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It's Ian here with my co-host Madeline. Hi Maddy. Hello. We asked you, our Science Weekly listeners, for your questions on how to get fit and healthy for 2025. And you delivered. We received loads of brilliant responses.
We've done our research and spoken to the experts. So today we're diving into everything from seed oils to use or not use, the scientifically proven ways to give up sugar, and whether some of us are just born with better immune systems to see us through the winter months. So let's get started. From The Guardian, I'm Ian Sample and this is Science Weekly.
Right, Maddy, let's hear the first question. And this comes in from Joe. Hi, everyone. I'm Joe, a regular listener, a science fan, and I live in Amsterdam.
This question comes up every year as we head into winter when everyone starts getting sick and I find myself debating with friends and family about how much control we actually have over how effective our immune systems are. So my question is what can science tell us about the relationship between genetics and environment when it comes to susceptibility to illness in day-to-day life?
So I think the place to start is the fact that it is a system and it's so complicated. I mean, it basically permeates every tissue, every cell in our bodies.
And this wasn't something that I could explain without some help. So I got on the line with John Trousdale. He's an emeritus professor at the University of Cambridge, where he was the head of immunology. And he's recently written a book called What the Body Knows, a guide to the new science of the immune system. And so I did something perhaps a little bit cruel. And I basically asked him to condense his whole book
down for me to explain in just a couple of sentences what the immune system is. It's actually difficult to define the immune system because it's actually throughout the whole body, very extensive. It covers everything from skin to saliva to your gut to your blood to all the different organs. They all have to defend themselves against a number of different diseases and I would argue that most diseases the immune system does impact, not just infection but
but other conditions that we get. How much of this system is down to our genetics then? I mean, are there people who are simply more prone to getting sick?
This is yet another difficult question to answer. And it is something that scientists are really still at the beginning of figuring out. When I put it to John, he did point out that it is clear that our genetics do play a really significant role in our immune system. But Ian, even though you can put some of this down to our genetics...
How our genes are expressed isn't necessarily even fully set in stone. Our environment can subtly change how they work.
And this is something known as epigenetics. So, I mean, this is all very messy. Well, this takes us on to Joe's question about the relationship between genetics and the environment and how that affects our susceptibility to getting ill in everyday life. And he's heard that early life plays a particular role.
When I asked John about this, he told me that most immunologists do think that the way that the immune system is conditioned in early life is key. To kind of illustrate this, he told me that conditions where the immune system is kind of overreaching itself, like allergies and asthma, they've been rising quite dramatically in the last 50 years.
And it isn't like our genetics have suddenly changed. So you'd argue that there has to be some early environmental changes that have impacted on our immune systems. And then there are studies looking into things like how you inherit your mother's microbiome.
and how that affects your own immune system, you know, being exposed to herb bacteria. Then going into other environmental factors like pollution that you're exposed to and your diet when you're young.
There are a lot of things that are going to influence this initial conditioning of your immune system, how it begins to develop, and to help set that balance early on. Because you want a reactive immune system, but you don't want it to overreact. That's when you get things like allergies. I suppose this leads us on to the question of how much impact we can have on our immune systems as adults and what factors actually influence it.
And this ties into another question we got from Elizabeth. Hello, Science Weekly. My name's Lizzie and I'm calling from London. My poor husband has been recovering from a nasty bout of flu and seems to get some nasty illness every year. So my question is, how can you improve your immune system beyond healthy eating and supplements? Are there small things you can do that make a difference?
Okay, well, I'm going to just hand over to John again because I can't put it any better than he did. I would argue that it's actually quite difficult to boost your immune system. I like to say that the immune system is like a kind of Rolls Royce, if you like. It doesn't need any improvement. It's perfect.
but you can damage it if you actually put water in the petrol or you drive it badly. However, there are things that you can do to make sure that you're healthy and the immune system is well balanced. One of course is to eat a healthy and varied diet. Also important is to keep vaccines up to date.
That is an immune booster, if you like, that really works. Other things you can do is to avoid obviously too much alcohol, don't do drugs, do some gentle exercise and respect hygiene so you don't want to be too clean, you don't want to be obsessive about it. Getting plenty of sleep seems to help
and avoiding too much stress, again, is evidence that certain kinds of stress actually can make you more susceptible to disease. The final thing I've mentioned is actually, oddly, keeping gums and teeth healthy seemed to have an effect. And a final point that John really wanted to make, he wanted to bust the vitamin C myth.
Right, so we've really latched onto this idea that vitamin C is this amazing immune booster, but there is no evidence for that above and beyond the fact that we need vitamin C in our day-to-day lives, but along with plenty of other vitamins like vitamin A, vitamin B12, B9, minerals like iron, to keep our immune systems functioning in a healthy way.
So if you want to have your orange juice, go ahead. It's not going to do you any harm. It's not going to hurt you. But I'm sorry to say it's probably not going to help massively. So you can't boost your immune system, but you need to eat healthily to avoid damaging it. And this takes us on to our next listener question, which came in from Alexandra.
