Food choices and eating behaviors significantly impact both human and planetary health. Recognizing the urgent need to promote diets that are healthy and have low environmental impacts while at the same time are socio-culturally acceptable and economically accessible for all, the Food and Agricultural Organisation (FAO) of the United Nations and the World Health Organisation (WHO) have developed guiding principles to achieve sustainable healthy diets (SHDs).
The Foundation of Sustainable Healthy Diets
A healthy and sustainable diet is a prerequisite for population and planetary health. The scientific rationale underpinning what is a healthy and sustainable diet is universal. Everyone shares a physiological need for energy and adequate amounts, types and combinations of nutrients. People source their energy and nutrient needs from foods that are themselves sourced from food systems. The physiological need and food systems’ sustainability have been shaped through evolutionary and ecological processes, respectively.
Historically, understandings of what constitutes a healthy diet were framed in terms of the consumption of adequate amounts of nutrients to prevent nutrient deficiency diseases. As nutrition science has evolved we have learned more about associations between dietary patterns, i.e. “the quantities, proportions, variety, or combination of different foods, drinks, and nutrients in diets, and the frequency with which they are habitually consumed” and health outcomes. The evidence for these associations has now been synthesised to inform more than 100 national dietary guidelines.
From these human health and well-being perspectives, a healthy diet has been defined as one that “promotes optimal human growth and development and prevents malnutrition in all its forms”. Conversely, when we are unable to consume a healthy diet, we may be at risk of malnutrition in all its forms which include undernutrition; micronutrient deficiencies; and overweight and obesity and resulting in diet-related noncommunicable diseases (NCDs), such as cardiovascular disease and diabetes.
FAO/WHO Guiding Principles
In response to the global need for diets that support both human and environmental well-being, the FAO and WHO organized an expert consultation to establish guiding principles for sustainable healthy diets. These principles take a holistic approach to diets; they consider international nutrition recommendations and the environmental cost of food production. The development of food-based dietary guidelines (FBDGs) should be a core element in the implementation of these SHDs in each country.
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These guiding principles take a holistic approach to diets; they consider international nutrition recommendations; the environmental cost of food production. The Sustainable and Healthy Diets Supplement contains one editorial and six expert papers that can be accessed online. The 6 papers presented are the product of the work done before, during, and after the expert consultation, culminating in an in-depth peer-review process. They are covering (1) the elements and definitions of healthy diets; (2) the role of healthy diets in environmentally sustainable food systems; (3) the role of sociocultural influences in shaping choices for sustainable diets; (4) the role of the food environment; (5) territorial diets; and (6) food safety implications of Sustainable Healthy Diets.
The information contained in this Supplement adds meaningful contributions toward the evidence base on how to transform toward more sustainable healthy diets while taking into consideration context-specific barriers and managing trade-offs. This comes at a critical moment, where countries and other stakeholders prepare for the forthcoming Nutrition for Growth Summit and the UN Food System Summit in 2021.
Three Interlinked Dietary Principles
This physiological need can be met, and food systems’ sustainability protected, by following three interlinked dietary principles:
- (i) Variety - to help achieve a nutritionally adequate diet and help protect the biodiversity of food systems.
- (ii) Balance - to help reduce risk of diet-related non-communicable diseases and excessive use of finite environmental resources and production of greenhouse gas emissions.
- (iii) Moderation - to help achieve a healthy body weight and avoid wasting finite environmental resources used in providing food surplus to nutritional requirements.
Scientific Rationale: Dietary Patterns, Health, and Sustainability
For millions of years, dietary patterns were determined by the availability of a wide range of minimally processed, ‘nutritious’ foods, i.e., foods which are sources of energy and nutrients. Requirements for energy and nutrients were shaped by evolutionary processes as human physiology continually adapted to shifts in dietary patterns. The food systems from which foods were sourced existed in harmony with ecosystems operating within ‘planetary boundaries’. Progressively, food processing innovations were introduced to help protect food safety, reduce spoilage of highly perishable foods, make food more edible at the household level and increase food appeal among citizens.
Modern dietary patterns have transitioned significantly from those present during most of human history. This transition is a consequence of rapid urbanization and changing lifestyles intertwined with food supply changes characterised particularly by the widespread displacement of minimally processed nutritious foods for ‘ultra-processed foods’ (UPFs). Ultra-processed foods are formulations of ingredients, mostly of exclusive industrial use, typically created by a series of industrial techniques and processes. Human physiology has not been able to adapt sufficiently to modern dietary pattern exposures, contributing to diet being a leading risk factor for the global burden of disease. Concurrently, ecosystems have not been able to adapt sufficiently to the operations of modern food systems that are fostering these modern dietary patterns, resulting in food systems being a leading contributor to multiple planetary boundary transgressions.
