ZOE Science & Nutrition - Trans fats: how worried should you be?

Episode Date: April 6, 2023

Trans fats have a bad reputation. But we now know a lot more about these fats than we did when the first horror stories about them emerged.  So, based on the latest science, just how worried should we be? Listen to today’s short episode of ZOE Science & Nutrition to find out.  Follow ZOE on Instagram: https://www.instagram.com/zoe/ Download our FREE guide — Top 10 Tips to Live Healthier: https://zoe.com/freeguide Studies referenced in the episode: Hydrogenation of Unsaturated Fats and Trans Fats Effects of dietary fatty acids and carbohydrates on the ratio of serum total to HDL cholesterol and on serum lipids and apolipoproteins: a meta-analysis of 60 controlled trials, published in The American Journal of Clinical Nutrition Association of dietary, circulating, and supplement fatty acids with coronary risk: a systematic review and meta-analysis, published in Annals of Internal Medicine  Potential of trans fats policies to reduce socioeconomic inequalities in mortality from coronary heart disease in England: cost effectiveness modelling study, published in British Medical Journal WHO calls for action to totally eliminate trans fat, ‘a toxic chemical that kills’ Trans fatty acids - are the effects only marginal? - published in American Journal of Public Health Fats and oils in human nutrition A trans European Union difference in the decline in trans fatty acids in popular foods: a market basket investigation, published in British Medical Journal Countries with regulations against industrially produced trans fats tripled over the past year Episode transcripts are available here. Is there a topic you'd like us to cover on the show? Email us to let us know!

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 trans fats. So Jonathan, we often talk about the good, the bad and the ugly when it comes to fats. And I think when people consider bad fats, trans fats are often a major area of concern for a lot of people due to its reputation. And so Sarah, what is a trans fat? And should we all be worried about them in our diet? Well, there's a really clear answer to this, Jonathan, and I think our listeners may be quite surprised by it. Fantastic. Let's get into it.

All right, Sarah. So for those of us who haven't been studying fats for the last 25 years, what is a trans fat? So interestingly, Jonathan, trans fats are actually a type of unsaturated fat. However, there's two different types of trans fats. One is produced industrially and the other is found naturally in products associated with ruminant animals like cows and sheep who ferment found naturally in products associated with ruminant animals like cows and sheep who ferment their feed in the digestion process. Okay and so what purpose do these trans fats provide? Okay so let's start firstly with industrially produced trans fats because I think when a lot

of people think about trans fats this is what will come to mind and these trans fats were originally used as a low-cost way to harden vegetable oils and thereby produce hard fats that firstly had a lower saturated fat content. So were perceived at the time to be healthier. And secondly, they had the advantage of being cheaper than other hard fats, such as butter or tropical oil, like cocoa butter, for example. And Sarah, hard fat, what does that mean? So when I talk about hard fats, I will talk about a fat that is solid at room temperature. And these hard fats are used often because and oils to produce fats with really diverse melting properties, which makes them suitable for a whole wide range of food applications,

and particularly in processed foods, which is why in the 1950s, for example, where their intake and use really soared. So what you're saying basically is they're great for food manufacturers to make all sorts of different products like very efficiently and cheaply? Absolutely. And also at the time that they were first used, they were considered to be potentially a healthier alternative because they were, like I said, unsaturated fats and therefore reduce saturated fat intake. And without getting too technical on us, please, Sarah, how do you make these trans fats? Do you sort of like boil up some regular fats? They're actually produced from unsaturated vegetable oils using a process called partial hydrogenation. And this involves reacting the oil with hydrogen in the presence of a catalyst such as nickel. So what it does is it changes

the format of this unsaturated double bond. So the fat has a more rigid structure and this is what causes it to have a higher melting point and therefore become a solid fat. And so this process of partial hydrogenation typically creates a fat with around 15% trans fatty acids, although it can actually be as high as 55% depending on the manufacturing process used. So if I explain what I've taken away, like that's some pretty serious chemistry, right? But you mentioned that actually they can be naturally occurring in some products too? Yeah, that's right. Trans fats can also be found in butter, in cheese and the meat of ruminant animals. So for example, in beef. However, these trans fats are different to the ones that are produced industrially, and that's really

