Under the Microscope:There are few subjects about which more nonsense is written than food, writes Prof William Reville
We have a great interest in food because eating is a primary human appetite and also because of the modern preoccupation with "eating ourselves healthy" and "eating ourselves beautiful". These latter preoccupations, for many, largely suck the natural pleasure out of eating.
A new book, The Gospel of Food: Everything You Think You Know About Food is Wrongby Barry Glassner (Ecco, 2007), aims to introduce some common sense into this area. In particular, Glassner advises that we should enjoy our food.
Glassner's advice on eating is aimed at average healthy people who are not suffering from any illness. He advises: "Enjoy what you eat, eat in moderation, eat a diverse diet that includes plenty of fruit and vegetables and everything will be fine. Following a healthy diet for most people who don't have special medical conditions is not really much more complicated than that. What we leave out in this culture is the enjoyment part. Enjoyment of a meal is important psychologically and emotionally - and also important physiologically."
In support of the latter claim, Glassner quotes a study in which Swedish and Thai women were fed a Thai dish that was too spicy for Swedish tastes. The Thai women liked the dish and absorbed more iron from the meal. When the experiment was reversed and the women were served potatoes, beans and hamburgers, food favoured by the Swedish women, the Swedes absorbed more iron. But, when the women were fed a nutritious sticky, flavourless paste, neither group absorbed much iron. I would support Glassner's advice as to what constitutes healthy eating. But, in addition, it is highly advisable to take plenty of aerobic exercise.
We naturally crave rich tasty foods because evolution has programmed us in this manner - historically, such foods were valuable and rare. We all have easy access now to calorie-rich food, and, if we over-indulge and take little exercise we grow fat. We are also bombarded with nutritional advice on the pros and cons of every fork-full of food that we eat. As a reaction against this we have mistakenly adopted what Glassner calls "the gospel of naught". This says the worth of a meal lies mainly in what it lacks - the less sugar, fat, salt, calories, carbohydrates, preservatives, additives, and so on, the better the meal. In Glassner's opinion, there is little or no science behind this "religion".
Very often yesterday's recommendation of a "healthy" food is condemned today. Glassner cites a book by Walter Willett (Chair of Department of Nutrition, Harvard), Eat, Drink and Be Healthy(Free Press, 2002), in which Willett condemn the potato "as part of the perilous pathway to health disease and diabetes, because we digest it into glucose which produces dangerous surges in blood sugar and insulin". This is to entirely ignore the fact, as Glassner points out, that the potato was the main source of sustenance in Ireland, providing the main source of calories, proteins and vitamins that kept people healthy in the 18th and 19th centuries.
Glassner accepts that many studies in nutrition come up with valuable new information, but he also warns that many other studies are flawed. Self-reported food surveys have limitations and, in other cases, sample numbers are too small. These problems are critically important when nutritional effects, as often applies, are small. In such cases, small errors can easily produce false results.
Glassner is not especially critical of fast food and doesn't cite it as a principal cause of the serious US obesity problem. He points out that the fast-food industry took off in the 1950s and 1960s, but obesity rates didn't start rising until the 1980s and 1990s.
All packaged foods now proudly display information on the nutritional value of the contents. This information can be useful, but usually only if you are knowledgable about nutrition generally. If not the information could be misleading - and sometimes it is downright wrong. We are all familiar with the blackcurrant drink Ribena, which is advertised as containing lots of vitamin C. Three years ago, two New Zealand schoolgirls tested the blackcurrant cordial in a school project to find that ready-to-drink Ribena contained almost no trace of vitamin C.
Glaxo Smith Kline (GSK) manufactures Ribena. They advertised Ribena claiming "the blackcurrants in Ribena have four times the vitamin C of oranges". When challenged, GSK said that their claim is correct as regards the actual fruits but did admit that they may have misled consumers. GSK is now in court in Auckland charged with misleading advertising. GSK points out that Vitamin C content of Ribena elsewhere in the world matches the claim on the label.