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Sustainable Diets for Personal and Planetary Health

Learning Objectives
1. Identify the impact of our population's food systems and dietary choices on climate change
2. Explain the special role of clinicians to scale the benefits of sustainable diet
3. Describe impactful food choices patients and physicians can make to lessen their environmental footprint and improve human health
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About the Gaples Institute
The Gaples Institute is an educational nonprofit that develops high-yield nutrition education, enabling physicians to meaningfully incorporate nutritional interventions for optimal patient (and self) care. Learn more.

  1. Nutrition and Health

Audio Transcript

Jeanette Brooks: Hello, you're listening to Medicine With a Fork, a podcast from the nonprofit Gaples Institute. We are an educational nonprofit that is advancing the role of nutrition and lifestyle in medicine. I'm Jeanette Brooks, the Director of E-Learning Experience at the Gaples Institute and the topic today is probably not something that clinicians are used to talking to their patients about—but it does have a major impact on both human health and the health of our planet. And that topic is sustainable diets. I'm with Dr Stephen Devries. He's the Executive Director of the Gaples Institute. Steve, welcome!

Stephen Devries, MD: Thank you. Great to be with you.

Brooks: Great to have you today. Let's get right into it. We know patient health is closely linked to what the patient eats. Get us started here, Steve—can you speak to how a patient's diet connects to these bigger, broader global challenges of climate change and sustainability?

Devries: We know that poor-quality diets are the number one risk factor responsible for premature deaths. And for climate change, it's interesting to note that food production makes up 30% of the total global greenhouse gas emissions.

Brooks: I can imagine some of the folks listening right now might be like, wait, I'm a doctor, I'm a health sciences person. I'm not a climatologist. What is special about a clinician's role?

Devries: First of all, clinicians have a personal stake in climate change, just like everyone else. But much more than that, physicians have the capacity to make an enormous impact, and it's all by way of their potential to have a scaling effect.

And let me explain what I mean by that. Each physician has an average of, say, a thousand patients in their panel. Now each of those patients eating three meals a day consume about a thousand meals a year. So a thousand patients eating a thousand meals a year. Turns out, each physician has the potential to impact a million meals a year.

Brooks: That's a really insightful lens, to see this with, it's such an enormous reach that a clinician has to influence that many meals. You mentioned we've got this double-edged sword of the health crisis and the climate crisis. So what is it going to take to fix these things?

Devries: Let's look at some specific dietary choices and their impact. Now we know from a health standpoint that replacing beef with plant sources of protein are associated with a whole host of health benefits, from reduced risk of diabetes to lower risk of cardiovascular disease and on.

But what about the impact of making a shift from, say, red meat to a plant-sourced protein? It turns out that the production of just one serving of red meat generates CO2, that is a startling 200 times the CO2 involved in growing a serving of beans. Two hundred times! And a serving of red meat generates 25 times the greenhouse gas emissions of either vegetables as a category or fruit.

Brooks: Wow. That's a remarkable difference. What's the connection between red meat and greenhouse gas?

Devries: It's largely about how cattle digest their food. Although humans can't digest fiber, cattle can, and they do so through a fermentation process that involves bacteria. This fermentation process produces as a by-product methane.

And that methane is literally belched by the cattle, into the atmosphere. Now, methane is an extraordinarily potent greenhouse gas, more than 50 times as potent as CO2. Actually 30 million cattle are slaughtered every year in the U.S. So the methane production associated with all those cattle make a really big difference.

Brooks: Wow. So it's all about the belches then. You mentioned that the process of fermentation is what's triggering all this. Does it matter if the cattle are grass-fed? I know a lot of people tend to think grass-fed beef is a better choice. Is it any better?

Devries: It would be logical to imagine that grass-fed beef has a smaller greenhouse gas footprint than conventional beef, but surprisingly it isn't so. There are likely small nutritional benefits to grass-fed, and some advantages for animal welfare. But since grass-fed cattle grow more slowly than grain-fed, they take longer to come to market.

And actually there's no overall reduction in greenhouse gas emissions from grass-fed cattle compared to conventional.

Brooks: So that longer time to come to market means more months—or years—of producing these belches, right?

Devries: Exactly right. More belching going on.

Brooks: I can imagine a lot of people might not be ready to cut out animal products completely. So are there some animal-based foods that are more climate-friendly than meat?

Devries: Animal products as a whole have a much greater impact on greenhouse gas production than plant-sourced foods, but even among the various animal products there are significant differences in greenhouse gas emissions. Per serving, red meat is certainly the leading source. Dairy has a fair amount, about 25% the greenhouse gas emissions of red meat. And then fish comes in a bit below dairy. For fish, the CO2 burden varies by species and how they're caught.

Here's an interesting fact: a category of seafood with an especially low greenhouse gas footprint is bivalves, like mussels. And mussels are particularly a favorable choice because in addition to having a low greenhouse gas footprint, they also have an especially high content of the cardioprotective omega-3s, EPA and DHA.

Brooks: That's really fascinating about mussels. I'm sure something surprising to many people. I know it was for me. Are there other factors besides greenhouse gases that come into play when we're trying to make more planet-friendly food choices?

