Are vegetables overrated—or underrated? Get the low-down on the health benefits of eating vegetables, learn whether they can prevent nutrient deficiencies, and find out how you should be incorporating them into your diet.
We have a simple question this week, but I’m sure it’s one that a lot of people actually wonder about. We all hear that we should eat a lot of vegetables, but is this one of these assumptions that we just don’t question and it’s actually not true? What does the research actually say about how many servings of vegetables a day we should eat? What are all the relevant issues? There are, of course, lots of relevant issues. We’ll try to cover the main ones in this episode.
Note: The Prescript-Assist supplements discussed in this article are no longer available. Please click here to learn more about a substitute, the Daily Synbiotic from Seed.
In this episode, we cover:
1:34 What Chris ate for breakfast
4:30 3 reasons to eat vegetables
15:02 How many servings of vegetables should you eat daily?
18:23 What types of vegetables to eat
Links We Discuss
- Chris Kresser on One Life Radio
- Environmental Working Group Dirty Dozen and Clean 15
- Eating on the Wild Side: The Missing Link to Optimum Health
Steve Wright: Good morning, good afternoon, and good evening. You are listening to the Revolution Health Radio show. This show is brought to you by ChrisKresser.com. I’m your host, co-author of SCDlifestyle.com, Steve Wright. With me is integrative medical practitioner, healthy skeptic, and New York Times bestselling author, Chris Kresser.
Chris Kresser: Hey, Steve. How’s it going?
Steve Wright: Really good today. How about you?
Chris Kresser: Good. I’m good as well.
Steve Wright: You’ve been doing interviews all morning, right?
Chris Kresser: Yeah, One Life Radio. I think they’re out of Dallas. They’re syndicated in a few other places. We’ve been doing a series of interviews. I love them. They’re great. They’re really interested in all this stuff. So I just finished that. Now we’ve got a really fascinating question I think.
Steve Wright: It’s amazing. Well, before we get to the question, number one, can people find those interviews online anywhere? Number two, I need to know what you had for breakfast.
Chris Kresser: As for number one, I’m not actually sure. That’s a good question. I know they tweet out when I’m going to be on the radio. I’m not sure if they have like an archive or something online. We’ll figure that out, and then we’ll post it on social media if they do.
Steve Wright: Awesome.
What Chris Ate for Breakfast
Chris Kresser: Number two, what I had for breakfast. You know, I’m the breakfast cook around here. That’s one of my main duties. Elanne gets to sleep in a little bit. I cook breakfast, hang out with Sylvie in the mornings. Then usually Elanne walks her to preschool; sometimes I do. Today, I made some sweet potato hash browns. They were cooked in a little bit of bacon grease, which makes them extra yummy.
Steve Wright: Nice. Do you keep the skin on or take the skin off?
Chris Kresser: I usually keep the skin on. I just grate them on a grater. Then we have this flat electric griddle, which is really nice. It cooks at uniform temperature, and allows us to cook quite a lot. Then I put a baking sheet on top, with like a weight on top of it, so that it presses them down. That tends to work better. Also, it steams them a little bit that way, so they cook faster. Then we had just good old-fashioned scrambled eggs, with a little bit of this hot chili sauce that Sylvie actually likes a little bit of nowadays.
Steve Wright: Cool.
Chris Kresser: Then we had some sauerkraut. Sylvie had a little bit of coconut yogurt, with some Prescript-Assist mixed in.
Steve Wright: A little secret.
Chris Kresser: You know, giving her some good probiotic love.
Steve Wright: Awesome, man. That’s great. It sounds delicious. I’ve said this like two years in a row now—or I don’t know how many years we’ve been doing this—but I’m coming to breakfast at your house.
Chris Kresser: We’ll be happy to have you. All right. I like this question because it’s so simple, and yet there’s so much to it. There are so many different directions we could go. Let’s give it a listen.
Adrian: How many servings of vegetables should I be eating daily and what kinds? Thank you.
Chris Kresser: Like I said, it’s a simple question, but I’m sure it’s one that a lot of people actually wonder about. We all hear that we should eat a lot of vegetables, but is this one of these assumptions that we just don’t question and it’s actually not true? What does the research actually say about how many servings of vegetables a day we should eat? What are all the relevant issues? There are, of course, lots of relevant issues. We’ll try to cover the main ones in this episode.
