What's That Rash? - Eat the rainbow: what can food colour tell us?

0:00ABC Listen. Podcasts, radio, news, music and more. Written from us. Written into us. These are the pages to which Australia returns. The ABC Radio National Top 100 Australian Books Countdown. Voting closes October 1st. Visit abc.net.au slash top 100 books to cast your vote. Are you the one who cooks at home?

0:38Oh, I am very lucky to be married to a very good cook. But no, I've been known to cook Norman. I can cook. You don't think I can cook? I haven't checked it. So, you know, I would have thought you're a great cook. You guess right. And knowing your partner, I'm sure he's a great cook too. But the question is to extent to which colour plays a role. So, you know, I do the health port with Priya after you had deserted me. Look.

1:01I'm still sorry about it. But Priya is very good. She is very good. And she's written a book for children about children's diet and she talks about rainbow colours, the colours of the rainbow in your diet. Do you think about the colours of the food you're cooking? I do even more now since Priya's catchphrase, Eat the Rainbow, got in my head. I always associated Eat the Rainbow with rainbow coloured lollies, but I understand that she actually means fruits and vegetables. Yeah, I don't think it's a lolly she's talking about somehow.

1:28Well, eating the rainbow is pretty much what we're talking about today here on What's That Rash? The show where we answer the health questions that everybody's asking.

1:38So today's question comes from Laurent who says, is a more intense colour like a deep orange sweet potato inherently healthier than a beige potato? Or for example, when I buy capsicum, is it better to grab a green, a red and a yellow one instead of all three being the same colour? I'm guessing that if I look down at my shopping basket and see dull colours, I'm doing something wrong. Does the colour of food matter for health? Good question.

2:07Great question. I'm so excited to talk about this. We've talked so much about fruits and vegetables before, Norman. But I don't think we've ever talked about the kind of vibrancy as a health indicator. We haven't. And just coming back to the lolly, we're not talking about food dyes here. We're talking about the natural colours of food. The natural colours of food. But everybody listening knew that anyway. But I just thought I'd better see it. Well, I feel like I just have a sense. I can feel in my waters that this is going to be a very diet-heavy discussion, probably a very Mediterranean diet-friendly discussion. So I'm just going to get a bunch of bell rings out of the way now just to- Okay, let's just go over the system. I'm feeling healthier already. I'm feeling healthier already. We're of course talking about lots and lots of vegetables, a hallmark of the Mediterranean diet and other similar diets. First things first, Norman. Why do fruits and vegetables even have colours? So one reason is cross-pollination. So it attracts pollinators.

3:03Another reason is that it might be a protection against ultraviolet light. Another reason might be that the chemical associated with the color, the phytochemical, in other words, a plant-based chemical, might protect against infection. Another one might be to do with the efficiency of growth. So there are all sorts of functions of these phytochemicals. And while people talk in humans of, you know, anti-oxidants, anti-inflammatory agents and so on, we'll come back to some of these specifics.

3:33It's better actually to talk about them as bioactive compounds. So they're, in other words, they're active within the plant. And it turns out they're also active in animals and people like you and me. I do love the fact that these are things that plants have evolved to protect themselves or to benefit themselves. And we love to just focus on how good they are for us. Not really think so much about the original benefit of the plant in question. So plants, thank you.

3:59Thank you for developing these things because we all benefit from it. And another just preface that's apart from the ringing of the bell is, thank you, is that we are talking about whole foods. So you and I are going to start separating out the colors and what the colors mean in terms of their chemistry. But the reality is, and it's worth seeing this right at the beginning, is that we're eating these colors in whole foods.

4:28in a matrix in the food itself. And in that matrix, in other words, that food web that these chemicals exist in have other chemicals in it. And there's a very complex chemistry that adds up to much more than the individual actions. So for example, you can have, say, resveratrol in the red skin of grapes and maybe watermelon or there are other bioactive compounds there too. But it's got to become available to your body.

4:56So you've got to be able to absorb it. You've got to be able to metabolize it. And it turns out that in whole foods and the mix of foods that you eat adds to the bioavailability of these compounds that we're about to talk about. Love that.

5:13fully endorse that, and yet we are going to break it down just a little bit because it's fun and it's really interesting to see what different fruits and vegetables give us and what better way to approach this than the rainbow, as Priya would say. Let's start at the top of the spectrum, red. What are we getting from red fruit and veg? You're getting a lot of things, but the one that's been best researched is lycopene.

