Perspective: Striking a Balance between Planetary and Human Health—Is There a Path Forward?

The global adoption of predominantly plant-based, sustainable, healthy diets will help reduce the risk of obesity- and malnutrition-related noncommunicable diseases while protecting the future health of our planet. This review examines the benefits and limitations of different types of plant-based diets in terms of health and nutrition, affordability and accessibility, cultural (ethical and religious) acceptability, and the environment (i.e., the 4 pillars underlying sustainable healthy diets). Results suggest that, without professional supervision, traditional plant-based diets (vegan, vegetarian, and pescatarian diets) can increase the risk of nutritional deficiencies among infants, children/adolescents, women, pregnant/lactating women, and the elderly. In contrast, flexitarian diets and territorial diversified diets (TDDs; e.g., Mediterranean and New Nordic diets) that include large quantities of plant-sourced foods, low amounts of red meat, and moderate amounts of poultry, fish, eggs, and dairy can meet the energy and nutrition needs of different populations without the need for dietary education or supplementation. Compared with vegan, vegetarian, and pescatarian diets, more diverse flexitarian diets and TDDs are associated with reduced volumes of food waste and may be more acceptable and easier to maintain for people who previously followed Western diets. Although flexitarian diets and TDDs have a greater impact on the environment than vegan, vegetarian, and pescatarian diets, the negative effects are considerably reduced compared with Western diets, especially if diets include locally sourced seasonal foods. Further studies are required to define more precisely optimal sustainable healthy diets for different populations and to ensure that diets are affordable and accessible to people in all countries.