For a great example of how our modern food supply got into such a mess, look no further than the history of bread. Back in the late 19th century mechanised roller-milling replaced the older, slower system of grinding grains between big stone wheels – a giant leap forward for food processing, and a step backward for human nutrition. With faster, finer milling came softer, whiter, more refined flour with a convenient longer shelf life – but minus the wheatgerm with its package of B vitamins, including folate, antioxidants and omega-3 fatty acids. What followed next were epidemics of pellagra and beri beri – diseases cause by lack of B vitamins that sent he flour industry into damage control, adding B vitamins to refined flour in the 1930s. More recently, the fact that many people are low in folate, lead to US flour being fortified with folate in the 1990s – a move which is also going ahead in Australia.

The moral of this story – that humans do better on food that’s as close to its original state as possible – is the subject of In Defence of Food the latest book from US writer Michael Pollan. author of The Omnivore’s Dilemma . In Defence of Food is partly about how progress in food processing created the western diet which in turn helped fuel new epidemics – like diabetes – which modern medicine is now trying to fix.

The book is also about what he calls the rise in nutritionism – our habit of focussing on what single nutrients or components in food – like fibre – can do for us rather than on the benefits of eating the whole food itself. ‘Nutritionism’ makes us think that you can make a processed food healthy simply by tossing in some extra nutrients – think refined breakfast cereals with some added fibre and vitamins.

An example of why whole foods are so hard to beat is the 2003 study, described by Pollan, that found that none of the individual nutrients in whole grains could fully explain why wholegrain eaters lived longer than other people. Even when people got the same amount of fibre, vitamins and minerals and so on from eating other foods with the same nutrients in them they still weren’t as healthy as the wholegrain eaters. What the researchers concluded was that there was something else at work and that it was probably food synergy – some kind of interaction between all the different components in wholegrains was creating an extra beneficial effect.

“Fortifying processed food with missing nutrients might be better than leaving them out,” Pollan writes. “But food science can add back only the small handful of nutrients that food sciences recognises as important today. What is it overlooking? As the whole grain food synergy study suggests, science doesn’t know nearly enough to compensate for everything that processing does to whole foods. We know how to break down a kernel of corn or grain of wheat into its chemical parts, but we have no idea how to put it back together again. Destroying complexity is a lot easier than creating it.”

As for escaping from a diet of highly processed food, Pollan’s advice includes:

– Don’t eat anything your great grandmother wouldn’t recognise as food

– Avoid food products containing ingredients that are a) unfamiliar, b) unpronounceable c) more than five in number.

– Avoid food products that make health claims (food products making health claims are in packets and more likely to be processed, he points out)

– Shop the peripheries of the supermarket and stay out of the middle – processed foods dominate the center aisles, while fresher food is around the walls.

– Get out of the supermarket whenever possible. Pollan’s advice here is to try and shop at farmer’s markets whenever you can.