5:38which is a bioactive compound. It is an antioxidant. And when we see an antioxidant, we're talking about a substance which counteracts the toxic effect of oxygen on our body. Yeah, you thought oxygen was good for you. Boy, are you wrong. Well, yes. We do a deal with the devil. We have to have oxygen to live. But when you breathe in oxygen and it gets used in the tissues, The oxygen comes as two oxygen atoms stuck together or two, and then it can break off into two oxygen atoms. And they are highly reactive, and they don't like being highly reactive. They want to stick to something so they stabilize. So in the environment, if you've got bare metal, bare iron, it will stick to the iron and oxidize the iron, and that's rust. And what we're talking about here in the body is exactly biological rust, so fibrosis changes to the way the immune system works.

6:31aging of tissues. All sorts of things are associated with oxidation. Atherosclerosis, the process of our arteries becoming blocked, so you get the cholesterol going into the cell, it becoming oxidized, inducing an immune reaction. So oxidation is incredibly important just with atherosclerosis and coronary heart disease. It's probably important with dementia as well. So lycopene and a lot of these compounds are actually powerful antioxidants but that's not all that they do and we don't fully understand all that they do but lycopene is one of them. Okay so lycopene equals red when we're going to like orange yellow veggies what are we getting? Well you are getting other antioxidants but the dominant one that people talk about are carotenoids. Carotenoids sounds like a disease. Well yeah that's right it sort of thickens your carotid or something like that. So some of these are actually metabolites on the way to vitamin A.

7:26So beta-carotene is one of them. So beta-carotene is a carotenoid. It's in sweet potatoes. This was mentioned by Laurent. Pumpkins, carrots, and it's converted into vitamin A, which obviously has benefits for the body. There's another carotenoid called lutein, which helps with eye health, possibly helps to prevent cataracts and age-related macular degeneration. So carotenoids are very important phytochemicals in the body.

7:54It's so funny that you say the thing about orange and yellow veggies leading to protecting your eye, because I always thought the carrots for your eyesight thing was a myth. You know, you sort of like, oh, eat carrots, you'll protect your eyesight. And you say, oh, why? And they go, have you ever seen a rabbit wearing glasses? But you're saying that that is actually true. Well, my mother used to say, I'll help you. I'll help you see it night, is what my mother would have said.

8:17and we actually tried it. Well there you go. Eating a carrot when I was cycling my bike at night. It was a pretty interesting thing to do. Okay so orange yellow vegetables, surprise they're also good for you. Let's go further down the spectrum to green. I think everyone knows green veggies are good. We probably will at least eye as a woman who has been pregnant associate them with folate. What else are we getting out of green veg? You get a lot out of green vegetables. You get carotenoids, you get indoles and saponins and Green vegetables. I don't know what those words mean. Well, a lot of people don't fully understand what they mean either. So I guess I guess me out of jail on that on that question. But there are particularly cruciferous vegetables like broccoli and kale and those sorts of things. Lucas, though, they have anti cancer effects. In other words, they seem to have a direct effect on cells multiplying and controlling cellular growth.

9:08which is like a cancer control thing. Cancer is uncontrolled multiplication of cells. But they also seem to have pretty much like plants. They also seem to have what's called a cytoprotective effect. They look as though they protect cells against the chemicals that might cause cancer, as well as being a source of folate. So greens and leafy greens are part of the mind diet. So it's a modification of the Mediterranean diet, but more leafy green vegetables, more berries, And because berries have many of the colors that we are talking about, which seem to go either directly to the brain or go to the bowel and change the microbiome. So the microbiome which crosstalks with the brain is sending much healthier messages to the brain.

9:56It's even just your very beautiful, simple explanation there, Norman. It's just really speaking to the fact that there are so many different systems at play when we're talking about what's happening with this fresh fruit and veg diet. We're talking about the microbiome. We're talking about, which means we're talking about the immune system. We're talking about cancer. We're talking about oxidization. We're talking about the brain. And I'm assuming that these are quite small effects.

10:20every single meal that you're getting, but it's cumulative over your life, over every meal that you eat. That's right. You have this consistency that builds up. And if you like, the microbiome is the bank here.

10:34Well, back to the rainbow. Blue slash purple. You were talking about berries before. What else are we getting here? You're getting a plant pigment called anthocyanin. That's what gives blue and purple fruits and vegetables the distinctive color. That's an antioxidant. It's also a cytoprotective. It protects cells. And again, generally thought of as pretty good for you. The skin of eggplant is part of that story as well.

