The study was led by Dr Helda Tutunchi of Tabriz University of Medical Sciences in Iran, together with colleagues, and takes the form of a systematic review and meta-analysis, the highest tier of evidence synthesis in medical research. Rather than relying on any single trial, the team systematically combined and re-analysed the results of all available randomised controlled trials testing wholegrain intake against cardiovascular risk factors. The trials included in the analysis were conducted across Asia, Europe, the United States, Canada, Australia and Brazil, giving the findings a broad geographic and dietary-cultural span that strengthens their generalisability.

The motivation for the work, Dr Tutunchi explained, stems from a long-standing tension in the nutrition literature. Population studies, known as observational research, have consistently linked higher wholegrain intake with better heart health, but individual clinical trials have produced mixed findings, leaving clinicians and guideline writers without a clear target. “Although higher wholegrain intake has long been linked to better heart health in population studies, clinical trials have produced mixed findings,” she said. “This left an important practical question unanswered: how much whole grain should people eat to meaningfully improve cardiovascular health?” By pooling every eligible randomised trial, the researchers aimed to resolve that uncertainty with numbers rather than impressions.

The results were striking in their breadth. Eating more wholegrain food reduced participants’ body weight and waist circumference, lowered both systolic and diastolic blood pressure, and improved blood lipid profiles, including reductions in total cholesterol, low-density lipoprotein cholesterol, often called LDL or “bad” cholesterol, and triglycerides. The analysis also documented reductions in fasting glucose and in interleukin-6, an inflammatory signalling molecule that is increasingly recognised as a contributor to atherosclerosis, the process underlying heart attacks and strokes. Importantly, the researchers graded the quality of the underlying evidence and found high-certainty support for improvements in body weight, waist circumference, total cholesterol and interleukin-6, with moderate-certainty evidence for benefits to LDL cholesterol, triglycerides, systolic blood pressure, fasting plasma glucose and insulin resistance as measured by the HOMA-IR index.

Perhaps the most actionable finding concerns dose. Benefits began to appear at intakes of around 30 to 40 grams of wholegrain per day, measured as dry weight, but the greatest improvements were seen at 60 to 100 grams per day, which corresponds to roughly four to six daily servings. The researchers illustrate what that looks like in practice: a bowl of oatmeal at breakfast, a sandwich made with wholegrain bread at lunch, and a serving of brown rice at dinner would together place a person squarely within the optimal range. This dose-response analysis is what distinguishes the new work from previous reviews, which typically asked whether wholegrains help without quantifying how much is needed.

Dr Tutunchi described the analysis as the largest and most comprehensive of its kind, but she was careful to spell out its limitations. Most of the included trials were relatively short, averaging about eight weeks in duration, which means the researchers cannot determine whether the observed benefits are maintained over years rather than weeks. In addition, relatively few studies evaluated very high intakes above 140 grams per day, leaving the effects at those levels uncertain. Crucially, none of the included trials assessed cardiovascular events such as heart attacks or strokes directly; they measured risk factors instead. Longer-term studies tracking actual disease outcomes will be needed to confirm that the improvements in risk markers translate into fewer cardiovascular events.

Despite those caveats, the researchers argue that the findings carry a clear practical message. “Increasing wholegrain intake is a relatively simple, accessible and affordable dietary strategy that can complement other lifestyle and medical interventions,” Dr Tutunchi said. She noted that the optimal intake of 60 to 100 grams per day sits toward the upper end of current dietary recommendations, so the results do not necessarily call for major changes to existing guidelines. Instead, they support public health strategies that help people move toward the higher end of current targets, encouraging swaps from refined grains to minimally processed wholegrain staples rather than dramatic dietary overhauls.

One of the study’s most conceptually important insights is that wholegrains appear to benefit cardiovascular health through several modest improvements acting together, rather than through one large effect on a single risk factor. The researchers observed parallel improvements across multiple physiological pathways, including blood lipids, blood pressure, glucose regulation, body fat and inflammatory markers. Although the change in any individual risk factor was generally modest, improving several risk factors simultaneously could compound into a substantially greater reduction in long-term cardiovascular risk. This multi-pathway model helps explain why single-marker trials may have appeared inconsistent: each trial may have captured only a fragment of the overall effect.

