber, um, food I know, but they do have lots of carbohydrates. It's not the same as nuts. I am probably going to end up extracting all of that, but it's just, it's gonna take a while, you know, I'm gonna get to it, including my bacteria, they're gonna get their way through. Whereas these nuts, it's sort of unusual. We're sort of struggling to get all the calories out before actually, it's coming out the other end. 

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[00:09:53] Dr. Sarah Berry: Yeah. And we've done, uh, what we call mastication studies, Jonathan, where - there are even more [00:10:00] glamorous than the pew 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.  

[00:10:45] Jonathan Wolf: And so that explains why, you know, the number of calories you consume might be much less than that 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 [00:11:00] to absorb.  

[00:11:00] Dr. Sarah Berry: Yeah, and this is another really interesting area of research that is looking at the effect of consuming whole nuts versus. Nut butters and finely ground nut powders. And what we know is if you commercially 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 um, the kind of techniques that you might use at home to grind nuts, or to make your nut butters, you are unlikely to be able to grind the nut, to an extent that you break all of the cell walls. So you are still likely to have a nut that has a lot lower, um, energy density. So lower calorie amount that's absorbed, uh, compared to if it was fully ground. 

[00:11:47] Jonathan Wolf: 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, um, 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 [00:12:00] whatever else, are also not going to be absorbed as much? 

[00:12:02] Dr. Sarah Berry: Yeah, that's right. And I've published research showing that the vitamin E and the blood after eating whole almonds are lots lower than the vitamin E after eating industrially ground almonds where all of the cell walls are broken down.  

[00:12:16] Jonathan Wolf: And Sarah, I remember you telling me something extraordinary, that there's a study about how many calories, different individuals, uh, extract from the same nuts and sort of showing this huge variation is that right?  

[00:12:30] Dr. Sarah Berry: Yeah. So there was a study carried out several years ago by David Bear in the US where they fed individuals nuts over some time, collected their poo, and had a look at how much energy was excreted from consuming nuts. And what this meant in real terms, is that for some people, a 30 grand portion of almonds, uh, resulted in them eating about 56 calories. And yet for other people, Eating a 30 grand portion of almonds resulted in [00:13:00] them eating about 168 calories. So that's a huge difference. And if you extract that over a week, that's a large amount.

I can't do the math off the top of my head, but I think that's about a 750-calorie difference. So, uh, Jonathan, I think. All of this taken together goes somewhere to explain why, what a lot of people fear, research has shown that nuts simply do not cause you to put on weight. And whilst the nutritional, uh, 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 great addition to your diet. 

[00:13:41] Jonathan Wolf: Wonderful. Can I tell you my Brazil nut story just to finish?  

[00:13:45] Dr. Sarah Berry: I haven't heard this one, so yes, please do...  

[00:13:49] Jonathan Wolf: So, um, because I was thinking about almonds and there's, you know, there's, uh, almonds are grown now commercially in, in a lot of places, but Brazil nuts can't be grown like in a, in a [00:14:00] plantation they haven't figured out how to do this. And I once went to, uh, the Amazon many years ago, amazing trip, just after I left my last company, and we sort of went deep into, uh, into the Amazon and the Brazil nut tree, it turns out is, biggest trees in the world. And so it's one of the biggest trees in the Amazon. It sort of sticks out to this huge tree.

And apparently, they're one of like the key trees in the ecosystem of, uh, of the Amazon. And these little nuts are coming to this massive sort of cannonball-sized thing that the Brazil nut tree, uh, grows. And then it falls from a height of, I'm making this up now, like 30 meters. So this huge thing that collapses to the ground and people who live locally, who are a lot of sort of indigenous people who've been there, you know, before Europeans even came to America, has come at a particular, the right season to harvest these sort of in the Amazon and take them to sell us. And they have to wear massive hard hats because actually if this thing falls on your head, it could kill you.

So I love this idea that you get this sort of Brazil [00:15:00] nut that's sort of in the supermarket just seems like nothing at all. But actually, it's sort of this kind of nuts that's come from the Amazon. So I always think about that when I have it. And also, of course, it's very ecological because, um, the Brazil nut tree can only survive because the whole Amazon around it is still being supported. They haven't figured out a way for it to grow. So I feel, uh, always. Quite good as well, that somehow you are, you're supporting some of the sustainability, which we know is a, is a big issue. So that is my Brazil nut story.  

[00:15:25] Dr. Sarah Berry: So Jonathan, I've been googling Brazil nut tree while you've been telling me that. Yeah. Um, and this is a total eye-opener to me, so, it looks like a coconut shell. And when you cut it in half, it's got like 50, 60 Brazil nuts inside it again, in case within their shell never knew that. 

[00:15:45] Jonathan Wolf: Amazing. Right. Wow. And apparently, so all of this is what I was told then. I thought you were about to tell me that all of this was a total lie that they just tell to these visiting western tourists. There is a particular animal, I think it's like, uh, something a bit like a chipmunk, which is the only [00:16:00] animal which can crack open the outer shell of this. So again, there's this like this whole amazing ecosystem where, uh, you can only have a new Brazil nut tree because of this animal that can break open this massive, um, thing. And I guess it like drags it off somewhere else or something. There's a way, to move it around. But I, I love this. There's something nice about the idea that you're connected to this, uh, this tree, thousands of miles away. 

[00:16:23] Dr. Sarah Berry: Uh, I'm now Googling what animal. I think it might be an agouti, but I'm not sure. Google's not quite quick enough.  

[00:16:29] Jonathan Wolf: We'll put this in the show notes. Sarah, what's your conclusion?  

[00:16:32] Dr. Sarah Berry: So, my final thoughts are that nuts are a great addition to anyone's diet. Having different types of nuts is great because whilst nearly all nuts contain a fantastic, uh, 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 try substituting your normal snacks for nuts. We know that about [00:17:00] 20% of our energy intake comes from snacks. If you can change your typical snacks to nuts, you'll see big improvements in your health.  

[00:17:06] Jonathan Wolf: Uh, I think the summary is, We think nuts are great. 

[00:17:10] Dr. Sarah Berry: We do. We agree on this one, Jonathan.  

[00:17:13] Jonathan Wolf: I, we do on so many. Well, if you'd like to discover how nuts can best fit into your life, you may want to try ZOE 's personalized nutrition program to improve your health and manage your weight. You can get 10% off by going to joinzoe.com/podcast. I'm Jonathan Wolf. 

[00:17:29] Dr. Sarah Berry: And I'm Sarah Berry.  

[00:17:31] Jonathan Wolf: Join us next week for another ZOE Podcast.

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