A diet for healthy people: a closer look at sugars, meats, ultra-processed foods, and foods for a healthy planet

Relevance and problem definition: why and when? 
World-leading researchers agree current food systems, covering food production to consumption, threaten human health and environmental stability. We are facing a ‘Global Syndemic’ constructed by three interacting pandemics co-occurring in time and place: obesity, undernutrition, and climate change (1).

The Global Syndemic and food systems
Obesity and undernutrition are forms of malnutrition, defined by the World Health Organization (WHO) as deficiencies, excesses, or imbalances in a person’s intake of energy and/or nutrients, resulting in diet-related noncommunicable diseases (2). Worldwide 1.9 billion adults are overweight or obese, whereas 462 million are underweight (2). About 50% of Dutch adults are overweight and 15% are obese (3). These conditions come with great burdens concerning societal costs and health related quality of life. A 2022 study estimated that the total costs by overweight and obesity (health care costs, patient and family costs, and other costs) among the Dutch population is more than 79 billion euros (4).

Energy and nutrient intake at the root of these issues are affected by food quality, repeatedly shown to relate to non-communicable diseases. For example, consumption of ultra-processed foods has been linked to increased prevalence of overweight, obesity, and cardiometabolic risks like diabetes type 2, opposed to fiber-rich diets with high levels of whole grains, fruits and vegetables, and healthy fats (5). The latter has increased quality through a higher nutrient-to-calorie ratio.

Imbalanced food intake is strongly driven by environments, characterized by physical, economic, political, and sociocultural aspects of micro (e.g., homes, workplaces, food service outlets) and macro (e.g., food marketing, health system, urban/rural development) settings (6). Practically speaking, reduced physical activity, calorie dense foods, and agricultural policies, put individuals at increased risk for developing chronic diseases (7). Recently, the gut microbiota has been identified to influence development of metabolic disorders, affected by diet, stress, and antibiotics (7). Perhaps controversially, it is beyond the power of the individual to control population outcomes concerning lifestyle-induced risk of chronic disease. People live in hostile environments causing metabolic illness beyond their conscious control. Transforming environments therefore promises an effective approach to fight malnutrition diseases, prioritizing prevention over healing.

Besides poor nutrition, the third pandemic contributing to the Global Syndemic is man-made climate change, a continuous topic of concern. Majority of academic literature reaches consensus on the role of humanity at the origin of climate change, with our food system, responsible for 20-30% of greenhouse emissions, as a root cause (8). Since the food system consistently recurs as a crucial factor central to each aspect of the Global Syndemic, critical essence of the food transition should not continue to be underestimated. 

Integrative solutions for interlinked global issues 
The past decade has been subject to development of strategies concerning the described issues. 17 Sustainable Development Goals (SDGs) by the United Nations (UN) aim to achieve a better and more sustainable future by 2030 (9). The Paris Agreement is an international treaty covering climate change mitigation, adaptation, and finance, signed by 196 parties (10). The 2018 National Prevention Agreement by the Dutch health council intends to reduce obesity rates, as well as obesity related diseases like diabetes type 2, cardiovascular disease, and liver disease, improve availability of healthy foods, and reduce smoking and alcohol use (11). Each of these strategies propose food system transformations for reaching their aims. Accordingly, an overarching approach considering the systemic and interrelated aspects of the syndemic is essential for balanced sustainable outcomes. Immediate strategic action is crucial to realize the envisioned future. 

The 21st century demands attention towards its window of opportunity for realizing a food system transition to sustainable manners for humanity and our planet. Researchers conclude that global collaboration and commitment on a “Great Food Transformation” has potential to provide healthy and sustainable diets by 2050 and beyond (12). Recently, the COVID-19 pandemic has been an eye-opener, showing how unhealthy dietary habits are detrimental to sustainable and flexible health statuses, with negative consequences like increased risk of hospitalization by an influenza infection. Lifestyle related diseases such as diabetes type 2, obesity, hypertension, and heart failure were attributable to nearly 2 out 3 COVID-19 hospitalizations (13). Therefore, current years after a global pandemic serve increased awareness and provoked innovation power for desired lifestyle changes. 

