Sugar on trial: What you really need to know
It has been called toxic, addictive and deadly, the driving force behind obesity, heart disease and diabetes. Is sugar really so bad?
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?
Sickly sweet (Image: Tim Georgeson/Gallerystock)
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.
So far so simple. But some researchers see something more sinister going on. To them, sugar isn’t just a source of excess calories: it is a poison.
The most outspoken is Robert Lustig, an endocrinologist at the University of California, San Francisco. Described by some of his peers as an anti-sugar evangelist, Lustig’s main beef is with fructose, a simple sugar found naturally in fruit but which is also a component of sucrose and HFCS.
The case against fructose is built on the fact that, unlike glucose, it doesn’t play an essential role in human metabolism (That is not to say we need to eat glucose; complex forms of carbohydrate such as starch supply all the glucose our metabolisms need). Our ancestors would have encountered fructose in fruit but in nothing like the quantities we eat today, so part of the argument is that our bodies are simply not adapted to deal with it.
To begin with, fructose is almost exclusively metabolised by the liver. When we eat a lot of it, Lustig and others say, much of it is converted into fat. Fat build-up in the liver can lead to inflammation and scarring and progress to cirrhosis. Fatty liver has also been linked to insulin resistance, a precursor to diabetes.
Toxic attack
Fructose is converted into energy, but Lustig claims that, unlike glucose breakdown, this produces lots of oxygen radicals, dangerously reactive chemicals that attack our bodies and cause ageing. To mop these up requires antioxidants, but how many you get often depends on the quality of your diet. “People who can’t afford better food don’t get the antioxidants. That’s one of the reasons why people in the lower socio-economic strata get sicker on the same dose of sugar,” Lustig says.
What’s more, unlike glucose, fructose isn’t regulated by insulin. This hormone keeps blood glucose levels stable and spurs the production of leptin, the hormone that lets you know when you are full. Fructose doesn’t affect leptin production; one small study even suggests it ups the level of its counterpart, ghrelin, the hormone that makes you feel hungry. In other words, fructose encourages overeating.
Finally, eating lots of fructose has been shown in both animal and human studies to boost levels of triglycerides in the blood, which increase the risk of hardened arteries and heart disease.
It’s a compelling argument that has captured imaginations: a lecture Lustig gave in 2009 has been viewed more than 4 million times on YouTube. Still, many nutrition scientists remain unconvinced. A number of studies have failed to find evidence that fructose is uniquely harmful – though these have been criticised because their authors received funding from food and beverage companies.
More credibly, in 2012 Tappy reviewed the case against fructose for the journal BMC Biology. He concluded that while there is cause for concern in people who already have a metabolic disease or are at risk of developing one, there is no evidence that fructose is the sole, or even the main, cause of these diseases. But the case remains open. “There are many unanswered questions,” he says.
Another sinister claim against sugar is that it warps eating habits by altering brain chemistry to make us want more. For several years neuroscientists have found it useful to compare energy-dense foods to addictive substances such as cocaine – at least in a metaphorical sense – because it equips them with the language to discuss their habit-forming properties. But is this anything more than a metaphor?
Several studies in rats have shown that a burst of sweetness affects the reward system in the brain in a similar way to cocaine. One study even gave cocaine-addicted rats the option between cocaine and sugar water. “Most turned away from the drug for the sweet reward,” says Ahmed, who ran the study.
That sounds damning, but is it also true in humans? Foods high in fat and sugar – called “hyperpalatable” foods – are known to trigger our reward systems by boosting dopamine levels much as addictive drugs do. And there is research suggesting that most people with conditions such as binge-eating disorder display similar psychological characteristics to people with substance abuse problems. But is that enough to condemn sugar as addictive? And how can you distinguish the allure of sugar from that of fat and salt in these foods?
Although some doctors find the evidence compelling enough that they treat obesity using techniques for treating addiction, the scientific case for food addiction is far from iron clad. Last year, for example, NeuroFAST, an independent, European Union-funded collaboration between 13 universities that produces “consensus statements” on controversial issues in nutrition science, reviewed all the relevant evidence from human studies. Itsconclusion: there is “no evidence” that food can be addictive.
Unsurprisingly, the sugar lobby agrees. “There is little evidence available from human studies, performed in a way that is representative of how food is consumed as part of everyday life,” says Glenys Jones from Sugar Nutrition UK, which is mainly funded by UK sugar manufacturers.
So if we can’t conclude that fructose is the culprit or that sugar is addictive, where does that leave us? Is it simply that too much sugar equals too many calories? Or has the entire case against sugar been overstated?
This question is now in the hands of the World Health Organization. Alarmed by reports of sugar’s dangers, its Nutrition Guidance Expert Advisory Group has been carrying out a review of the evidence with a view to making some recommendations.
As part of that process, last year Lisa Te Morenga, a researcher in human nutrition at the University of Otago in New Zealand, reviewed the research on the relationship between sugar and body weight. She concluded that it wasn’t necessarily eating too much sugar that was making us fat, but eating too much of everything. “There was no difference between higher and lower sugars when the energy people were consuming was exactly the same,” says Te Morenga. In other words, if total calorie count was controlled for, people didn’t get any fatter when more of those calories came from sugar. These findings, too, were welcomed by the sugar industry.
So is the white stuff off the hook? Not so fast. When Te Morenga looked at studies that more closely replicate food choices in real life – that is, when participants weren’t held to precise calorie counts – those who ate a lot of sugar tended to consume more calories overall and gained more weight. And the most important source of sugar was one that has been high on the list of obesity campaigners’ concerns for years: sugary drinks. This was yet more evidence that sweetened drinks really do cause weight gain – which is the strongest reason to point the finger at sugar.
