#211 - AMA #36: Fruits & vegetables—everything you need to know

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Welcome to Ask Me Anything episode number 36. I'm once again joined by Nick Stenson.

In today's episode we talk about all things fruits and vegetables.

We compiled some of. You may recall a list of questions around this subject that came through the.

Website, through social media, and directly through the users.

And we've tried to organize this podcast around the themes of those questions because we literally received thousands of questions. Conversation basically goes as follows. We look at the idea of fruits and vegetables being uniform, which of course they're not. So we talk about how they're similar and how they're different in terms of.

Many features of their nutritional value.

We think about specifically the fiber, sugar and other nutrient content of fruits and vegetables as ways to assess their relative value. We comment on the difference between eating them or drinking them, and how processing fruits and vegetables can change their properties. Talk about naFLD and type 2 diabetes and ask the question of whether or not those specific diseases require a different nutrition strategy when it comes to fruits and vegetables. We then get into some of the science around the good and the bad of phytochemicals, which we get asked a lot about. Talk about organic versus non organic handling of food and if different preparation strategies can affect the nutrient value of fruits and vegetables. We round out the discussion by talking about supplementing fruits and vegetables through things like multivitamins or green powder. So if you're not a subscriber, you'll only be able to listen to a sneak peek version of this episode, but.

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One last thing to note is that based on the timing of when we recorded this, we weren't able to do it via video. So this will be an audio only episode, although the show notes will be very helpful because that includes a number of charts and graphics that we use in the episode. So without further delay, I hope you enjoy AMA number 30 36.

Peter, welcome to another ama. How you doing?

I'm doing well. We just spent the last 15 minutes talking about why season four of drive to Survive was not good, so I wish we could continue on that discussion, but I don't think anybody wants to hear us talk about Formula one anymore.

Yeah, it will be interesting to see. I mean, on the positive front, we picked a topic for today that you're second most excited about in terms of right after Formula one, which is nutrition, and in particular, fruits and vegetables. So I'm sure the excitement we had in our little Intro on Formula 1 will be carried over to this one. What do you think?

I think it's hilarious that most people listening to this don't appreciate the sarcasm in your comment that might be true.

This one's not via video, so they can't see you smirking and smiling over there, so they might think we're being dead serious.

This is polar opposite discussion. All things Formula one, all things fruits and vegetables. I think just to completely show my hands to the audience, this is not a topic I'm particularly interested in diving into, but this is as close to taking one for the team as I've ever done in my life. The only reason we are having this discussion is because of you. You, meaning not you, Nick. You. The listeners, the subscribers have asked so many questions on this topic that I simply can't avoid this any longer. If we're going to be true to our principles of trying to answer questions people have, we have to do this. I spent a little bit of time in therapy trying to understand why I don't want to talk about this. And that's only slightly an exaggeration, I think. Here's what it comes down to. I think everybody kind of has this narrative that fruits and vegetables are like, quote, unquote, good. Fruits and vegetables are good. Everybody should eat their fruits and vegetables. Have your five to six servings a day. It's all really good. Good, good, good, good. Okay. But the reality is we don't really know that much. It's true on average. And certainly all of the epidemiology would suggest that that is correct. People who eat more fruits and vegetables are healthier than people who don't. And as you'll see as we get into this discussion, I think there's plenty of evidence to suggest that that's the case. But if you really get into the details of this stuff, I think there's far less that's known than is represented as true. And I actually think that's a broader concept that applies to nutrition in general, which also speaks to why, of all the chapters I'm struggling with in trying to wrap up in my book, the nutrition chapter is the one that is Hands down, posing the greatest difficulty. And it's not because I don't have anything to say. It's because there's less to say definitively than I would have said 10 years ago or five years ago. And beyond a couple of really obvious things. Too much food is bad. Too little food is bad, too little protein is bad. Certain micronutrients are essential. Certain things are toxic. The obvious things like avoid E. Coli in your food. It starts to go from really clear, absolute knowledge to probable knowledge very quickly, quicker than it does with sleep, with exercise, and even with pharmaceuticals. And yet it's the one area where I think people speak about things in more absolute terms than they do in anything else outside of maybe their religion and their politics.

