Episode 61 - New research: Nuts contain up to 26% less calories than we thought they did

New research: Nuts contain up to 26% less calories than we thought they did

New research highlights the actual energy (kcal/kJ) absorbed from nuts was significantly less than what’s on the food label.

The energy content of all food globally is done using the Atwater System - a system founded more than 120 years ago by Wilbur Atwater.

But this system is flawed - it doesn’t take into consideration what happens inside our gut and how our body metabolises food.

Nuts and seeds have a tough fibrous exterior. We don’t fully break them down to extract the energy from them or absorb the fat. A portion remains ‘locked’ into their fibrous cell walls and excreted out. Which is an important reminder that calorie counting should be used as a tool rather than a strict mandate.

So don’t be afraid to start including a healthy 30g (1.06 ounce) serving of mixed nuts and seeds on a daily basis!


Why I don’t think you need to calorie count as a triathlete, listen to Episode 59 HERE 

Read the 2012 study on almonds HERE

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Episode Transcription

Episode 61: New research: Nuts contain up to 26% less calories than we thought they did

Taryn Richardson  00:00

Welcome to the Triathlon Nutrition Academy podcast. The show designed to serve you up evidence-based sports nutrition advice from the experts. Hi, I'm your host Taryn, Accredited Practicing Dietitian, Advanced Sports Dietitian and founder of Dietitian Approved. Listen as I break down the latest evidence to give you practical, easy-to-digest strategies to train hard, recover faster and perform at your best. You have so much potential, and I want to help you unlock that with the power of nutrition. Let's get into it.

Taryn Richardson  00:42

Hello, and welcome to the podcast this week. I am pretty much back in action after a relatively quiet week last week off the back of opening the Triathlon Nutrition Academy. And I've got some pretty exciting podcast episodes coming to your ears as we hurtle towards Christmas.

Taryn Richardson  00:58

Today, I want to let you in on some new-ish research really highlighting that we don't understand energy and calories of foods as much as we thought we did - and particularly with a food like nuts. There's a new systematic review that's not actually published yet, which is a review of the 21 published papers on the topic of nuts and their kilojoule content or calorie content to date. So they're pulling that together and giving a bit of a summary about what we know so far about the actual energy content of nuts. It's coming out of the University of Wollongong and it was presented at the Dietitians Australia conference last month. And what they found is that the actual kilojoule, or calorie content of nuts, that we actually absorb in our body, was significantly less than what's on the food label - up to 26% less calories, which is huge!

Taryn Richardson  01:53

So currently, all of the energy content of every single food is determined with the Atwater system and that's used globally. It was something that was developed in the 1900s and before by dude called Wilbur Atwater. And it's a system for calculating the total energy value - so kilocals/kilojoules of foods. And like I said it was founded over 100 years ago. And now I'm not going to go too far into the details of specifically what it is. One - it's a bit too deep. Two - it doesn't really matter. But a quick summary is that to determine the calorie or energy content of a food, and to measure that for you, so it can give you a calorie amount on a label or in the tracking app that you use to count your calories. What they do is they burn the food in a bomb calorimeter. They also factor in your fecal and urine losses. And we're trying to determine that based on the amount of grams of fat in the food, the grams of protein in the food, the grams of carbohydrate and alcohol in a particular food.

Taryn Richardson  02:59

And that's that seed self defense mechanism. Think about in nature. Birds will eat nuts and seeds or grass seeds or whatever it is, and it goes straight through them and out the other side as well because that seed needs to become a plant. And for that to happen, it needs to get into the ground. And that happens within our bodies as well. There's a lot of defense mechanisms of nuts and seeds that block it from being digested and absorbed because its role is to continue living.

Taryn Richardson  02:59

And the Atwater system dictates that calories per gram of carbohydrate and protein are 4 - so a gram of carbohydrate is 4 calories. A gram of protein is 4 calories. Fat is 9 calories per gram and alcohol is 7 calories per gram. But the system is flawed because it doesn't take into consideration what actually happens inside our gut. And how our body metabolises that food. Yes, you can burn food to determine its total energy content. But we don't burn food inside our gut. What actually happens inside is this complicated metabolic process. And something like nuts and seeds, they have this very fibrous outside and all their cell walls are really fibrous as well. And so what happens when we eat those foods, we don't fully break them down and extract that energy from them or absorb all of the fat in them either. Or a portion of it kind of remains locked inside their fibrous cell walls, and we just excrete it out. You think about something like whole flax seeds or linseeds, depending on where you are in the world. If you're eating them whole, often they go in one end and come out the other completely unscathed.

Taryn Richardson  04:14

So side note, that's why I often suggest people eat things like LSA mix - which is a mix of linseed, sunflower seeds, and almonds, all kind of ground up into a nut meal. Because those nuts and seeds are broken down. We've kind of busted through that fibrous wall already before we go and digest it. And the body is more likely to absorb those nutrients from that food, if that's the case. I've always thought about foods like that, but it's nice to have some research to back that up now.