important to remember. Well, Sarah, we did a bit of research on the history of trans fats. So apparently the process of this partially hydrogenating vegetable oil was created as a cheaper alternative to butter around 1910, so a long time ago. And as you said, at first, they were believed to be a healthy alternative to saturated fats because they were unsaturated. And in the US, they used oil from soybeans, while in the UK, they use rapeseed or canola oil, as it's known. And it's, as you mentioned, in the 1950s that margarine became one of the products and that that really rose to prominence. Yeah, Jonathan. So it was a cheap alternative to butter. And also many people had

fridges for the first time and margarine was spreadable right out of the fridge, unlike butter. So it was considered something of a wonder product, especially throughout Europe and North America. But margarine at this time was reliant on trans fats and it wasn't wonderful for the health of our customer. Which is funny because I grew up with margarine, first in the States and then in the UK. As I've mentioned a number of times, my dad was diagnosed with high cholesterol when he was very young. So all the butter was banned from the house, right? But margarine, well, that didn't have saturated fat. So that was sort of okay and you had to have something to spread on your toast. And this was, you know,

my memory of this is in the 80s. So while I've read that actually there were already some concerns about trans fats in the 70s, you know, this certainly hadn't reached my house. And I know that, you know, my mom and my dad were choosing this very much as sort of trying to make the best health decision about what to eat. Yeah, that's not surprising, Jonathan. And the consensus on trans fats really changed in the 1990s. And there was really good evidence coming out to show that trans fats increased bad LDL cholesterol and reduced good HDL cholesterol, which leads to an increased risk of heart disease, and also impacted other unfavourable health outcomes, such as inflammation. So much of this research was produced and presented to the World Health Organisation, who recommended the removal

of industrial trans fats from foods in 1994. In fact, just to illustrate how unfavourable trans fats are on our health, the accumulated evidence now shows that for every 2% of energy from trans fats, and this is about four grams of trans fats for someone eating, let's say, 2000 calories a day, there's about a 25% increase in cardiovascular disease risk. And this is huge. I mean, Sarah, that's terrifying, right? Like what you're saying, I think is even just this very small amount of these industrial trans fat was leading to a massive rise in heart attacks and strokes? That's correct. Okay, so if the World Health Organization advised that trans fat should be banned back in the 90s, why are we still talking about them today? So we're still talking about them because in fact, in the West, we've seen a real change in

the food industry's approach to trans fatty acids. And there are now no trans fats in any of the foods in the UK and the US now, except for either these naturally produced trans fats found in dairy or certain imported foods. But Jonathan, with the removal of trans fats comes the problem of what do we replace them with? Ultimately, we still need fats with variable melting profiles and varying levels of hardness. So the question is, do we return to the use of unhealthy animal fats? Or do we use often expensive and unhealthy tropical oils? Or do we find alternative industrial processes to create new hard fats? So Sarah, just to confirm, are you saying that trans fats are actually illegal now in the US and the UK? So in the US, the grass status was removed

a number of years ago, so they are no longer allowed to be included in the US in food products. In the UK, there was voluntary removal and use alternative fats and alternative processes. So I find it reassuring that it's not in the food, but I'm also a little shocked that it isn't actually outright banned in the UK in the way that it is in the US. Is this surprising to you, Sarah? Well, in contrast, I find it incredibly reassuring that the food industry took responsibility in the UK without legislation. And so Sarah, what have they replaced these trans fats with?

So the food industry now uses a combination of techniques and it differs between the US and the UK. So typically in the US, they use a process called full hydrogenation. And what this does is it starts with a oil like soybean oil, and it turns it into a really hard fat, so even harder than a trans fat. This is then blended with a liquid oil such as an unhydrogenated, so the original soybean oil, again, or maybe a rapeseed oil. And what they do is they blend it in varying ratios to produce a fat that has suitable melting points depending on the final product. For example, whether it's used for a pastry or a biscuit or a spread, all requires slightly different levels of hardness, so slightly different melting points.

