Two large studies recently questioned the assumption that the more stringently people with diabetes control their blood sugar levels, the better their heart health. In the studies—both published in The New England Journal of Medicine—people who pushed their levels lowest actually had worse outcomes (more heart disease deaths) than people who controlled sugar levels less strictly. Nutritionist Constance Brown-Riggs, who specializes in helping people live with diabetes, helps interpret the news:

Study buddy: “The studies involved people with vascular disease or multiple heart disease risk factors,” Brown-Riggs says, so it’s not clear yet how the news applies to others. “People with diabetes should not change their treatment goals based on these studies,” she adds. “Good glucose control can slow the progression of complications such as kidney disease and nerve and eye problems, along with cardiovascular problems,” Brown-Riggs says. People with signs of heart disease might need to control those risk factors—high cholesterol and blood pressure, for example—by using drugs instead of suppressing blood sugar below diabetes levels (as the people in the study did).

How low should you go? Brown-Riggs lists the general guidelines for blood-glucose levels, adding, “Consult your health care team for your own treatment plan.”

Fasting and before meals: 90 to 130 mg/dL (milligrams per deciliter of blood)

After meals: less than 180 mg/dL at peak (an hour after the start of a meal)

A1C levels: under 7 percent (A1C is a measure in twice-yearly blood tests; they show your average blood sugar level over the past three months)

A separate study has turned up evidence that a Mediterranean diet is beneficial for people with diabetes.

What it is: A Mediterranean diet includes fresh fruits and vegetables, beans, whole grains, olive oil, nuts, yogurt and cheese, fish, poultry and eggs; red meat is seldom eaten. Typically, portions are small.

Why it helps: “These foods supply ample fiber,” Brown-Riggs says, “which slows food leaving the stomach and being digested, slowing the speed of glucose entering the blood stream.” The diet also offers omega-3 fatty acids (fish) and monounsaturated fat (olives), which may control some blood fats and “bad” (LDL) cholesterol levels.

What to do: Consult a registered dietitian; find one through the American Dietetic Association (800.877.1600 or