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Principle 1: Dietary Variety
Dietary variety refers to eating a variety of nutritious foods every day. Apart from breast milk in the first six months of life, no single food can supply an appropriate balance of all the nutrients necessary for health. Foods with similar characteristic nutrients and nutrient profiles can be grouped into distinct food groups based on their type and nutrient composition. Many countries with food-based dietary guidelines identify 4-6 ‘core’ food groups: starchy staples, vegetables, fruits, dairy foods, other ‘protein foods’ and fats and oils. A nutritionally adequate diet can best be achieved by selecting foods from both across and within the core food groups while prioritising minimally processed foods. These foods should be consumed in amounts recommended in dietary guidelines. A number of countries have undertaken dietary modelling activities to estimate a minimum number and reference size of food serves to be eaten daily from each food group to enable nutrient intake recommendations to be met.
From a health perspective, foods can differ substantially in their composition of nutrients and more than an estimated 26,000 other bioactive compounds. Dietary variety increases the likelihood of consuming an adequate amount, type and combination of nutrients and other bioactive compounds for promoting nutritional health and preventing nutritional deficiency diseases. Synergistic effects among nutrients within and between foods are also instrumental in varied diets positively impacting on health. Conversely, risk of consuming excessive amounts of certain nutrients and other bioactive compounds that may be present in high concentrations in some foods may be reduced through dietary variety.
From a sustainability perspective, consuming a variety of foods helps to protect the biodiversity of food systems by promoting the production of a wide range of genetically diverse food crops and species. Food crop and species biodiversity helps increase the resilience of food production to threats from pests and diseases in agroecosystems. This biodiversity may also help contribute to higher and more stable yields as well as lower land clearing and use of harmful agrochemicals.
Principle 2: Dietary Balance
Dietary balance refers to the relative dietary proportions of the different food groups from which foods are selected. Dietary imbalances arise when the total amount of foods from one or more food groups is consumed in excessive or inadequate amounts relative to the total amount of foods consumed from other food groups. Two dietary imbalances are receiving particular attention. First, in many high-income countries, it is reported there is too low an intake of nutritious plant-source foods relative to animal-source foods. Fruit, vegetables, legumes (e.g. lentils and beans), nuts and whole grains (e.g. At least 400 g (i.e.
Currently, the WHO (and other UN agencies) does not provide explicit advice on quantities of animal-source foods to include in a healthy and sustainable diet.
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Concerning the imbalance of minimally processed nutritious foods relative to UPFs; UPFs are not an essential component of a healthy and sustainable diet. These foods often contribute superfluous energy, ‘risk’ nutrients (added sugar, salt and industrial trans fatty acids) and industrial ingredients, while displacing minimally processed nutritious foods, from dietary patterns. Less than 30% of total energy intake from fats. Less than 5 g of salt per day. Reducing excessive dietary intake of UPFs will help correct dietary imbalances not only directly by reducing dietary intake of risk nutrients and industrial ingredients, but also indirectly by increasing dietary intake of minimally processed nutritious foods (assuming the maintenance of a relatively constant dietary energy intake). The amount of UPF that might be accommodated within a healthy diet will vary with a person’s nutrient and energy requirements.
From a sustainability perspective, consuming an excessive amount of animal-source foods relative to nutritious plant-source foods can have significant adverse impacts in terms of greenhouse gas emissions, land use and degradation, water use and pollution linked to nutrient-rich fertilisers, and other environmental indicators. Consuming an excessive amount of UPFs relative to minimally processed nutritious foods is associated with biodiversity loss and soil degradation, excessive use of finite environmental resources such as water and food packaging waste, especially plastics. These multiple adverse sustainability impacts resulting from excessive consumption of UPFs are even more concerning given these foods are surplus to nutritional requirements.
Principle 3: Dietary Moderation
Dietary moderation refers to consuming enough food to provide for but not exceed the body’s energy needs. It is essential for optimal growth and development (until physical maturity is reached), to maintain a healthy body weight and composition (post-maturity), and to allow for a level of physical activity consistent with long-term good health (all ages).
From a health perspective, people who consume enough food to provide for but not exceed their body’s energy needs generally have a healthy body weight and composition, and a lower risk of experiencing many diet-related NCDs, such as cardiovascular disease and type 2 diabetes, relative to people whose energy needs are exceeded. People who consume an excessive number and/or size of food serves from each food group beyond that necessary to meet their body’s energy needs may become overweight or obese. Living with overweight or obesity is associated with metabolic problems and an increased risk of many diet-related NCDs. Conversely, children unable to consume enough food to meet their energy needs may have their growth and development stunted. Stunting is also associated with poor physical, mental and functional health problems. Adults unable to consume enough food to meet their energy needs over an extended period will suffer from undernutrition and will be vulnerable to adverse health outcomes. Both stunting and underweight are a consequence of challenges with food accessibility, affordability and availability.
From a sustainability perspective, consuming excessive amounts of food not only contributes to overweight and obesity, but also because it is surplus to meeting the nutritional needs of the consumer it is a waste of the finite environment.
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