Int. J. Environ. Res. Public Health 2011, 8 366 The second limitation is that these strategies have been designed to address the problems of hidden hunger and food insecurity predominantly in rural areas. They are less suitable for urban areas, though the number of urban people that depend on urban agriculture for their food needs is growing rapidly. The third limitation is that these approaches focus on only two, though crucial sectors—agriculture and nutrition—while leaving aside other important ones. Socio-economic factors such as people’s education, women’s empowerment, cultural beliefs, infant and young child feeding practices, intra-household food distribution and social norms are key determinants of people’s access to adequate and nutritious food, and their dietary behaviours, and can themselves be affected by changes in diets and nutritional status. Food-based solutions to improve food security have surely contributed to our knowledge on the effectiveness of integrated approaches as these case studies demonstrate, and it is important to emphasize these types of approaches when designing interventions [43,45,57]. These studies provide strong evidence that education and knowledge enhancement are key components as well as working with women as agents of change. The strategic linkages between health, culture, environment and agriculture and nutrition to combat hidden hunger have been described as ―food systems‖, ―field fortification‖ and ―food based‖ strategies [58,59]. It is in these food systems that ecological concepts can be of particular use to study and optimize the sustainability and nutritional value of the underlying food systems. 5. Food and Nutrition Systems Community and household food security depends on underlying social, economic and institutional factors, which ultimately affect the quantity, quality and affordability of food as well as nutrition, health and wellbeing [60,61]. Conceptually, this can be thought of as a system—a set of elements that function together as collective units which have properties greater than the sum of their component parts. Food systems are dynamic and depend on agriculture, food, eating and health. Policy makers, development agencies and governments often talk about a ―health system‖ or a ―farming system‖ as something that is the total sum of all the organizations, institutions and resources whose primary purpose is to improve health or food production. A resilient food and nutrition system involves people, as consumers, as the central focus. This system also ensures that environmental integrity, economic self-reliance and social well being are maintained and emphasized. A healthy food and nutrition system is self-reliant, controlled, accessible, safe, sustainable, resilient and food-secure. It ensures that links are made between sustainable natural resource management, food production, food consumption and nutritional health [62]. Sobal and colleagues provide a cohesive ―food and nutrition system approach‖, which can help in the design of more comprehensive policies and programmes [62] which encompasses characteristics from food chain, cycle and web models (Figure 2). Following their definition, this system consists in ―the set of operations and processes involved in transforming raw materials into foods and transforming nutrients into health outcomes, all of which functions as a system within biophysical and sociocultural contexts‖ [62].