Now in Europe and the UK, we don't use fully hydrogenated fats and instead we typically blend together liquid oils. So we blend together oils such as rapeseed oil with tropical oils such as palm oil and coconut oil. And we use a very special process called intrasterification. And that was what the topic of my PhD was. So for once, I'm glad to get that word into one of our podcasts. Well done, Sarah. And so why do we use different fats between the UK and the US the end food seems quite similar this is all down to consumer perception so in the UK the consumer perception of fully hydrogenated fats is that they're bad for us so they see the word hydrogenation and

they can't distinguish between that it's full hydrogenation or partial hydrogenation it's got the word hydrogenation oh my gosh it's going to kill us it's bad foration or partial hydrogenation. It's got the word hydrogenation. Oh my gosh, it's going to kill us. It's bad for us. So the UK food industry responded to consumer demand, consumer perception, and therefore found alternative processes that would be considered acceptable to the consumer. So are you saying that in this particular case, these partially hydrogenated fats are bad, they produce trans fats, but actually, you know, if you see fully hydrogenated fats are bad, they produce trans fats, but actually, if you see fully hydrogenated fats, they're not bad for us at all and you shouldn't worry?

So not exactly. It's a little bit more graded than this. So what's really clear is that the process of partial hydrogenation that produces these harmful trans fats are bad for us. That's clear. That's conclusive. Full hydrogenation though is a different process. And in this process, it changes a liquid unsaturated oil to a saturated fat. And it typically changes it to a saturated fat called stearic acid that seems to have a neutral effect on our blood cholesterol. It doesn't produce trans fats. However, because it does form a saturated fat, we know that it may have some unfavorable health effects, but certainly nowhere in the region that a trans fat would. So don't rush out and stuff your mouth full of this, but it's not going to

have these terrible effects that I think you were describing with the trans fat. Is that how I should understand it? Absolutely. It's just creating a saturated fat from an unsaturated fat. And if we were to compare it with a natural saturated fat, it would be no worse for us than a natural saturated fat. What about the rest of the world? Yeah, so cost is a huge factor. Most countries have now eliminated trans fats. The one country that we know is still a big user of trans fats is Russia, but that's one of the few countries that I'm aware of that produces foods with these trans. And countries with regulations against industrially produced trans fats have tripled just in the last three years alone as the wealth organization pursues their global goal to eliminate it totally from foods throughout the world by 2023.

All right, Sarah, so what's the conclusion? Should our listeners be concerned about trans fats? No. And the reason we shouldn't be concerned about trans fats in the UK or the US is because they are simply not in our food anymore from industrial sources. Those which are naturally occurring also don't seem to have the negative effects that these industrially produced trans fats have using this process of partial hydrogenation. So what about the replacements for these trans fats? How should our listeners think about these replacements? So I think, Jonathan, we first have to separate out the health effects of fats versus the functionality of fats. But we have to think about the ingredients functioning for the food that we're eating. And so for many applications, for pastries, for spreads,

you need to have fat that has that suitable melt profile. And this is why we either need to have quite unhealthy saturated fats such as coconut oil or butter or lard, or we use these other alternative processes that we talked about. And so we need to compare within groups of fats that are functionally equivalent their health effects to make the right choices. So by that, let's say compare margarine spread and compare that with butter. They are used as functional equivalents. They are used interchangeably. Now the fair comparison is to say which of those is healthier rather than is that spread more or less healthy than olive oil because you wouldn't use it for the same function.

And I think it's quite clear that a lot of these commercially produced seed oils, dare I say it, are actually more healthy for us than many of the animal-based functional equivalents. It's brilliant, Sarah. Thank you so much for sort of sharing with us some of those complexities. If after today you've stopped worrying about trans fats, but you do want to add more of the right good fats into your diet, then you may want to try Zoe's personalized

nutrition program to improve your health. 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.