Devries: Water utilization is another area that's very relevant to the topic of sustainability, and the category of food to bring up there are nuts.

Nuts have a really broad range of health benefits. And we've talked about that in an earlier podcast. But the downside is that some nuts require a great deal of water to grow. Cashews in particular require the most, almonds somewhat less, walnuts, still less, and peanuts require the least amongst all nuts. So, important to point out that all nuts, including peanuts, do have the important health benefits.

And I would say the recommendation in general is for people to use a portfolio of nuts while they're eating, and not limit their nut consumption to those that require the highest water consumption.

Brooks: Okay. Interesting that peanuts require the least water of those nuts. So it sounds like the biggest takeaway is that it's best for people and the planet if we can steer patients toward more healthy plant-sourced foods and fewer animal products. Is there a way to break this down into some very granular guidance that physicians can give to their patients?

Devries: Yes, there's some very helpful guidance that was made available by the EAT-Lancet commission. And this commission included 37 leading scientists from 16 countries and included a wide range of disciplines, from human health to agriculture to sustainability experts. And the recommendation sought to integrate the best evidence that supports dietary patterns for both personal and planetary health. The commission tried to identify the broadest approach possible that would fulfill these goals—an approach that certainly includes an entirely plant-sourced diet, which we know would be optimal for planetary health and is an excellent choice for personal health as well.

But at the same time, they realized that many people aren't ready to eat a completely vegan diet, or perhaps that is an aspiration for some people, but they might need some time to shift toward that goal. So EAT-Lancet developed a plan that included an upper limit maximum for animal products. And that plan included no more than one serving of dairy per day; a maximum, if red meat is consumed it all, of one small portion per week; along with two servings of chicken per week as a maximum; and two servings of fish per week. Now mind you, again, these are maximums and not recommended amounts, but they do allow a system that would maximize sustainability efforts while still optimizing human health and allowing for some flexibility.

Brooks: Yeah, that's a really important distinction you make: that these are maximums and not targets. I think that there's some wiggle room that the commission gave for patients who aren't ready to give up all animal products.

What do you recommend then Steve, for physicians who are ready to have this conversation with their patients, they want to leverage this unique role that they're in as clinicians. How do they get there? What can they do?

Devries: The most important step you can take is to talk to your patients about the double benefit that good dietary choices can make. It's both a bonus for personal health and the environment, and a great tool that can help you in that effort is a completely free interactive resource that our nonprofit, the Gaples Institute, developed along with Dr Walter Willett, who was the lead author of the EAT-Lancet paper and a professor at the Harvard T.H. Chan School of Public Health. You can get that resource at Plate4PlanetMD.org. It's just 10 minutes of interactive learning, but it packs a lot of actionable steps that physicians can take for themselves, for their patients, and even at their workplace.

Brooks: Awesome. Plate4PlanetMD.org. Steve, thank you so much for giving clinicians some really tangible and impactful tools to help their patients get healthier, and to help preserve the planet in the process. I'm so glad that this is getting the attention it deserves.

Devries: Thank you. It's a really important topic and I hope that all clinicians take this information to heart.

Brooks: Thank you, Steve. And for our listeners, we should also mention the resources that Steve shared at Plate4PlanetMD.org are amazing tools for getting this conversation started with your patients about sustainability, but there's even more that you can take advantage of.

For an even deeper dive into how to leverage nutrition in your clinical practice, the nonprofit Gaples Institute also offers an on demand 4-hour interactive nutrition CME course. AMA members get a discount, and it's a really rapid way to build the knowledge and confidence you need to talk to patients about their diet, even in the midst of a busy clinical setting. There's a wealth of content there.

The course also includes patient-education resources that you can download and duplicate. You can check out that course by going to NutritionForDocs.org. Thanks again, Steve. And thank you everyone for listening in today. We're looking forward to connecting with you again next time on Medicine With a Fork.

Audio Information

© Copyright 2022 - Gaples Institute


Dr Devries is the salaried executive director and Jeanette Brooks is the salaried director of e-learning for the Gaples Institute, an educational nonprofit that offers accredited continuing medical education courses for sale to health professionals. Courses are developed entirely through philanthropy to the Gaples Institute, a nonprofit that does not seek or receive corporate support. Neither Dr Devries nor Jeanette Brooks receive royalties or personal consideration of any kind from the sale of these courses. This podcast was developed with no corporate support.

Willett  W, Rockström  J, Loken  B, Lang  T, Vermeulen  S,  et al.  Food in the Anthropocene: the EAT–Lancet Commission on healthy diets from sustainable food systems.  The Lancet. 2019. 393(10170): 447-92.Google Scholar
Clark  M, Tilman  D.  Comparative analysis of environmental impacts of agricultural production systems, agricultural input efficiency, and food choice.  Environmental Research Letters. 2017;12(6): 064016.Google Scholar
Willett  WC, Hu  FB, Rimm  EB, Stampfer  MJ.  Building better guidelines for healthy and sustainable diets.  The American Journal of Clinical Nutrition. 2021;114(2):401–4.Google Scholar

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