This post summarizes a new preprint from the Humane and Sustainable Food Lab at Stanford titled “Taking a bite out of meat, or just giving fresh veggies the boot? Plant-based meats did not reduce meat purchasing in a randomized controlled menu intervention.”
The paper reports on an online RCT where participants were asked to select taco fillings from one of three menus designed to mimic the options at Chipotle. They could choose from both meat- and plant-based options.
The randomized treatment was whether participants saw
- one plant-based option (veggie & guacamole)
- two (veggie + ‘Sofritas,’ an existing plant-based meat analogue (PMA) that you can get at Chipotle)
- or three (veggie + Sofritas + ‘Chick’nitas,’ a hypothetical chicken-analogue PMA).
The treatment was embedded in a series of decoy questions about choosing pens and t-shirts to obscure the purpose of the study.
The main outcome was whether people chose a meat-based taco filling or not. Our second outcome was whether Chick’nitas reduced demand for chicken specifically among meat-based options. All outcomes were hypothetical, and price was held constant.
4,431 people selected a taco filling.
We powered the study to detect a 5 percentage point (pp.) reduction in meat selection, the smallest effect size which we thought might prompt Chipotle or someplace similar to consider adding a new PMA.
Unfortunately, we didn’t find an effect of that magnitude.
Compared to having just veggies:
- adding Sofritas reduced demand for meat by 1.14 pp. (95% CI [-3.30, 1.02], p = .30).
- adding Sofritas and Chick’nitas reduced demand for meat by 2.14 pp (95% CI [-4.36, 0.08], p = .06).
Adding Chick’nitas modestly but insignificantly decreased demand for chicken, but simultaneously, demand for steak increased. Going from no PMAs to two decreased demand for veggies & guac from 9.2% to 5.7%.
See table below for full breakdown.
No-PMA Arm (n = 1,501) | Status Quo Arm (n = 1,479) | Chick’nitas Arm (n = 1,451) | |
| Chicken | 613 (40.8%) | 580 (39.2%) | 516 (35.6%) |
| Steak | 412 (27.4%) | 411 (27.8%) | 434 (29.9%) |
| Beef Barbacoa | 184 (12.3%) | 185 (12.5%) | 182 (12.5%) |
| Carnitas | 129 (8.6%) | 138 (9.3%) | 139 (9.6%) |
| Veggie | 138 (9.2%) | 98 (6.6%) | 83 (5.7%) |
| Sofritas | n/a | 56 (3.8%) | 40 (2.8%) |
| Chick’nitas | n/a | n/a | 42 (2.9%) |
| Declined to order | 25 (1.66%) | 11 (0.74%) | 15 (1.0%) |
| Meat | 1,338 (89.14%) | 1,314 (88.8%) | 1,271 (87.6%) |
| Non-meat | 138 (9.19%) | 154 (10.4%) | 165 (11.4%) |
Men, Republicans, people without a four-year college degree, and people who ate more than ten or more servings of meat per week were all more likely to select a meat-based taco filling than folks in other categories.
We don’t know if we’d have found bigger effects in stores. Our experiment didn’t include any sensory information, so perhaps the Chick’nitas would have been more appealing in person, but perhaps not.
Key takeaways
Making an additional plant-based option available did not meaningfully change meal selections. This held for both a long-standing PMA option (Sofritas) and a novel one (Chick’nitas). Reducing meat consumption is a hard problem, and achieving price-, taste-, and convenience- parity won’t obviously do the trick either.
Technology will likely play a large role if we are to transition away from factory farming, as it has for past externalities; but we also see an important role for culture and attitudinal change, as well as changing the choice architecture of meal environments and actively promoting plant-based options.
Thanks for sharing the data for the paper. Based on a fairly quick re-analysis, it appears that a decline in selection of chicken can be detected - but as you note, choice of alternative red meats tends to increase slightly, and some of the increase in selecting the new plant-based meat is driven by fewer people selecting the other veg-based options.
