The science behind how food, nutrition, and health interact is highly complex. This complexity drives scientific debate but also makes it difficult to translate evidence into simple, actionable guidance for policymakers and consumers. Navigating this intricate landscape, international organizations and national governments work closely with scientists to define what healthy and sustainable diets should look like. The 2025 report by the EAT‑Lancet Commission is a recent example of a broad, global scientific assessment.
However, many people today trust wellness influencers more than science-based recommendations, widening the gap between evidence and public belief. This fuels lively discussions but also uncertainty and frustration.
The ongoing discussion around ultra‑processed foods (UPFs) in particular is a clear example of this disconnect, with science, media, policy and public perception often moving in different directions as evidence continues to evolve.
Diets evolved within globalized food systems
At a recent event on Planetary Health and Healthy Diets at the Istituto Svizzero in Rome, co-organised by the World Food Systems Center, we explored the bigger picture:
- What’s the purpose of our food system?
- Who shapes it?
- How can we work together to make healthier diets easier for everyone?
A clear message emerged: the debate is not about blaming people or demonising foods, but about understanding how our diets evolve and how they can be improved.
For thousands of years, humans have fermented, dried, milled and cooked food to stay safe and reduce waste. In the last decades, processed foods, frozen meals, and canned ingredients were symbols of progress, comfort and convenience. Modern lifestyles and industrial marketing made them feel essential. Processing remains essential for safety, affordability, and functioning global food supply chains. Today, they remain the reality for millions in a globalized world where highly processed options are cheap, available everywhere, and heavily advertised. As a result, fresh fruits and vegetables are increasingly less accessible than processed options. Still, processed foods should not dominate our diet.
The concern is not processing, but ultra‑processing, where food is transformed so much that its structure and function change in ways that may have health implications that are still not fully understood. The NOVA classification helps describe this by grouping foods according to the degree of processing and defining UPFs as industrial formulations with multiple processing steps and additives such as emulsifiers and sweeteners.
Science on healthy diets is complex
Tools like NOVA can help consumers or regulators to identify broad patterns, but they are not the ideal foundation for scientific debate. Research shows a clear trend: people who eat many UPFs face higher risks of various diseases. Yet UPFs differ widely. Sugary drinks, processed meats, and additive‑rich products show consistent negative effects. Meanwhile, nutrient‑rich UPFs like tofu, fortified plant‑based milks, or whole‑grain breads can still offer important nutrients or affordable calories (Chen Z. et al., 2023; Cordova R. et al., 2023; Touvier, M., 2026).
The scientific question is not whether some UPFs can harm health, but why, and how. Many researchers are, for example, examining whether the risks come from ultra‑processing itself or from the typical composition of some UPFs: high sugar, salt, and unhealthy fats and low beneficial nutrients. The microbiome adds another layer of complexity. This vast, constantly shifting community of microbes affects metabolism, nutritional uptake, and health impact. Science is only beginning to understand how it responds to different food items, their degree of processing, structures, additives and contaminants.
Because of these uncertainties, it is difficult to determine precisely how UPFs influence metabolism, long‑term health and the future role of personalized diets. They also show why nutrition science matters: clearer guidance depends on a deeper understanding of how the human body works. This requires more research, not less.
Who should we trust?
Despite the complex links between nutrition, processing and health, some principles are simple. No single meal determines health but consistent patterns do. Regularly eating vegetables, fruits, whole grains and pulses, with processed foods kept occasional, remains one of the strongest and most consistent findings in nutrition science. Reports such as the one on the Planetary Health Diet offer clear, evidence‑based guidance while still allowing flexibility for culture, taste and access.
Yet how these messages are received depends strongly on cultural context. Food science research and practice helps develop evidence‑based guidance, but this guidance only works if people trust it. Personalities often overshadow facts, and myths can spread faster than evidence. Wellness content on social media frequently circulates long before scientific research is communicated or understood.
Scientific communication is a delicate balance. If scientists emphasise too much complexity, they risk losing the audience; if they simplify too much or call for transformative or drastic individual behavioural change, they risk being accused of activism. In this environment, good science communication requires storytelling, transparency, and a good understanding of the larger context to support better choices for policy makers and consumers alike.
Who is responsible?
We all should help move diets in a healthier direction. Simple guidance can help: a colourful plate filled with fruits, vegetables and whole foods provides diverse phytonutrients is a practical starting point for eating in ways that support both human and planetary health.
Research on UPFs and their links to health outcomes must continue, but this should not delay action to restore, protect and promote diets based on whole foods. Scientists and research institutions must communicate clearly and honestly. Policy makers must use evidence to shape policies and regulations supporting healthier food environments. Industry and retailers must contribute by reformulating products and offering healthier options at fair prices. And citizens need to understand that science evolves; not because experts are confused, but because evidence deepens over time.
Closing the gap between evidence and public belief will depend not only on better science, but on building trust in how that science is shared, understood, and applied.