Steve Wright: You mean it’s not going to be simple, Chris?
Chris Kresser: You know, it is kind of simple. I think you should eat vegetables. So if you’re short for time and you don’t want to listen to the rest of it, that’s really the takeaway—eat a lot of vegetables. Eat them throughout the day with each meal, if you can, and I think you’ll be better off. End of story. Let’s talk about them from a few different perspectives.
3 Reasons to Eat Vegetables
The first would be nutrient density, because that’s often what we’re concerned with in terms of what we put into our bodies. I’ve talked a lot in my book and elsewhere—in presentations, conferences—about how animal products, particularly organ meats and even muscle meats, are much more nutrient dense than a lot of people think, and in many cases, more nutrient dense than fruits and vegetables. A while ago, maybe several years ago now, I published a chart on my website that compared the nutrient density of liver, beef—just muscle protein, beef—and then blueberries and kale. In many of the nutrients, you would see that liver was orders of magnitude higher than both blueberries and kale, with some exceptions. It’s important to note though that a lot of these nutrient-density scales, when we talk about these comparisons, they’re focusing on the nutrients that we know are essential for health, so a lot of the vitamins and minerals that we need to function properly. And that’s how it should be, right? I mean, those are the proven nutrients that we know we need and can’t live without. However, it’s also true that there’s a whole other class of nutrients that are important, and that recent research is showing are increasingly important. They may not be essential in the sense that we absolutely can’t live without them, but they are very important and have been shown in numerous studies to reduce the risk of death, reduce oxidative damage and inflammation, and just make our bodies function better. These are the so-called phytonutrients. All of the antioxidants, which actually we know are pro-oxidants that stimulate our own body’s natural antioxidant defense systems …
Steve Wright: Whoa, whoa, whoa. What does phytonutrient mean?
Chris Kresser: Plant nutrient basically.
Steve Wright: Okay.
Chris Kresser: There are a number of these that we see in both fruits and vegetables. I’m going to try and stay focused on vegetables, because that was what the question was. But of course, when we’re talking about phytonutrients, they’re also present in vegetables and starchy tubers and things like that. They may not technically be considered vegetables. So what we know is that fruits and vegetables are very high in these kinds of nutrients, and are the best source of these nutrients. You won’t find these as much in animal products, like organ meats and meats. I think that alone is a compelling reason to eat vegetables, even if organ meats and meats are more concentrated sources of things like vitamin A, for example, or choline. That’s the nutrient density perspective.
Steve Wright: Just to wrap that up, so phytonutrients are plant- and fruit-based compounds that are antioxidants, which are found nowhere else? That’s basically a class of things that aren’t other nutrients that we’ve already established as vitamins or minerals?
Chris Kresser: Exactly. There are things like lycopene in tomatoes. There are things like resveratrol, which are found in grapes and wine. I’m sure a lot of people have heard there are compounds that are found in turmeric and spices, like the curcuminoids, and things like quercetin that are found in some fruits and vegetables. Of course, you see these things popping up in supplements a lot too, because there’s a lot of research behind them and they have potent effects. But what the most recent research shows is the way that they have their antioxidant effect is actually by being pro-oxidants, by stimulating mild oxidative damage, and that upregulates our body’s natural antioxidant defense system. So it’s a hormetic effect, just like exercise has a hormetic effect. And there is more and more research suggesting that this is really, really important, and probably one of the main reasons that we benefit from eating fresh fruits and vegetables. That’s the nutrient density perspective.
