Amy Campbell is a registered dietitian and Certified Diabetes Educator who has been working in the field of diabetes for many years. She is the author of several books about diabetes, including 16 Myths of a Diabetic Diet and Staying Healthy with Diabetes: Nutrition and Meal Planning. In addition, Amy is a lecturer and frequent contributor to several diabetes-related websites.

Sugar seems to have replaced fat as the latest dietary villain. About 15 percent of Americans’ daily calorie intake comes from sugar. That’s about 300 calories a day.

According to the United States Department of Agriculture, we consume 156 pounds of sugar each year (translated: 31 five-pound bags of sugar). We far surpass the American Heart Association’s recommendations to limit our added sugar intake to no more than 100 to 150 calories per day (that’s six to nine teaspoons of sugar). And we’ve woefully failed at meeting the World Health Organization’s sugar goal of no more than 10 percent of daily calories. Let’s face it: we have a real sweet tooth, which is apparently causing us all sorts of problems.

Sugar woes

Sugar has never been proclaimed as being a health food. It’s been linked with causing cavities and weight gain. But few people (except maybe dentists) seemed overly concerned about it.

Times have changed. Sugar may be more dangerous than we once thought.

For example, in one study, people who consumed more than 21 percent of their daily calories from added sugar had double the risk of death from heart disease compared to people who took in fewer than 10 percent of calories from sugar. In another study, eating sugar compromised the immune systems of healthy volunteers by 50 percent for up to five hours. A study published in the Journal of the American Medical Association has linked eating sugar to higher triglyceride and lower HDL levels. Other studies point to the sweet stuff as a cause of cancer, aging, liver disease, increased belly fat, and addiction (keep in mind that not all of these studies meet the “gold standard” of research, which is randomized clinical trials).

Sugar and diabetes

Does eating sugar cause diabetes? Ask a diabetes expert or a diabetes organization such as the American Diabetes Association and they’ll likely answer “no.” They may go on to explain that type 1 diabetes, for example, is a genetic condition with causes that are still unknown. Type 2 diabetes is a condition of “insulin resistance,” caused by many factors, such as being overweight, family history, age, and ethnicity.

In fact, healthcare professionals have spent a lot of time and energy dispelling the myth that eating sugar causes diabetes. Much research has been done to examine the effects of all sources of carbohydrate on blood sugar levels, and it has shown us that eating sugar and eating starch has the same effect on blood sugar levels.

But what if the diabetes experts are wrong? Researchers published a study in the journal Mayo Clinic Proceedings that may prompt experts to re-examine the current belief that sugar isn’t a cause of diabetes.

In this study, which was actually a review of scientific literature, the researchers set out to determine which food factors are most harmful related to diabetes and to find out if all calories are indeed truly equal. They looked at various types of carbohydrate, such as starch, sucrose, glucose, fructose, and lactose.

They found that added fructose (not the fructose naturally found in fruits and vegetables) was linked to worsening insulin levels and glucose tolerance, precursors to diabetes.

Added fructose was also blamed for promoting belly fat, the harmful kind of fat that can lead to inflammation and high blood pressure.

Their conclusion? Added fructose is one of the biggest instigator for diabetes and risk of heart disease, so people should reduce their intake of this sweetener to less than five percent of total calories to lower the risk of “diabetes-related morbidity and mortality.”

Take-home messages

Does this study prove that consuming added sugars causes diabetes? It’s really too soon to say for sure. The study certainly gives us food for thought, however. Other studies have linked the intake of sweetened beverages to an increased risk for diabetes. But it’s important to keep in mind that this study was based on a literature review and was not conducted as a clinical trial. Also, we know that other factors contribute to diabetes risk, not just sugar. Does sugar affect people’s diabetes risk differently based on, say, weight, family history, level of physical activity, or ethnicity? We don’t have all the answers yet.

We can likely all agree that people in the United States can benefit from cutting back on their intake of refined carbohydrates, especially sugary drinks. And there’s plenty of evidence that eating nutritious, whole foods, like fresh fruits, vegetables, whole grains, lean proteins, and healthy fats can provide a host of health benefits. Let’s stick with these messages for now until we learn more. And maybe we’ll hear healthcare providers answer the question, “Does sugar cause diabetes?” with, “Maybe. We don’t know for sure yet.”

To learn more about sugar:

Sugar or Fat - What's Worse?
9 Hidden Sources of Sugar
For Diabetics, Simple Sugars Aren't So Simple