ZOE Science & Nutrition - Nightshade vegetables: hazard or health food?

Episode Date: March 23, 2023

Nightshade vegetables — even the name is ominous. Some people believe they exacerbate arthritis and can cause inflammation. So, should we avoid them? In today’s short episode of ZOE Science & Nutrition, Jonathan and Will ask: What are nightshade vegetables, and how can they benefit our bodies? Download our FREE guide — Top 10 Tips to Live Healthier: https://zoe.com/freeguide Studies referenced in the episode: Potato glycoalkaloids and adverse effects in humans: an ascending dose study  Effect of red pepper on symptoms of irritable bowel syndrome: preliminary study  Treatment of arthritis with topical capsaicin: a double-blind trial  In defence of potatoes: How resistant starch from potatoes affects the gut microbiota  Health benefits of eating tomatoes emerge  Episode transcripts are available here. Want to create your own podcast? Contact Fascinate Productions to bring it to life.

Hello and welcome to Zoe Shores, the Bite Size podcast where we discuss one topic around science and nutrition. I'm Jonathan Wolfe, and today I'm joined by Dr. Will Bulsiewicz. And today's subject is nightshade vegetables. These veggies have gotten a really bad rap. Some celebrities avoid them, others claim that they make their arthritis worse or they cause inflammation. So, Will, I don't even know what a nightshade vegetable is. Is this something else I've got to start worrying about or is it just a load of nonsense? That's exactly what we're going to look at.

And spoiler alert, our investigation involves green potatoes. Green potatoes do go on. So Will, what are these mysterious sounding nightshade vegetables? So Jonathan, nightshades are plants from a large family of plants called Solanacea, and the group includes more than 2,000 varieties. The group also includes many common vegetables like tomatoes, peppers, potatoes, eggplant, which of course you would refer to as an aubergine. Nightshades are found in plenty of our usual sauces and spices as well, Jonathan. So classic condiments like ketchup or hot sauce, or some of our spices that we often reach for, garam masala and paprika. And then tobacco,

many people don't realize is also a nightshade. So I think no one listening to this podcast is going to be surprised they should give up tobacco. But what's the big deal about the rest of this? I mean, I can't even imagine giving up tomatoes. So why do people have this fear around nightshade vegetables? Well, the concern comes from some of the specific phytochemicals or plant-based chemicals that you will find in nightshades, specifically alkaloids or glycoalkaloids that include solanine, capsaicin, or like with tobacco, nicotine. These alkaloids are nitrogen-based organic substances that are produced by plants, and they have a rather intense impact on both human and animal physiology. I mean, even at low doses,

they can affect our physiology. So for humans, that impact in some cases is extremely desirable, but in other cases, it could be toxic or it depends on the dose. It could be both. So this I do know. So some nightshades really are dangerous. So Belladonna is also known as deadly nightshade. And Will was explained to me earlier that that's because it contains these alkaloids. And I'm sure many of our listeners remember that scene in Romeo and Juliet where Juliet fakes her own death. So apparently it's thought that this poison would have been Belladonna. And this was sort of well understood at this time when Shakespeare was writing it. I actually have my own brush with death story

about Deadly Nightshade, however. And apparently my mother had like driven to like the library in this little car park. I had a little brother, just a couple of years younger, really little. So I got out, my mother was trying to, you know, get this little baby out of the car seat. And I'd gone over to like the side of the road

and there was this Deadly Nightshade with these beautiful looking berries. And I'd gone over to like the side of the road and there was this deadly nightshade with these beautiful looking berries. And my mother saw it and she's immediately like, Jonathan, you absolutely mustn't eat that. That's poisonous. It's really dangerous. Apparently I looked at her straight in the face, grabbed a whole bunch of these berries,

looked directly at her, stuffed them in my mouth and swallowed them. My mother freaked, grabbed me, put me back in the car, drove straight to the hospital. They pumped my stomach. I was fine because it was all dealt with rapidly, but it wasn't a lot of fun. What I am sure about though, is I'm now very careful about eating berries that I find in the woods. So I think that clearly, I understand that deadly nightshade is not a vegetable that we should mess around with.

