A central topic of most debates on sustainable food systems is the complex role of livestock, meat and dairy. This is due to their connection to many issues of moral and practical concern related to food systems; affecting both humans and the environment, and animal's own interests. The picture is complex. And because different stakeholders bring different worldviews and perspectives, people often disagree about the appropriate role of livestock, meat, and dairy, in sustainable food systems. Yet demand for meat and dairy consumption is expected to grow considerably, and as a result, debates around livestock-related issues are becoming increasingly prominent. Understanding these helps to provide a broader understanding of food systems more generally.

The environmental and nutritional attributes of different food types can vary greatly. Consequently, diets composed of different sets of food types, will differ in their environmental footprints, and in their nutritional quality; so affecting human health. When such differences are multiplied by many millions of people, the overall effect is considerable. Human diets are, therefore, an important point of interconnection in food systems via which change is driven – for better or worse – by shifts how people consume. At least in theory, diets might provide a means by which to achieve both health and environmental goals simultaneously. But the reality is not so simple. Understanding these complexities, helps provide a window on both the opportunities and difficulties of taking a food systems approach, and on the important role that diets play.

Eating patterns (or diets) are an important point of interconnection in food systems between human health and wider environmental impacts. Shifts in how people consume towards sustainable health eating patterns can bring multiple benefits. And when they are undertaken by whole populations, their overall effects can be considerable. Although there is much we still don’t know, the broad trends of what sustainable health eating patterns look like are known well enough to take action today. However, this presents another difficult challenge: how can eating patterns (at the individual and population scale) be shifted towards those that are healthier and more sustainable? Understanding this problem and its potential solutions provides a useful primer on the way in which consumption in food systems takes place through a combination of human choices (whether conscious or not), and is influenced by the wider contextual environment that actively constrains and influences these choices.

Diseases that pass between animals and humans are responsible for many of the diseases affecting people worldwide, especially in developing countries. Animals (wild and domestic) also play an important role in the emergence and spread of entirely novel human diseases, with the potential for large impacts on human health, such as bird flu. Another aspect of this to which livestock contribute, is the rise and spread of resistance to antibiotic drugs. One outcome of sustainable food systems is that they should be health promoting. It is, therefore, useful to understand the interconnection between infectious diseases in human and animals, and how these risks may be amplified or reduced by changes in farming systems.