An accompanying editorial by Dr Cecilie Kyrø of the Danish Cancer Institute in Copenhagen and colleagues places the findings in a broader historical and scientific context. More than half a century ago, the surgeon Sir Denis Burkitt and colleagues proposed that the refining of staple carbohydrates, which strips out cereal fibre as whole grains are converted to refined grains, underpinned a broad spectrum of so-called Western diseases through effects on stool bulk, intestinal transit time and the colonic environment. Whole grains, by definition, retain all three main parts of the cereal kernel, the bran, germ and endosperm, in the same proportions as in the intact grain, whether consumed as whole kernels, flakes, or milled into flour for bread and other foods. The editorial authors highlight that the dose-response analyses provide quantitative evidence to inform food-based dietary guidelines, and note that evidence from research into other disease endpoints suggests the benefits of wholegrain foods extend substantially beyond cardiometabolic disease.

The editorial also frames the findings as a challenge for clinicians and policymakers alike. For clinicians, the message is described as reassuringly simple: encouraging patients to replace refined grain foods with minimally processed whole grains is likely to yield modest but meaningful improvements in body weight, waist circumference and blood lipids, perhaps particularly in individuals with type 2 diabetes. At the population level, even small shifts in these markers can translate into substantial reductions in cardiometabolic events. The current United States dietary guidelines recommend two to four servings of whole grains per day, and the trial evidence indicates that higher intakes than presently recommended in some guidelines may be optimal for cardiometabolic health. From a policy perspective, the editorial authors argue, the real challenge is to make minimally processed wholegrain staples accessible, affordable and culturally acceptable, while avoiding a drift toward ultra-processed products that merely add whole grains to otherwise highly processed formulations. In other words, the source of the grain matters as much as the quantity, and the public health opportunity lies in returning whole grains to the centre of the plate in their least processed form.

Subject of Research: The effect of wholegrain consumption on cardiovascular disease risk factors

Article Title: Four to six servings of wholegrain per day lowers risk factors for heart disease

Article References: Four to six servings of wholegrain per day lowers risk factors for heart disease. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: wholegrain, cardiovascular disease, meta-analysis, diet, cholesterol, blood pressure, European Heart Journal, nutrition, randomised controlled trials, inflammation, dietary guidelines, LDL cholesterol

The Lancet series, spearheaded by Carlos Monteiro and colleagues, advanced the hypothesis that ultra-processed foods are displacing long-established dietary patterns, degrading diet quality and driving up rates of obesity, type 2 diabetes, cardiovascular disease and other chronic conditions. The authors judged that the evidence fulfilled seven of the nine Bradford Hill criteria, the classical framework used to infer causation from observational data, and called for policies promoting dietary patterns based on whole foods. Crucially, they urged that the need for further evidence should not delay public health action. Ibsen and his co-authors, including Michael Fridén, Georgia D. Tomova, Natalia Ortega and Peter W.G. Tennant, counter that these are strong claims which underestimate the importance of grounding policy in established evidence that transparently acknowledges uncertainty. Their argument is not a defence of industrial food production but a methodological critique with real stakes for how governments regulate diets.

The core of the critique concerns the Nova classification system, the four-category framework that places foods in group 4, the ultra-processed category, described by Monteiro and colleagues as branded, commercial formulations made from cheap ingredients extracted or derived from whole foods and combined with additives. The BMC Medicine authors accept that this describes a commercially coherent cluster of products, but insist it is not biochemically coherent. The category sweeps together foods with long-established evidence of harm, such as processed meat, sugar-sweetened beverages and sugary foods, alongside items with far weaker evidence of harm, including many dairy products and breads. It also conflates well-characterised nutritional problems, such as excess fat, salt, sugar and calorie intake, with speculative and poorly understood concerns about food texture, industrial processing and additives. In causal inference terms, ultra-processed food is a multidimensional exposure, and the authors argue it is arguably fundamentally unsuitable for causal enquiry in its current form.

This heterogeneity has practical consequences that ripple through the research literature. Because studies of ultra-processed foods typically compare broad intake categories, they produce averaged, context-specific results that may dilute the large effects of genuinely harmful foods while simultaneously incriminating foods or food features that are neutral or even beneficial. A statistical association observed for the category as a whole may be driven almost entirely by its worst members, yet the resulting headline implicates everything from fizzy drinks to wholegrain industrial bread. The authors warn that this makes it extremely difficult to judge how past research translates into policy in different food environments, particularly where certain foods and features, such as salt content or sugary drinks, are already subject to dietary guidelines and legislation. In other words, the bluntness of the exposure measure risks misdirecting interventions that could otherwise be sharply targeted.

