Trans fats have a bit of a reputation.
Knowing what to put in your body and how it affects you can be difficult — especially as technological evolutions continually shift our understanding of nutrition. How can we tell if we’re holding on to dated ideas?
The tale of trans fats falls right into this category — is the horror story to be trusted, or do we have more to learn?
In today’s short episode of ZOE Science & Nutrition, Jonathan and Sarah ask: What are trans fats, and should we be worried about having them in our diets?
If you want to uncover the right foods for your body, head to joinzoe.com/podcast and get 10% off your personalized nutrition program.
Referenced in today's episode:
Hydrogenation of unsaturated fats and trans fat, an article in LibreTexts Chemistry
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
WHO calls for action to totally eliminate trans fat, ‘a toxic chemical that kills’, an article in UN News
Trans fatty acids: Are the effects only marginal? published in American Journal of Public Health
Fats and oils in human nutrition, a report organized by the United Nations (UN) and the World Health Organization (WHO)
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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 bited-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 trans fats.
[00:00:17] Sarah Berry: 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 their reputation.
[00:00:31] Jonathan Wolf: And so Sarah, what is trans fat? And should we all be worried about them in our diet?
[00:00:36] Sarah Berry: Well, there's a really clear answer to this, Jonathan, and I think our listeners may be quite surprised by it.
[00:00:41] Jonathan Wolf: 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 are trans fats?
[00:00:52] Sarah Berry: So interestingly, Jonathan, trans fats are a type of unsaturated fat. However, there are two different types of trans [00:01:00] fats. One is produced industrially, and the other is found naturally in products associated with ruminant animals like cows and sheep who ferment their feed in the digestion process.
[00:01:10] Jonathan Wolf: Okay. And so, Purpose, uh, do these trans fats.
[00:01:16] Sarah Berry: Okay, so let's start firstly with industrially produced trans fats. Cuz 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 oils like cocoa butter, for example.
[00:01:43] Jonathan Wolf: And, Sarah, hard fat. What does that mean?
[00:01:47] Sarah Berry: So when I talk about hard fats, I will talk about the fat that is solid at room temperature. And these hard fats are used often because they have suitable melting points for lots of applications in [00:02:00] foods. And we can blend these trans fats with other fats and oils to produce fats with really diverse melting properties, which makes them suitable for a whole wide range of food applications, particularly in processed foods, which is why in the 1950s, for example, when their intake and use soared.
[00:02:20] Jonathan Wolf: So what you're saying is great for food manufacturers to make all sorts of different products, like very efficiently and cheaply?
[00:02:28] Sarah Berry: 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 reduced saturated fat intake.
[00:02:42] Jonathan Wolf: 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?
[00:02:51] Sarah Berry: They're, they're produced from unsaturated vegetable oils, uh, using a process called partial hydrogenation. And this involves [00:03:00] 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 so this process of partial hydrogenation typically creates a fat with around 15% trans fatty acids, although it can be as high as 55% depending on the manufacturing process used.
[00:03:28] Jonathan Wolf: So if I explain what I've taken away like that's some pretty serious chemistry, right? Like, but you mentioned that they can be naturally occurring. In some products too.
[00:03:39] Sarah Berry: Yeah, that's right. Trans fats can also be found in butter, cheese, and the meat of ruminant animals, so for example, in beef. However, these trans fats are different from the ones that are produced industrially, and that's important to remember.
[00:03:54] Jonathan Wolf: Well, Sarah, we did a bit of research on the history of trans fats. So apparently the process of this partially [00:04:00] 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 U.S. they used oil from soybeans. While in the U.K. they used rapeseed or canola oil as it's known. And it's as you mentioned in the 1950s, margarine became one of the products that rose to prominence.
[00:04:26] Sarah Berry: Yeah, Jonathan. So it was a cheap alternative to butter, and also many people had fridges for the first time, margarine was spreadable right outta 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 customers.
[00:04:48] Jonathan Wolf: Which is funny because I, I grew up with margarine, um, first in the States and then in the U.K. Um, you know, as I, as I've mentioned several times, um, my dad was diagnosed with high cholesterol when he was very young. [00:05:00] 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, uh, on your toast. And this was, you know, when my memory of this is in the, in the eighties. So while I've read that, actually there were already some concerns about trans fat in the seventies, 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.
[00:05:28] Sarah Berry: Yeah. That's not surprising. Jonathan. And the consensus on trans fats 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 unfavorable health outcomes such as inflammation.
So much of this research was produced and presented to the World Health Organization which recommended the removal of industrial trans fats from foods in [00:06:00] 1994. Just to illustrate how unfavorable, trans fats are on our health, the accumulated evidence now shows that for every 2% of energy from trans fats, 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.
[00:06:21] Jonathan Wolf: 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 fats lead to a massive rise, in heart attacks and strokes?
Okay. So if the World Health Organization advised that trans fats should be banned back in the nineties, why are we still talking about them today?
