How toxic is sugar?
Sugar has been a hot topic for some time. In Australia, anti-sugar campaigners, including author and former lawyer David Gillespie and journalist Sarah Wilson, are encouraging us to give up all foods and drinks containing added sugars.
US paediatrician and endocrinologist Professor Robert Lustig, along with several colleagues, caused a stir when they labelled sugar toxic and called for it to be taxed in the same way as alcohol. (See Lustig's lecture Sugar: the bitter truth)
Their article published in the journal Nature, they argued:
- the amount of added sugar consumed in processed food is linked to the increasing prevalence of chronic diseases such as heart disease, cancer and type 2 diabetes
- many of the long-term health effects of excessive consumption of sugar are similar to those of alcohol
- sugar is not just another form of empty kilojoules
- processed foods containing added sugar need to be regulated in a similar way to alcohol.
Lustig says the sugars added to processed food are causing metabolic syndrome, a collection of conditions (such as high blood pressure, carrying too much fat around your abdomen, and high blood sugar) that often occur together and increase your risk of type 2 diabetes, stroke and heart disease.
But Professor Peter Clifton from the Baker IDI Heart and Diabetes Institute says the health impacts of sugar may have been over-stated.
He says there are no controlled studies showing that eating sugar causes high blood pressure or that cutting sugar alone reduces high blood pressure.
"Sugar is just another form of over-consumed calories, easily available and very palatable but no more metabolically deadly than starch or fat calories and certainly not equivalent to alcohol."
Accredited practising dietitian Jemma O'Hanlon agrees the health risks associated with sugar have been overstated.
"When it comes to chronic diseases, there is insufficient evidence to link sugar with heart disease, type 2 diabetes or cancer directly," O'Hanlon says.
Fructose is at the centre of the sugar debate.
In Australia, processed foods are sweetened with sucrose (derived from cane sugar), which is made up of one molecule of glucose and one molecule of fructose.
In the United States, processed foods are sweetened with high fructose corn syrup, which contains marginally more fructose than cane sugar.
Those who have a hard-line stance against added sugar say it's the fructose component of sucrose that creates health problems and should be avoided altogether.
Research suggests that fructose may have a tendency to stimulate, rather than satisfy appetite. Also fructose can only be broken down in the liver and Lutsig argues consuming too much fructose can ultimately lead to chronic disease and liver toxicity.
Nutritionist Dr Rosemary Stanton agrees there is some evidence showing fructose, when consumed in very large quantities, might be converted into fat.
"But the very large amounts are much more than the amount of sugar that most people eat, even with our high sugar diet."
Some animal studies have found excessive consumption of fructose:
- may lead to insulin resistance, obesity, type 2 diabetes and high blood pressure
- may stimulate, rather than satisfy your appetite
- over the long-term also led to abnormal increases in body fat, especially in the abdomen, and a rise in circulating blood fats called triglycerides.
But a 2012 review of human research concluded that fructose doesn't cause any more weight gain when substituted for other carbohydrates in diets with similar calories.
"There are lots and lots of studies that show if you give somebody 100 calories of fructose or 100 calories of glucose there is no huge difference in the body's ability to turn that into fat. You'll turn that into fat if you've already had too many calories."
While whole fruit is high in fructose, health experts like Professor Kerin O'Dea from the Sansom Institute for Health Research agree that cutting fruit is not necessary for those wanting to cut down on sugar.
"I am quite comfortable with dietary sugars if they come from whole foods such as fresh fruits and vegetables, as the sugar is diluted with water, fibre and other nutrients," she says.
Is sugar addictive?
Lustig also argues that sugar is toxic because it is addictive, citing research that shows eating sugar lights up the same reward centres in the brain activated by tobacco, alcohol, nicotine and heroin.
Other research has also found that sugar, and the taste of sweet, stimulate the brain by activating beta endorphin receptor sites (the same parts of the brain that are activated when people take heroin and morphine.)
But Australian diabetes expert Dr Alan Barclay disagrees and says few studies in humans consuming realistic amounts of sugar in real foods support this 'sugar is addictive' hypothesis.
Barclay quotes a review of the literature regarding sugar and addiction by Professor David Benton, of Swansea University in the UK, who says "there is no support from the human literature for the hypothesis that sugar may be physically addictive".
The problem with sugary drinks
However when it comes to the consumption of sugary drinks, the research shifts slightly with some studies suggesting consumption of sugary drinks may increase your risk of type 2 diabetes and metabolic syndrome.
Nutritionist Rosemary Stanton says research shows quite clearly that sugary drinks are a problem.
