The moment a theoretical model is transformed into a universal normative reference, problems emerge. As in the case of the “Planetary Diet.”

The recent article published by Competere on the “Planetary Diet” provides a useful opportunity to revisit a topic that has become increasingly central to public debate on food and nutrition over the last few years: the gradual transformation of nutrition from a complex and pluralistic scientific field into a domain of global normative design. What is particularly interesting is that many of the reflections now reiterated in the commentary by Emily and Erik Meijaard had already been anticipated, with remarkable foresight, in Pietro Paganini‘s 2023 book “iFood: How to Escape Food Ideology?“. In an era in which news cycles and interpretations age at extraordinary speed, and where many media narratives last only a few months, some of the insights contained in that volume appear surprisingly robust and, in several respects, confirmed by the subsequent evolution of the global debate.

The central issue is not, as it is often superficially portrayed, a conflict between sustainability and individual freedom, or between public health and markets. The real question is far deeper and concerns how food systems are currently conceptualised. The Planetary Diet, developed by the EAT–Lancet Commission, was born from an objective that is, to a large extent, widely shared: reducing the environmental impact of the global food system while improving human health outcomes. However, when a theoretical model is transformed into a universal normative reference, problems inevitably emerge that are not merely nutritional or environmental, but also epistemological, economic, cultural, and political.

Medieval controversies over universals

To understand the nature of this difficulty, it may be useful to revisit, perhaps unexpectedly, one of the great philosophical controversies of the Middle Ages: the debate over universals. In the realist tradition rooted in Plato and Augustine, represented also by Anselm of Canterbury, universals possessed genuine reality. They were not arbitrary labels but expressed real structures of being that could be known through reason. This position was challenged by Roscelin of Compiègne, one of the earliest medieval nominalists, to whom the famous phrase universalia sunt flatus vocis is traditionally attributed: universals are not independent realities but merely names used to group concrete individuals. Peter Abelard sought a middle ground, arguing that universals were neither independent entities nor meaningless sounds, but mental concepts grounded in observable similarities among individuals. Finally, William of Ockham brought nominalism to its most rigorous formulation, maintaining that only concrete individuals truly exist, while universals are logical and linguistic tools developed by the intellect to organise knowledge about the world.

Viewed from today’s perspective, this ancient debate appears remarkably relevant to the field of nutrition. The modern notion of a “Universal” or “Planetary” Diet effectively reintroduces the problem of universals in contemporary form: a theoretical model built upon statistical averages, environmental objectives, and nutritional criteria that risks being transformed into a global normative prescription despite the profound biological, ecological, cultural, and economic diversity of human societies. In this sense, the problem with universal dietary models does not necessarily lie in their stated objectives, but rather in the epistemological risk of treating a theoretical abstraction as though it were equivalent to the concrete complexity of real food systems.

The problem with contemporary universalist diets

The point is not to deny the existence of environmental or health-related problems associated with contemporary food systems. Doing so would be difficult to defend seriously. The problem lies instead in the implicit belief that enormously complex food systems can be reduced to a single, optimal, centrally designed framework, applicable with minor quantitative adjustments to the entire global population. This reduction of complexity is precisely what Paganini identified with particular clarity when he spoke of the “iPhone-ization of nutrition”: the progressive standardisation of food according to global industrial logics designed to be easily communicated, easily scaled, and easily governed.

The metaphor is especially effective because it concerns not only food products themselves but also the underlying cultural model. For millennia, human food systems developed as territorially embedded biological patterns shaped through the co-evolution of environments, plant and animal species, energy availability, agricultural practices, culinary cultures, and social organisation. Contemporary universalist diets, by contrast, tend to transform food into an abstract combination of nutrients, calories, emissions, and health indicators, potentially detached from the historical and territorial contexts in which food acquires meaning.

In this respect, Competere’s critique is interesting not because it is “against” the Planetary Diet, but because it highlights the practical difficulties involved in translating such a model into functioning systems. The examples cited in the commentary are significant. A theoretically optimised diet may require a level of cognitive calculation incompatible with everyday consumer life; it may overlook differences in economic accessibility across social contexts; and it may generate unintended environmental consequences when implemented globally.

The case of vegetable oils and meats

The case of vegetable oils, also discussed by Paganini, is emblematic of a broader challenge affecting the entire universal-diet approach. Palm oil is frequently portrayed as a symbol of ecological harm. Yet, from an agronomic perspective, it yields exceptionally high per-hectare, meaning that its complete replacement with lower-yielding crops could substantially increase global land use and pressure on ecosystems. The same reasoning can be extended to meat and, more broadly, to animal-source foods, which are progressively marginalised in many universal dietary frameworks. Here too, reducing the food system to a few linear variables, direct emissions, resource use, or aggregate metrics, risks overlooking the biological, nutritional, agronomic, and socioeconomic complexity of livestock production, as well as its capacity to convert biomass inedible to humans and utilise marginal lands unsuitable for efficient crop production. This is a classic example of what happens when complex systems are approached with simplified, abstractly optimised models.

At this point, a fundamental issue often neglected in public debate becomes apparent: food systems are not merely technical optimisation problems. They are historical assemblages in which biology, ecology, economics, culture, symbols, traditions, technologies, and social relationships interact. For this very reason, universalist solutions inevitably come into tension with the real diversity of human societies. As H. L. Mencken famously observed, “For every complex problem there is an answer that is clear, simple, and wrong.” This is precisely the risk that emerges when highly articulated food systems are reduced to universal models built upon a handful of aggregated variables and transformed into globally applicable normative prescriptions.

Towards a form of food-based social engineering

Another aspect also deserves attention. The contemporary appeal of universalist diets does not depend solely on their claimed, though not necessarily demonstrated, scientific robustness. It also stems from their extraordinary compatibility with today’s media environment. Simple, morally legible, and globally standardised messages are far easier to communicate than the actual complexity of human nutrition. In this process, nutrition risks are gradually being transformed from an experimental and probabilistic discipline into a form of food-related social engineering, in which narrative simplification becomes an integral part of public policy design.

Naturally, no one argues that food systems should remain unchanged. Diets evolve continuously, as they always have throughout human history. Nor would it make sense to deny the need to address problems such as obesity, malnutrition, or environmental sustainability. However, recognising the necessity of change does not automatically entail accepting the idea that a single optimal diet exists for all human contexts.

Perhaps this is the most interesting insight that emerges from Paganini’s book in light of current debates. The challenge posed by universalist dietary models is not merely nutritional or environmental. Still, fundamentally epistemological: it lies in the risk of confusing an abstract representation of the food system with the food system itself. And real food systems, like all great historical human constructions, are far less linear, far less predictable, and far more complex than any global model can realistically encompass.