Dr Rupy: Is sugar in fruit toxic? It is a really common question that I get here at the Doctor's Kitchen about whether people should be having any fruit in the diet because of the high sugar content. Does fruit even have a high amount of sugar in it? Today we're going to be doing a deep dive into this topic, talking about which fruits that you should be having every day or every other day and then which fruits should be treated as a luxury item rather than a daily staple. And with me today, I've got Sakina who is researcher and science writer at the Doctor's Kitchen. How are you doing, Sakina?
Sakina: I'm doing good. It's been a calm day in the studio and we have the guests coming over later to make some food, so a good lunch.
Dr Rupy: Yeah, yeah, we're going to have a good lunch. Let's dive into it. So we're going to talk about the science behind sweetness, why plants even produce sugars, how sugar in in fruit is handled by the body, the different types of sugars that we have. We're going to answer this question that is really common, which is, you know, which is better, fructose or glucose, what the difference is between those two are. And some tips to enjoy fruits whilst being aware of the blood glucose levels. But first, there are three takeaways from our readings, right? What's the what's the first one in your opinion?
Sakina: The first one I would say is enjoy your fruits. Overall, I think the main conclusion that we came to with the readings and the research we've done is that we shouldn't be worrying about fruits and we shouldn't be seeing them as something that is dangerous or bad for you. Because yes, they contain sugars, but they also contain a lot of beneficial compounds that you get from plants like polyphenols, fibre, flavonoids, and they can mitigate the impact of sugar on blood glucose levels and they provide lots of other health benefits that are important to consider. In terms of different types of fruits, focus on whole fruits rather than juice, for example, just for the impact on blood sugar levels and to get fibre and all those compounds. And then you could make a difference between staples like berries and kiwis that you could add to your porridge for example in the morning, and luxury items like mango or exotic fruits that are a bit higher in sugar.
Dr Rupy: Yeah, yeah. So we're going to separate them out into sort of like autumnal and summer fruits that are like, you know, things that you can have perhaps more regularly than the other more exotic fruits. And we're going to go into exactly how much of the sugar is actually contained in those different types of fruits. The second thing I think is pairing fruits with proteins and healthy fats. And a good friend of mine, Jessie, has been on the podcast talking about putting clothes on your starches or putting clothes on your carbohydrates. And that sort of applies to fruits. So, you know, combining fruits with proteins or healthy fats, whether it's peanut butter or cheese. I know. I'm not just calling you out there because you're French and you like the cheese, but cheese and fruit is a really, really good combination. And I think since you've been working with us, you've sort of been introduced to this world of combining fruits and savoury dishes.
Sakina: And telling everyone about it, including my dad. And my dad is now having a handful of nuts in the morning with his breakfast, which I'm really proud of. And my housemates and just that idea of combining sources of carbohydrates of sugar with other sources, which also makes the food taste better in my opinion. Like having an apple with nut butter or any or nuts or yogurt or something like that also makes the the meal or the snack more filling and and tastes good and adds flavour. So yeah, definitely been changing my habits.
Dr Rupy: Yeah. And the third thing is, I would say, focus on reducing added sugars rather than sugars per se in fruit. So, you know, a lot of people sort of melt together, a lot of people mishmash fruit with added sugars, whether it's coming from sweets or candy bars or whatever it might be. But they should be seen as very separate. And there's a lot of organizations, the WHO that are warning people about the negative impact of added sugars in the diet, rightly so, but that shouldn't be unnecessarily applied to whole fruits, which as people listening or watching this on on YouTube will find out a little bit more about why that is not the same.
Sakina: Yeah, I think it's a really important example of context matters and trying to move away from simplistic views of nutrition where a nutrient is deemed as bad or good. And so we want to ban all foods that contain it. We're trying to add a bit more nuance and make sure that the context and the food source is more important than one component of a food and it's about the dose and the context, what the food comes with. So it's kind of adding a bit of nuance to the discussion, which helped me move away from fear mongering and and kind of being scared of eating foods and worrying too much.
Dr Rupy: Exactly, exactly. Let's go to the basics, right? So, why do plants make sugars in the first place? This is I think a really interesting place to start this discussion because before you understand why what kind of fruits you should be eating for the sugar content or the polyphenol content, the fibre content, we need to understand the basics of why plants even, you know, produce sugars. So you did a bit of reading around this.
Sakina: Which is really cool. I didn't know about this before, but it's quite interesting because there is a purpose for plants, like there is one for humans, but there is a purpose as well for sugars in plants, especially for growth and development, but also for the production of other compounds that are beneficial for us and for plant's defense, like carotenoids and polyphenols, they need sugar. And it's so important for plants that they even have processes in place to regulate the production of sugars. So it is an essential element of plant growth and development that we shouldn't overlook and we can't just deem it as bad because they have a purpose for humans and plants. So I think that was quite interesting to read about. I don't know about the processes and the pathways and all of that, but I would want to know because it's quite cool.
Dr Rupy: Yeah, definitely. And I think, you know, this begs the question as to how plants have been bred over the last, you know, few hundred years to change their sugar properties. And I know anecdotally from friends of mine that are involved in the agricultural industry, it is possible to manipulate growing conditions, whether it's the soil, whether it's the temperature, whether it's, you know, the actual plant itself, the cross-breeding and and the different types of seeds that we now have, to change the sweetness of a particular ingredient, whether it's something like a banana that's changed massively from the wild bananas that we would have had access to thousands of years ago, to strawberries and and even vegetables.
Sakina: Tomatoes, yeah.