A few considerations as a result:
Finally, what are your thoughts on the ecological validity of the experiment? Naturally, people can't see or smell the options, as you note in the paper, but the experiment also takes place in the absence of repeat visits, advertising, and hearsay about how X or Y tastes really good, has to be tried etc. I'm not totally surprised that just adding an option to the end of a virtual menu doesn't greatly shift behavior, but that also seems a slightly reductionistic model of what plant-based advocates might expect would happen in such a situation, which might be more to do with norm shifting, decreasing difficulty enabling people to switch over time etc. I hope that does not come across as overly critical, because I'm also really pleased to see a rigorous attempt to put ideas to the test and challenge assumptions. [edit: I haven't thoroughly read you paper, so apologies if you already discuss this]
Hi James, neat visualizations, and very validating that you were able to extend our work like this! We worked hard to make our materials legible but you don't really know how well that went until someone actually tries to use them 😃 So this is great to see.
The cleaned data set was very nice to have access to and clear - the only thing that wasn't clear to me was whether any exclusions were actually applied on the basis of the attention checks, and what the correct answers to the attention question were, but this may be in your documentation already, I just had a fairly quick look and downloaded the csv and got going.
Thanks for the thorough response -
Thanks for doing and publishing this study! It's so helpful to get a clearer picture on this, even if we don't like the answers. As a validation of your findings, in 2015, Chipotle told Vox that sofritas were 3.5% of sales, very close to your 3.8%.
Interesting! I believe I missed that interview, although a rep told the Times that same year that "sofritas accounts for about 3 percent of fillings."
I recently learned that Steve Ellis (Chipotle founder) tried predominantly plant-based fast casual in 2024; apparently it didn't work out (although I'm still seeing a Yelp page?) and this winter he told Eater that “veganism...is very polarizing, I’ve learned.”
In a separate interview Ellis said “I think people will eat more plant-based diets and make that part of their life if there are better options,” [emphasis added], which I agree with. But I basically think that that no single effort is likely to change the game, in part because the most effective interventions are unusually challenging to scale.
(Also, Chipotle tried out free shipping on plant-based options in 2021, which is an intervention I'd love to formally evaluate! But I'd bet that appetite for that kind of thing is lower nowadays. The whole market is a long way from where it was then.)
I'll share my view on this as a consumer. Almost every time I see a PMA on a menu, I expect to get the following things if I order that option:
- Smaller quantity
- Worse macros (That is, I expect that the PMA will have a higher fat/carb:protein ratio than chicken breast)
- Often, an upcharge to boot
This expectation might be irrational on my part; an aftereffect of being vegetarian in the 1990s before the current generation of PMAs was released. When I was a full-time vegetarian, I frequently observed restaurant meals for vegetarians contained both less calories and less (sometimes almost no) protein. I guess the upshot of the above is that I believe achieving price- and nutrition- parity would strongly influence me.
Finally, I think I tend to do better at making choices that align with my ethics at the supermarket rather than at restaurants.
Hi Chris, a few thoughts about this:
I agree with Chris's point here - I always go for sofritas but it's very frustrating, they literally give you less than what you can see them serving with the meat options.
The protein ratio is also very important. For me - and I am confident for other consumers too - the protein is not fungible with other macros or nutritional content. One is trying to add protein to the meal, not to generically be 'healthy'. I don't think that pointing out the good fiber content, or increasing it, helps at all in this dimension.
Totally, I did not mean to suggest that protein and fiber are fungible. Rather I wonder if plant-based options might do better to play to their strengths, one of which is fiber.
