The aim of this document is to propose a definition of healthy diets and related evidence, thus permitting the alignment of terminology for the Food Systems Summit. 

Definition 

Diets are the combination of foods consumed over time. A healthy diet is health-promoting and disease-preventing. It provides adequacy without excess, of nutrients and health-promoting substances from nutritious foods and avoids the consumption of health-harming substances. 

A nutritious food is one that provides beneficial nutrients (e.g. protein, vitamins, minerals, essential amino acids, essential fatty acids, dietary fibre) and minimizes potentially harmful elements (e.g. anti-nutrients, quantities of sodium, saturated fats, sugars). Although some recent progress has been made on the nutrient-profiling of foods – with its limitation that it mostly applies on commercially produced and packaged foods - there are several evidence gaps and controversies related to the characterization of healthy diets and nutritious foods:  

• Imperfect characterization of population nutrient requirements to avoid deficiency and promote health: several limitations exist to set average nutrient requirements and upper tolerable limits and some experts call for a more consistent approach. Although there is  evidence  on the potential health effects – both positive and negative - of consuming specific foods, in order to optimize human health outcomes based on individual characteristics, dietary recommendations may be personalized but science is still far from achieving this goal; 

• Imperfect knowledge of the nutrient and “anti-nutrient” content of food such as substances that influence nutrient absorption and the nutrient bioavailability, although substantial advances have been made; 

• Lack of consensus and standardized definitions related to food processing and health implications: even though the implications of highly processed foods on human health, particularly those high in sugar, trans fat and salt, are not under debate, urgent consensus is needed on how to classify highly processed foods, define food processing categories and operationalize the implications for the private sector; 

In regards to the consumption of health-harming substances, food safety refers to all those hazards (biological, pathogens, chemicals, metals), whether chronic or acute, that may make food injurious to the health of the consumer. Despite the heavy burden of disease in low-and middle-income countries (LMICs), the monitoring of food-borne hazards and risks and related disease outcomes is predominantly done in high-income countries (HICs). Food safety priorities for countries include addressing risks from farm to table, changing from reactive to proactive approaches, and adopting a risk analysis approach to ensure prioritized decision-making. Building food safety capacity is essential as the application of good practices, i.e. good agricultural practices (GAP), good manufacturing practices (GMP), good hygienic practices (GHP), and the Hazard Analysis Critical Control Point system (HACCP) is challenging. 

Approaches to translating healthy diet into specific food-based recommendations 

Three approaches have typically been used: 

• Observing existing dietary patterns associated with a lower prevalence of specific diseases. One well-known example is the Mediterranean diet. There are several limitations to using such dietary patterns as the basis for recommendations as they do not account for local availability and the affordability of food types or the cultural traditions and acceptable of foods; 

• A second approach has been to quantify the specific dietary intake patterns associated with multiple outcomes - both human and environmental or planetary health. This perspective approach includes recommendations to guide a “sustainable, healthy diet”, such as eating local, minimizing processed food, consumption of specific quantities of foods or groups of foods, has received criticism on several fronts, including the lack of consideration of food affordability; 

• Finally, the World Health Organization (WHO) has identified a series of guiding principles for healthy diets that seek to address all forms of malnutrition and related health issues. This indicative approach is designed to permit contextualization of recommendations to individual characteristics, cultural contexts, local foods and dietary customs, and has been translated into food-based dietary guidelines (FBDG) in more than 100 countries. Their content may vary by country or region but generally include a set of recommendations for foods, food groups, and dietary patterns that minimize the risk of deficiencies, promote health, and prevent disease in specific contexts. 

Conclusion 

To inform policy and programmatic action, healthy diets must be translated into specific food-based recommendations. The FAO and WHO have now set out a series of guiding principles to achieve contextually appropriate sustainable, affordable, healthy diets.