Dr Rupy: Yeah, yeah.
Sakina: Yeah, reading about we we write a newsletter called Seasonal Sundays about seasonal ingredients and I learned a lot about that history of how plants have evolved through time and through selective breedings and farmers selecting for certain traits that are deemed likable or attractive traits for customers. And often it is the size and the sweetness and yield. And so throughout generations of selective breeding, plants have evolved. And I don't know what the impact of that is on how we metabolize those those fruits and compounds.
Dr Rupy: Yeah. The likelihood is that we have probably increased the total sugar content of fruits, for example, particularly in the case of things like bananas and and berries and and other ingredients like apples and and pears. However, the extent to which those total sugars have increased is not comparable to, you know, the processed foods and the candy bars that a lot of people have likened to. I know you were in a sort of difficult situation when somebody was telling you about how like an apple is the equivalent of a sugar bomb. And you know, that is just categorically not true. We know there are polyphenols in apple, we have fibre in apple, there's a whole bunch of other benefits that you have when in a whole food compared to like a candy bar or a processed food. So that that's definitely something that I I think we want to underline despite the fact that yes, breeding practices have changed the sugar content of the ingredients. I think one thing to sort of rule of thumb is, we're going to go through some of the the fruits and the different sugar quantities, but in general, the bitterness that corresponds to the powerful antioxidants and polyphenols that we find in vegetables, for example, has been muted in a lot of cases. That's why broccoli probably would have tasted a lot more bitter back in the day, the wild broccoli for example.
Sakina: Yeah. Yeah, I think there was a study comparing wild and cultivated apples and they from from memory, so I would have to double check that. From from memory it was the acid component that was different rather than the sugar component. Which is quite interesting. So I think you're right, it's more of a decreased acidity compared to maybe an increased sweetness in some cases at least.
Dr Rupy: That that's a really interesting sidebar. Maybe we should talk a bit about that because, you know, most people would assume that the sugar content is the only driver of sweet taste, but it's interesting, like you mentioned, there are other volatile compounds that also correspond to the sweetness that we we actually taste.
Sakina: Yeah, there was a study looking at the impact of those volatile compounds, so compounds that create aroma, on the perception of sweet taste. I think it was apples. Yeah, and they found that volatile compounds can explain up to 33% of the perception of sweet taste. So it means that you can taste a food as sweet because of those aroma compounds that create this perception of sweet taste, but it doesn't mean that it doesn't correlate exactly with the amount of sugar in the food or which I think is quite interesting and I had no idea about. I I assumed that sugar means sweet taste and that's it, but it's not the end of the story.
Dr Rupy: Yeah, so there's this complex sort of array of components of our food that actually correspond to the perception of sweetness. So if you do taste something and it tastes really, really sweet, it doesn't automatically mean it's like full and full of all these different types of sugars. It could actually be these volatile compounds that explain a massive amount. If you think about it, like there's an opportunity there to create a different type of fruit, let's just say, like an apple that tastes sweeter but actually doesn't change the total sugar content, whether it's a monosaccharide that we'll talk about and explain in a second or a disaccharide like the glucose, fructose and sucrose quantity, but just the perception of sweetness. There's somebody out there is going to be listening to this and it's going to figure out a way in which to increase the sweet perception without the total sugar content.
Sakina: Well, you're you're in a innovative mindset because that study published in Nature actually concluded that those non-sugar sources of sweetness can be used for improving flavour and attractive traits without increasing the sugar content. So I think people are already looking into it, which could potentially could have other issues in terms of selective breeding and maybe we also need to learn to appreciate foods that are not too sweet. But it is an interesting way to breed plants in a more advantageous way for our health potentially. So it has been that study is looking into it. It's quite an interesting one to link to.
Dr Rupy: We're going to do like a deep dive I think into taste and perception and you know, how all these different things impact our enjoyment of food, you know, including things like texture and combination of food and stuff. Because I think that's a real interesting area that a lot of parents know too well because a lot of kids are like sort of averse to that that sort of alkaline bitter taste with reason, there's an evolutionary reason. But that sort of training of your taste buds is very effective and it can take as little as a couple of weeks to completely change your your perception, right?
Sakina: Yeah, we definitely need to look into that. I'm super interested.
Dr Rupy: Let's talk a bit more about the actual amounts of sugar in these different ingredients. So if you're watching on YouTube, we're going to pull up this graph, or not graph, sorry, a table with the different types of fruits and the total sugar content as well as the types of sugars that are broken down there. But if you're listening, we'll talk through this. Let's let's let's look at some of the sugar content in these different fruits. Talk us through the different spectrums of of fruits that we have here from from berries and kiwi to the more exotic ones.
Sakina: So we were talking about kind of categorizing fruits in terms of summer or you know, more hot weather fruits like berries in the UK. And then autumnal or winter fruits like pears and apples and then more exotic fruits for the UK. So those that we import, like bananas, mango, grapes, grapefruit, kiwi. And so we looked at the sugar content using a UK database. So obviously nutritional content varies greatly.
Dr Rupy: It does a lot.
Sakina: Which we've learned. But basically fruits contain from 5 to 10, 12 grams, sometimes 18 grams like bananas of sugar per 100 grams. But compared to a fruit product with added sugar like a candy bar for example, that's still quite low. You know, a candy bar would be like 48 grams per 100 grams. So it's still not comparable to that.