The second pillar of the critique concerns mechanism. Monteiro and colleagues argued that firm mechanistic knowledge is not necessary for immediate public health action, invoking historical examples where beneficial interventions preceded complete biological understanding. The response does not reject that logic outright, but points out an awkward fact: many of the mechanisms proposed to explain the harms of ultra-processed foods are not unique to ultra-processing. High energy density, one of the leading proposed pathways to weight gain and chronic disease, is found in homemade chocolate cakes just as much as in factory-made ones. Soft food texture, another candidate mechanism that may accelerate eating speed and increase energy intake, characterises fruit smoothies and homemade bread as well as industrial products. Evidence from randomised trials suggests that texture, rather than ultra-processing itself, could be a key driver of higher energy intake, and a controlled feeding study in which ultra-processed and non-ultra-processed meals were matched for hyper-palatability, energy density and texture found no difference in ad libitum energy intake among US adolescents eating from a buffet.

Recent randomised evidence adds further nuance. In a crossover trial comparing two diets that both adhered to UK dietary guidelines, one based mostly on minimally processed foods and one mostly on ultra-processed foods, both groups lost weight over eight weeks, with the minimally processed group achieving a modestly greater loss of 0.96 kilograms. That result suggests processing level is not the dominant determinant of outcome when overall diet quality is held constant. The authors also challenge a hypothesis advanced by Monteiro and colleagues in response to earlier criticisms: that while a Nova 4 food is not automatically worse than any food in a lower category, the ultra-processed version of a particular food will always be worse than its less processed equivalent. The response notes this hypothesis is currently unsupported by evidence, because relatively few studies compare individual ultra-processed foods with direct non-ultra-processed equivalents, and not all of those that do find the ultra-processed option worse. Comparisons of plant-based meat with unprocessed red meat, plant-based milk with cow’s milk, and artificially sweetened beverages with water have observed no short-term differences in health outcomes.

Underlying all of this, the authors identify a deeper structural problem with the evidence base: most studies compare Nova 4 foods with Nova 1 minimally processed foods, a contrast that bundles processing effects together with profound differences in nutrient composition, energy density, cost and social context. If ultra-processing and industrial additives are truly independent causes of adverse health, the authors argue, that effect should be detectable in comparisons between Nova 4 and similar Nova 3 processed foods, which differ more narrowly in degree of processing. Such research would also be far more directly useful for population health, offering straightforward paths to reformulation and dietary guidance rather than asking populations to reverse the deep social and economic changes that have reshaped food environments. Expecting people to substitute shop-bought food with home-cooked meals from minimally processed ingredients, the authors suggest, is unrealistic for those whose livelihoods do not support it, and any isolated policy premised on that assumption is unlikely to succeed.

The way forward, they propose, is disaggregation. Future research should move away from treating ultra-processed foods as a monolithic category and instead examine specific subtypes and features, such as texture, energy density and particular additives. Monteiro and colleagues have explicitly argued against subtype analyses, citing methodological challenges including confounding and measurement bias, but the response contends these challenges are not solved by studying monolithic variables. Indeed, the opposite may be true. Eliminating confounding between groups with very different exposure profiles, such as the highest versus lowest quartile of ultra-processed food intake, is far harder than between more modest contrasts, such as processed versus unprocessed red meat. Moreover, creating a summary variable from a series of mismeasured components can exacerbate measurement error when the errors are correlated, as is typical in dietary data, meaning the composite Nova variable may be less reliable than its parts.

The authors are careful to draw a clear line between critique and complacency. They state that the consumption of soft, hyper-palatable, energy-dense foods high in fat, sugar and salt is almost certain to be harmful, that many such foods are ultra-processed, and that for many people reducing ultra-processed food intake will probably be beneficial by cutting exposure to exactly those products. What remains unclear, they emphasise, is whether ultra-processing confers additional, unique harms beyond these well-established properties. They also invoke research on science communication showing that acknowledging uncertainty protects rather than undermines public trust, and that unwarranted certainty is what most generates scepticism. Given nutrition science’s history of confident but mistaken causal claims, from antioxidant supplements onward, they argue that candour about the limits of the ultra-processed food evidence is a scientific necessity, not a rhetorical weakness.