I would also say that I've never noticed if the Sofritas portion is smaller than the equivalent animal-based portion but if that were true on average across Chipotles, it would suggest some interesting follow-ups:
As a side note, it seems that many people I talk to IRL have somewhat extreme beliefs about how much protein they need & don't have a good sense of how much protein is in grains and legumes, but that is a post for another time. (Update: a little research suggests, indeed, some confusions around this topic, but also generally low enthusiasm for PBAs)
Truly shocked by the research above. Another reminder of just how far one drifts from the norm when getting enthusiastic about a particular topic. I really thought (despite personal experience to the contrary) that everyone knows cottage cheese is high protein and peanut butter has some protein, but not great macros (high fat:protein ratio).
I think we've drifted well away from the habits of normal consumers now, but I will add say that there seems to be some agreement that protein intake up to 1.6 grams per kilogram of body weight per day (g/kg/day) tends to maximize resistance exercise-induced gains in muscle mass.
There's probably some room to lower that by looking for a point of decreasing marginal returns, but it seems to me that most weight lifters will target 1.6 + some safety margin that makes them feel good.
My main point here is that among weight lifters who are paying attention to science, there's a very clear answer to how much protein we need (or choose to consume for gains).
I wonder what the optimal protein intake is for trying to increase power to mass ratio, which is the core thing the sports I do (running, climbing, and hiking) ask for. I do not think that gaining mass is the average health/fitness goal, nor obviously the right thing for most people. I'd bet that most Americans would put losing weight and aerobic capacity a fair bit higher.
Sure, I'm not making a strong claim that they consistently actually are giving smaller portions across stores but in my experience they often do. It may also have to do with how sofritas does not heap well on the spoon, relative to mounds of chicken or beef bits. The sofritas tray is also often almost empty, and maybe they don't refill it so much due to not wanting it to end up going to waste - I've had multiple times where they just scrape some last bits out when they should refill it and get a proper spoonful. But apologies if this is turning into a chipotle review thread!
I agree that people have somewhat extreme beliefs about how much protein they need, but it's going to be hard to tip that trend. I think plant-based advocates are also often ignorant though with respect to the optimal amino acid profiles of protein for fitness/muscle building purposes. BCAAs, for example, are often much lower than in animal proteins, even if the protein number is high. When people wade in but don't know these things, it can invalidate their overall point.
[edit: The above relates to spaces in which I think the 'more protein = better' trend evolved from, but protein listed on everything has taken on a bit of a mind of its own. I'd be interested to know actually whether now there is just a generic perception that protein = healthy, in which case other healthiness factors could be somewhat fungible - just not for the sorts of people I was thinking of]
I'd be interested in research, or conducting research even, on people's perceptions of these kinds of things if there were interest in it.
To pile on: a local Mexican chain also consistently puts less of PMAs into their tacos than they do meat.
I'm generally a "hit the 1.6g/kg/day target" kind of guy and have been ignoring BCAAs. The effect of branched-chain amino acids supplementation in physical exercise: A systematic review of human randomized controlled trials - ScienceDirect suggests that's still a valid strategy, but I'm open to learning more.
I can't access to look at the specific studies but unfortunately most exercise science is like nutrition science generally (very hard to control, considerable participant variability) but with even smaller samples/statistical power, and insufficiently long periods to observe effects. They also rarely target vegetarian or vegans, so this combination is even less known about. The 1.6-2g/kg/day target is reasonable and supported, but there is an interesting body of research about BCAAs and in particular mechanistic work on the 'leucine threshold' for stimulating muscle protein synthesis, with suggestions to bump up leucine when taking plant-based proteins for maximal triggering of MPS. I'm not 100% convinced such work is correct, but enough to implement elements of it. Whether it is completely proven or not my concern raised above was that many plant-based advocates might not be aware that there is even something to consider beyond just protein or macros.
Happy to discuss further but cognizant of hijacking the discussion with something not actually related to the interesting report the authors provided!
Interesting, but I'm not sure this captures the main potential benefit of adding plant-based meat options. These options improve the experience of being a vegan - thereby increasing takeup/retention of veganism - rather than being appealing to meat-eaters in the moment. I would be way more likely to be vegan if there were vegan meat alternatives everywhere I went (including meat-heavy experiences like Christmas, BBQs, holidays), as opposed to just salad and lentils. Even when they aren't that tasty, the fake meat makes me feel less "left out".