Dr Rupy: Yeah. Just to underline that point. So literally if you imagine, let's say an apple that is around 80 to 100 grams, but let's assume that's 100 gram apples versus 100 gram chocolate bar. You know, the amount of sugar in an apple is in this case almost 12 grams per 100 grams of that material versus a chocolate which is almost 50 grams. So like a very, very different big difference in the total sugar amount. But then also as we'll go into, you know, it's it's about what else is in that product as well that can determine whether it has a healthful or harmful effect on the body.
Sakina: Yeah. That's the that's a point that we'll go into for sure because it's not just about, that's the point we're trying to make as well, it's not just about the actual number, the actual amount of sugar. There is a difference between different fruits, like berries tend to have lower sugar amounts, like raspberries, blueberries, strawberries. They have a lower total sugar and they have a higher levels of glucose and fructose compared to sucrose for example. But then exotic fruits like banana, mango, lychee tend to have higher levels like 18 grams for banana or 10 grams per 100 grams for mango. So it could be that you you can kind of decide which foods you want to be your daily staples because they have lower amounts of sugar, but it's not the the final word on that because it's not this number is not the most important thing that we should be looking at, but there is a range.
Dr Rupy: Within the ranges of those different types of fruits, there were some really surprising numbers that we we came across, right? Including blueberries versus strawberries. Now, if you asked me, I would have said hands down, strawberries definitely have more sugar than blueberries. Is that correct?
Sakina: Yeah, me too. I would think that too, but actually from that data, there's a slight difference, like a two grams difference or three grams difference, but blueberries actually have a slightly higher sugar content than strawberries, which is surprising because of the taste, I think. I think strawberries tend to taste a bit sweeter in my opinion.
Dr Rupy: Yeah, and it could be again from those volatile compounds that give the perception of sweetness versus versus the the actual total sugar content. And I guess even though there is a two or actually three gram difference, so strawberries have 6 grams of sugar total sugar per 100 grams, blueberries have 9 grams per 100 grams. The fold difference is 50%. So it's actually 50% more in blueberries. More more total sugar content. Totally, yeah. So even though the absolute numbers are quite low, the relative difference is quite different. And I wouldn't have expected that.
Sakina: Yeah, me too. And same for kiwi for example. It's it's classified as an exotic fruit, but it actually has quite a low sugar content compared to other exotic fruits like mango or bananas. Which is quite interesting.
Dr Rupy: Plus you have extra fibre because you can eat the skin.
Sakina: Yeah. Yeah, you were telling me about that. I was very surprised. I've never actually tried to eat the skin, but my friend does. And the first time I saw that, I was I was like, what? You can eat a kiwi like an apple, just bite into it. It's quite hairy, isn't it?
Dr Rupy: Yeah, it is quite hairy. The first time I ever saw anyone do it was actually my wife. So she used to make these sort of smoothie packs, which I think are quite useful, I think, like in the morning if you want like a quick smoothie or whatever, although I don't really have like fruit smoothies. She would literally cut them whole with the hair on and everything and put them in these freezer packs. And so in the morning just put them into the blender and then blend them all up. And I was like, why are you not peeling them? You're going to get lots of bits of hair in your smoothie. But you can definitely eat the skins. As long as you I need to start that. I'm sure it's good for you as well.
Sakina: Yeah, yeah, you've got extra fibre. You just got to make sure that, you know, we've done a podcast on pesticides and organic foods and stuff. And kiwi, I don't believe is particularly high in pesticides, but you do want to make sure that you are washing your vegetables and your fruits. And in particular with bicarb, right?
Dr Rupy: Yeah, you can use baking soda. We were doing, there's a newsletter coming out where one of the readers asked about baking soda. We're completely going on a tangent but soaking in baking soda could actually remove pesticide residues on the surface. So which I don't do either. So another thing that I might add to my routine.
Sakina: Yeah, yeah, definitely. So and just to sort of clarify this section on the total sugars, even though, just to underline this point, it is not the most important sort of area to focus on. The highest amount of total sugars per 100 gram in fruits appear to be bananas, grapes, mango, and actually apple and pear surprisingly quite high. But as we're going to go into a little bit later, they do have a lot of other elements like particular types of fibres. I know if we if we do talk about this a little bit later, but pears have like a grittiness whenever you bite into them and that actually corresponds to a particular type of fibre that is unique to pears that actually give us a whole bunch of different benefits as well.
Dr Rupy: And we'll go into the mechanisms of why that can modulate the blood glucose response, which is very interesting I think. So we definitely don't need to get too carried away by the numbers, but it is it is interesting to see those amounts. And then there's the different types of sugars as well that we looked into.
Sakina: Yeah, so yeah, let's talk about the different types of sugars that you find in these.
Dr Rupy: Yeah, so there's different types of sugars that are classified as single sugar molecules like glucose and fructose that are known as monosaccharides. And more complex structures like sucrose, which is basically two glucose and a fructose molecule combined, and known as disaccharide. And so in mature fruits, the major sugars are sucrose, fructose and glucose, but some fruits like exotic fruits like mango, peach, pineapple, they have a higher sucrose content compared to other fruits. So there is a difference in the amount like we said per 100 grams, but also in the types of sugars that we find in fruits.
Sakina: Yeah, and there appears to be different ways in which the body metabolizes these different types of sugars. We're going to go into that a little bit later on. But overall, we can't really say that a particular sugar is healthier than another one, just that it is metabolized slightly differently. I know there was a trend toward like people saying particularly like five, six years ago that a natural sugar like honey or agave is better for you than, you know, table sugar. And whilst it has marginally increased amount of antioxidants and some other attributes, I can't say that is true because it really does come down to dose.
