28.01.2019 |

Scientists call for a shift to healthy diets from sustainable food systems

The planetary health diet is mainly plant-based (Photo: CC0)

Feeding a growing population of 10 billion by 2050 with a healthy and sustainable diet is possible but we need to change dietary patterns, improve food production and reduce food waste. This is the message of a major new report published by the EAT Lancet commission in mid-January. It was written by 37 scientists from 16 countries with expertise in various fields including health, nutrition, environmental sustainability, food systems and political governance. “Food systems have the potential to nurture human health and support environmental sustainability; however, they are currently threatening both,” the authors warn. Current diets are one of today’s greatest causes for ill-health worldwide. They are not only increasing the burden of obesity and diet-related non-communicable diseases, but are also damaging the planet. “Global food production threatens climate stability and ecosystem resilience. It constitutes the single largest driver of environmental degradation and transgression of planetary boundaries,” said Prof Johan Rockström, co-chair of the commission and one of the lead authors. “A radical transformation of the global food system is urgently needed. Without action, the world risks failing to meet the UN Sustainable Development Goals and the Paris Agreement.”

The authors argue that the lack of scientific targets for a healthy diet have hindered efforts to transform the food system. Therefore, they developed detailed science-based targets for both healthy diets and sustainable food production. The “planetary health diet” requires global consumption of foods such as red meat and sugar to decrease by about 50%, while the intake of nuts, fruits, vegetables, and legumes must double. “To be healthy, diets must have an appropriate calorie intake and consist of a variety of plant-based foods, low amounts of animal-based foods, unsaturated rather than saturated fats, and few refined grains, highly processed foods, and added sugars,” says co-chair Dr Walter Willett from Harvard University, USA. The planetary health diet allows 2,500 kilocalories per day and consists of about 35% of calories as whole grains and tubers, protein sources mainly from plants. It includes only 14g of red meat per day but 500g per day of vegetables and fruits. “The food group intake ranges that we suggest allow flexibility to accommodate various food types, agricultural systems, cultural traditions, and individual dietary preferences – including numerous omnivore, vegetarian, and vegan diets.” The authors found that the global adoption of the reference dietary pattern would improve the intakes of most nutrients and could avert between 10.9-11.6 million premature deaths per year.

A shift towards the planetary health diet would also achieve the second target of sustainable food production, making sure that the global food system exists within planetary boundaries. “Five key environmental processes regulate the state of the planet,” explains Rockström. “Our definition of sustainable food production requires that we use no additional land, safeguard existing biodiversity, reduce consumptive water use and manage water responsibly, substantially reduce nitrogen and phosphorus pollution, produce zero carbon dioxide emissions, and cause no further increase in methane and nitrous oxide emissions.” The authors stress the need to decarbonise the food value chain from production to consumption by 2050 and to maintain greenhouse-gas emissions at or less than 5 Gigatonnes of carbon dioxide equivalent per year for methane and nitrous oxide associated with food production. “There is no silver bullet for combatting harmful food production practices, but by defining and quantifying a safe operating space for food systems, diets can be identified that will nurture human health and support environmental sustainability,” Professor Rockström added.

The Commission proposes five strategies to adjust what people eat and how it is produced. First, policies to encourage people to choose healthy diets are needed. Alongside advertising restrictions and education campaigns, affordability is also crucial, and food prices must reflect production and environmental costs. As this may increase costs to consumers, social protection for vulnerable groups may be required. Second, agriculture needs to be refocused from producing high volumes of a few crops, most of which are used for animal production, to producing a diverse range of nutritious foods from biodiversity-enhancing food production systems. Third, the authors say we need to sustainably intensify agriculture by reducing yield gaps on cropland, improving the efficiency of fertiliser and water use, recycling phosphorus, implementing climate mitigation options and enhancing biodiversity within agricultural systems. They also call for an effective governance of land and ocean use, for example through protecting intact natural areas on land, prohibiting land clearing and restoring degraded land. Finally, food waste must be at least halved. “Designing and operationalising sustainable food systems that can deliver healthy diets for a growing and wealthier world population presents a formidable challenge,” said Rockström. This requires nothing less than a new global agricultural revolution. (ab)

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