The policy implications are concrete. Rather than a generic targeting of ultra-processed foods, the authors point to taxes on sugar-sweetened beverages, salt reformulation targets and front-of-pack labelling schemes as examples of acting on specific, well-characterised exposures that have meaningfully improved population health without requiring resolution of the contested question of whether processing itself is harmful. These approaches, they argue, offer clearer and more actionable paths than asking consumers to navigate the uncertain boundaries of the Nova classification on their own. The debate is unlikely to be settled quickly, but its resolution will shape dietary guidelines, food regulation and labelling policy worldwide, determining whether the next generation of nutrition policy is built on the broad brush of processing categories or on the sharper, slower work of disentangling which specific foods and features actually drive disease.

Subject of Research: Causal inference limitations of ultra-processed food research and implications for public health nutrition policy

Article Title: Public health policy should be grounded in established evidence that acknowledges uncertainty: a response to The Lancet series on ultra-processed foods

Article References: Ibsen, D. B., Fridén, M., Tomova, G. D., Ortega, N., & Tennant, P. W. (2026). Public health policy should be grounded in established evidence that acknowledges uncertainty: a response to The Lancet series on ultra-processed foods. BMC Medicine, 24(1), Article 522. https://doi.org/10.1186/s12916-026-05214-y

Image Credits: AI Generated

DOI: 10.1186/s12916-026-05214-y

Keywords: ultra-processed foods, Nova classification, nutrition epidemiology, causal inference, public health policy, dietary guidelines, food processing, energy density, food texture, The Lancet, BMC Medicine, diet-related chronic disease

The study, known as the EffectS of non-nutritive sWeetened beverages on appetITe during aCtive weigHt loss (SWITCH) trial, represents the longest and most comprehensive randomised controlled trial on non-nutritive sweetened soft drinks to date. Led by Professor Jo Harrold, Dean of Psychology at the University of Liverpool, and Professor Jason Halford, Professor of Biological Psychology & Health Behaviours at the University of Leeds, the research team followed 493 adults with overweight or obesity over a period of 104 weeks. This extended duration is critical, as previous studies often lacked the longitudinal depth necessary to assess long-term metabolic effects. The trial was funded by the American Beverage Association, but the research team maintained full independence, retaining complete control over data analysis and reporting to ensure scientific integrity.

Participants in the trial were randomised to consume either water or commercially available diet beverages daily. The diet beverages contained specific non-nutritive sweeteners, including aspartame, acesulfame potassium, and sucralose, all provided at levels well within the established safety thresholds set by the European Food Safety Authority. The primary objective was to determine whether these sweetened beverages would disrupt appetite regulation or cause long-term metabolic harm compared to water. The structured behavioural weight management programme ensured that both groups received identical dietary and lifestyle interventions, isolating the beverage variable as the sole point of differentiation. This rigorous design allows for a direct comparison of the physiological impacts of non-nutritive sweeteners versus plain water in a real-world weight loss context.

The results of the 104-week trial revealed that there was no clinically meaningful difference in weight loss between the two groups. Participants consuming non-nutritive sweetened beverages lost an average of 4.8 kilograms, while those drinking water lost 3.7 kilograms, a difference that was not statistically significant. More importantly, both groups demonstrated sustained weight reduction over the two-year period, even during the final year of the trial when participants were no longer receiving direct behavioural assistance. This finding is particularly significant because it indicates that the benefits of weight loss are not merely temporary or dependent on continuous external support. The data suggest that replacing sugar-sweetened drinks with non-nutritive sweetened beverages or water can lead to durable improvements in body weight without the metabolic penalties previously feared.

Beyond overall body weight, the study examined a range of secondary outcomes, including waist and hip circumference, body composition, and various metabolic biomarkers. Both groups experienced decreases in waist and hip circumference and improvements in body composition, indicating a reduction in visceral fat. Metabolic biomarkers, such as blood pressure and cholesterol levels, showed no clinically meaningful differences between the non-nutritive sweetened beverage group and the water group. This lack of adverse metabolic effects is a crucial finding, as it directly addresses concerns that artificial sweeteners might negatively impact cardiovascular health or glucose metabolism. The consistency of these positive outcomes across multiple physiological parameters reinforces the conclusion that non-nutritive sweetened beverages are a safe and effective component of a weight management strategy.