[00:06:41] Sarah Berry: So we're still talking about them because, 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 U.K. and the U.S. now, except for either these naturally produced trans fats found in dairy or [00:07:00] 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?
[00:07:23] Jonathan Wolf: So Sarah, just to confirm, are you saying that trans fats are illegal now in the U.S. and the U.K.?
[00:07:29] Sarah Berry: So in the U.S. the GRaS status was removed several years ago, so they are no longer allowed to be included in the US. in food products. In the U.K. there was voluntary removal and use alternative fats and alternative processes.
[00:07:46] Jonathan Wolf: So I, I find it reassuring that it's not in the food, but I'm also a little shocked that it is outright banned in the U.K. in the way that it is in the U.S. Is this surprising to you, Sarah?
[00:07:59] Sarah Berry: [00:08:00] Well, in contrast, I find it incredibly reassuring that the food industry took responsibility in the U.K. without legislation.
[00:08:07] Jonathan Wolf: And so Sarah, what have they replaced these trans fats with?
[00:08:12] Sarah Berry: So the food industry now uses a combination of techniques, um, and it differs between the U.S. and the U.K. So typically in the U.S., they use a process called full hydrogenation. And what this does is it starts with an oil, like soybean oil, and it turns it into a really hard fat, so even harder than trans fat. This is then blended with liquid oil, such as a nonhydrogenated to the original soybean. Again, or maybe a rape seed oil.
And what they do is blend it in varying ratios to produce 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 require slightly different levels of hardness, so slightly different melting points. Now in Europe and the U.K., we don't use fully [00:09:00] hydrogenated fats.
And instead, we typically blend liquid oils. So we blend oils such as rape seed oil with tropical oil, such as palm oil and coconut oil. And we use a very special process called interesterification. And that was what the topic of my Ph.D. was. So for once, I'm glad to get that word into one of our podcasts.
[00:09:20] Jonathan Wolf: Well done, Sarah. And so, why do we use different fats? You know, between the U.K.and the U.S., the end food seems quite similar.
[00:09:27] Sarah Berry: This is all down to consumer perception. So in the U.K., 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 and partial hydrogenation. It's got the word hydrogenation. Oh my gosh, it's gonna kill us. It's bad for us. So the U.K. food industry responded to consumer demand, and consumer perception, and therefore found alternative processes that would be considered acceptable to the consumer.
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[00:09:57] Jonathan Wolf: So are you saying in [00:10:00] that, in this particular case, these partially hydrogenated fats are bad? They produce fat trans fats, but, you know, if you see fully hydrogenated fats, they're not bad for us at all. And you shouldn't worry.
[00:10:13] Sarah Berry: Not exactly. It's a little bit more graded than this. So what's clear is that the process of partial hydrogenation that produces these harmful trans fats are bad for us. That's. Uh, 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 steric acid that seems to have a neutral effect on our blood cholesterol. It doesn't produce trans fat, however, it does form a saturated fat, we know that it may have some unfavorable health effects, but certainly nowhere in the region that trans fats would.
[00:10:56] Jonathan Wolf: So don't, don't rush out and stuff your mouth full of [00:11:00] this, but it's not, it, it's, it's not gonna have these terrible effects that I think you were describing with the trans fat. Is that how I should understand it?
[00:11:06] Sarah Berry: Absolutely. It's just creating saturated fat from
unsaturated fat. And if we were to compare it with natural saturated fat, it would be no worse for us than natural saturated fat.
[00:11:18] Jonathan Wolf: What about, what about the rest of the world?
[00:11:21] Sarah Berry: 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 industrial-produced Trans fats have tripled just in the last three years. As the World Health Organization pursues its global goal to eliminate it from foods throughout the world by 2023.
[00:11:56] Jonathan Wolf: Alright, Sarah, so, so what's the conclusion? Should our listeners be [00:12:00] concerned about trans fats?
[00:12:01] Sarah Berry: No, and the reason we shouldn't be concerned about trans fats in the U.K. or the U.S. is that 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.
[00:12:23] Jonathan Wolf: So what about the replacements for these trans fats, how should our listeners think about these replacements?
[00:12:30] Sarah Berry: So I think, Jonathan, we first have to separate the health effects of fats versus the functionality of fats. But we have to think about the ingredients functioning for the food that we are 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 large, or we use these other alternatives [00:13:00] 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?
Cause 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 more healthy for us than many of the animal-based functional equivalents.
[00:13:44] Jonathan Wolf: It's brilliant. Sarah, thank you so much for sort of sharing with us some of those, um, 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. [00:14:00] You can get 10% off by going to joinzoe.com/podcast. I'm Jonathan Wolf.
[00:14:05] Sarah Berry: And I'm Sarah Berry.
[00:14:06] Jonathan Wolf: Join us next week for another ZOE Podcast.
This podcast was produced by Fascinate Productions.