Then whenever we talk about food and the value of food, we think a little bit about calorie density. So vegetables are relatively high in water content. They have a relatively high fiber content, which we’re going to talk about in a second. But they’re relatively low in calories, and therefore, they’re pretty satiating. So you can eat a lot of them. You feel filled up. But they’re not super calorie dense, so you’re not going to put on weight. I know a lot of people think calories have nothing to do with weight loss. We’ve talked about that before. I don’t agree with that perspective. I don’t think it’s the only consideration, but it definitely is one consideration. So when you look at the kind of diet that I typically recommend for weight loss, it’s very high in protein and it’s high in foods that are low on the calorie-density scale, like non-starchy vegetables and even some starchy vegetables. Sweet potatoes are relatively low on the calorie-density scale. So these foods make us feel satisfied. They fill us up. They nourish us in a lot of different ways. They’re also not likely to make you gain weight. We know now that excess weight and its complications is the number one cause of death for middle-aged men and women, which is pretty sobering. So many people are overweight these days, it’s easy to kind of dismiss it and not take it seriously. But the research is continuing to show that especially being significantly overweight is a major health concern. There was just a study that came out, that I tweeted, that suggest the metabolically-healthy obese phenotype—which has been discussed before—probably doesn’t exist. If you follow those people for a long enough time, they’re more likely to develop disease than people who are not obese. Okay. That’s the calorie-density perspective.
Then arguably, one of the most important or the most important reason to eat vegetables is the microbiota-accessible carbohydrates it contains. So this phrase is kind of technical. Microbiota-accessible carbohydrates, or you can shorten it as MACs.
Steve Wright: That’s a great marketing term. Everybody is going to use that soon.
Chris Kresser: Well, this is not my term. This came from Justin Sonnenburg out of Stanford. He’s a microbiologist who, together with I believe his partner in work and in life—I forget her name—wrote a book about the microbiome, that I think my agent and publisher’s publishing. So I’m looking forward to reading it. He’s very sharp. He came up with this term. He and his wife, I believe, published a paper about microbiota-accessible carbohydrates. They proposed this as an important definition instead of using the term fermentable fiber, which we often use to talk about the types of carbohydrates that feed beneficial gut bacteria. There are a lot of problems with that terminology. There are a lot of problems with the classification of insoluble and soluble fiber, which has been an old way of talking about it. So they’re proposing this new way of talking about it, which is microbiota-accessible carbohydrates. These are all of the carbohydrates in foods that are accessible to the gut flora, and able to be fermented and converted into energy by those bacteria and other organisms.
We’ve talked about this so much; I’m not going to spend that much time on it. But these carbohydrates are crucial to feeding our beneficial bacteria, which, in turn, play numerous important roles in our physiology and health. You can get these in other ways. You could potentially supplement with these types of fibers and you wouldn’t necessarily have to get them from vegetables. But when you look at things from an evolutionary perspective—which, of course, we do—you’ll find that most of our ancestors ate a lot of plants. I mean, there are definitely exceptions. There are the Maasai who ate primarily milk, blood, and meat from the cattle that they raise, although they weren’t hunter-gatherers; they were pastoralists. Then you have the Inuit who ate a lot of meat or fish, sea mammals. Of course, there’s been some research recently that suggests they actually ate more plants than we thought they did. But there are always outliers. When you look at the average hunter-gatherer society, you actually find that they ate a lot of plants and a huge diversity of plants. For example, the Alyawarra tribe in Africa ate 92 different species of plants.
Steve Wright: Per week? What was the sample size?
Chris Kresser: Just overall, like in their diet.
Steve Wright: Okay.
Chris Kresser: Those are fruits, tubers, and vegetables spread across all three of those categories. But if you compare that to today, 80% of the world’s population today live on four principal plants, which are wheat, rice, corn, and potatoes.
Steve Wright: What about kale? We can’t forget kale.
Chris Kresser: Well, that’s a smaller percentage of the population.
Steve Wright: Okay.
Chris Kresser: It’s a dramatic difference. The diversity in all of the nutrients and antioxidants that are found in these plants, and all the different types of fiber that are found in these plants, makes a huge difference in terms of the effect on the gut microbiota and the effect on overall health. I think that is one of the reasons that hunter-gatherers were relatively protected from disease, compared to people in the modern world. So I think the nutrient-density argument is strong for eating plants or vegetables. The calorie-density argument is strong. Then the microbiota-accessible carbohydrates, feeding, maintaining, nourishing your beneficial gut bacteria is another strong reason. Hopefully, I’ve convinced you that it’s a good idea to eat vegetables.
How Many Servings of Vegetables Should You Eat Daily?
In terms of exactly how many servings, I think a good benchmark is to try to eat some vegetables with every meal. For breakfast, for me, that’s often sauerkraut, but sometimes it could be other kinds of fermented vegetables. I’ll sometimes steam some kale and put a little drizzle of olive oil on it, and have that for breakfast. Or I’ll chop up some kale and put it in with my eggs. You know, Steve, it’s all about the kale.
