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Diet and Diabetes Risk

Are beans really the magical fruit?

Over 1.4 million Americans are diagnosed with diabetes every year and that number is expected to rise. Diabetes doesn’t come cheap either. In 2012, diabetes cost $245 billion, 2.3 times what expenditure would be without diabetes, and still remains the 7th leading cause of death. The key to improving these statistics is prevention. While moderate exercise and a diet consisting of healthy fats, fiber, fruits, and vegetables can prevent or delay type 2 diabetes in high-risk patients, there could be a crucial ingredient in the recommended diet to making prevention a success; legumes. Already proven to be an important food for people with diabetes, legumes have a low glycemic index, high amounts of B vitamins, and valuable minerals.

Few studies have been performed to assess the association of a diet high in legumes and prevention of diabetes, and those completed have shown inconsistent results. The PREDIMED trial was designed to “examine the association between the consumption of total non-soy legumes and its different subtypes (dry beans, chickpeas, lentils, and fresh peas), and the risk of type 2 diabetes development in a Mediterranean population at high cardiovascular risk.” The trial was a randomized, multi-center, parallel group trial that included a total of 7,447 men and women between the ages of 55-80 who were at high risk for cardiovascular disease and had hypertension, hypercholesterolemia, low HDL, overweight/obese, smoked, or had a family history of premature coronary artery disease. Patients excluded from the study were those who had drug or alcohol abuse, severe chronic illness, allergies to nuts or olive oil, and later excluded patients with type 2 diabetes at baseline.

To establish a baseline, each patient completed a Food Frequency Questionnaire (FFQ) and measurements of blood pressure, blood samples, and body measurements were taken. The FFQ, along with the other measurements, was taken yearly for a median of 4.3 years to convey long-term diet effects. Patients were split into four groups based on legume consumption and each individual patient was assessed for time to diagnosis of type 2 diabetes, time of death, or to the last check-up. A subsequent analysis was performed to assess the effects of substituting half a serving of legumes a day for half a serving of protein.

Out of the 3,349 people who were included in the final assessment, 266 developed type 2 diabetes during the defined study period. The average consumption was 19.76 g/d of total legumes with the lowest group consuming 9.64 + 3.55 g/day and the highest group consuming 34.60 + 17.24 g/day. Participants in the highest legume consumption group were less likely to develop type 2 diabetes than those in the low consumption group even after adjusting for BMI (HRs: 0.65; 95% CI: 0.43, 0.96; P trend ¼ 0.04). High lentil consumption alone had an approximate decrease in development of type 2 diabetes by 33% compared to those in the low consumption group (HRs 0.67; 95% CI: 0.46-0.98; P trend= 0.05). After assessing the impact of replacing half a serving of protein with half a serving of legumes a day, there was a trend towards lower risk of type 2 diabetes, but the results were not significant [Meat(HR: 0.58; 95% CI: 0.32, 1.05; P-value =0.07), Fish (HR: 0.59; 95% CI: 0.34, 1.03; P-value =0.07].

While the study demonstrated statistically significant inverse relationship between legume consumption and development of type 2 diabetes, areas of weakness limit extrapolation of data to the general population. The study was conducted in Spain and included primarily older Caucasian adults. Considering the wide variability in typical diet, types of legumes consumed, and ethnic development of type 2 diabetes, and cardiovascular disease risk, a larger and more inclusive study would need to be performed. The rapidly rising rate of diabetes creates great need for similar studies that show the benefit of diets high in legumes reducing the risk of developing type 2 diabetes and possible other related diseases.

Practice Pearls:

  • High legume consumption can lessen the chance of developing type 2 diabetes compared to low legume consumption.
  • High consumption of lentils shows the greatest benefit out of all the legumes individually.
  • A diet high in proteins and plant-based foods, as well as moderate exercise, should be recommended to patients with high risk of developing type 2 diabetes and potentially other disease states.

References:

Statistics About Diabetes.” American Diabetes Association. Web. 06 Apr. 2017.

“Preventing Diabetes.” Centers for Disease Control and Prevention. 09 Nov. 2016. Web. 06 Apr. 2017.

Becerra-Tomas N, et al., Legume consumption is inversely associated with type 2 diabetes incidence in adults: A prospective assessment from the PREDIMED study, Clinical Nutrition (2017), http://dx.doi.org/10.1016/j.clnu.2017.03.015

 

Tenzing Dolkar, BSc., PharmD Candidate 2017, Lake Erie College of Osteopathic Medicine, School of Pharmacy