Dr Rupy: Yeah, and the food, the food itself. I think more than the type of sugar being one sugar is bad and the other is good, it's more about what the food is and what other things it comes with, what do you eat it with and this whole matrix effect that is more relevant I think to talk about.
Sakina: Yeah, definitely. So that's added sugars, right? So that's, you know, less than six teaspoons of sugar per day, less than one can of coke per week. Let's look at the other side. So, you know, what about the intake of whole fruits? Because that still contains sugar, but as we've mentioned, it has the antioxidants, the fibre. What what does the research tell us about the potential beneficial effects on health?
Dr Rupy: So because of this amount of this content of sugar in fruits, research has been looking at is it a problem? So is there a problem eating sugar from fruits? Does it increase the risk of disease like added sugars do? And actually most research found that there's a beneficial effect on overall health. So there's a reduced risk of stroke, heart disease, obesity, cancer. And actually studies looking at fasting blood glucose found that whole fruits reduce fasting blood glucose and they've even recommended for patients with diabetes. And that's from a recent meta-analysis. So it's actually recommended. And so all these detrimental effects that you see from added sugars are not seen for whole fruits, which we'll explain why. And there was also a cohort study called the Australian Diabetes, Obesity and Lifestyle Study involving 7,675 participants about 54 years of age. And they showed that moderate fruit intake of about two servings, and they included apples, bananas and oranges. Oh, even bananas. Which I was quite surprising. Had a 36 lower risk of developing type two diabetes compared to those who ate from the lower intake, so less than half a serving of fruit per day. So more whole fruits despite the sugar content is linked to overall beneficial effects even for type two diabetes, which is kind of counterintuitive if you just focus on the sugar.
Sakina: Definitely. Yeah, yeah. And I guess just to sort of caveat as we always do with the seasonal Sundays newsletters and whenever we talk about these kind of studies, there are a lot of limitations when we do these kind of cohort studies. There is the obvious one which is the healthy user effect. So someone who is going to be consuming a lot more fruits in their whole form, whether it is a banana, which is particularly high in sugar, compared to someone who's having less than half on average a piece of fruit per day, is likely to be doing other activities that could also contribute to a reduction in the risk of developing type two diabetes. Like they might be going for more walks, they might be having more whole foods and less processed foods in their diet. They might be of a higher sort of socioeconomic strata, so they have all these other benefits of, you know, better financial security, all the rest of it. So there's definitely some nuance to those studies.
Dr Rupy: Yeah, it doesn't mean causation. It doesn't mean that eating a banana will prevent diabetes. And there's also, it depends what you're comparing it with as well. If you're replacing a banana, if you're replacing a food product high in sugar like a candy bar with a banana, obviously there will be a beneficial effect. But if you're replacing, I don't know, like a green leafy vegetables for example with a banana, it might not be the same protective effect. So those studies definitely have some limitations, but I think it's interesting that there is beneficial effects of whole fruits in general in people's diet.
Sakina: Yeah, yeah. This can definitely be confusing for a lot of people because, you know, a lot of people like they equate sugar in added in sort of sugar sweet beverages or candies and sweets and all that kind of stuff with fruit. Let's sort of steel man the argument for what that cohort study actually showed. Let's assume that, okay, fruit does have this beneficial effect. What are the potential mechanisms that enable fruit to have this protective effect? Dose is something I always come to. Why don't we talk a bit about dose?
Dr Rupy: We've already sort of alluded to it earlier, but Yeah, we've talked a little bit about the difference between the difference in amount of sugar between, for example, a medium-sized apple that will contain 17.4 grams of sugar and an average-sized candy bar that will contain about 31 grams of sugar. We talked about it in 100 grams earlier, so it's slightly different amounts. But so in terms of amount, the difference between a whole fruit and a food product is quite significant. So that's one thing, one of the first differences between whole fruits and added sugars, but there's more.
Sakina: Yeah, yeah, there's definitely more. So the second thing I I always want to sort of push toward people is this idea of the food matrix. So fruits versus processed foods, very, very different, despite, let's say, they have the same amount of sugar because you're also consuming the different types of fibres that will blunt the absorption of that sugar into your digestive tract and then into your bloodstream where it can be processed by the liver and the other sinks like muscles and fat cells. You also have polyphenols and these polyphenols can also have an impact on the absorption of of blood across into your different cells as well. That can also have a satiating effect. So these different polyphenols can also impact your overall energy consumption. There's a whole bunch of other elements that you are consuming in a whole fruit versus a processed food with let's say the same total amount of sugar in in the actual product as well.
Dr Rupy: Yeah, this food matrix effect is quite interesting I think because it shows that there is huge complexity in nutrition. So the all the foods we're eating come in a very complex structure of loads of components, some that we don't even know, we're not aware of yet. And so it's really more complicated than just saying this one nutrient equals this effect. It's it's all really complicated. We don't know yet how it's absorbed, released, and it's an ongoing area of research.
Sakina: Let's double click on the sort of food matrix effect here. So I want to I want people to understand exactly why the food matrix is so important. So number one, like I said, it slows down the release of sugars. The way it does that is soluble fibres that you find in, let's say, an apple. We're using apple quite a bit today, but I'm an apple fan. A doctor an apple a day keeps the doctor away. This soluble fibre forms what's called a viscous gel. And that sort of gel slows down or attenuates the absorption of the sugar across into the bloodstream and that ultimately will lower the glucose spike that you have after consuming said apple or after a meal. So these sort of dietary fibres are really important, not just from the blunting of that, but it also it gives your microbes interesting extra bits of food so that they can thrive and a better diverse microbiota also better fuels and and partitions that sugar so you don't have it just dumping straight into your bloodstream.
