Twenty-first-century challenges for food and nutrition security include the spread of obesity worldwide and persistent undernutrition in vulnerable populations, along with continued micronutrient deficiencies. Climate change, increasing incomes and evolving diets complicate the search for sustainable solutions. Projecting to the year 2050, we explore future macronutrient and micronutrient adequacy with combined biophysical and socioeconomic scenarios that are country-specific. In all scenarios for 2050, the average benefits of widely shared economic growth, if achieved, are much greater than the modelled negative effects of climate change. Average macronutrient availability in 2050 at the country level appears adequate in all but the poorest countries. Many regions, however, will continue to have critical micronutrient inadequacies. Climate change alters micronutrient availability in some regions more than others. These findings indicate that the greatest food security challenge in 2050 will be providing nutritious diets rather than adequate calories. Research priorities and policies should emphasize nutritional quality by increasing availability and affordability of nutrient-dense foods and improving dietary diversity.