Why do you think that is? I mean, I know you've spent a lot of time thinking about this and looking at it, and my immediate thought goes to the podcast we did with David Allison. And David talked about how if you worked on a pancreas and you're at a dinner party, it's hard to talk about that because unless someone else works on the pancreas, they're not going to know the details. But with nutrition, it's. Everyone eats every day. It's in their face every day. You know what works for you? First question would be, why do you think that is? The second question is, is it because people are trying to speak in absolutes? Because what works for them might genuinely work for them, but it's not guaranteed to be widespread across a variety of people?

I think what you said, if David came up with that example, I don't remember that. About the pancreas, that's really funny. But I think there's an absolute truth to that, which is we all have expertise in nutrition, albeit not necessarily scientific, not necessarily broadly applicable, not necessarily nuanced, but there's no one on this planet who doesn't have expertise of some sort with this thing, because we all do it every single day. Not everybody exercises every day. Most of us aren't conscious when we sleep, but we're conscious and we make deliberate choices when we eat every single day. And so, yeah, I think we generally have a sense of, this works for me. This doesn't work for me. I think there's also a very significant cultural and social component to this thing as well. So I think that's where the tribalism comes from around nutrition. I think on the flip side, it's very difficult to acquire reliable knowledge in this space, and I think there are some really good scientists working on the mechanistic side of nutrition. There's people who are really under very tightly controlled conditions elucidating some of the most interesting knowledge with respect to energy balance, with respect to appetite, with respect to fuel partitioning, food reward, all of these things. I think these things are very interesting. The problem is they're nearly impossible to do this type of work in large sample sizes over long durations. And you need large sample sizes and long durations to infer hard outcomes that we care about, which are prevalence of disease or incidence of disease and ultimately mortality. And so therefore, to get insights on those topics, you have to rely almost without exception on epidemiology. That's not entirely true. There are some reasonably well done, large clinical trials, but they require thousands of people and many, many years. And that means your interventions had better be very, very, very simple if you're going to achieve compliance over that period of time. So all of this is to say nutrition is very hard. And when we rely on epidemiology, we're struggling to necessarily get it right in areas where the hazard ratios end up being quite small. I won't get into all of that now because we've talked about that so much, but when you get hazard ratios like 1.19, it's very difficult to know that you've captured and removed all of the biases that fed into that.

The work that the people you were talking about, what they're doing. Do you think in the short term we'll be able to have more concrete answers? Or is this one thing where you think just given all the limitations, it might be a long time before we have a lot of concrete, really solid insight on this.

There's certain people I like to have on the podcast, and at least at the time of this recording, I haven't had them on yet, although I think we will. I mean, Kevin Hall, I think, is really doing some super interesting work. And I know Kevin well. Right. I've known Kevin for over 10 years and I've worked very closely with him in a previous project. And I think Kevin is, I think, one of the most thoughtful people on the subject of energy balance. And I think that's the type of work that can be studied over shorter periods of time. I mean, those are areas where you can get answers to questions in months. You don't need years to get answers, you can get them in months. Now, maybe you'll get different answers in years, but you're getting pretty interesting answers in months. And you don't need thousands of people. You can actually do These in tens of people, provided you're using very precise instrumentation. People like Kevin Rudy Leibel, Eric Ravison. I have somewhat of a bias because I've worked with them and I know them, and I think they're good thinkers. They're able to answer those types of questions, but they can't answer the questions that we're about to talk about today. They can't answer the questions that are still vexing me, like, are omega 6 polyunsaturated fats inherently healthy or harmful? This is a very vexing question. And I'm sitting here trying to write about it in a book, and I don't know what to say because I've seen pretty compelling evidence. For example, looking at the unpublished, initially unpublished data from the Minnesota coronary experiment that completed in 1973, didn't get published in its first rendition until 1989, and then wasn't reexamined and republished until, I don't know, something like 2013. If you look at those data, you can make a very compelling case that omega 6 polyunsaturated fats, as substituted for saturated fats, could actually be viewed as harmful. But then you look at a whole bunch of other data and you think, no, any harm associated with those fats is purely due to the confounders of what they track with the seed oils that show up in low quality foods and junk foods. It's not the seed oil that's the problem, it's the junk food that's the problem. So that's just another example of, I think, questions that have profound importance. I'm not really clear at this point if I have a sense of what the answers are.

