ZOE Science & Nutrition - Why eating nuts makes you healthier, according to science

Starting point is 00:00:00 Hello, and welcome to Zoe Shorts, the Bite Size podcast where we discuss one topic around science and nutrition. I'm Jonathan Wolfe, and today I'm joined by Dr. Sarah Berry. And today's subject is nuts. And Jonathan, this is a subject I absolutely love. I've done loads of interventional human studies measuring the effects of eating nuts on people's health. Well, the good news is we had lots of listeners worried that nuts are full of fat and therefore are bad for you. Well, I hope that they'll be very surprised by what we're about to discuss then. Good. Let's go nuts. Sorry about that.

Starting point is 00:00:44 Right. So it's important before we get into the nutritional value of nuts to point out that there's lots of different ways of consuming nuts. But 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 people 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. So six grams is literally just a couple of nuts a day then, Sarah? Yeah, that's right, Jonathan.

Starting point is 00:01:16 Which is a shame because I know they're packed full of nutrients. In fact, I've heard Tim describe the nut as a tree egg. And Sarah, you know how much you like the nutrients in eggs. Yeah, absolutely. And mixed nuts contain so many great nutrients. They contain fiber, they contain vitamin E, magnesium, selenium. And nuts are also very high in fat, but they're particularly high in monounsaturated fats, which we know are the healthy type of fats. So Sarah, let's get into the nuts and bolts of things, shall we?

Starting point is 00:01:48 Oh my gosh. I've got loads more of these today. It's a great one. How do nuts affect our health then? In particular, I've read that nuts might be good for our hearts. Yeah, nuts do 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

Starting point is 00:02:20 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 are 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 know that oxidized LDL cholesterol can build up in the walls of your arteries. It can cause them to become thicker and to stiffen, reducing just how much blood can actually get through these arteries, which can lead to atherosclerosis, which is the first step towards heart disease and strokes. And there's lots of different studies that have measured this. And there's a number of different ones that have found that people who eat various types

Starting point is 00:03:06 of nuts see a drop in the levels of these oxidized bad LDL by up to about 30%. Now, on top of that, there's also impact on inflammation, isn't there? 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. It just comes up over and over again on these podcasts and elsewhere. Now, 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 an inflammation, what they call like inflammatory markers in those papers. Yeah, that's right, Jonathan. We see with lots of different types of nuts like walnuts, almonds, pistachios, if you eat over a long period of time a portion of these nuts a day, you have a reduction in many of these different types of

Starting point is 00:03:55 inflammatory measures. We also know that there's an impact of eating nuts for people that have metabolic syndrome and type 2 diabetes. We know that they improve insulin sensitivity. We know that they reduce your fasting blood glucose. But interestingly, they also improve your blood vessel function. And this is something I've looked at in my own research. And I think it's important to say at this point that I have received a lot of funding from the Ulmer 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 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

Starting point is 00:04:40 almonds. So almost like how elastic they are. And finally, there's some evidence as well, just emerging that nuts might even prevent memory loss as we age, although this is still at quite early stages of research. So that's all pretty amazing. These tiny nuts are definitely punching well above their weight. Oh, how many more of these jokes are we going to have, Jonathan? Okay, Jonathan, we haven't even mentioned the fiber that's in nuts, which is another great property of nuts. And fiber, simply put, is the nut cell walls. And in one 30-gram portion of peanuts, there's about two and a half grams of fiber. And this is in comparison to a pack of salted crisps or potato chips, which has less than one grams of fibre. And there's

Starting point is 00:05:26 really compelling evidence linking high fibre intake to reducing the risk of many chronic diseases. And even death, which I'm particularly keen on. So, you know, as you increase your dosage of fibre, actually your life expectancy increases. And this is rare, right? There's very few things actually where you see really clear impact, not just on some sort of disease, but actually whether or not you're going to live longer. Yeah. And fiber is the one nutrient that every nutritional scientist in the world agrees we need to be getting more of. 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 full of fiber and this fiber basically works to feed your healthy gut bacteria. So Sarah, it seems pretty clear nuts have lots of benefits. They're also surprisingly well studied

Starting point is 00:06:14 in terms of sort of the research that you're talking about compared to a lot of the topics where we say, you know, there's like three studies in the whole world ever. And it seems like particularly clear to do with cardiovascular health. So, you know, sort of heart disease and strokes. 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. So what makes the humble nut even more special is their structure. And this is what I call the food matrix. So Sarah, most people only know the matrix

Starting point is 00:06:50 as like a hit film 30 years ago. So could you explain 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 labeling 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.

Starting point is 00:07:29 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 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 labeling. And Jonathan, from the studies that I've done where we collect poo after people have eaten whole nuts, you actually see these whole

Starting point is 00:08:08 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 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?

Starting point is 00:08:43 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 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. And so if I'm eating,

Starting point is 00:09:25 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

Starting point is 00:10:03 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.

Starting point is 00:10:45 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 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

Starting point is 00:11:37 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

Starting point is 00:12:17 variation. Is that right? Yeah, absolutely. So there was a study carried out a number of years ago by David Baer in the US where they fed individuals carried out a number of years ago by David Bear 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 a large amount. I can't do the maths off the top of my head, but I think that's about 750 calorie difference. So Jonathan, I think all of this taken together goes some way to explain

Starting point is 00:13:07 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 your diet. Sarah, what's your final conclusion? So my final thoughts are that nuts are a 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.

Starting point is 00:13:54 And my other top tip is to actually try substituting your normal snacks 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. I think the short summary is we think nuts are great. We do. We agree on this one, Jonathan. As we do on so many. Well, if you'd like to discover how nuts can best fit into your life,

Starting point is 00:14:20 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 slash podcast. I'm Jonathan Wolfe. And I'm Sarah Berry. Join us next week for another Zoe podcast.

ZOE Science & Nutrition - Why eating nuts makes you healthier, according to science

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