Low Fat-Vegetarian-Vegan diet shown to improve glucose control, slow diabetes progression.
With diabetes on the rise, dietary modifications have shown to improve outcomes. Recent studies have shown a strong association between lowering fat, meat, sugar, sodium and alcohol intake while adding more fruits, vegetables, whole grains, and an overall lower glycemic load has reduced the risk of type 2 diabetes.1 In the only non-weight loss diet trial, The Women’s Health Initiative (WHI) Dietary Modification Trial (DMT) set out to prove that a low-fat diet can improve health outcomes. Endpoints of this study included: incidence of breast cancer, colorectal cancer, cardiovascular disease and diabetes. This 8.1-year-long trial failed to show a significant reduction in diabetes prevalence or disease progression. Barbara Howard et al. decided to take a second look at WHI DMT in hopes of finding a significant improvement in the management of diabetes.
A randomized secondary analysis was performed on the data collected from WHI DMT. The purpose of this analysis was to evaluate more specifically the outcomes related to diabetes and what lasting effects they have shown in a time frame of 8.1-17.3 years. In the initial trial, the intervention group received nutrition education, behavioral coaching, and group sessions while the comparison group only received educational health pamphlets. Adherence was evaluated through questionnaires and fasting blood glucose readings at baseline, years 1, 3 and 6. For the secondary analysis, 47,023 of the original 48,835 WHI DMT postmenopausal women were included. That sample size was further divided into 45,579 women without prevalent diabetes and 1,444 women with baseline diabetes and on oral agents. Exclusion criteria included type 1 diabetes and insulin only use. Diabetes progression was assessed through bi-annual and annual questionnaires. Women were asked to report any new use of oral antidiabetic agents or insulin injections. Medication inventory was conducted one year following randomization.
Outcomes of diabetes developed and progression were assessed by using four time-to responses. Outcomes one through three were used for women who were not knowledgeable about diabetes at baseline: (T1) time from randomization to first report of oral agent, (T2) Time from randomization to first report of insulin and (T3) time from oral agent initiation to first report of insulin. The fourth outcome was used for women with baseline diabetes and already on an oral agent: (T4) time from randomization to first report of insulin. Cox regression model was utilized to determine the association between dietary changes and all four outcomes. A linear mixed-effect regression model was used to assess longitudinal glucose readings. Finally, subsample analyses were used to define baseline characteristics. SAS statistical software version was used for statistical analyses. Censoring was applied at the end of the intervention if the patient died or was lost to follow-up.
Results showed that there was no significant difference in baseline characteristics between the two groups. Assessing the intervention groups, the outcomes were reported as follows: Outcome (T1) showed a reduction in oral therapy initiation: hazard ratio (HR) of 0.95 (95% CI 0.88 to 1.02); (P=0.13). Outcome (T2) showed that women without baseline diabetes were less likely to be started on insulin therapy: HR of 0.74 (0.59 to 0.94); (P=0.01). Outcome (T3) showed reduced rates of oral therapy initiation, but a progression from oral agents to insulin: HR of 0.82 (0.64-1.04); (P=0.10). Outcome (T4) showed that there was no reduction in risk for insulin use: HR of 0.92 (0.75-1.14); (P=0.47). Analysis of the fasting blood glucose measurements resulted in non-adherence for the intervention group more than the comparison group (P=0.01) for the total years. This intervention resulted in a 25% reduction risk of developing glucose >100mg/dL if the baseline was <100 mg/dL (odds ratio: 0.75 (0.61-0.93); (P=0.008)). Although this trial did not focus on weight loss, the intervention contributed to 1.9 kg loss in the intervention group compared to the control group’s 0.4kg in a year.
Overall, this study showed that in an 8.1-year time frame, initiation of insulin therapy can be avoided by making dietary and behavioral modification. Implementing a low-fat diet and more vegetables, fruits, and grains can indeed improve glycemic control and slow the progression of diabetes. This is a successful approach through nutrition education. Some strengths of this study include its duration and reproducibility. There were a few limitations with this study. One limitation is that the outcomes assessed did not align with the original trial’s outcomes, cancers, and cardiovascular disease. Secondly, medication inventories were not detailed. Lastly, this trial included one sex and the majority were Caucasian women leaving error for lack of generalizability. More longitudinal dietary studies should be conducted to assess its effects on diabetes progression.
- A low-fat diet can help improve glycemic control and slow the progression of diabetes.
- Adherence to oral medications can prevent initiation of insulin.
- Nutrition education for patients should be easily accessible and provided to all patients.
Cradock, Kevin A., et al. “Diet Behavior Change Techniques in Type 2 Diabetes: A Systematic Review and Meta-Analysis.” Diabetes Care, vol. 40, no.12, 21 Dec. 2017, pp. 1800-1810., doi:10.2337/dc17-0462.
Howard, Barbara V., et al. “A Low-Fat Dietary Pattern and Diabetes: A Secondary Analysis From the Women’s Health Initiative Dietary Modification Trial.” Diabetes Care, 27 Dec. 2017, pp. 1-8., doi:10.2337/dc17-0534.
Adrianna Jackson, Doctor of Pharmacy Candidate: Class of 2018; LECOM College of Pharmacy