Steve Wright: It’s all about the kale, man.
Chris Kresser: Or I’ll have some spinach.
Steve Wright: Of course, spinach has just gotten kicked right in the junk.
Chris Kresser: Spinach is good with eggs. I love spinach. I’ll sometimes put spinach in a smoothie if I have one. So there are lots of different ways. Sometimes, like especially this time of year, as we get into the winter, I’ll often have soup for breakfast. It’s a really good way to start the day. I’ll have a bunch of veggies in there. Then for lunch, I’ll have either a salad or other greens or vegetables with lunch, probably also some fermented veggies on the side. Then for dinner, I’ll usually have a large serving of vegetables. Then I’m also eating tubers and starchy plants throughout the day. Like today, I had sweet potatoes for breakfast. Everyone who listens to this show knows that I often have plantains in the morning. Then I’ll have taro or yuca at another time during the day, and good old-fashioned white potatoes as well. So if you just aim for eating vegetables throughout the day with your other meals, I think that’s a perfectly legitimate approach.
Steve Wright: This is just something that floats my mind as part of this conversation. What about the green supplements? The, “I’m not eating enough vegetables, so I can have this powdered thing.” Or, “I’m eating a lot of vegetables, and I’m just trying to up my health.” Where does this fall into this talk?
Chris Kresser: I think those things have value. I mean, ideally, you get all the nutrients that you need from whole real foods. For a lot of people, that’s possible. For some people, that may be difficult for a number of reasons. Number one, where they live. Maybe they don’t have access to good, nutrient-dense vegetables, which we’re going to talk a little bit about some of the factors involved there in a second. Maybe they have impaired absorption and digestion, so eating either raw or even cooked vegetables is hard for them to absorb in that form, and if they put a green power, which is sort of pre-digested in with the smoothie, it’s a little bit easier for them. Maybe they’re dealing with chronic illness and oxidative stress, and they need just extra antioxidant support. I do a lot of testing on my patients who are really sick. We find levels of lipid peroxides and oxidative stress markers that are really off the charts. In those cases, either supplementing with a green powder or actually taking some supplemental antioxidants can really help, even if they’re on a nutrient-dense diet. So once again, it really depends on the person. If you’re just generally healthy overall, I think just eating a healthy, nutrient-dense diet with fresh, raw or cooked fruits or vegetables is fine without any addition. But if you’re dealing with any of the issues that I mentioned just now, then certainly those things can play a role. Let’s talk about some other considerations.
What Types of Vegetables to Eat
Let’s assume I have convinced you that eating vegetables is important. But I want to talk now about what some of the considerations are in terms of eating vegetables, namely, like what types of vegetables in terms of how they’re grown, how they’re harvested, how they’re stored, and all of that. I do think organic is important. No news flash there. I’ve talked a lot about why I think organic is important. I know there have been some high-profile studies suggesting that the nutrient content in organic vegetables is not higher than nonorganic vegetables. I’ve written some articles criticizing those studies, as has Mark Sisson and a number of other people. I think there’s plenty of research to show that organic fruits and vegetables are generally higher in nutrients when you look at a broad diversity of nutrients. They’re also lower in pesticides, which even those studies admitted. You know, we’re still learning about the effect of pesticides. I think this is something where the precautionary principle applies. If there’s a chemical in our food system, there’s evidence that it can be harmful, and we’re still studying it, I think it’s best to avoid that if you can. I know finances are an issue for people in terms of buying organic produce. There is the Environmental Working Group’s Dirty Dozen and Clean 15, which can help you decide, if you have limited resources, where to apply them in terms of the organic produce to get the most bang for your buck. Because there are certain fruits and vegetables that are heavily sprayed, and you definitely want to get those organic if you can. Then there are others where pesticide residues are generally pretty low. If you have to save some money, those would be the ones to buy conventional. But as I’ve often said, the whole organic/nonorganic thing I think is actually one of the least important factors when you consider what kind of fruits and vegetables you should be buying. It is crucial, but there are others that have a bigger impact on the nutrient density and then overall health value of the vegetable and fruit.