Are there science-based approaches to cutting down on processed sugars like chocolate and candy? This is the classic January question, isn't it? And the first place my mind went when I read this question was,
why is it so hard to cut down on processed sugars? And I don't know, Ian, whether you've ever seen any videos online of babies trying ice cream for the first time. If you haven't seen them, I'd really recommend going and watching them because you can see the moment that the sugar hits their system and they get this rush of dopamine, you know, that feel-good hormone. It's honestly so funny.
But anyway, after we get the dopamine, we also get this energy boost. And this all reflects what Catherine Appleton, a professor of psychology at Bournemouth University who researches human eating behaviour, said to me when I called her up and asked her why we can't resist sugar. So when we're first, very first born, we have a preference for the sweet taste.
possibly associated with the energy that's in the natural world associated with sugars and the fact that they're very easy to digest. Obviously, that energy is required for growth, survival, etc., etc. But then as we get older, a lot of the foods that are sweet also have a higher proportion of fat in them as well. And we also have a high preference for fat.
Both of these preferences will be feeding in to drive high sweet food intakes. So how do we overcome this powerful temptation? There are a few different ways to come at this question. And I want to start with this idea of willpower and self-control.
And actually, scientists really don't agree about what willpower and self-control actually are. Is this an ability to shift your attention away from the thing that's tempting you? Is it managing your emotions? Is it an ability to focus on long-term goals? Is it all of these things together? And do these things even fall under one umbrella?
Some psychologists conceptualise this ability to resist short-term temptation for long-term goals as a kind of muscle or a bank of energy that you use up throughout the day. But what psychologists do seem to agree on is that a key thing here is making things easier for yourself by forming helpful habits and breaking out of the not-so-helpful ones. So I got in touch with
Provost Professor Emerita of Psychology and Business, Wendy Wood, who researches habit formation and she's written a book, Good Habits, Bad Habits, the Science of Making Positive Changes That Stick. So what does Wendy say about how to make good habits and get rid of the bad ones? When I chatted to her, one of the things that she really emphasised was context.
Changing context is very helpful because then the habit isn't triggered. And this is one reason why people often report that they find it easiest to form new habits soon after they've moved around.
or when they started a new job, because the old habits aren't activated. So changing your breakfast context, if you always eat out at a fast food place, that's what you should decide not to do. Don't go there. Make sure that you have lots of fruit, lots of oatmeal, other things that are healthy in your house.
And make time to eat them before you leave for work or school in the morning. So those cues aren't there. Another key point was to do these things enough times that you basically stop thinking about what you're doing and your actions kind of feel very familiar and effortless. We get up in the morning, we brush our teeth. We don't think, do we want to brush our teeth?
Is it good to brush our teeth? Those are not decisions we make because it's a habit. And that's how you want healthy eating to feel as well. There's also some good data from clinical psychology. This is called habit reversal therapy. And it was used with people with tics and other sorts of unwanted behavior.
they practice over and over again a competing behavior. Interesting. So forming these better habits will help, but that takes time.
What are some of the other evidence-based techniques people can try while they're trying to reduce their sugar intake? So for this one, I'm going to hand straight over to Catherine Appleton, who we heard from earlier. So firstly, be aware of what it is you're eating. So read the packets for the sugar content. Can you simply reduce the portion sizes that you're consuming? So instead of having, you know, three biscuits with your coffee,
try and cut down and just have two instead. If you can make small changes, they're more likely to be sustainable over the long term. Be mindful also of when you're eating your sweet things, how you're eating them. Are you more likely, for example, to be consuming snacks in front of the TV? Is that something that, again, one small change, so just not having snacks available when you're watching TV, will that be enough to help?
And Ian, just to add another technique to that, that both Catherine and Wendy mentioned, kind of in different ways, but that I really like is this idea of swapping things out. So there is good evidence that making substitutions can be an effective way of consuming more healthy foods.
and fewer of those less healthy foods. So personally, I like to eat dates, which are nice and sweet, in place of my chocolate in the evenings. Look, everyone is different. So
part of this whole thing is going through some of these techniques and just seeing what works for you. One thing I think I need to work on, Maddy, is this sort of four o'clock slump where I get to that time of day and I really feel myself flagging and it's very easy to go twix hunting.
But I know that I should be going for a banana and a satsuma or something like that. And I have done that on occasion. But I always end up just less happy and perhaps even less productive after doing it. Did you get any other tips? Well, look, I understand and empathise with that, Ian. So I'll give you one of my other techniques that I also asked Catherine about. And this is something I personally term the barrier method. So...
If I'm in the shops and I can't resist picking up a bag of sweets, this is my rule. I can put it in my shopping bag, but I'm not allowed to go straight to the tills. I have to do a lap around the shop. Now, this seems silly, but a lot of the time it's enough space for that kind of more logical, long-term thinking to kick in and overcome that initial impulse and
And just to make one final point, which goes back to your 4pm slump and your need for a Twix, is that after the lap of the shop, if I still want those sweets or biscuits or chocolate, I buy them. And Catherine really did emphasise that to me, that if...
it is fine to have a bit of sugar. There's the potential for a lot of psychological issues along the lines of feeling guilty or feeling upset, becoming obsessive, these types of issues. So your physical health might improve, but your psychological health will potentially be damaged. If you try and take it too extreme, I think...