The fact the fake meat options are displacing the pure vegetable options at all, is a sign that they are improving the experience of being vegan.
Obviously, this study does still tell us something about how appealing/unappealing vegan meat options are to people, and the results have updated me downwards a bit. But not by a huge amount. I very rarely see my meat-eater friends order vegan options (whether vegetables or fake meat); and I very rarely see my vegan friends break their veganism because there was only a vegetable option rather than a fake meat option. So I think I would have predicted broadly similar results.
It is very possible that this will have transformative effects! Two pieces of counter-evidence worth contending with though:
P.S. on the subject of meat-heavy celebrations, I am going to a pig roast tomorrow and expecting to be able to eat nothing, so I'll just bring my own food or eat beforehand...but I'm used to this dance 😃
Thanks that's really helpful. You're right it doesn't seem like increased prevalence of fake meat options is leading to any significant increase in % of vegans. I do find this quite hard to marry with my personal experience - I am way more vegan in my home city (where there are good, widespread vegan options) than when travelling abroad. And I'm fairly sure I would not choose to identify as vegan/veggie at all if I lived in a country where there were far fewer options. But the stats would suggest that veganism is in fact quite inelastic to this. Strange!
Hope your hog roast wasn't too difficult - sending solidarity! I had a jackfruit hog roast alternative once, I appreciated the effort but it wasn't very nice...I'm sure Beyond could have done a better job.
I appreciate y'all studying this and helping us learn more about what we can do to advance plant-based options, and I especially love that it is open access. I do have some questions tho.
(A) "Despite widespread optimism, simply increasing the number of PMAs on restaurant menus may not consistently reduce meat selection." Is this a reasonable expectation of any new food ingredient? Are there studies that show just adding a new ingredient, any ingredient whether plant-based or not, to a menu would result in uptake of it?
It seems to me, and I could be missing something, that this study might be studying the habitual nature of consumers, and less so their preferences about plant-based meat. A possible way to have controlled for this would be to have a new animal meat item and see how many people chose it.
If your general model of consumers, or people generally, is that they are cognitive misers, it seems that model would predict this result regardless if the additional items were plant based or meat based. So the casual factor would be habit, not the kind of protein. That would still be informative for plant-adoption and be a large barrier, but it be saying less about plant-based preferences and more about just needing to do proper UX and marketing.
(B) I saw y'all did awareness checks on what people thought the point of the study was, but curious why y'all didn't do an awareness check on whether they noticed if there was a plant-based option in the menu or not? Like how many people are taking the time to read the small grey on white text? And with steak or chicken, you don't need to because those are familiar and instantly understood. Without that, it is unclear to me, whether you are testing people's preference for plant-based options or their ability to notice new items.
Hi Dorsal, thank you for your kind words about the work and thoughtful questions. I agree with Seth's reply and would add for (A), there is some evidence of this effect for plant-based foods in general, for example: Garnett 2019, Parkin 2021, and Pechey 2022. I don't know of any studies which have tested adding animal-based meats.
Thank you for the studies, will take a look. I would think you could find either adding a new meat-based products and its affects in the marketing literature or something analogous -- though I haven't looked.
something along these lines, though not exactly
thank you! I will give it a read
Hi Dorsal, good questions:
I appreciate the thoughtful reply. My view hasn't changed to much, but I have updated towards more uncertainty.
Regards (2) however, I think the text being subtle is the opposite of "experimental realism" as when businesses introduce a new product they often give it a graphic treatment that highlights it and explain its value to customers.
Also, regarding Lewis' comment, I don't know how much a figure from 2015, a decade ago, when there was far less familiarity and knowledge of PMA can be regarded as converging evidence for your outcome.
Excited to more research in this area! : )