Dr Rupy: Yeah, I think it's really important that there's this two effects. There's the gel and then there's also the production of those beneficial products from our gut microbes that we love talking about. And that also influences glucose control. And then polyphenols also can have an impact on blood sugar levels, which I also wasn't really aware of the exact mechanisms before. And for example, there is one apple polyphenol, which I will let you pronounce the name of.
Sakina: Phlorizin.
Dr Rupy: Phlorizin. And it was shown to inhibit sodium glucose co-transporters. So it led to a decrease of glucose transport and so it reduced glucose spike. And in human studies, apple extract rich in that polyphenol was seen to attenuate blood glucose and insulin after a glucose challenge. So polyphenols also can help kind of attenuate this blood glucose response after you eat a whole fruit. Which is which is very interesting.
Sakina: Yeah, definitely. And there was um there was some elements of the glucose podcast that I did where I talk about reducing insulin resistance. And insulin resistance, as a reminder for people, is one of the mechanisms by which type two diabetes or poor glucose control can appear. And when we contain whole fruits that can that have all these different flavonoids and polyphenols, it appears that that can actually improve one's insulin sensitivity. So making your cells more sensitive to the hormone that drives sugar from your bloodstream into the cells where it can be appropriately partitioned and not put you at risk of things like type two diabetes. That I think is particularly fascinating and that may come to a head a little bit later on when we talk about this study that is sort of perplexing for us about processing fruits into a smoothie versus a whole fruit. But there's another way as well. So we've we've already done three, so that's slowing down the release of sugars, regulating the uptake of sugar, decreasing insulin resistance.
Dr Rupy: Satiety, as you mentioned before, which is quite a big one as well. There was a difference between, for example, drinking orange juice. You're you're consuming way more whole oranges when you're drinking a glass of orange juice. I think it would be like three, four, maybe five whole oranges.
Sakina: Oh, sometimes it can be like eight.
Dr Rupy: More. Yeah, compared to eating a full orange, it will make you full pretty quickly because of that fibre. So there's also that satiety element, which means that yes, there is sugar in fruits, but you will eat less because it makes you full quicker. So you'll be less inclined to eat more.
Sakina: Yeah, yeah. And I think um, you know, part of this whole matrix of ingredients that you're consuming with the fibres and and all the other elements that you find in like a a whole apple or orange, um will show that it it can increase the production of short chain fatty acids by improving the diversity of your microbes as well. So just to sort of underline the point that it's not just um the uh sugar uh dose and and the impact on insulin resistance, there are other health mechanisms that are being activated when you consume this. We haven't even talked about like, you know, nutrigenomics and the turning on and turning off of certain uh genes in your in your body as a result of consuming whole foods. But you can basically see that the effects of consuming food that has yes sugar in really has a multitude of different effects rather than just, you know, the sugar spiking capability of it.
Dr Rupy: Yeah, so it's zooming out about just the sugar and seeing that it also supports overall health, which is good for your your body's ability to handle the sugar as well.
Sakina: Yeah. As I know I'm going to get asked about it, people will say, okay, but what about fructose? Now I've heard fructose is bad because it mainlines to the to the liver, it's processed slightly differently, it's worse than glucose because, you know, it it essentially is absorbed by your body in a different way that can be overall negative. What about fructose?
Dr Rupy: So I looked into it a little bit because yeah, there is a quite a bad reputation of fructose. So fructose is a simple sugar, it exists naturally in foods, either in free form or a one-to-one combination as sucrose, like we talked about. But actually a recent meta-analysis of human studies concluded that chronic consumption of fructose is neither more beneficial nor more harmful than equivalent doses of sucrose or glucose for glycemic and metabolic outcomes. So there's not enough evidence right now to say that fructose is more harmful than glucose, for example. But there is a bit of nuance in that and there's a bit more complexity to that that we can we can go into as well.
Sakina: Yeah, yeah, because it seems that, like we've alluded to earlier, it really does come down to dose, right? So depending on the amount of fructose that you are consuming, and just to sort of underline this point, a lot of sugar sweet beverages do have fructose as the main ingredient, this this high fructose corn syrup, or there are a number of other names for it. I think there's something like 100 other names for these kind of syrups that are added at very high concentrations that does appear to have a negative effect. But that's really down to the dose rather than the fructose itself, right?
Dr Rupy: Yeah, because it gets very quickly into your bloodstream in those doses. So consuming too much fructose in a short period of time can overwhelm your capacity to handle the fructose and then it spills over into the liver. So it's the dose, yeah, the spillover effect, which is the dose that has a negative health effect, not really the fructose itself. Like we said earlier, we can't really say right now with the research that one sugar is worse than another or bad for health, but that high dose that we find in those fructose syrup and and added sources is what would be the issue and driving health problems.
Sakina: Yeah, so it seems that, you know, I think I like this idea of the spillover effect because if you have a bucket and you empty that bucket, let's say every 12 hours, as long as you keep to the dose that your bucket can hold, it's okay. If you start adding in multiple bucket loads of fructose in this case, such that it spills over the sides, the spillover of the side is going to cause a leaky floor, that's going to cause mold, that's going to cause like a disruption to the integrity of your floor and then it's going to so that's a glib example of exactly what is essentially going on in your body right now. Your your body does have the capacity to hold some amount of of fructose and and remove that fructose every 12 hours, let's say in this example. But it's the over consumption, it's the overfilling of our buckets that leads to these these poor health effects.