One of the most notable findings from the trial was the impact on sugar intake. Both groups experienced a decrease in overall sugar consumption, but the reduction was slightly greater in the non-nutritive sweetened beverage group. This suggests that using diet drinks as a substitute for regular sodas can effectively reduce the total caloric and sugar load in a person’s diet. The trial’s findings directly address recent World Health Organization guidance, which had advised against using non-sugar sweeteners for weight control due to uncertainty in observational studies. By providing long-duration, randomised controlled evidence, the SWITCH trial offers a robust counterpoint to these earlier recommendations, highlighting the limitations of observational data and the importance of controlled clinical trials in informing public health policy.

Professor Joanne Harrold emphasized the significance of these findings in the context of public health research. She noted that the University of Liverpool is a leading research-intensive institution with a strong focus on public health, and these results demonstrate that concerns about sweeteners disrupting appetite or causing weight gain are not supported when tested in a rigorous, long-term randomised trial. The study builds upon previously published evidence from the International Journal of Obesity in 2023, which showed similar short-term results. By extending the follow-up period to 104 weeks, the current study provides the long-term clinical evidence that has been missing from international discussions. This continuity of research underscores the importance of longitudinal studies in resolving scientific controversies and guiding evidence-based dietary recommendations.

Professor Jason Halford concluded that the study provides the long-term clinical evidence that has been missing from international discussions. For people trying to manage their weight, non-nutritive sweetened beverages offer an effective alternative to sugar-sweetened drinks and perform equivalently to water over two years. This conclusion is supported by the comprehensive data collected during the trial, which included detailed assessments of appetite, metabolic health, and body composition. The findings suggest that the fear of artificial sweeteners may be unfounded, and that these beverages can be a valuable tool in the fight against obesity and related metabolic diseases. The study’s implications extend beyond individual health, potentially influencing global dietary guidelines and public health policies aimed at reducing sugar consumption.

The SWITCH trial’s findings have significant implications for the food and beverage industry, as well as for regulatory bodies and health organizations. The data support the safety and efficacy of non-nutritive sweeteners, which could lead to a re-evaluation of current guidelines and a greater acceptance of diet drinks as a healthy alternative. The study also highlights the importance of rigorous clinical trials in resolving scientific debates and informing public health decisions. As the global burden of obesity continues to rise, the need for effective and safe weight management strategies is more urgent than ever. The SWITCH trial provides a strong evidence base for the use of non-nutritive sweetened beverages in this context, offering hope for a healthier future for millions of people around the world.

In conclusion, the SWITCH trial represents a significant advancement in our understanding of the effects of non-nutritive sweetened beverages on weight management and metabolic health. The long-term, randomised controlled design of the study provides robust evidence that these beverages are equivalent to water in supporting weight loss and long-term weight maintenance. The findings challenge previous concerns and offer a new perspective on the role of artificial sweeteners in a healthy diet. As the scientific community continues to explore the complex relationship between diet and health, the SWITCH trial serves as a model for rigorous research and evidence-based decision-making. The results of this study may inform future research and policy, contributing to a better understanding of how we can combat obesity and promote public health in the 21st century.

Subject of Research: Long-term clinical effects of non-nutritive sweetened beverages on weight management

Article Title: Major trial examines no-sugar sweetened soft drinks

Article References: Major trial examines no-sugar sweetened soft drinks. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: non-nutritive sweeteners, weight management, randomised controlled trial, metabolic health, aspartame, sucralose, acesulfame potassium, appetite regulation, public health, dietary guidelines, Major, trial

The authors of the response, led by researchers affiliated with the Center for Epidemiological Studies in Health and Nutrition at the University of São Paulo, include Carlos A. Monteiro, the epidemiologist who first proposed the Nova classification in the late 2000s. Their critics contend that ultra-processed foods, or UPFs, lump together harmful and benign products in a way that makes causal inference and policy unreliable. The São Paulo team counters that this criticism rests on a fundamental misunderstanding of what Nova measures and how the epidemiological evidence has been generated.

Nova, they explain, does not classify foods by nutrient composition, biochemical coherence, or expected biological effects. Instead, it sorts foods into four groups according to the extent and purpose of industrial processing: fresh and minimally processed foods, processed culinary ingredients, processed foods, and ultra-processed foods. The standard exposure metric used in most prospective studies is the dietary share of UPFs, meaning the proportion of total energy intake derived from Group 4 products. This metric, the authors argue, captures the health effects of the ultra-processed dietary pattern as a whole, reflecting the real-world displacement of the first three Nova groups, which form the basis of traditional healthy diets, by industrially formulated products.