What was going on there, Will? Well, if we talk about poisoning with nightshades, so belladonna being the example, going back to Romeo and Juliet, a person's pupils will become very dilated. Their heart rate will start to pick up. We call that tachycardia. In some cases, they become very confused or even have hallucinations. This sort of package of symptoms that I've just described, we actually have a medical term that we use for this. We call them anticholinergic. So these anticholinergic symptoms actually can be really beneficial. So belladonna has been used to ultimately lead to new drug developments. And an example of a drug that's been developed using these concepts is atropine. I've personally

given atropine to patients when they need it. And you give this medicine in that emergency situation and it gently brings their heart rate back up. It's amazing. And I guess a brilliant example of something we talk a lot about on the show, right, which is sort of food as medicine. But I think it is a sort of example, isn't it, of just thinking about our food as a sort of inert substance, which has just got calories and fat. It's just so far away from the reality of what we evolved to eat, which is this

immensely complex set of different foods with, I think we now believe, 100,000 chemicals and growing as we're able to better measure them. Yeah. Who knows how many, to be completely honest with you. I think the other comment on this real quick, Jonathan, is that the dose is important. So I think, again, let's not be fearful of these things where something taken at the right dose, it can be extremely healthy and beneficial to us. Now, all of that said, I think we agree that the appropriate dose of belladonna is probably none. But what about my tomatoes and my peppers, my aubergines. Is it because of this that people are concerned that eating nightshade, these other nightshade vegetables could lead to health issues? There's no evidence, Jonathan, that consuming these normal nightshade foods that you will find

in your supermarket or your farmer's market, or you grow in your garden in normal amounts is toxic. There's no evidence for that. And, you know, I will say like, if there's something that we could have a concern about, it's green potatoes. When potatoes are exposed to sunlight, the light will actually turn them green. And that's because this chemical that I referenced earlier, solanine is developing. But even in research where they start feeding people these glycoalkaloids from potatoes in a controlled way, even then there weren't any issues. I mean, basically, you would need to eat a massive amount of affected potatoes to become seriously ill. Either way, it's funny. This is another one of the things that my mom always told me. You can't eat the green bits on potatoes. I remember, you know, you've got to cut them out. The other thing

I read, and we had a lot of questions from listeners about, was what about gut damage from the nightshade chemicals? Is there any risk there? Well, rodent studies have suggested that the glycoalkaloids in potatoes could injure the gut microbiome. Rodent studies are not the same as human studies. In these rodent studies, the mouse or the rat may be getting pumped up with concentrated chemical extracts or a completely unnatural diet. And it's not the same as a person who is cooking with extracts or a completely unnatural diet. And it's not the same as a person who is cooking with a tomato or a pepper. And I think that's something that, you know, I've heard a lot of scientists talk about on this show, Will.

Just because there's a study on, you know, mice or rats that show something happens, you know, very often when you then apply it either to humans and even more so sort of to humans in the real world with their normal behavior, you don't see any of the results that you saw in these animals. These animal-based studies, Jonathan, they are good for building theories or hypotheses. They're good for helping us to understand mechanisms, but they are not proof in and of themselves. We should always move to verify them in human-based studies to ensure that the way that it works in humans is the same as what we see in these sort of animal models. So it's definitely possible for people to be sensitive to these types of foods. It may not be because they're nightshades.

I mean, let's not necessarily assume that it's the fact that it's a nightshade that's causing the trouble. So in many cases, it's instead a food intolerance that's causing the problem. Good. So I don't need to give up my tomatoes. I'm very happy about that. Could any of these sort of alkaloids and other chemicals in these plants we're talking about actually be helpful for our plants? 100%. I mentioned earlier that one of the alkaloids is capsaicin, which is the part of a pepper that makes it have heat or spice. And there's actually a significant amount of research in my space as a gastroenterologist, Jonathan, with irritable bowel syndrome, where people with irritable bowel syndrome who took a capsaicin supplement actually saw significant improvements

in their abdominal pain and bloating when compared to a placebo. So capsaicin, by the way, is also commonly used to treat joint pain. You can find capsaicin at your local drugstore, and it's intended for people that have arthritis. And if we go back to potatoes for a moment, there are some redeeming qualities for potatoes. In fact, there are ways in which potatoes are really good for our gut microbiome. And that's because potatoes are very high in what's called resistant starch. Basically, it's able to escape digestion, passing all the way through the intestine, and it gets broken down by our gut microbiome in our colon. And it releases in a powerful way, short chain fatty acids like butyrate. And we know