Dr Rupy: Which I think is quite reassuring. And we talked about it even in sense of, for example, when we talked about aluminium and nitrates and a lot of the compounds that are deemed bad for us, we have an ability and a capacity to handle them, which for me was really reassuring to read about those mechanisms that the body has to either remove or handle, manage, store compounds that can be harmful at a high dose. So low doses were defined as less than 10 grams per meal, which is equivalent to levels obtained from a fruit. So there was an animal study that for was quite interesting in terms of the mechanisms of how that said that the gut may help to shield the liver from damage by breaking down the sugar before it even reaches the liver. So we often talk about the problems of spilling into the liver and causing liver build up and damage. But actually at small doses of less than 10 gram per meal, maybe it will never reach the liver according to that animal study and the gut will help protect and prevent fructose from reaching the liver in the first place.
Sakina: That makes a lot of sense because, you know, there are enzymes like fructokinase for example that are actually expressed in the small intestine. That was new to me because I thought that only happened in the liver. But the fact that you can break down these products in the gut such that your liver does not become overwhelmed, that's really interesting.
Dr Rupy: Yeah, I thought so too. I'm sure you need human studies to confirm those mechanisms, but it's quite a it was published in Nature. And so it's quite an interesting mechanism that could be reassuring to know that at low doses, we shouldn't be worrying too much about fructose, especially from fruit because it's so low.
Sakina: Yeah. There also is this interesting catalytic effect of fructose that again was new to me. I remember sort of coming across this during my masters about fructose potentially being beneficial for glycemic control.
Dr Rupy: At low doses. Yeah, at low doses of less than 10 grams. There was a clinical study involving healthy individuals but also people with diabetes. And they found that small doses of fructose of less than 10 grams reduced glycemic responses after a meal by about 15 to 30%. So that's low doses because it could stimulate the activity of glucokinase and increase the storage of glucose. So it's kind of nudging your body to to do its job.
Sakina: Isn't that crazy? Yeah. Which I also thought was very surprising. And it's really this dose matters and context matters argument that we're seeing.
Dr Rupy: So like there there's like a a little phrase that my mom always tells me like a little bit of sugar is is not bad for you, it's actually good for you. And I was like, mom, honestly, like minimize the sugar as much as possible. Again, I'm probably going to get going to get an I told you so. Because of this catalytic effect.
Sakina: Yeah, I'm sure, I'm sure there's other areas. I mean, a bit like exercise, that I'm sure there's other areas about health where a little bit of kind of nudging or stimulation can actually promote your body's ability to handle toxins and to handle other compounds.
Dr Rupy: You know, I see this in a clinical context. So people who are on a very strict ketogenic diet, let's say, where they minimize carbohydrates of all different forms, whether it's refined or whole. If you offer them an oral glucose tolerance test, which is a test where you consume a lot of sugar in a very small amount of time, and at defined points at 30 minute intervals, you measure their blood glucose level through a finger stick. Often you'll find that they've lost their tolerance of sugar such that their body doesn't know what to do with the sugar and it just goes straight into the blood in the bloodstream and it measures as if they are at diabetic levels despite not having any carbohydrates in the diet. And I feel it's somewhat related to a lot of these different mechanisms that we've just been talking about. Not only the catalytic effect of fructose, but also the fact that you've got some microbes in your gut that if they are stimulated enough, they will start breaking down certain sugars and ensuring that they are partitioned into the cells appropriately before they go to your liver or before they end up in your bloodstream. I I I find this is why like, you know, nutrition is very, very complex and it can't be boiled down into these sort of sound bites that you hear on the on on the internet.
Sakina: For sure. And we can't just demonize compounds or you know, increase fear because actually, yeah, there is a lot of complexity to it which we're still understanding. Like a lot of these studies are small studies or animal studies and we're still exploring and understanding these mechanisms a bit more.
Dr Rupy: Yeah, yeah. Juice.
Sakina: Yes. Yeah, fruit juices.
Dr Rupy: I always get asked about fruit juices. Should you get veg juices rather than fruit juices? I have opinions on veg juicing that I have to admit are probably not as informed as they should be. Veg juicing is generally going to be okay because it doesn't refine the sugar like fructose that you find and you're getting some of those other sort of beneficial bitter compounds. That's probably a topic for another day. Fruit juices I I have staunch opinions on and I generally say to people, stay clear of fruit juices unless you're you want to enjoy like an orange juice on holiday, you know, whilst you're having brunch or or whatever it might be. Talk to us a bit about fruit juices and the the the sugars found in fruit juice.
Sakina: Yeah, we should definitely look into vegetable juices because I don't know much about that. But I think the general principle is that when you're juicing fruits, whole fruits and maybe vegetables, probably vegetables as well, you're breaking down the natural structure. So you're breaking down the fruit matrix that we talked about. And so that has more impact than we can even understand. And so it frees the sugars from the plant cells and it also removes the fibre. So it means that the absorption of glucose into your bloodstream will be very different than when you're eating the whole fruit and it will be much quicker. And then there's there's also that dose that we talked about as well before, which is fruit juice contains like four, five, six, seven oranges compared to one. So you're getting more sugar, more quickly because it's freed from its structure. So it's going straight to the bloodstream and it's causing a way quicker rise in blood glucose compared to a whole fruit. I think it's quite interesting because fruit juice company will often say on their bottles like natural fruits or natural sugars and see it as like kind of a selling argument that it should be good for you. But actually this is kind of the proof that natural sugars doesn't mean that much and it doesn't mean healthy because the structure and the the the food matrix that the sugars come with is also important and that is removed when we're eating fruit juices, when we're drinking fruit juices.