10:57So it's not part of the rainbow, but it was part of Laurent's question. So I want to talk about brown and white fruits and veggies as well, because they're not all rainbow-colored. Are we getting anything out of a vegetable that is brown or white? Yes, you are. Garlic, you're getting allicin, which has antiviral, antibacterial properties. Some people believe that it's also protective against coronary heart disease.

11:20You get potassium, you get fiber, you get B vitamins. So you get all sorts of benefits in terms of micronutrients from those as well. And it's also healthy that you're not eating, you always trade off in your food choices. And if you're eating those vegetables rather than unhealthy proteins or unhealthy fats, then you're ahead.

11:46Okay, I see. So in addition to the nutrients you're getting out of that food, it's also maybe giving you satiety so that you're not turning to other things that are less healthy to fill your tummy up.

11:56I'm interested in talking about some of these phytonutrients. You said some words before that I've literally never heard in my life. Others are ones that we have maybe heard a bit about in recent years, if you're super into health, the certain compounds that you might find in pepper or in turmeric. Some of these foods or some of these compounds have been kind of known in traditional diets and traditional medicine for a while. And they're maybe seen as a little bit woo from Western medicine. I think that's right.

12:26And that's partly because doctors get really lousy nutrition education. My nutrition education came from when I started becoming a health journalist rather than what I learned from medical school. There was one medical researcher in Britain when I was training who didn't believe the cholesterol was dangerous. It was that bad at times. So I think that we have ignored the power of diet. And what we haven't talked about are the kind of generic families that these compounds belong to, like flavonoids, polyphenols, alkaloids, terpenoids. But it's all part of the defence mechanism of plants, which benefit us in their diversity. And diversity is the key here, that you're not throwing the dice on one particular food type or one particular family of bioactive compounds.

13:18And what I also want to talk about here is, we said this at the beginning, that we were deliberately going into this trap of talking about these individually. But there's a lot of evidence that how you prepare your food, how you cook it, makes a difference to the effect of these drugs. You talked about turmeric. So the active compound in there, or one of them, is curcumin. So for example, the availability of curcumin is enhanced by peppering, which is in pepper.

13:47So putting pepper on your food could well release some of these phytochemicals to become more bioavailable in your body. It looks as though fermenting food like you say yogurt also makes some of these antioxidants and these bioactive compounds more available. Cooking is as chemistry as any chef will tell you and cooking at a moderate heat with extra virgin olive oil can release some of these substances. Now, work done in Melbourne by the late Karen O'Day and her colleagues, looking at the classic fruit that...

14:23You're talking about tomatoes. I think we've said this before. I think you've told the story about three times, Norman, but say it again. We love to hear it. You tell us the story. Go on. What's the story of tomatoes? Oh, okay. I'm not going to do my Scottish accent because I can't. But you take a tomato. How about you just do your Italian accent? No, I don't want to get cancelled. But if I remember you correctly, Norman, you take a tomato, that's great. You take a tomato and you match it with...

14:48extra virgin olive oil that is bringing out some of the bioactive compounds from the tomato. But if you take the tomato and you cook it on a moderate medium heat with extra virgin olive oil then you release a lot of those bioactive compounds and that's the best version of that. And it also, this is me editorialising, tastes delicious. You got it right. Yes.

15:10I've only heard it like five or six times. And it's an illustration of how potent these bioactive compounds are and you can't possibly buy anything that comes close in the pharmacy. I think that's an interesting thing to pick up on this idea about buying supplements because there's a temptation to do that or if you don't feel like you're getting a balanced enough diet that you can kind of like top yourself up with supplements. But the thing with supplements is you've got to be able to isolate something and then make it shelf stable and then package it into a format that can be shipped probably all over the world and then be bioavailable to you by the time you actually put it in your mouth and eat it and to be able to provide that product at a price that is acceptable to a consumer. When you see how dynamic these chemicals are in vegetables and fruit, you kind of see that it's almost an impossible ask to do that.

16:02And in food, it's at a lower dose. And dose matters. And some of these substances may well perform differently at the drug level dose. And when you take one of these supplements, you're taking them at the level of a medication, a drug. You're not taking them at the level that you would take them in the mix of foods. And the one I always quote is vitamin C. So vitamin C in foods at a lower dose is an antioxidant. It's a bioactive compound that's really good for you.

16:31In high doses, it becomes a pro-oxidant. It speeds up tissue aging. And it's likely that the others have the same dose effect. Nobody understands why that occurs. But dose matters and the dose might not be good for you taken as a supplement. So a question that I wanted to come to. So Laurent was asking about different fruits and vegetables and their kind of relative colourfulness.