What, who, and where?
Envisioning sustainable food practices
Food is a linking factor within the unbalanced, complex, multidimensional human and planetary health system. According to the UN Food and Agriculture Organization (FAO), sustainable diets are diets with low environmental impacts which contribute to food and nutrition security and to healthy life for present and future generations, they are protective and respectful of biodiversity and ecosystems, culturally acceptable, accessible, economically fair and affordable, nutritionally adequate, safe, and healthy, while optimizing natural and human resources (14).  However not all food components with a low environmental impact are healthy, like sugars, and some food groups, like meats, support healthy ageing providing high quality proteins and nutrients like iron, but have a high environmental impact. 

Answering the urgent need for strategic scientific action to improve current food practices, 37 world-leading scientists from various fields of human health, agriculture, political sciences, and environmental sustainability have formed the EAT-Lancet commission. Considering the link between human health and environmental sustainability, the commission developed a universal healthy reference diet defining scientific targets for various food groups, claimed to be able to feed 10 billion people within a safe operating space for food production (12). The EAT-Lancet diet is mostly plant-based, consisting of fruits and vegetables, whole grains, legumes, nuts, and unsaturated fats, with moderate intakes of seafood and poultry, and low to no intakes of red meat, processed meat, added sugar, refined grains, and starchy vegetables. This framework establishes ranges for the amount per food group to stay within for global sustainability, yet practical implementation of the reference diet should recognize feasibility and viability. So-called ‘science-based targets’ consider specific contexts where implementation of scientific targets is desired. Science-based targets entail a local approach to realize the global picture and are therefore dependent on the starting point of a country. 

In the past 3 years, several countries have investigated EAT-Lancet related to their local context, including the United States, Brazil, Spain, Italy, Denmark, Germany, the United Kingdom, and India (15-22). Generally, implementation of the EAT-Lancet pattern is not considered strict or prescriptive. Adjustments for populations and population subgroups promote changes that are not too large to preclude people from adopting a more sustainable diet. Depending on the traditional diet of a country, the direction and degree of health and sustainability impacts of promoted dietary alterations also vary. Furthermore, there is a need to further investigate the impact in vulnerable populations, like those who are already living with a chronic condition, as well as children and elderly. 

The Dutch context
Potential reference diet adjustments for the Netherlands have not yet been explored. Moreover, it is not known to what extent adopting the EAT-Lancet reference diet impacts health among the Dutch population. Some food groups may be sustainable but not healthy, whereas others are more healthy but less sustainable. The 2015 dietary guidelines by the Dutch health council already promote increased intake of plant-based foods for their positive health effects, however insufficient is known about the impact of decreased intake of dairy and meat (23). Furthermore, the degree of change and corresponding effects likely differ for subgroups in the population, defined by certain consumer characteristics which are yet to be studied in cohorts with large numbers of Dutch citizens. Previous studies within the Lifelines cohort in the North of the Netherlands have moreover pointed out geographical (i.e. neighborhood) effects on health outcomes following determinants such as diet (24). A next step would be to examine intraregional dietary sustainability distribution, alongside health outcomes. In essence, upon changing food consumption as part of the global problematic food system, the research gap concerning feasibility, magnitude, and health impact of dietary alterations in the Netherlands should be addressed.

How?
Systems determining food consumption
Moving forward, determining systems underlying food consumption is critical to induce proposed changes. In this project, we will study the determinants of food patterns (aim 2). Several factors are under investigation for their impact on food decisions, yet evidence remains mainly suggestive. In a review of literature reviews, social-cognitive determinants have been associated with dietary behavior among adults, including the theory of planned behavior, habit and automaticity, sedentary behavior, and screen time (25). Among youth, a similar review found evidence of additional social-cultural determinants closely related to dietary behavior, like familial influence (26). Ten themes for familial influence concern knowledge, attitudes, and practices: nutrition education, child involvement, family illness experience, family health, cultivation of preference, family motivation, home meals and food availability, time and cost, parenting style, and parental practical knowledge and attitudes (27). Similarly, another theoretical framework proposes a social and cultural meaning system determining family food practices and potential childhood obesity (28). This framework covers geographical neighborhood characteristics and food environments, cultural schemas, and capabilities and functioning (relating back to the previously mentioned socio-cognitive environment). Moreover, familial research in the north of the Netherlands revealed generational differences in relation to food practices (29). Other determinants suggestively relevant for food consumption are sensory aspects such as taste and preference (30), impulsiveness (31), and other environmental prompts (32). A combination of individual and environmental factors is thus highly relevant for understanding food consumption patterns.