One of those is how quickly you consume the plant after it was harvested. Whether it’s local or not essentially is what that comes down to. And we know that today, a lot of produce that’s sold at the large supermarket chains is grown hundreds, if not thousands, of miles away, like in places like California, where I live, or Florida or Mexico. I wrote an article a while back and there was this statistic in there that blew a lot of people away, that the average carrot has traveled 1,700 miles before it gets to your dinner table. The problem with that is that as soon as you take a plant out of the ground, it starts losing its nutrition. Broccoli is an especially notable example of this. It starts losing some of its cancer-fighting compounds within 24 hours after you harvest it. And after just a few days, those compounds are really low. They’ve dropped considerably. So it still will have other vitamins and things like that, but some of these phytonutrients really, really start dropping as soon as you harvest them. Once I read that in Jo Robinson’s book—which I’ll tell you more about in a second—now, when we go to the farmer’s market on Saturday to buy broccoli, Saturday night is broccoli night. We don’t let it sit around in the refrigerator for very long.
Steve Wright: What about the people who can only get access to, say, frozen organic broccoli? The flash freezing that they are claiming about, is that a way to maybe help with this?
Chris Kresser: Yeah. Frozen fruits and vegetables are often a better choice, believe it or not, because in many cases, they’re flash frozen right after they’re harvested, so there’s not as much time for the nutrients to degrade. Also, cooking method makes a difference. But let me finish with the harvest, and then we’ll come back to that. The total vitamin C content of red peppers, tomatoes, apricots, peaches, papayas, they have all been shown to be a lot higher when the crops are picked right from the plant. Spinach—which is one of the best sources of folate, which is a very important nutrient—loses almost 50% of its folate eight days after it’s picked. Again, if you consider a scenario where it’s picked, shipped 1,500 miles—and vegetables are shipped in dark trucks, and then they’re stored in a dark warehouse. Then if they’re in the display on the supermarket, they’re underneath. They’re in the dark. Where there’s dark, there’s no light, photosynthesis, and there’s more nutrient loss that occurs there. So ideally—and I know, again, this isn’t possible for everyone—if you want to maximize the health benefit and nutrient density of your vegetables and fruits, for that matter, you’d buy them locally at a farmer’s market. Or even better than that, you grow them in your backyard. But of course, again, that’s not possible for everybody.
Another question is I guess the heritage of the plant. So how they are grown—whether they are domesticated or wild. This is what Jo Robinson talks a lot about in her book, Eating on the Wild Side. It’s a fantastic book. Her argument, which I think there’s a lot of research to support, is that one of the biggest differences between the diet of our ancestors and our diet today is not just in the basic composition of what they ate, but in the nutrient composition of the foods they ate. Over many, many years, we’ve domesticated a lot of crops. We have a lot of reasons for doing that. Generally, in many cases, we’re trying to make certain fruits and vegetables sweeter, to be more palatable. We change them in ways that made them easier to grow and more resistant to pests, or larger and more appealing visually. A lot of these changes, unfortunately, have had an adverse impact on their nutrient content. For example, the ancestor of the sweet corn that we eat today was 30% protein and 2% sugar, but today’s corn is 4% protein and 10% to 40% sugar. That’s an almost unrecognizably different plant. There’s a species of wild tomato that has 15 times more lycopene, which is the antioxidant compound in supermarket varieties of tomatoes. There are some varieties of native potatoes from the Andes down in South America that have 28 times more phytonutrients than the standard old Russet potato that you buy in the supermarket. So the varieties of foods that we choose are important in terms of nutrient density, and what we can do is try to choose more wild plants that are less domesticated. For example, there’s a wild plant called purslane, which has six times more vitamin E than spinach, seven times more beta carotene than carrots, and 14 times more omega-3 fats than some other dark leafy greens. We can choose wild plants like that. We can eat a lot of spices and herbs, which tend to be still kind of in their more wild state. The nutrient density chart that I published in my book—that was based on data from Mat LaLonde—showed that herbs and spices were number two, second only to organ meats, in terms of their nutrient density. So including a lot of wild herbs and spices in our diet is a good idea.