Taryn Richardson  05:11

So how do they figure it out that nuts contain way less calories than we thought they did using this Atwater system? What they do is they follow people for a defined period of time, and control their diet. They know exactly what's going in - everything gets weighed. And they also then burn that food as well. So they'd make replica meals - everything specifically controlled. They know exactly what's going on. And then they also do the same thing with everything going out. So they can see how much energy somebody is extracting from that food.

Taryn Richardson  05:45

And so what they found is that almonds had 18 1/2 kilojoules per gram, when they were actually absorbed in the body - which is 26% less than what's measured by the Atwater system. Walnuts had 21.8 kilojoules per gram - which is 22% less. Cashews had 20.5 kilojoules per gram - which is 14% less than what's measured. And pistachios had 22.6 kilojoules per gram - which is 5% less than measured by the Atwater system.

Taryn Richardson  06:16

And so that's another important reminder, and potentially another tick in the NO box for why calorie counting is not particularly useful. So if you're putting 30 grams of almonds into your calorie counting device, it's going to give you the amount of kilojoules or calories determined by the Atwater system - which we now know is up to a quarter less than that. So if you haven't listened to my episode around why you don't necessarily need to count calories as a triathlete, go back and listen to Episode 59.

Taryn Richardson  06:49

There was another great study in just almonds a few years ago, where they did the same thing. They've measured everything that everyone ate, they followed them for a period of time, and they also measured everything that came out. And what they found with almonds in this particular study was that a 28 gram serving of almonds was equivalent to 129 kilocalories - which if you compare that to the Atwater method, that dictates that a 28 grams serving of almonds is 168 to 170 kilocals per serving. So it's a 32% overestimation.

Taryn Richardson  07:23

And one thing that is important from this study - I'll link it in the show notes if you do want to dive in to the research, but there was individual variation, which makes sense too, right? We're going to extract a different amount of nutrients from our food compared to the person sitting next to you. So one person's variation was as low as 105 calories per serving. So they extracted even less. Whereas another person extracted 151 calories per that 28 gram serving. So they extracted even more. And so again, another kind of tip for calorie counting - your body is not going to draw that exact amount of energy from that food - that that food label dictates. And that may be totally different to your partner or your training buddy or your kids. There will probably be a shift in the amount of calories that are dictated on nuts and seeds and muesli bars and nut bars and things like that in the coming years. This systematic review is kind of the first step in trying to collect all the data that we've got at the moment of people doing these types of studies with specific nuts and seeds. And then there'll be a global shift in this.

Taryn Richardson  08:32

So don't be afraid of including nuts and seeds in your diet. They are really good fats. And the more different varieties of nuts and seeds that you can include, the better. They have a different profile of fats - mono, polyunsaturated, unsaturated fats. And you know I'm a big advocate for plant based diversity. The more different types of plant based foods we can include in our week, the better. So don't be afraid of including nuts and seeds. A healthy serving that we should be including daily is 30 grams, or a bit over an ounce  (1.06 ounces is 30 grams). And you don't have to eat that as a small handful of nuts on its own. You certainly can, but you could include it in your breakfast. It could be included in your meusli, your Bircher muesli, your baked oats. Make sure if you're making smoothies that are a complete meal, you're putting some nuts and seeds in there. These are the types of fats that we need to be injecting in our diets and minimising the processed, saturated fats that come from chocolate, deep fried foods, ice cream, really fatty meats.

Taryn Richardson  09:40

So put down that salami stick and grow and grab yourself a small handful - 30 grams - of mix nuts. Only 2% of Australians eat the recommended 30 grams serving a day, potentially because you think it's going to cause weight gain. It’s actually a massive study - I can link that in the show notes as well - that showed that eating nuts is not linked to weight gain, or higher BMI or increased body fat. So nuts aren't going to make you fat. But also eating them regularly has been associated with a 22% reduction in risk of premature death, 29% reduced risk of coronary heart disease, 21% reduced risk of cardiovascular disease, and a 13% reduced risk of developing Type II diabetes. 

Taryn Richardson  10:26

So if you're not including nuts and seeds in your diet, because they're too high in calories, you can scrap that information and start increasing your intake to at least 30 grams a day to get all of those health benefits and huge range of nutrients. So there you have it! Nuts contain up to 26% less calories or kilojoules than we thought that they did before. Watch this space for clearer guidelines and future research because it's definitely coming. And I'll link those papers in the show notes if you do want to dive in to the nut research.

Taryn Richardson  10:58

Thanks for joining me for this episode of the Triathlon Nutrition Academy podcast. I would love to hear from you. If you have any questions or want to share with me what you've learned, email me at [email protected]. You can also spread the word by leaving me a review and taking a screenshot of you listening to the show. Don't forget to tag me on social media, @dietitian.approved, so I can give you a shout out, too. If you want to learn more about what we do, head to dietitianapproved.com. And if you want to learn more about the Triathlon Nutrition Academy program, head to www.dietitianapproved.com/academy. Thanks for joining me and I look forward to helping you smashed in the fourth leg - nutrition! 

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