"If you take in calories in liquid form then you don't eat less of anything, but if you eat a piece of bread you will under most circumstances eat a bit less of something else."
Clifton also says drinking too many sugar-sweetened drinks can cause moderate weight gain as the extra liquid calories are not matched by a reduction in calories from other foods.
And we all know that sugary drinks, and foods containing added sugars, affect your oral health.
"There is a clear association between sugar consumption and dental caries, and this has been known for many decades," O'Hanlon says.
How much sugar are we eating?
One major sticking point in the sugar debate is whether Australia's sugar consumption has increased.
Gillespie says "based on ABARE data (the Australian Bureau of Agriculture and Resource Economics), which is the only current available data that is likely to be trustworthy, we are probably consuming at least a kilo of sugar per person per week," he says.
He maintains the ABARE data shows that our sugar consumption has significantly increased.
But Barclay says it's clear we are eating less sugar and getting fatter, a situation he has dubbed 'the Australian paradox'.
He wrote a paper for the journal 'Nutrients', based on analysis of consumption, national dietary surveys and food industry data.
"In Australia, there was a reduction in sales of sweetened beverages by 64 million litres from 2002 to 2006 and a reduction in percentage of children consuming sugar-sweetened beverages between 1995 and 2007," Barclay wrote.
Yet, he says, obesity increased over the same timeframe.
"The implication is that efforts to reduce sugar intake may reduce consumption but may not reduce the prevalence of obesity," he wrote.
But Stanton says it's impossible to know exactly how much sugar people are eating "because we haven't collected the data".
"I am unable to say whether we are eating more or less sugar and I believe that no-one can say are we eating more or less sugar. I would doubt we are eating less ... but I can't say for sure because we have no data."
How much should we eat?
While we might not know exactly how much sugar we do consume, most of us eat some form of added sugar every day.
You'll find added sugar in foods we know are bad for us – such as soft drinks, lollies, cakes, biscuits, pies and pastries – but also in supposedly healthy foods such as juices, canned foods, pre-made sauces and breakfast cereals.
"Sugars found in nutrient-poor foods are the ones that are increasing our waistlines and therefore, increasing our risk of obesity and type 2 diabetes," O'Hanlon says.
"My concern is that if people are consuming more of the highly processed, sugary foods and drinks, chances are they're consuming less of the healthy foods like fresh fruit and vegetables, wholegrains and dairy foods," she says.
The World Health Organisation recommends added sugars make up no more than 10 per cent of our daily food intake, while new US data suggests we should limit added sugars to 5-10 per cent of our total daily intake.
The current Australian Dietary guidelines (released in 2003) are less prescriptive, recommending we consume only moderate amounts of foods containing added sugar.
However, the draft form of new guidelines recommends limiting 'intake of foods and drinks containing added sugars'.
Stanton says the WHO recommendation on sugar consumption is "quite reasonable, it means you can have your piece of cake sometimes".
"I think people can cope with not too much, a message about limit or not too much. But if you say have absolutely none, nobody is going to stick to that for too long."
The bottom line
No-one would argue that eating a diet full of sugary drinks and high-sugar foods, such as confectionary, biscuits and cakes, will make you put on weight.
But it's quite likely that those who spurn sugar lose weight because they stop eating processed foods and choose healthier options.
Many experts believe it is possible to maintain a healthy diet and enjoy the occasional treat.
Says Stanton: "Once you go to the extreme of 'I can't have any sugar' then you've lost the feasts, you've lost the ritual, you've lost the pleasure. On the basis of no strong evidence.
"I have no problem with people cutting down on sugar, but to say that sugar is worse calories than other calories is an exaggeration and a distortion of the facts."
It's also important to remember that sugar isn't the only ingredient that you need to avoid. If avoiding sugar means you eat less processed food and more whole foods – fruit, vegetables and whole grains – then that's a good thing. But if you're swapping sweet treats for fatty or salty ones then you're not doing yourself any favours.
Taming your sweet tooth
If you want to reduce your sugar intake then you need to do more than simply cut back on soft drink, lollies, cakes, biscuits and pastries.
You also need avoid those less obvious processed foods that contain excessive amounts of added sugar, in particular:
- Sugar-laden breakfast cereals – some of these contain up to 30 per cent sugar (see Choice's breakfast cereal review for more information)
- premade meals and sauces
- supposed 'health foods' such as muesli bars and other snacks found in the health food section
- spreads including jams and sugar-free fruit spreads, as well as less obvious suspects such as peanut butter.
by Sophie Scott and ABC Health & Wellbeing