Dr Rupy: Absolutely, yeah. Now this brings us on to a perplexing study that we came across looking at 20 people because using the same logic that you've just articulated right now about, okay, the more you remove fibre, the more you disrupt the matrix, the higher the likelihood that you are introducing a processed product that's going to be harmful, quote unquote, into your body or more harmful because of the the impact of sugar on on in your bloodstream. There was a study looking at 20 people and they randomized them to blended fruit and whole fruit and they measured their glycemic response. I would have said whole fruit, you know, that wouldn't have blunted, that wouldn't have spiked their blood sugar as much as the blended fruit. What actually happened?
Sakina: Yeah, they actually found the opposite. Surprise. So actually, yeah, it was quite surprising. They found that blended fruit resulted in a lower glycemic response compared to whole fruits, which is a bit counterintuitive for me. And obviously it's a very small study. It's it's only 20 participants and it was published quite recently. So we need more research on that. But the authors think that blended fruits could reduce glucose levels because the blending could release all those compounds that we talked about like fibre and polyphenols from the fruit matrix more than when we chew food, fruits. And so the release of that could then have a positive effect. And compared to juice, you still keep the fibre when you're blending fruits. It's just that it's blended like when we chew food. So I guess it it could kind of make sense, but it shows that we need to learn more about those nuances.
Dr Rupy: Definitely. Yeah. And I also think like, A, it was a 20 person study. B, it hasn't been repeated, not so that I can see. And I think one of the sort of hallmarks of proof within, if I mean, if you use the Bradford Hill criteria for example, you know, you have to have it replicable. It has to be replicated in multiple different centers, not just the same center or the same researchers, but from people from, you know, ideally different institutions in different countries. This hasn't been repeated, so I say this with a lot of reservation, but that is really surprising that you'd see that even in 20 people, you know, I I would have I would have lost my money if that was a bet.
Sakina: So, look, as a general rule of thumb, I would say whole fruits can be considered a healthy addition to our diets even if they contain sugar. But what about sort of all different types of fruits in that sort of context? Because a fruit is not a fruit, is not a fruit. There are all different types, right? We've just talked about grapes and bananas versus berries. Tropical fruits, is this something that we should be avoiding?
Dr Rupy: So we would say kind of yes because of the amount of sugar, but then there's actually I think is it's another topic of debate because there's also a study that a human trial that compared fresh mango compared to isocaloric low fat cookies. So it all comes back to this idea of context and what you're comparing it with. So compared to isocaloric fresh low fat cookies, fresh mango reduced blood sugar levels, which is expected. So we still can't say that, you know, it's bad, completely bad to eat tropical fruits. There's even a systematic review that suggested that all sources of fruits, including tropical fruits and dry fruits were associated with a reduced risk of cardiovascular risk disease compared that is comparable to that of vegetables. And the authors even went as far to suggest that preventing people from eating certain fruits like tropical fruits could cause unintended harm because from people preventing people from meeting their fruit and vegetable requirements. So I think we shouldn't be demonizing tropical fruits because they have a higher sugar amount, which is the conclusion that these researchers came to. But they do have a higher sugar content compared to other fruits like we talked about in the beginning. So maybe they shouldn't be your daily staples. Maybe it shouldn't be the first thing you eat in the morning on an empty stomach. But compared to having another sweet food and compared to not eating at all, not eating fruits or vegetables at all, it's still better to have a banana or a mango than, you know, to completely remove your portion from the day.
Sakina: I think that's a a really important point to to know about the isocaloric low fat cookie. So a lot of people would demonize perhaps the fruit because of the sugar content and opt for something else that is processed that has perhaps low fat or healthy on the packaging. So if you have an isocaloric, that that's a funky word for saying exactly the same amount of energy. So you have a let's say a banana or a mango and you have a cookie and they have the same amount of calories. Let's just call them 100 calories. They have the same amount of sugar because the cookie is low fat and the banana or mango is relatively higher in sugar compared to other fruits. The fruit does better than the isocaloric cookie because of all the other attributes that the cookie just will not have because it's a refined processed product. So I think when you're at the counter or you're grabbing a coffee and you're making that decision between something that you need that is satiating or something like a snack that you want and you are looking at a sort of well packaged in dark green sort of processed food but that actually has like healthy or low fat on it compared to the the banana, let's say or the apple that doesn't have any of those uh um sort of funky labels, you really want to be opting for the the whole fruit in that context, let's say.
Dr Rupy: Yeah. But so yeah, so food combinations, um I think are is an interesting point that you talked about in that podcast that you did on glucose hacks. So I didn't go into the mechanisms and the studies on that, but there I think you you went into details about it in that pod and the one with Jessie as well. But yeah, I think a general thing would be those tropical fruits can be more of a dessert or more of a sweet luxury treat. And then our staples would be lower sugar foods like blueberries, strawberries, blackberries, kiwi, citrus fruits, frozen blueberries when it's out of season. Yeah. Because otherwise it's really expensive. And and then what you eat the foods with or food timing as well. So eating those foods, those fruits with sources of protein and healthy fats to lower that glucose response. So there can be kind of strategies of how you eat foods if you are worried about glucose response and to just make the meal a bit more complete in general.