The response draws an analogy with the Mediterranean diet to defuse the charge of heterogeneity. Foods within the Mediterranean pattern differ widely in nutrient profiles, texture, palatability, and potential health effects when considered in isolation, yet they are routinely grouped as a single dietary exposure in epidemiological studies and dietary guidelines. Variability within a category, the authors insist, does not invalidate the category. The same logic applies to ultra-processed foods: heterogeneity within the pattern does not undermine its relevance as a dietary exposure or as a target for policy.

Central to the São Paulo group’s argument is the claim that harmful attributes co-occur systematically in ultra-processed foods as a consequence of the manufacturing processes and ingredients needed to achieve their commercial purpose. These attributes include disrupted food matrices and excessive energy density that accelerate eating and increase energy intake; engineered hyper-palatable formulations that override satiety signals; additives such as emulsifiers and non-sugar sweeteners that have been linked to gut and metabolic dysfunction; and toxic industrial contaminants, including chemicals that leach from plastic packaging. Nutrient imbalances, they argue, are largely a downstream consequence of the expansion of this dietary pattern rather than its defining feature, which is why a nutrient-by-nutrient approach is insufficient to explain or reverse the global rise of diet-related chronic disease.

The authors also reject the criticism that the mechanisms linking ultra-processed foods to health outcomes are too non-specific to be meaningful. Mechanisms linking dietary patterns to health outcomes, they note, do not need to be specific: the beneficial effects of the Mediterranean diet are not discounted simply because fibre, unsaturated fats, and antioxidant compounds also appear in other dietary patterns. What matters is that harmful attributes are more prevalent and more systematically combined in ultra-processed diets than in traditional diets based on Nova Groups 1 through 3. Beyond driving nutrient imbalances and energy-dense eating, ultra-processed food intake is inversely associated with health-protective compounds such as flavonoids and phytoestrogens, and directly associated with processing-generated toxic compounds and potentially harmful additives. Soft textures, reduced chewing frequency, and faster eating rates further facilitate excess energy intake, and some researchers have argued that many ultra-processed products meet established criteria for addictive substances.

Crucially, the response points to experimental evidence that directly tests whether the health effects of ultra-processed diets can be explained away by poor nutrient profiles. Dozens of prospective studies have found associations with chronic disease even after adjusting for fibre, sodium, sugar, and saturated fat. Randomised crossover trials have shown that ultra-processed diets lead to higher energy intake and weight gain even when meals are matched for key nutrients. A recent UK trial found that non-ultra-processed diets adhering to national dietary guidelines produced better cardiometabolic outcomes than ultra-processed diets modified to meet the same criteria, a result the authors say reinforces the conclusion that reformulation does not neutralise harm.

On the charge that epidemiological studies rely on unrealistic comparisons and are confounded by other dietary components, the authors argue that the criticism inverts the logic of nutritional epidemiology. Dietary pattern analyses are not designed to isolate the effects of specific foods or nutrients; they estimate the health effects of real-world diets with high versus low ultra-processed food intake, implicitly capturing the displacement of unprocessed and minimally processed foods. Paradoxically, they contend, analyses of specific ultra-processed subgroups are more vulnerable to confounding, because they attempt to compare individual products against their non-ultra-processed counterparts within complex diets. Measurement error, meanwhile, is mitigated by validated protocols and trained raters, and its non-differential nature tends to underestimate true associations rather than fabricate false ones.

The authors concede a nuance on comparators: in countries such as the United Kingdom and the United States, where traditional diets based on Nova Groups 1 through 3 are no longer the default, comparisons between ready-to-consume processed and ultra-processed products may be relevant, and a more incremental policy approach starting with feasible targets may be warranted. But they stress that the Lancet Series was not designed for these settings alone. In most countries, cooked meals still predominate, and the evidence on the health effects of displacing traditional diets with ultra-processed products is particularly relevant. Early comprehensive policies targeting all ultra-processed foods, they argue, could help other nations avoid the dietary crises observed in the UK and US.

