IMAGINE you are sitting at a table with a bag of sugar, a teaspoon and a glass of water. You open the bag and add a spoonful of sugar to the water. Then another, and another, and another, until you have added 20 teaspoons. Would you drink the water?
Even the most sweet-toothed kid would find it unpalatably sickly. And yet that is the amount of sugar you are likely to eat today, and every day – usually without realising it.
Sugar was once a luxury ingredient reserved for special occasions. But in recent years it has become a large and growing part of our diets. If you eat processed food of any kind, it probably contains added sugar. Three-quarters of the packaged food sold in US supermarkets has had sugar added to it during manufacturing. You can find it in sliced bread, breakfast cereals, salad dressings, soups, cooking sauces and many other staples. Low-fat products often contain a lot of added sugar.
It's hardly controversial to say that all this sugar is probably doing us no good. Now, though, sugar is being touted as public health enemy number one: as bad if not worse than fat, and the major driving force behind obesity, heart disease and type II diabetes. Some researchers even contend that sugar is toxic or addictive.
As a result, health bodies are gearing up for a "war on sugar". The World Health Organization wants us to cut consumption radically. In the US, doctors and scientists are pressing food companies to reduce sugar and be more open about how much they add; in the UK a group called Action on Sugar has just launched a campaign to ratchet down sugar. Politicians are mulling taxes on sugary drinks. But is sugar really that bad? Or is it all a storm in a teacup – with two sugars please?
When nutrition scientists talk about sugar they are not fretting about sugars found naturally in food such as fruit and vegetables, or the lactose in milk. Instead they are worried about added sugar, usually in the form of sucrose (table sugar) or high-fructose corn syrup (see "Sugar basics").
Our early ancestors would have been totally unfamiliar with these refined forms of sugar, and until relatively recently sugar was a rare and precious commodity. Only in the 1700s, after Europeans had introduced sugar cane to the New World and shackled its cultivation to slavery, did it become a regular feature of the Western diet. In 1700, the average English household consumed less than 2 kilograms of table sugar a year. By the end of the century that amount had quadrupled (see diagram).
The upward trend has continued largely unbroken ever since. Between the early 1970s and the early 2000s, adults in the US increased their average daily calorie intake by 13 per cent, largely by eating more carbohydrates, including sugar. In 1996, the average US adult swallowed 83 more calories per day from added sugar than in 1977. Today, yearly sugar consumption in the US is close to 40 kilograms per person – more than 20 teaspoons a day.
The sugar rush has many causes, but one of the most important was the invention of high-fructose corn syrup in 1957. HFCS is a gloopy solution of glucose and fructose that is as sweet as table sugar but has typically been about 30 per cent cheaper.
Once this source of sweetness was available, food manufacturers added it liberally to their products (see charts). "Because hunger is no longer an important factor in most developed countries, what can make people eat more?" asks Serge Ahmed, a neuroscientist at the University of Bordeaux, France. "Food pleasure. And what creates food pleasure? Sugar."
Unfortunately, it is a guilty pleasure. Not all scientists see eye to eye on the health effects of sugar but there is one point on which most agree: we don't actually need it. Luc Tappy, a physiologist at the University of Lausanne in Switzerland, sums it up: "You cannot live without essential fats. You cannot live without protein. It's going to be difficult to have enough energy if you don't have some carbohydrate. But without sugar, there is no problem. It's an entirely dispensable food."
All that unnecessary sugar adds calories to our diet, so it is no surprise that the rise in consumption coincided with the rise of obesity and related problems such as type II diabetes. In 1960, around 1 in 8 US adults was obese; today more than a third are. Since 1980, obesity levels have quadrupled in the developing world to nearly 1 billion people. One recent study found that for every additional 150 calories' worth of sugar available per day in a country there is an associated 1.1 per cent rise in diabetes.