Why does it matter if we consume calories in liquid rather than solid form? Think of it this way. It takes about 2.5 oranges to make a glass of juice. But drinking a glass doesn’t make you feel as full as eating two-and-a-half oranges. That’s because the fibre in the fruit makes you feel fuller for longer.
As Te Morenga puts it, “all sugar-sweetened drinks really do is contribute calories to the diet” – but without making you full. This is partly because fructose – which can make up 65 per cent of the sugar in drinks from soda fountains – doesn’t activate the fullness hormone leptin.
This lack of satiety from sugary drinks makes it possible to consume many more calories at a sitting than you would otherwise. Having a sugary drink with a meal, for example, doesn’t make you eat less (and replacing it with a diet drink might not help – see “Just one hit”).
This lack of satiety in exchange for calories seems to have long-term consequences. Several epidemiological studies have linked the consumption of sugary drinks with increased risk of obesity, type II diabetes and heart disease. That’s why soda is a prime target for public health officials: so far legislators in 30 US states have tried and failed to restrict sales in some way, the most famous being New York City’s thwarted attempt to ban super-sized sodas last year.
The failure, in part, can be put down to campaigns by the food industry, which has a long history of waging war against threats to its profits – as the WHO knows only too well.
The WHO’s upcoming sugar advice won’t be the first of its kind. Ten years ago it tried something similar. After reviewing the evidence it concluded that people should get no more than 10 per cent of their calories from “free sugars” (see “Sugar basics”), otherwise they wouldn’t be getting a balanced diet. That was about half of what people were actually consuming.
Industry threats
The sugar industry went ballistic. The US Sugar Association wrote to the director general of the WHO, pointing to a report from the US Institute of Medicine suggesting that 25 per cent of daily calories was an acceptable sugar intake, and threatening to put US funding for the WHO in peril if the report was widely circulated. It sent a similar letter to then-US Health Secretary Tommy Thomson.
The report and its 10 per cent figure were still published, but with little fanfare – and almost no impact. Many researchers contacted by New Scientist were unsure whether it had ever been released, or if it had, if the 10 per cent figure was included.
The new WHO guidelines are still a work in progress, but an early leak suggests they are likely to go further and recommend that just 5 per cent of daily calories come from free sugars. That would mean cutting current consumption by two-thirds, to about 8 teaspoons a day for men and 6 for women. By way of comparison, a standard can of cola contains 10 teaspoons.
This figure won’t go down well with the industry. Marion Nestle, professor of nutrition, food studies and public health at New York University, expects them to play dirty again, citing parallels between their tactics and those used by the tobacco industry of yesteryear.
“This is about marketing,” she says. “They lobby behind the scenes to make sure that no government agency makes regulations they don’t like, they fund election campaigns to do the same thing, they attack critics.” They also try to influence the science: “In general the food companies sponsor research to give them the answer they want.” WHO director Margaret Chan has echoed Nestle’s concerns.
So what can be done? There are signs that the WHO has learned lessons from 2003. The anticipated 5 per cent consumption figure appears to be based not on evidence about sugar’s link to obesity, but to a less controversial condition: tooth decay.
One of the WHO’s analyses looked at the relationship between sugar and dental cavities. Led by Paula Moynihan at Newcastle University in the UK, the review concluded that there was evidence – albeit of very low quality – to justify reducing intake to 5 per cent to minimise risk of tooth decay.
If correct, that might look like smart tactics by the WHO. It will be harder to attack this recommendation as everybody knows that sugar rots your teeth. But the poor quality of evidence leaves plenty of room for the industry to manoeuvre.
Not all anti-sugar campaigners, though, see the industry as the enemy. For the past two decades, Graham MacGregor of the Wolfson Institute of Preventive Medicine in London has been spearheading a global campaign against dietary salt. He and his colleagues have persuaded the food industry to reduce added salt by about 30 per cent. Now they are trying to do the same with sugar. “There’s no point screaming at the industry, it doesn’t do any good,” he says. “You have to work with them.”
That, however, is a long-term project, which is why many public-health researchers advocate more aggressive tactics. In October, for example, theBMJ published projections that a 20 per cent tax on sugary drinks could reduce the number of obese people in the UK by 180,000.
Of course, taxes drop the debate squarely into familiar political territory: the nanny state versus individual responsibility. Do governments have a duty to intervene or is it down to people to look after themselves?
Te Morenga isn’t convinced that sugar is the uber-villain of our health woes, but is confident that the way sugary foods are marketed makes us eat more than we need. “Maybe people should take more personal responsibility,” she says. “But we’re letting food companies spend millions of dollars to convince people to buy their products – or that soft drinks are a perfectly normal thing to have with a meal.”
While politicians weigh up their options, for individuals, the advice is quite simple: try to reduce how much sugar you are consuming. Above all, avoid sugary drinks. “It’s the easiest thing to do,” says Tappy.
Of course, critics of efforts to curb sugar intake will counter that if you simply eat well and exercise, sugary drinks and snacks can be reasonable indulgences. That’s true, so far as it goes. But there is also another simple truth about sugar: however much you might want it, you really don’t need it.
This article appeared in print under the headline “Sickly sweet”
Source: http://www.newscientist.com/article/mg22129540.500-sugar-on-trial-what-you-really-need-to-know.html