The third question is how you actually store and prepare the vegetables. Again, Jo Robinson covers this in her book. This is something I learned a lot about. It wasn’t really on my radar screen to that extent until I read her book. Some examples there would be berries. Most forms of berries actually become richer in antioxidants the longer you cook them. So cooking berries and then canning them, or even buying canned blueberries, are more nutritious than fresh blueberries, which is kind of wild to think about. The same is true for tomatoes. The longer you cook tomatoes, the more benefits they provide. Canned tomatoes are actually more nutritious than fresh tomatoes for that reason. If you’re using garlic in a dish, chopping the garlic and then letting it rest for 10 minutes before you put it into the dish dramatically increases the allicin content. And allicin, A-L-L-I-C-I-N, is an active ingredient in garlic. It plays an antimicrobial role. So if you’re sick, you feel like you’re getting sick and you want to use garlic to help you get well, it’s not really a question of whether it’s raw or cooked that’s the most important. It’s if you chop, you’re basically activating that hormetic defense system in the plant and upregulating the plant’s antioxidant defense system. Then all of those compounds are expressed. If you give that 10 minutes to sort of work, and then you eat it, it’s going to have much greater allicin content, like I said. Then there are other examples. We’ve talked about this before in a different context. But if you cook potatoes, just white potatoes, and then you let them chill for 24 hours, you change the plant considerably. You increase the resistant starch content. Resistant starch is a microbiota-accessible carbohydrate and has a lot of benefits. You also lower the glycemic index of the potato. So somebody, for example, who has blood sugar issues, that gets a big blood sugar spike when they eat cooked potatoes, could potentially eat potato salad that’s been cooked and cooled for 24 hours without any issue. They might really benefit from that in terms of their gut flora and their blood sugar, because resistant starch has been shown to reduce blood sugar in a lot of studies. So paradoxically, eating potato salad, which they would probably avoid because of its carbohydrate content, could actually help with their blood sugar.
As you can see, I have a remarkable ability to take a simple question and make it extremely complex. Hopefully, that wasn’t TMI, too much information there. We can summarize by saying eat vegetables and fruits, for that matter, regularly. They have a lot of beneficial nutrients in them that are difficult to find in other foods. Eat locally and organic whenever possible. Eat some wild plants when possible, herbs and spices. Less cultivated plants like dandelion and purslane are good examples. Be conscious of how you’re preparing and storing vegetables. I didn’t actually talk about storage very much, other than the broccoli thing. But Jo has some really good examples of how you can store vegetables to preserve their nutrient content. One example is lettuce. If you bring lettuce home, you pull it apart, you soak it in water, and then you store it in a particular way, it’s going to preserve the nutrient content and lessen the chance that it’s going to break down. Again, I really recommend her book. It’s called Eating on the Wild Side. It’s got some really great information in there that’s not being talked about very much in the Paleo/primal nutrition world, but I think it’s pretty important.
Steve Wright: It sounds like one other thing is don’t just eat kale every day. Like, eat a variety.
Chris Kresser: Yeah.
Steve Wright: There’s phytonutrients in all of these plants, some of which we don’t even yet know about or what they do. But the reality is, don’t get locked into one type of meal. Rotate your stuff.
Chris Kresser: That’s a really good point, Steve. It’s true. For many of our ancestors, they did eat a much greater variety of plant foods than we eat. So it pays to branch out a little bit, try new things, get ideas from cookbooks and things like that. Last week, we talked about the 14Four, which is my new, total mind-body, 14-day reset program that’s now available at 14Four.me. For those of you that are new to this kind of eating, you’re maybe feeling a little overwhelmed with all this information, 14Four is a really great way of quickly jumping in, but getting a lot of support in the process. There’s a two-week transition phase that helps you ease into it and prepare yourself, and kind of ramp up into that 14-day reboot program. This will help you to make the kind of dietary choices that we’re talking about in this show, to start eating more nutrient-dense food, anti-inflammatory food, and food that’s going to make you feel your best, in addition to supercharging your stress management, your sleep, and your daily movement routine. Go over there and check it out. If you feel like you need some support in this area, it’s 14Four.me. We’ll be back next week with another question.
Steve Wright: Continue to please submit your questions at ChrisKresser.com/podcast. Thanks, everybody, for listening. It’s been a great show, Chris. I like going deep on this stuff.
Chris Kresser: Thanks, Steve. We’ll see everyone next week.