16:55a sweet potato versus a normal beige potato. And I think we've sort of said that you can, you're getting something different out of all those different veggies. Eat the rainbow, trust in the power of diversity. That's great for you. My question now, Norman, is if I'm looking at, say, two carrots or two capsicums and one of them is brighter colored than the other, does it follow that it has more of those compounds, those beneficial compounds in it than the duller colored vegetable?

17:24Well, if you're comparing carrot to carrot, it's possible that it does. I mean, I'm not sure the research has really been done on the intensity of color in a given, you know, when you're comparing fruit against fruit, you know, most carrots, most blueberries, they all look the same. And so the difference is probably going to be marginal. I think more is, well, if you look at your basket of fruit, which I think it's what Lauren was saying, and you got tatties in there, you got potatoes in there, and you got turnips, and you've got capsicum. And he was also saying, should you have when you're buying

17:52capsicum should you buy capsicum that's of different colour. The answer is probably yes, because red capsicum is going to have a lot of lycopene, green capsicum is going to have a lot of stuff that's in green vegetables and yellow pack capsicum has got its own mix. So a mix of capsicum is probably a very good idea to have rather than just obsessing on one. Variety is the rule of the day and also your dietary pattern. So not getting too obsessed with individual elements of it. It's how you cook, how you prepare it. So if you've got colorful food with a large variety that's constantly changing and refreshing and cooked at a moderate heat so you're not killing the food, that's the way to go.

18:37Yeah, it's really hard to sort of zoom in so tightly on an individual bioactive compound. But what we do know from big epidemiological studies, where you're looking at big, big groups of people and their patterns, like you say, is that when you have high intakes of plant products, you're looking at lower risks of chronic diseases and your chances of death. So in aggregate, there's this protective factor going on. And I think the story here is that we're really talking mostly about vegetables and diversity, aren't we?

19:04Yeah, it was interesting to me. Some of the research that we looked at sort of talked about dietary diversity, and we've talked about it a lot, this idea of, you know, mixing things up. It's good for your microbiome. But what stood out to me was that the emphasis really was on the diversity of vegetables or fruits and vegetables that you were eating, and less on the diversity of, say, the protein sources or even the grains you were eating, that it was this vegetable diversity that was most protective. By the three colours of capsicum.

19:32Keep that variety going. Don't get too obsessed when you've got a few potatoes and turnips in the bag as well. They're going to do you good. Just keep that diversity going. Experiment and cook. Cook in the Mediterranean style. Eat the rainbow. Well, thank you so much, Laurent, for the question. If you have a question you want us to have, go out. Our email address is that rash at abc.net.au. What's in the mailbag? Norman, we are still getting responses to our episode on noses and sleep.

20:02But every single one of them is so fascinating. So Alex says, we had the episode where we said it was rare for smells to wake us up. Well, Alex says, I stupidly left an old car battery on a charger last night in our downstairs workshop, which started to off gas. My younger daughter woke me at six a.m. asking what the smell was. My wife and both teenage daughters all reported that they'd had dreams involving sulfur, rotten eggs and a gas fire.

20:30And Alex, like any sensible bloke, slept through it all, clearly. It's actually a bit scary, Alex. I'm glad you were well enough to write that email and I hope that you've opened some windows in your house. Stephen says, for sleep, I've recently discovered earworm songs as very effective in stopping the relentless thoughts that keep me awake. They don't have to be annoying. Just whatever pops into my head when I need it. Conversely said Stephen. Oh my gosh, Norman, you're going to love this.

20:56When I wake up tired and need to get going, I let my mind rip with some train of thought, usually a petty, pointless indignation that sees me bounce out of bed like a startled rat. Ah, so my imagery of ABC managers is right to get me going. That's good.

21:12Anyway, Jenny says, I am a late adopter to podcasts and have been listening to yours every time I run and walk. If I'm driving home and your segment is on the radio, I change stations so I can save it for my run or walk. Jenny, I love this. So I bet you, Jenny, you're a sort of person who, you know, you get a plate in front of your food and you really keep the nice stuff to last.

21:36Well, actually speaking of keeping the nice duck to last, Jenny says, if you can turn that last piece of music into a on repeat 30 minutes, that would be great. I love it and do a little dancey thing. People driving past must think what in the world is this lady doing? Jenny, you know, you're just one of us. Jenny says, I'm training for a big hike. I'm sure I will be hearing loads more fabulous episodes and doing lots of little jigs along the way to this little number. See you next week. See you then.