© Photo: Spencer Platt, Getty ImagesA new study raises concerns about the availability of products with sugar, such as soda.
New study doesn't prove cause and effect but raises questions about sugar's role in diabetes.

Sugar is under the microscope again.

A recent study looked at sugar and type 2 diabetes rates in 175 countries including the USA over the past 10 years and found that increased sugar availability in the food supply was associated with higher rates of type 2 diabetes.

The research showed that for every additional 150 calories of sugar (the amount in a 12-ounce can of soda) available per person per day, the incidence of type 2 diabetes rose by 1%. Although the study doesn't directly prove cause and effect, it has raised new concerns about sugar.

Almost 26 million U.S. adults and children have diabetes. In diabetes, the body does not make enough of the hormone insulin, or it doesn't use it properly. Insulin helps glucose (sugar) get into cells, where it is used for energy. If there's an insulin problem, sugar builds up in the blood, damaging nerves and blood vessels.

USA TODAY talked to the study's lead author, Sanjay Basu, an assistant professor of medicine at Stanford Prevention Research Center. He's a medical doctor and a statistician. The study was conducted while Basu was a medical resident at the University of California-San Francisco.

We also talked to endocrinologist Elizabeth Seaquist, president-elect of medicine and science for the American Diabetes Association and professor of medicine at the University of Minnesota Medical School.

Q: What did the study show about sugar and type 2 diabetes?

Basu: It showed that obesity itself can't explain all the trends in type 2 diabetes, but a lot of the changes can be explained by sugar availability. We can't test how much sugar goes into everyone's mouth in 175 countries, but we can see how much they buy. And in every country except the U.S., most people eat almost all of what they buy. With statistics, we can't prove anything, but we can show associations.

Seaquist: The study raises the hypothesis that sugar may have an impact on diabetes risk above that associated with its caloric content alone. People who are eating a lot of sugar may also be eating a lot of calories, and we know that eating more calories than you need is associated with type 2 diabetes risk.

Q: Do you think it's possible that sugar can cause type 2 diabetes? If so, why?

Basu: There are several laboratory studies that show that sugar has a unique effect on the pancreas and liver. It seems to trigger a reaction that leads to the body not properly responding to our natural insulin.

Seaquist: I don't think we can say that yet. We know that increased calories above what you need to maintain lean body weight will increase your risk for type 2 diabetes.

Q: What is your best advice to someone with diabetes or pre-diabetes on sugar intake?

Basu: Frankly, the American Heart Association (AHA) put out recommendations that are quite smart. On average, we consume about 22 teaspoons a day of sugar, mostly added sugars. The heart association recommends no more than 9 teaspoons of added sugars a day for men and no more than 6 for women. But because sugar is in everything, it's hard to reach the AHA level and not be a health nut all the time.

Seaquist: People should follow a well-balanced diet that provides the calories necessary to achieve their weight goals. If they are overweight, that would mean they need to eat fewer calories to facilitate weight loss. Anyone with pre-diabetes should follow the recommendations of the Diabetes Prevention Program that includes modest weight loss and 150 minutes of exercise a week.

Q: Is it possible that some people are more sensitive to sugar than others?

Basu: It's quite possible. We are doing a study now to determine if we can significantly reduce diabetes risk through a low-sugar diet. These kinds of studies take a long time to do. In the meantime, with my child, I would try to reduce their intake of sugar while we continue to do these studies. There's no evidence it hurts them, and there's emerging evidence that it could really help.

Seaquist: This is a testable hypothesis for which we don't yet have an answer.

Q: Does obesity increase the risk of type 2 diabetes? Why?

Basu: It looks like it does, and overall calories contribute to obesity.

Seaquist: Type 2 diabetes runs in families, which suggests that genes are important in causing type 2 diabetes. We do not yet have a test to identify who has the specific genes that render susceptibility to type 2 diabetes. For some people, becoming obese makes a person develop diabetes at a younger age than they would have had they never become obese. Obesity causes insulin resistance, and people with the genes for type 2 diabetes may be unable to make enough insulin to overcome the insulin resistance caused by the obesity.

Some facts about diabetes:
Almost 26 million children and adults (8.3% of the U.S. population) in the USA have diabetes.

18.8 million people are diagnosed; an additional 7 million are undiagnosed.

There are two major forms: type 1 and type 2. In adults, type 2 diabetes accounts for 90% to 95% of all diagnosed cases.

79 million Americans have pre-diabetes and are at risk for developing type 2 diabetes.

Symptoms of diabetes include thirst, hunger, tiredness, blurry vision, healing problems and frequent urination. However, not all people with diabetes have symptoms. Even if they aren't having symptoms, people who are obese, older or have a family history of diabetes, as well as African Americans, Mexican Americans and American Indians, are at increased risk of developing type 2 diabetes.

About one in three Americans people may develop diabetes by 2050 if something isn't done to reverse the trend, government statistics show.

Diabetes may lead to heart disease, stroke, kidney failure, foot and leg amputations and blindness.

Source: Centers for Disease Control and Prevention and the American Diabetes Association