This idea of demonising food takes us on to our third and final listener question for this episode, because Tabitha got in touch to ask about the science behind seed oils, which, if you believe the influences online these days, are behind all kinds of ailments. Yeah, and...
This is also something that Robert F. Kennedy Jr., Trump's pick for health secretary and proponent of the Make America Healthy Again movement, has claimed is poisoning us. And sure, there are some pretty bananas assertions out there. But Tabitha got in touch with some really interesting questions about seed oils.
I'm Tabitha, I'm a science teacher from Birmingham. I'm wondering what oil I should be cooking with. Ignoring calorie density, I always thought that sunflower oil was quite good for you, no saturated fats, no cholesterol, but I'm told it's so heavily processed that our bodies can't metabolise it effectively. Is that true? And is there a risk from carcinogens being released at really high temperatures or temperatures you're cooking at? I'm veggie and I've always thought of animal fats as being extremely bad for you, but is there actually an argument that they could be better?
So what about her first question then? Is sunflower oil so heavily processed that our bodies can't metabolise it?
I'm going to take a few steps back in answering this one. To get oil from seeds, whether that's sunflower seeds, rapeseed, that's canola if you're in the US, grapeseed, sesame seeds, you have to dry them, steam them and press them. The problem is it's difficult to squeeze out much oil by pressing alone.
So then a chemical solvent called hexane is used to extract more of the oil. And you might hear that hexane is used in paint thinners, in cleaning agents, and that it's toxic. Now, this is true. But the hexane is taken out of the oils with distillation and evaporation processes, leaving
trace amounts that are considered by all health and safety bodies safe. Finally the oil is bleached and deodorized to make it look and taste better. This isn't your household bleach or anything like it it's actually done with a kind of clay. Again this is safe and
Really, the only downside to these processes is that they can sometimes reduce some of the nutrients that you would naturally find in oils. And that's why the cold pressed oils and extra virgin olive oil are more expensive and said to be better for you. But either way, you can definitely still metabolize all of these oils naturally.
And actually, oils are often processed to be more stable at high heat. Which actually takes us to Tabitha's next question, which is, does oil release carcinogens when hot? So every oil has its own smoke point. This is the temperature at which the oils begin to produce a smoke. And processing oils can actually remove some of the compounds that cause them to smoke.
But the smoke point is basically an indicator that the oil has reached a temperature where it's going to start degrading and going to begin producing chemicals that could be harmful and potentially carcinogenic. However...
This is kind of theoretical. If you're cooking at home, it is highly unlikely that you are heating the oil to a point and for long enough where it's going to be degrading enough that it's in any way harmful for you.
If you're using the same oil for weeks and weeks on end to deep fry your chips and leaving it out the whole time, that could expose you to carcinogens. But I don't think that's what any of us really are probably doing with our oils at home. So what oil should Tabitha be cooking with? So starting off from a health perspective...
One thing you might hear raised is the issue of the omegas, these fatty acids. Now, seed oils tend to have omega-6, which is often associated with inflammatory properties. But more than 15 randomised control trials have shown that refined seed oils have no effect on inflammation in the body.
And actually, there is evidence that they can lower the so-called bad cholesterol LDL. And also when it comes to omega-3, which is in things like nuts and fish, actually it is also in some seed oils like flaxseed.
And we know this is anti-inflammatory. So going back to Tabitha's question, which one should she use? Well, from all the reading that I've done, I would say olive oils are a good bet. They're often said to be the healthiest and especially extra virgin olive oil.
That can be expensive. So perhaps when you're cooking, it's worth using other seed oils. And when it comes to animal fats, so that's butter, ghee, lard, tallow, these are high in saturated fats, something that has been shown again and again to raise blood cholesterol. So
So I guess the key thing here, Ian, is that classic message we always hear, variation and moderation. That is what is going to save you money and be healthier for you as well. And eat plants. And eat plants. Yeah, there's the advice. Lots of plants and lots of different ones too.
Thanks, Maddy. I feel like you should go and put your feet up now. Thanks, Ian, but I won't be putting them up for long because I'm going to be seeing you again on Thursday for some exercise advice. Thanks again to Madeline and all the listeners and experts who contributed to this episode.
And if you're after something to listen to next, I'd like to recommend Monday's episode of our sister podcast, Today in Focus. In it, the journalist Jenny Kleeman tells Helen Pidd about a revolutionary new therapy for treating psychosis, where patients confront an avatar of the voices in their head. It's really worth a listen.
And that's all from us today. This episode was produced by Madeleine Finlay and Josh Inchana. The sound design was by Joel Cox and the executive producer was Ellie Burey. We'll be back on Thursday with part two of our listener questions special. See you then. This is The Guardian. The Guardian.
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