from our research that these short chain fatty acids are beneficial to our health. So Will, having seen what happens to my blood sugar when eating a potato, you're going to have to be very convincing here. Okay. So let me sort of give a pro tip, something that's really worked for me in bringing potatoes in a healthy way into my diet. You can actually get more resistant starch by heating and then cooling your potatoes, Jonathan. And so each time that we heat and cool

a potato, Jonathan, we're actually producing more of this resistant starch, which provides benefits to our gut bio. Well, I think that's a great tip. And I'm afraid I'm still going to be swapping out potatoes for foods that score better for me. You know, for someone like me with poor blood sugar control, really any of these starchy foods with sort of low levels of fiber, like potatoes, tend to lead to these huge blood sugar spikes. And then we're offering these big dips sort of two or three hours later that make you feel tired and hungry. So I think I'm going to be sticking to the peppers and the aubergines and the tomatoes out of the nightshade family and leaving the potatoes with

you? Well, I think that's all very fair, Jonathan. But I think that what you're speaking to is your personalized approach to how you attack your diet using Zoe scores, using the information that you have learned from Zoe, such as your blood sugar control and seeing how your blood sugar control is correlated to the way that you feel. So I think this is very important, but also being the CEO of a personalized nutrition company, you know, there's no one size fits all that what works for you may not be what works for other people. Absolutely. And I don't want all the potato farmers across the world, like chasing after me and saying I'm all anti-potato. So let's just say, I agree. I think nothing should be off the table. And the last thing I'd leave you with, though, which is really interesting, is I went to Peru once a long time ago. And this is where the potato comes from.

And what's really interesting is when you go to Peru, there are like 50 different varieties of potato. They're mainly really small. They're really colorful. We're now eating this incredibly managed food that's been optimized to create this enormous potato that's all starch and no fiber and really easy to grow and all the rest of it. And so sort of wildly different from the sort of big variety of plants that we had. would be if I was eating those Peruvian potatoes, that I would see a very different set of responses than I do with the white potato that I would buy from my grocery store. I am wholeheartedly on board with that. And also the fact that you mentioned the colors of the potatoes, which those colors actually imply that there's specific phytochemicals, many times polyphenols that are beneficial to our health. So for you, it may be a blood sugar focus, but for some people it's about improving their digestive health, improving their

gut health. Part of the proposition here from my perspective is that when you heat and cool the potato, you are producing a resistant starch, which is really beneficial to your gut microbes and yet very easy to tolerate for people that have digestive health problems. And so this is an opportunity to start to add some heating and cool potatoes into your diet to get those resistant starch benefits without having to suffer through digestive problems. Before we fall off the important topic of the nightshade vegetables, we also had a lot of questions from listeners saying, is it true that nightshades can lead to autoimmune disease? Is there any truth to that? There's really no credible evidence that would implicate nightshade vegetables and autoimmune

diseases, to be honest with you, Jonathan. If anything, if we take a step back and look at the bigger picture here, we see a lower incidence of autoimmune disease in people who are consuming a nightshade-heavy Mediterranean diet, you think about these tomatoes and these peppers and the eggplant, and it's like, we're describing a Mediterranean diet. And yet the Mediterranean diet is widely accepted as a healthful diet, has research to suggest lower likelihood of developing autoimmune disease. And that's because the polyphenols and the fiber and the phytochemicals that all support our microbiome, that balance our immune system, and in essence are the opposite of inflammatory. So Will, what's the verdict then? Should we be wary of the nightshade? I think we should be wary of the green potato. I don't think that we should

be consuming berries on the side of the street in Washington, D.C. that we're not getting from our market. But these nightshades, specifically the tomatoes, the peppers, the eggplant or aubergine, these foods, when consumed as part of a balanced, healthful, diverse diet, are anti-inflammatory, beneficial to our gut microbiome. What we're missing here is that we should be adding more of these foods and crowding out the things like fried foods, unhealthy fats, sugary beverages. We need more of these types of foods and less of these other ones. If after the show, you'd like to try Zoe's personalized nutrition program to learn how to eat for your body and improve your health, you can get 10% off by going to joinzoe.com slash podcast. I'm Jonathan Wolfe.

And I'm Dr. Will B. Join us next week for another Zoe podcast.