74th Scientific Sessions of the American Diabetes Association (ADA):

Type 2 Diabetes Reduced by Changes in Diet Quality

Researchers at the Harvard School of Public Health in Boston determined that by improving the quality of a person’s diet, Type 2 Diabetes (T2D) could be prevented. Interestingly, the study results were independent of lifestyle changes. Doctor Sylvia H. Ley, PhD, a postdoctoral fellow at the Harvard School of Public Health presented, Changes in Overall Diet Quality, Lifestyle and Subsequent Risk of Type 2 Diabetes: Three Cohorts of US Men and Women during the 74th Scientific Sessions of the American Diabetes Association on June 14, 2014 in San Francisco, California.

Study Rationale
Dr. Ley explained the rationale behind the study, specifically that diet was important in diabetes prevention, which led her research team to examine food-based approaches. “We learned over recent years that dietary patterns—not just one food item, but the overall quality of food intake has some impact on diabetes prevention,” Dr. Ley stated.

Study Data
The research team looked at three different cohort studies performed in the United States, which followed participants (n=148,479) for more than 20 years. Study exclusion criteria included people with a history of diabetes (type 1, type 2, gestational), cardiovascular disease, or cancer.

  • Nurses’ Health Study I (1976-2010)
  • Nurses’ Health Study II (1986-2010)
  • Health Professionals Follow-up Study (1989-2011)

Every two years participants were asked to record any incidence of diabetes, and every four years they were asked about their diet (eg, dietary patents, diet quality). Dr. Ley’s team used the Alternative Healthy Eating Index (AHEI)* score to assess diet quality. “When we looked at these scores, people who improved their scores by 10% or more had actual reduction in their incidence of diabetes four years later. Whereas, people who worsened their scores by 10% or more had an increased risk of developing diabetes,” Dr. Ley stated.

During Dr. Ley’s presentation, five types of diets were associated with a lower risk of diabetes:

  • Mediterranean diet1
  • Dietary Approaches to Stop Hypertension (DASH)1
  • Vegetarian and vegan1
  • Dietary guidelines—Alternative Healthy Eating Index (AHEI)1
  • Prudent dietary pattern1

*AHEI includes red meat, nuts, sugar-sweetened beverages, fruits, vegetables, polyunsaturated fat, trans fat, omega fats, moderate alcohol consumption, sodium, and whole grains. These foods have been shown to reduce the risk of diabetes and improve glycemic control and blood lipids in patients with diabetes.1

Furthermore, it was determined that it didn’t matter whether study participants started out as poor eaters or healthy eaters. It was learned that participants who improved the quality of foods eaten benefited by a lower incidence of diabetes.


  1. Ley SH, Hamdy O, Mohan V, Hu FB. Prevention and management of type 2 diabetes: dietary components and nutritional strategies. The Lancet. June 2014;383(9933):1999-2007.
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