Could too much sugar be deadly? The biggest US study of its kind suggests that the answer is yes, at least when it comes to fatal heart problems.
It doesn't take all that much extra sugar, hidden in many processed foods, to substantially raise the risk, the researchers have found, and most Americans eat more than the safest amount.
Being in the highest risk category in the study means your chance of dying prematurely from heart problems is nearly three times greater than for people who eat only foods with little added sugar.
For someone who normally eats 2,000 calories daily, even consuming two 340-millilitre cans of soft drink substantially increases the risk. For most American adults, sodas and other sugary drinks are the main source of added sugar.
Lead author Quanhe Yang of the US Centres of Disease Control and Prevention called the results sobering and said it was the first nationally representative study to examine the issue.
Scientists aren't certain exactly how sugar may contribute to deadly heart problems, but it has been shown to increase blood pressure and levels of unhealthy cholesterol and triglycerides; it may also increase signs of inflammation linked with heart disease, said Rachel Johnson, who is the head of the American Heart Association's nutrition committee and a professor.
Yang and colleagues analysed national health surveys between 1988 and 2010 that included questions about people's diets. The authors used national death data to calculate risks of dying during 15 years of follow-up.
Overall, more than 30,000 American adults aged 44 on average were involved.
Previous studies have linked diets high in sugar with increased risks for non-fatal heart problems, and with obesity, which can also lead to heart trouble. But in the new study, obesity didn't explain the link between sugary diets and death.
That link was found even in normal-weight people who ate lots of added sugar.
"Too much sugar does not just make us fat; it can also make us sick," said Laura Schmidt, a health policy specialist at the University of California, San Francisco. She wrote an editorial accompanying the study in Monday's JAMA Internal Medicine.
The researchers focused on sugar added to processed foods or drinks, or sprinkled in coffee or cereal. Even foods that don't taste sweet have added sugar, including many brands of packaged bread, tomato sauce and salad dressing. Naturally occurring sugar, in fruit and some other foods, wasn't counted.
The researchers had death data on almost 12,000 adults, including 831 who died from heart disease during the 15-year follow-up. They took into account other factors known to contribute to heart problems, including smoking, inactivity and excess weight, and still found risks for sugar.
As sugar intake increased, risks climbed steeply.
Adults who got at least 25 per cent of their calories from added sugar were almost three times more likely to die of heart problems than those who consumed the least - less than 10 per cent.
Dr Jonathan Purnell, a professor at Oregon Health & Science University's Knight Cardiovascular Institute, said while the research doesn't prove "sugar can cause you to die of a heart attack", it adds to a growing body of circumstantial evidence suggesting that limiting sugar intake can lead to healthier, longer lives.