The policy implications are stark. The authors acknowledge that nutrient-focused interventions, such as trans-fat bans, sodium front-of-package warnings, and taxes on sugar-sweetened drinks, are valuable but insufficient, because they operate within the existing corporate food system and encourage reformulation without addressing the underlying production model. Removing trans fat does not eliminate other industrial contaminants; reducing salt does nothing to address energy density, soft texture, and engineered hyper-palatability; and cutting sugar often means increasing amounts of harmful additives. Several countries have already incorporated Nova into their dietary guidelines and implemented policies targeting ultra-processed foods, actions the authors say are justified by more than one hundred prospective studies, randomised trials, and mechanistic investigations. Scientific uncertainty, they conclude, should always be acknowledged, but it should not be conflated with complexity, nor should heterogeneity within a meaningful category justify inaction. In their view, the case for treating ultra-processed foods as a systemic driver of the pandemic of diet-related chronic disease is robust, and policy responses should reflect that reality.

Subject of Research: Scientific debate over the Nova classification of ultra-processed foods and the evidence linking them to human health outcomes

Article Title: Response to: Debate in relation to “Ultra‑processed foods and human health: the main thesis and the evidence”

Article References: Rezende, L. F. M., da Costa Louzada, M. L., Martinez-Steele, E., Cannon, G., Levy, R. B., Jaime, P. C., & Monteiro, C. A. (2026). Response to: Debate in relation to “Ultra‑processed foods and human health: the main thesis and the evidence”. BMC Medicine, 24(1), Article 525. https://doi.org/10.1186/s12916-026-05217-9

Image Credits: AI Generated

DOI: 10.1186/s12916-026-05217-9

Keywords: ultra-processed foods, Nova classification, dietary patterns, nutritional epidemiology, public health policy, chronic disease, food industry, randomised trials, food additives, Mediterranean diet, BMC Medicine, dietary guidelines

The study, led by Erhan Tang and colleagues including senior authors Yaqi Li and Xiang Gao, is a technical exercise in connecting three large and very different datasets. The researchers started with the National Health and Nutrition Examination Survey, or NHANES, the ongoing federal program that collects detailed 24-hour dietary recall data from a representative sample of the US population. They then linked those dietary records to the Food Patterns Equivalents Database, which translates the foods people report eating into standardized food group amounts, and to the Food Commodity Intake Database, which converts those foods into the raw agricultural commodities from which they are made. Finally, each commodity was assigned a greenhouse gas emission factor drawn from the Database of Food Impacts on the Environment for Linking to Diets, a life-cycle assessment resource developed at the University of Michigan. This chain of linkage allowed the team to estimate the emissions embedded in any hypothetical diet, including the dietary patterns prescribed by successive editions of the Dietary Guidelines for Americans.

Life-cycle assessment, the methodological backbone of the study, deserves a moment of explanation because it is what makes such comparisons possible. Rather than counting only the emissions from, say, a tractor burning diesel in a wheat field, life-cycle assessment tallies greenhouse gases across the entire production chain: fertilizer manufacture and application, fuel for machinery, enteric fermentation from cattle, manure management, feed production, processing, packaging and transport. Each kilogram of a given commodity acquires a carbon intensity value expressed in kilograms of CO2 equivalents, a unit that folds methane and nitrous oxide, both far more potent warming agents than carbon dioxide, into a single comparable figure. Because beef and other ruminant products involve both methane-belching animals and resource-intensive feed crops, their carbon intensities dwarf those of legumes, grains and most vegetables. When a dietary guideline nudges the population toward more protein, the arithmetic of these intensity values determines whether the national food footprint shrinks or balloons.

The headline result, 5.46 kilograms of CO2 equivalents per 2,000 kilocalories for the 2025–2030 guidelines, becomes more meaningful when set against its predecessors. The 32.8 percent jump relative to the 2015–2020 and 2020–2025 editions is not a rounding artifact; it reflects a deliberate shift in nutritional philosophy. The scientific report underpinning the newest guidelines elevated protein recommendations, and protein foods, in the American food supply, are dominated by meat, poultry, eggs and dairy. The researchers’ decomposition of the emissions increase points squarely at this higher recommended protein intake as the primary driver. In other words, a guideline written to protect American hearts and metabolisms would, if followed, quietly expand the climate footprint of the American plate by roughly a third. The finding exposes what the authors describe as a misalignment between health goals and environmental sustainability, a tension that has been building in nutrition policy for years.