I mean, we could skip answering these questions and just do a what Grinds My Gears episode with Peter Attia for the next hour if that would be more entertaining for people on that train of thought. Just to give people a background, what we did is we receive a lot of questions on nutrition, fruits and vegetables. So we compiled them. And then a few months ago, it feels like you went to Twitter and Instagram and also said, hey, we're thinking about doing a podcast on this. What questions do you have? And there was just hundreds and hundreds and hundreds of questions that came through which kind of made us realize, okay, there's interest here and we should probably try and work through these. So what we're going to do is we're going to go through these questions, but do you want to set the tone a little bit? Which is one, we're not going to give clear Cut guidelines on what people should and shouldn't eat. It is variable depending on your metabolic health diet what you're already eating. But the hope is the information we give you here, you'll be able to apply it to your life to help you understand this subject better and ultimately have better nutrition, whatever that means for you.

Yeah, I think there's another point that I would add to that, which is, and this is true of nutrition in general, don't confuse the optimal diet for you in a state of health versus the optimal diet for you in a state of sickness that's trying to restore your health. They aren't necessarily the same thing. So I'll use just one example because it's germane to our topic. When we work with patients who are metabolically healthy, I've never once restricted the amount of fruit they consume. When I work with a patient who has type 2 diabetes and non alcoholic fatty liver disease, I will actually restrict how much fruit they consume. Now, I'm not going to say they shouldn't have any fruit, but if that's a person who's eating four bananas a day and watermelons and apples and pears and peaches, I am going to say actually, we're going to have a better chance improving your metabolic health if we at least temporarily reduce the volume of that significantly reduce the burden of fructose on your liver. Because fructose and ethanol are, at least to my reading of the literature, pretty uniquely poised to make a sick liver sicker. So again, does that mean that that person's going to always be restricting fruit? No, not necessarily. Does that mean it's the only way to do it?

No.

You could probably just completely restrict other calories and not restrict fruit as much and you might achieve the same benefits. But empirically it seems easier in those people to reduce fructose intake and to do so through fruits. There's multiple different ways to think about this, but I think it is important for people to not extrapolate from the hill that they're sitting on to the hill that anyone else is sitting on. How I eat today to preserve my health is probably different from not probably. It's unquestionably different from how I was eating 15 years ago when I was in the process of trying to improve my health from a place that was actually below where it is today. Keep all of that in mind.

Yeah, I think that's really good. And just for everyone listening, do you mind just giving that quick definition of metabolic health again, just so everyone is on the same page of what that is and what you mean by that?

Yeah, I mean, I think there's a lot of different ways you can define it. It's sort of like BMI can be used to define overweight and obesity and that's the way we do it. It's not really great. I think body composition would be a better way to do it. Similarly, I think the quickest and easiest and dirtiest way to define metabolic health is probably to use the criteria for metabolic syndrome. So metabolic syndrome is basically defined in a somewhat binary fashion, which is you have three or more of the five criteria or you don't. Those five criteria are truncal obesity, high blood pressure, high fasting glucose, high fasting triglycerides and low HDL cholesterol. And we'll list in the show notes exactly what the criteria are. They differ slightly between men and women. We don't look at that in our patients truthfully, because we're not trying to make assessments at a population based level. So we're looking at many more factors beyond those things. Looking at oral glucose tolerance tests, looking at uric acid levels, homocysteine levels, looking at the entire lipid profile and then looking at functional testing. So looking at how the mitochondria perform in a zone 2 test. So how much lactate is a person producing at rest, and then how much lactate do they produce under increasing amounts of workload? And all of those things then factor into our assessment of metabolic health.

That sounds good and it kind of fits well into the first question that we were going to tackle here, which is someone reached out and said fruits seem to exist on a spectrum. Many are high in sugar and are calorically dense. Could you help break down the glycemic content of common fruits and how this matters in determining best choices for different diet staples? I know this could vary person to person in terms of determining the quote unquote best choice, but I think just even breaking down how to think about the sugar content, the various nutrients in fruits, how would you do that with a patient?

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