What's the 'true cost' of all the different kinds of milks? Researchers tried to find out

MARK BRODIE: If you’ve spent any time in the milk section of a grocery store lately, you know there are a lot of options. And they go beyond the traditional skim, 1%, 2% or whole milk choices — to include containers of oat, almond, soy, pea and coconut milk, to name a few.

Each of those kinds of milk has their dedicated fans. And each has its own price. But that price goes beyond what’s on the shelf at the market.

New research aims to find the "true cost" of different kinds of milk, including its impact on health, the environment and the labor it takes to produce it.

Kathleen Merrigan is the executive director of the Swette Center for Sustainable Food Systems at [Arizona State University] and a professor in the School of Sustainability. She worked on the study, and when she came by the studio recently to talk more about it, I asked what first got her interested in looking into what she's calling the true costs of different types of milk.

KATHLEEN MERRIGAN: Well, I've been involved in food and ag policy throughout my career. And I've worked really closely with dairy, so I'm always interested in what's going on. And we've seen declines in milk consumption in this country. I also have young adults in my family — my children. And I have seen very passionate talk at the dinner table, at the breakfast table, the lunch table, about what the right choice is.

My daughter is a firm supporter of oat milk and my son, dairy milk. So, that just got my curiosity going. At the same time, we're seeing an international movement on true cost accounting, which is a new methodology to try to understand what food really costs. And so those two things coalesced. Interest from my children and this true cost accounting methodology.

BRODIE: Well, and please correct me if I'm wrong, but it sounds like basically what you found is that, you know, you have to sort of look at what's important to you to determine if, you know, a particular type of milk is more or less expensive than what you think it ought to be.

If the environmental factors are more important to you, then that might lead you in a particular way. If the actual cost that you're paying at the grocery store is what's most important to you, that might lead you in a totally different way.

MERRIGAN: Absolutely. And the true cost is not being used to rank like, this is the top choice and your second, third, fourth. It's to create a transparency for consumers and policymakers alike. The Swette Center, where I work, we're very focused on policymaking, and we want to make sure that policymakers have the best information when they're writing the next farm bill, when they're doing annual appropriations. When they're designing our programs at the U.S. Department of Agriculture.

So it's not necessarily down to the individual consumer for our work, though there are things that individual consumers can derive from this study.

BRODIE: Did anything about what you found surprise you?

MERRIGAN: [LAUGHS] No, not exactly. But I will say that the response to this study has surprised me.

BRODIE: How so?

MERRIGAN: People have very strong feelings. ASU put something out on the Instagram account. And almost immediately we had 2,000 engagements, which is pretty high. It reminded me back when the New York Times ran a piece of: nutrition experts, what are the nutrition myths they hope would die? And I was asked to be one of those nutrition experts.

Now I'm more of a policy person, but I've been involved in nutrition science and policy for enough years. I guess I get to put that hat on. And my choice of a myth was that plant-based milks are better for you. This ran in the New York Times — actually run this story a few different times over the course of a couple years. And immediately there were like 800 almost hate mails, you know, in the comment section of the New York Times about my posting on that.

BRODIE: That's a lot.

MERRIGAN: It's a lot. I think because milk is really important in the American diet.

BRODIE: And has been for a while.

MERRIGAN: Always. And especially for young families. You know, people are really hoping to get the best, healthiest food for their children, particularly at a young age. And so, for example, in the organic industry, for many people, the first organic product they ever buy as a consumer is milk. So we know that there is that tie there.

And milk is very emotional. I heard a story on KJZZ recently about the controversy about skim versus 2% versus whole milk. And I know people are really engaging in that. And that's part of the discussions with the upcoming new version of the dietary guidelines for Americans. So it's almost a third-rail issue, perhaps. I don't know.

BRODIE: It's interesting because I think if — the idea of like: What is good for you? I feel like most nutritionists would tell you there's no overarching answer to that question. I mean, obviously some things are not great for most people, like lots of candy, lots of sugary soda, things like that.

But when it comes to milk, I would imagine for some people their body needs more calcium or their body needs more particular vitamins, or maybe their body needs more protein. And that's the way that they should go. And it's not everybody needs 1% milk, or everybody needs oat milk, or everybody needs dairy milk.

It kind of depends on who you are and your body, right?

MERRIGAN: Absolutely. So we're getting into this era of what some people describe as prescription medicine. You don't need exactly what I need, and it depends on age and hereditary factors and the like. We know, for example, from our study, if you're really focused on protein, dairy milk is going to be the best choice.

If you're really focused on sodium, oat milk is going to be the poorest choice. So you can go into the study, and Dr. [Mauricio R.] Bellon did a great job in all these tables and analyses and modeling. If people want to go into the details, they'll find it.

But you can sort of figure out, what's best for me.

BRODIE: Do you find that the different factors that lead to costs are interrelated with each other? Like, for example, do the environmental costs affect maybe the cost that we pay at the grocery store? And ... does maybe the amount of, you know, the labor factors, does that impact the environmental factors, which maybe also impacts the cost? Are these interrelated or are they separate sort of discrete factors here?

MERRIGAN: Yes, they're interrelated, but I don't think our study goes to that depth. That's the next frontier, I suppose.

BRODIE: I'm curious, since this research has come out, how have the conversations at your kitchen table changed — if they have — between your two kids?

MERRIGAN: I was just with my daughter the last few days, and she bought — on my credit card, by the way — a half-gallon of oat milk. So I'm not sure this study has had huge impact on my children. I don't know if it will have an impact on consumers A, B and C.

But I do hope that the study contributes to more nuanced conversations about dietary choices, and particularly around milk and alternative beverages. And secondly, that the study contributes to this evolving methodology that we're calling true cost accounting.