Sakina: Yeah, yeah, for sure. Okay, so let's let's wrap up and and have three key takeaways. So I would say, you know, as a doctor, as someone who is interested in trying to increase the nutrient density of people's diet, eat your fruits. For the majority of people, I don't think you should be worried about eating fruits. There are certain circumstances where people are on strict ketogenic diets for therapeutic reasons or they're on low carb again, again for therapeutic reasons. I can see the rationale for removing high sugar items from one's diet, but for most of us, we need to be aware of our sugar intake, but not aware of our fruit intake. And there are levels to that as well, which I guess is the second point about whole foods and the the the benefits to health.
Dr Rupy: Yeah, so focusing on whole fruits rather than juice or other sources of sugar compared to other sweet foods, most people will benefit from consuming whole fruits. And I don't think we should be worried about them, especially when you're swapping, as you said, a sweet food for a whole fruit. Generally for overall health, it will be beneficial and and provide loads of compounds like we talked about and like we talk about on seasonal Sundays, there's just so many compounds that come with those fruits and we've been eating them for so long and they have a rich history as well linked to to humans and our culture. So I don't think we should be banning fruits.
Sakina: Yeah, yeah. What's your favorite fruit actually on that?
Dr Rupy: What's my favorite fruit? I actually like kiwi. I know it's a bit of a weird answer. Because I know it's not the most exciting. I do like mango as well. Mango is like a treat. But I like kiwi. I like berries. Depends what I'm eating it for, like if it's just by itself or in something.
Sakina: My new favorite is mangosteen. I've never had that. I know, I hadn't had it before. I went to Malaysia and it is an incredible sort of citrusy, mangoy mix that, you know, sometimes mango can be quite over sweet in my, you know, with my palate and stuff. Like my dad, my parents absolutely love it. You know, Alphonso mango is like a proper Indian thing. But like mangosteen I think for me is the nice balance between sweetness and citrus, which I I really appreciate. And blackcurrants as well. I'm a big blackcurrant fan. Love blackcurrants. One of the highest levels of anthocyanins in blackcurrants. The beautiful colour, yeah, stains your fingers and all the thing. So I guess sorry, the third point before we get I need to try that fruit.
Dr Rupy: Yeah, you need to try. Can you find it in the UK or not? Uh, probably imported unfortunately. But yeah, but definitely if you ever find yourself in Malaysia. I need to travel more. Yeah, yeah. The third point I would say is focusing on reducing added sugars. Added sugars is the energy the is is the enemy, I would say. You know, 15% of our overall energy intake comes from added sugars, which is crazy. We we should be, you know, making sure that we are reducing added sugars as much as possible, hence the issues around sugar sweet beverages. And it would be pertinent to reduce our sugar intake, but that does not extend to fruits. I think they're they're very, very different. So those are sort of three points. Is there anything else that we missed?
Sakina: I have one last question to ask you. What do you think? So my housemate asked me that. She was like, could if fruits are so good, could you could your five a day be fruits? Or do you still need vegetables or you know, if could you just eat five fruits, five a day?
Dr Rupy: Yeah, I think this really comes down to the question less about like fruits but more about diversity of the different ingredients. And if you are going to be essentially expending more of that quota on fruits, what are you what's the trade-off? What are you excluding? And I would say you're probably going to be getting to those levels where you're over consuming fruit like we were just talking about like the five or six oranges. Like that's a lot of fibre, that's a lot of sugar to be having as five, you know, five or six portions. And you want a diversity of different ingredients as well. So I would say instead of having all five of your fruit, all five of your five a day on fruit, diversify it, get some of those bitter compounds, get some of those vegetables as well as fruit as well.
Sakina: Yeah. Yeah, I would, yeah, that's a good.
Dr Rupy: And I would also say there's probably no clear cut answer as well. As we've discussed after looking at these studies, it's very difficult to actually put your stake in the ground and actually say, you know what, if you process any fruit, it's going to have a worsening effect on your glucose levels. That was a massive surprise to me. And so, you know, everything that I just said about like five a day, that's a hunch, that's just based on my sort of opinion, but I haven't come across any studies that comparing Yeah, I mean, maybe there are some, but I I haven't either.
Sakina: Yeah, yeah. We should probably look into that. Yeah, we should. Always more topics.
Dr Rupy: Any favorite recipes with fruits then that you have in your day-to-day?
Sakina: I would say there is a new recipe with cranberries, kale and spiced celeriac chips that's coming on the Doctor's Kitchen app. And that's going to be a perfect sort of celebration side dish for Christmas or Hanukkah or New Year's or whatever you're celebrating at that time of year. I think it's wonderful. And it's got these dried goji berries that we soak and all are scattered them over the the kale and everything and it's like it's a delicious way of enjoying veggies. Because you're getting all those different fats, those different, because we add nuts to it, you're adding all the different types of fibres from the kale and you're having celeriac which is like one of those underutilized ingredients with those spices and it's got cinnamon in as well. And we know cinnamon has a a glucose blunting effect.
Dr Rupy: Yeah, that's another thing that I don't know if we mentioned in terms of combining fruits, putting them in savory meals, which I never, never do. But I really want to start doing that, just throwing pears and apples into my into my stews or my salads and stuff like that because that's another way to eat fruits and add a sweet touch to meals without only eating the fruit by itself. So that's another thing I think to add to my habits that you've inspired me.
Sakina: It's something I put in my diversity bowls every day.
Dr Rupy: Nice.
Sakina: Good stuff.
Dr Rupy: Good.
