Do you like green eggs and ham?

Would you, could you, eat a dog (yes, a dog)? Would you if it were a dog raised for food in a factory farm? Could you if dog meat were very cheap? Should you if it were said to have excellent nutritional qualities? Would you if a politician said it were your duty to do so? Could you if a friend served it on a special occasion? Should you if you were on the edge of starvation and had no other choice?

Your response would probably be like that of the character offered green eggs and ham in the Dr Seuss book:

"I do not like them here or there/ I do not like them anywhere/ I do not like them in a boat/ I would not, could not, with a goat/ I will not eat them in the rain/ I do not like them on a train/ I do not like them in a box/ I will not eat them with a fox./ I do not like them Sam, I am."

What is it about eating that provokes such strong reactions to certain foods? And why is it that many of us seem no longer to care about its effect on our health or worry about the production and long-distance transport of food from farmed landscapes to our plates? Why, too, would we treat the idea of eating a dog or a fox with dismay while contentedly consuming pigs, cattle, sheep and chickens in such huge numbers?

The most political act we engage in daily is to eat. We vote every few years but we eat every day, and those choices can make a difference to farms, communities and landscapes near and far. But to what extent are these choices freely made?

Walk into any supermarket today and you would be unaware that our food systems have problems. An average European retail outlet contains 25,000 food products. This great choice suggests to consumers that little can be wrong. Food prices have stayed low, too, with a much smaller proportion of family budgets spent on food than just 25 years ago. So, food in Europe and North America is now plentiful and cheap. What could be wrong with that?

Look a little more closely and we can see that hunger is still widespread in developing countries. Yet, at the same time, malnutrition caused by overeating has for the first time in human history become a major health hazard. The costs of obesity in Europe and North America now exceed the costs of smoking, and in several developing countries there are now more obese people than hungry ones.

How are our food choices shaped? Once, it was by the availability of wild animals and the skills of our ancestor hunters and gatherers. Now we can make all kinds of selections - yet many invisible hands are shaping these choices. In the UK, the advertising budget of food companies is greater than government expenditure on public health. In the US, food companies spend $12 billion (£6.6 billion) a year on television advertising targeted at children. And what do they advertise - fruit, or sugar-rich and fat-rich foods?

This is the background for two new books on the politics and structures of food systems, and the way our choices are influenced: The Politics of Food , edited by Marianne Elisabeth Lien and Brigitte Nerlich, and Food Wars , by Tim Lang and Michael Heasman. Fundamental changes have occurred in our farm and food systems, and these appear to bring us only benefits. But scratch the surface, and this mirage of abundance and diversity hides a battle for consumers' wallets. Of course, this is no different from any other economic sector - except that the outcome from food systems will shape many of our environments as well as our bodies.

Lang and Heasman set out a conceptual model for recent changes based on three competing paradigms: the current and dominant productionist paradigm, the newly emerging life-sciences integrated paradigm and the ecological integrated paradigm. These differing paradigms shape how we perceive problems with our farms and food, how we develop and organise common rules, norms and sanctions, and how we develop and deploy new technologies and policies.

Left to the market, agricultural and food systems can deliver much, but they are unlikely to improve the supply of environmental and health-related public goods and services. In most institutional and economic circumstances, there is a need for the positive intervention of public policy. Sadly, we are not very good at this. No one is quite sure what the answers are, but Food Wars contains an enormous amount of useful data and perspectives that can help - on diet-related diseases and their burden on healthcare systems; on the nutrition transition; on the emergence of type II diabetes as a world health problem; on food policy and food safety; on policy responses; on food cultures and good diets; on the Slow Food movement; on the widespread decline of cooking skills; and on the growth of corporate power and emergence of food company clusters.

The Politics of Food contains a set of dispassionate and welcome essays on global food systems, with particular emphasis on the UK, France, the Czech Republic, Japan, Palestine, Australia and the US. As the editors indicate, food has become a contested field, with recent scandals and scares defining many concerns in industrialised countries. Consumers have daily choices, but they are also confused. Should we worry, or simply be content about great abundance in the supermarkets that are coming to dominate most domestic food sectors across the world?

In these essays, a particular highlight is Efrat Ben-Ze'ev's on the memories that Palestinian refugees have about the foods that come from their former villages and environments. Here, fruits and herbs are not anonymous commodities but rather have the "scent of Palestine". Foods carry stories, meanings and personal identities, and help to bind people together.

In another essay, Lien investigates food taboos: why are some of us content to eat cows but not dogs and kangaroos? In Britain, we do not eat guinea pigs (although in Ecuador you would be expected to do so), but we are happy to consume 5 million pigs a year. Some Japanese eat whale meat; others are concerned that such choices will lead to the extinction of whales. In Australia, many kangaroos are shot each year to control their numbers, and some people eat them; other people campaign against such practices. These preferences shape the politics of food and environmental organisations.

Other essays address food risks, the foot-and-mouth crisis, BSE, Western food in Japan, food standards and food rhetorics. We are reminded, though, that at the heart of most problems is inequality, and unless this can be addressed seriously, we are likely to see hunger and obesity stalk our world for years to come.

So will consumers try the green eggs and ham? Or will it depend on whether they have been branded and advertised, or grown locally and sold at a farmers' market? Will they feel that their choices can influence the politics of food? Will policy-makers take on some of the fundamental challenges of ensuring that safe and wholesome food is available to and eaten by all? The future of the world food system will be shaped in part by answers to these questions.

Jules Pretty is professor of environment and society, Essex University.