Diet high in protein, processed meat raises risk of diabetes

Daniel M Keller

September 16, 2011

Lisbon, Portugal - Results of a large population-based study show that a high protein intake is associated with an increased incidence of type 2 diabetes. In presenting their results here at the European Association for the Study of Diabetes (EASD) 2011 Meeting, Swedish researchers suggest that replacing protein with carbohydrates, especially breads and cereals rich in fiber, may be preferable for avoiding incident diabetes.

Diets low in carbohydrates but high in protein and fat have shown positive effects on weight reduction and glycemic control, but other studies have shown that a high protein intake, especially animal protein such as processed meats, is associated with an increased risk of type 2 diabetes.

Lead author Ulrika Ericson (Lund University, Malmö, Sweden) told meeting attendees that the study included 27 140 individuals (10 550 men) 45 to 73 years old who participated in the Malm ö Diet and Cancer Cohort and did not have diabetes at baseline. The researchers gathered information on weight, height, lifestyle, and socioeconomic factors. Dietary data were obtained through a seven-day registration of cooked meals, a detailed 168-item questionnaire covering other meals, and a 45-minute interview.

Between 1991 and 2006, 1709 incident cases of type 2 diabetes were identified. Using a Cox proportional hazards model with adjustment for several potential confounders, researchers found that, for both genders, participants with the highest intakes of protein were at increased risk of developing diabetes, Ericson told the audience. The highest quintile of protein intake was associated with a 37% increased risk of type 2 diabetes compared with the lowest quintile (hazard ratio [HR]=1.37; p for trend <0.001).

High intake of processed meat was also associated with an elevated risk of diabetes (p=0.01), as was intake of poultry and eggs. There was no association of diabetes risk with intake of fish or red meat, but when all animal sources of dietary protein were considered together, an increased risk was seen. "So this indicates that protein per se may be of importance," Ericson concluded.

"For carbohydrate intake, we did not find any overall association with type 2 diabetes," she said. "However, we found significant interaction with sex (p=0.02). In men, high carbohydrate intake tended to be protective," reducing the risk of type 2 diabetes by about 23%. There was no significant effect of carbohydrate intake for women. Overall, fat intake was not associated with the risk of incident diabetes, but there was trend toward protection for women in the highest quintile of fat intake.

For both men and women, fiber intake was not associated with any change in risk, but the intake of fiber-rich breads and cereals showed a significant association with reduced risk of type 2 diabetes, with the highest quintile of intake having an HR of approximately 0.71 (p=0.002).

In summary, Ericson said a protective association exists with a high intake of fiber-rich breads and cereals. And although high protein intake has been shown to be effective for short-term weight loss and glycemic control, it is associated with an increased risk of type 2 diabetes. So the results of this trial suggest caution when considering high-protein diets. However, she said it is too early to make dietary recommendations based merely on the observed associations.

Session moderator Dr Leszek Czupryniak (Medical University of Lodz, Poland) said in an interview that a study limitation is its retrospective nature and dependence, in part, on diary data derived from self-reports with the attendant possibility of imperfect memory.

He said high protein intake may facilitate type 2 diabetes and metabolic disturbances, mostly through the elevation of low-grade inflammation. On the other hand, such diets can facilitate weight loss, which could counterbalance the increased risk. "But that needs a prospective study, not a retrospective analysis just taking the dietary questionnaires," Czupryniak advised.

Looking at the study as a whole, he said that apparently eating a diet low in fat and high in plant fiber is beneficial. "We're not sure about protein content of the diet, and that probably depends on the condition of a subject, as well as genetics, which can affect a person's response to diet," Czupryniak said.

"What the future holds is probably that we will need various diets for various genetic backgrounds, but we will have to be able to define it somehow," he observed.

Ericson and Czupryniak reported having no relevant disclosures. The Swedish Research Council provided support for the study.

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