WEDNESDAY, Feb. 27 (HealthDay News) -- It's a common belief that type 2 diabetes is caused by eating too much sugar. While it's not nearly that simple, a new study bolsters the connection between the disorder and sugar consumption.
The study found that even when researchers factored obesity out, an association still remained between the amount of sugar in the food supply and a country's rate of diabetes.
"The old mantra that 'a calorie is a calorie' is probably naive," said study lead author Dr. Sanjay Basu, an assistant professor of medicine at Stanford University. "Some calories may be more metabolically harmful than others, and sugar calories appear to have remarkably potent properties that make us concerned about their long-term metabolic effects. This study also suggests that obesity alone may not be the only issue in [the development of] diabetes."
Results of the study are published Feb. 27 in the journal PLoS One.
The prevalence of diabetes in the world has more than doubled over the last 30 years, according to study background information. That means nearly one in 10 adults in the world has diabetes, and most of those have type 2 diabetes. (The less-common type 1 diabetes is an autoimmune disease that's not related to food intake.)
Although the development of type 2 diabetes is associated with obesity and sedentary lifestyles, not everyone with type 2 diabetes is overweight, according to the American Diabetes Association. A genetic susceptibility to the disease is also believed to play a role.
Previous research has suggested that obesity isn't the only driver in the development of type 2 disease, and some studies have pinpointed excessive sugar intake, particularly sugars added to processed foods.
To get an idea of whether sugar plays an independent role in type 2 diabetes, Basu and his colleagues reviewed data from the United Nations Food and Agricultural Organization on the availability of foods in 175 countries. They also obtained data on the prevalence of diabetes in adults from the International Diabetes Federation.
Using statistical methods to tease out certain factors, such as obesity, the researchers found that the availability of sugar in the diet was linked to diabetes. For every additional 150 calories of sugar -- about the amount in a 12-ounce can of sweetened soda -- that were available per person daily, the prevalence of diabetes rose 1 percent in the population.
And, this rise was independent of obesity, physical activity and other factors that might contribute to the development of type 2 diabetes, the investigators found.
But, when the researchers looked at 150 additional calories per person a day from other sources, they found only a 0.1 percent rise in the rate of diabetes.
Basu said there are likely a number of ways that sugar might contribute directly to the development of diabetes, such as increasing insulin resistance and inflammation.
However, it's important to note that this study doesn't prove that sugar causes diabetes, it only found an association between them. Basu also noted that the study was done on a population level, so it doesn't predict an individual's risk of type 2 diabetes based on the amount of sugar consumed.
The study also wasn't able to distinguish between types of sugar, such as high-fructose corn syrup or natural sugar. Other research has suggested that high-fructose corn syrup, in particular, may be linked to higher rates of diabetes. A recent study in the journal Global Public Health found that the rates of type 2 diabetes were 20 percent greater in countries where the use of high-fructose corn syrup was higher.
For its part, a sugar industry group agreed that the inability to differentiate between sugars was a significant limitation of the study.
"The correlation discussed in this paper relies on lumping together natural sugar with the man-made replacement, high-fructose corn syrup," the Washington, D.C.-based Sugar Association said in a prepared statement. "It is difficult to reconcile the correlation drawn between sugar and diabetes [in this study] given the fact that Americans are consuming far less natural sugar today than we were for most of the last 100 years," they noted.
Meanwhile, Dr. Joel Zonszein, director of the Clinical Diabetes Center at Montefiore Medical Center in New York City, said that type 2 diabetes is a complex disease, and that its development is multi-factorial. "Eating a lot of sugar is not good, especially the sugar substitutes like fructose and sucrose. But, I wouldn't underplay the importance of exercise and caloric intake," Zonszein said.
"And, you have to have individuals who have a genetic abnormality first before you can have type 2 diabetes," he added.
But, if you've been diagnosed with type 2 diabetes or prediabetes, Zonszein said one of the most dramatic changes someone can make is to stop drinking sweetened drinks. "When patients can stop drinking sugary drinks, their diabetes improves. It's simple, and it makes a big difference," he said.
Learn more about type 2 diabetes from the American Diabetes Association.
SOURCES: Sanjay Basu, M.D., Ph.D., assistant professor of medicine, Stanford University, Palo Alto, Calif.; Joel Zonszein, M.D., director, Clinical Diabetes Center, Montefiore Medical Center, New York City; Feb. 27, 2013, statement, Sugar Association, Washington, D.C.; Feb. 27, 2013, PLoS One, online