A food system covers all the elements (environment, people, inputs, processes, infrastructures, institutions, etc.) and activities that relate to the production, processing, distribution, preparation and consumption of food, and the outputs of these activities, including socioeconomic and environmental outcomes. Making a food system nutrition-sensitive entails applying a nutrition lens to all its activities, considering all forms of malnutrition. First, an analysis of the food system and nutrition situation shall be done, based on which interventions shall be planned and implemented, explicitly designed to improve nutrition by taking the constraints of the food system into account. This shall be followed by monitoring of impacts. Possible questions can be 'Will activities improve (or harm) the nutrition situation?' or 'Which of the possible activities would best enhance better nutrition--while considering other aspects such as productivity or income?' or 'Are the currently produced and processed foods meeting the nutritional requirements of populations? If not, what needs changing, and is this feasible?' To answer most of these questions, data are needed to design, implement and monitor nutrition-sensitive activities within the entire food system. Two important datasets are food consumption, e.g. FAO/WHO GIFT platform, or food composition data (FCD). For example, in food production, FCD can be used to inform decision makers which agricultural products have the optimal nutrient composition to reduce malnutrition using foods. Those foods should then be included in large or small scale production, seed or research programmes and policies; or in incentives considerations to enhance production while lowering prices. A useful tool is FAO's newly developed Nutrient Productivity Scale which combines yield/production of different agricultural goods per hectare with their content of nine nutrients (energy, protein, dietary fibre, iron, zinc, calcium, vitamin A, vitamin C and folate) which is then compared to human nutritional requirements. Biodiversity needs to be considered as nutrient content differ significantly among the varieties or breeds of the same food, making the difference between nutrient adequacy and inadequacy. If foods or varieties with high micronutrient contents were produced or consumed in higher quantities they would eliminate micronutrient deficiencies worldwide. For that, FDC are needed, including data on different varieties or breeds delivered by different production systems. During food storage and processing, some foods and nutrients are lost or wasted. FCD are key to develop new approaches to reduce food and nutrient losses or waste; enhance value chains of e.g. nutrient- dense fruits and vegetables; or develop food products being naturally enriched by adding highly nutritious foods. Food labelling is part of trade and marketing and useful in guiding food choices. Food Based Dietary Guidelines (FBDG) can inform policies, guide nutrition education, and inform consumers about healthy food choices at all ages and conditions. For all these purposes, FCD are needed on raw, cooked, processed and biodiverse foods. Although FCD are needed to formulate and implement appropriate food system policies, they are absent for over 99% of the global foods produced and consumed. This should urgently be addressed to effectively and sustainably reduce malnutrition rates worldwide.