Food systems, context matters here, are an enormous climate problem in their own right. A landmark analysis cited by the researchers estimated that food systems are responsible for roughly a third of all anthropogenic greenhouse gas emissions globally. Within that total, the distribution is wildly uneven: animal products account for a disproportionate share of emissions relative to the calories and protein they deliver. This is why dietary change has repeatedly surfaced in climate mitigation literature as one of the few levers that requires no new technology, no infrastructure investment and no waiting period. Systematic reviews, including a widely cited analysis by Aleksandrowicz and colleagues, have consistently found that shifting diets toward less meat and more plants reduces greenhouse gas emissions, land use and water use simultaneously. Against that backdrop, a national guideline that pushes emissions upward by nearly a third runs visibly against the current of the evidence.

The United States is not alone in facing this dilemma, but it is a particularly consequential case. National food-based dietary guidelines around the world have been scrutinized for their environmental content, and a global review published in The Lancet Planetary Health found that most countries still omit sustainability considerations entirely from their official dietary advice. Meanwhile, the EAT-Lancet Commission on healthy, sustainable and just food systems has championed planetary health diets that deliberately cap red meat and emphasize plant proteins, framing dietary guidelines as a rare policy instrument that can serve both human and planetary health at once. Previous American editions of the guidelines have themselves been criticized on this front: a 2015 proposal to include sustainability language in the guidelines was famously stripped out during the political process. The new analysis suggests that the pendulum has now swung in the opposite direction, with the 2025–2030 edition not merely ignoring emissions but actively increasing them relative to its predecessors.

The technical machinery behind the study also matters for reproducibility and future research. The team made their analytical pipeline public, releasing all SAS code through GitHub so that other researchers can audit, replicate or extend the analysis. They also confronted a mundane but genuinely difficult data problem: the most recent NHANES dietary cycle, covering 2019 through March 2020, introduced food codes that did not exist in the older Food Commodity Intake Database. To handle this, the researchers constructed a bridging dataset that maps newly introduced food items onto proxy codes with established commodity profiles, allowing emissions estimates to remain consistent across survey cycles. Supplementary tables document the commodity group classifications and the specific emission factors applied to each. This kind of methodological transparency is increasingly demanded in diet sustainability research, a field where small choices about emission factors and food mapping can swing headline numbers substantially.

It is worth being precise about what the study does and does not claim. The 5.46 kilograms per 2,000 kilocalories figure is a projection of what would happen if Americans adhered fully to the recommended dietary patterns, not a measurement of what they currently eat, and actual American diets diverge from the guidelines in many ways. The estimate also captures greenhouse gas emissions specifically, not other environmental impacts such as biodiversity loss, pesticide runoff or freshwater depletion, which follow somewhat different food-specific patterns. And because the analysis is built on life-cycle emission factors attached to commodities, it inherits the uncertainties of those underlying assessments, which vary by production region and farming system. None of these caveats, however, undermines the central comparative finding, because the same methods and data were applied across all three editions of the guidelines. The 32.8 percent increase is an apples-to-apples comparison of three official dietary blueprints scored on an identical carbon accounting framework.

The broader implication is that the next revision cycle of the Dietary Guidelines for Americans may need to confront sustainability not as an optional add-on but as a core design constraint. The researchers argue that their findings highlight a structural misalignment: a guideline process that optimizes for nutrient adequacy and chronic disease risk can, without anyone intending it, produce dietary patterns that are materially worse for the climate than the ones they replace. Given that the guidelines cascade through institutional food procurement, nutrition education and the Special Supplemental Nutrition Program for Women, Infants, and Children, the emissions consequences scale far beyond individual dinner tables. Whether future editions can reconcile the protein recommendations with lower-carbon protein sources, such as legumes, nuts and whole grains, remains an open policy question. What the new analysis makes unmistakably clear is that the era of treating dietary guidance and climate policy as separate conversations is over, and the numbers now exist to hold both to account.

Subject of Research: Projected greenhouse gas emissions of the US Dietary Guidelines for Americans 2025–2030

Article Title: Latest US dietary guidelines are projected to increase diet-related emissions

Article References: Tang, E., Yu, Z., Li, Y., & Gao, X. (2026). Latest US dietary guidelines are projected to increase diet-related emissions. Nature Food. https://doi.org/10.1038/s43016-026-01433-x

Image Credits: AI Generated

DOI: 10.1038/s43016-026-01433-x

Keywords: dietary guidelines, greenhouse gas emissions, carbon footprint, nutrition policy, life-cycle assessment, NHANES, protein intake, food systems, sustainability, climate, Nature Food, public health