Evidence suggests that adhering to a Dietary Approaches to Stop Hypertension (DASH), may lower hemoglobin A1c (HbA1c), fasting blood glucose (FBG), and insulin levels in those with metabolic syndrome or diabetes. The diet does not have a significant effect on blood glucose in healthy populations.1-8 The DASH diet promotes fruit, vegetable, and low-fat dairy food consumption while reducing saturated fat and cholesterol intake. It is recommended for the management of hypertension based on the extensive evidence of its blood pressure lowering effects, but its benefits are not limited to blood pressure.4 Some small studies have shown blood-sugar-lowering benefits in non-diabetic populations,9,10 but the overall quality of evidence is not strong in this population.
Zade et al. carried out a two-arm parallel randomized clinical trial to determine the effects of the DASH diet on 60 overweight and obese patients diagnosed with non-alcoholic fatty liver disease.2 Participants were randomly assigned to follow the DASH diet or control diet for an eight-week period. The control diet had the same macronutrient content as the DASH diet, but it was higher in refined grains and sweets and lower in fruits and vegetables. At the end of the trial, the DASH diet did not significantly reduce participants’ FBG more than the control diet did. However, in an analysis of the change in insulin levels during the DASH diet versus the control diet, the DASH diet significantly reduced insulin levels (3.3 ± 3.4 vs. 1.1 ± 3.8 µIU/mL, p=0.01) and HOMA-IR (0.8 ± 0.8 vs. 0.2 ± 0.9, p=0.01) more than the control diet. The authors concluded that the DASH diet had a beneficial effect on markers of insulin metabolism.
A 2019 umbrella review by Chiavaroli et al. supported these findings and expanded upon them.3 The blood glucose, HOMA-IR, and insulin levels of participants following a DASH diet were compared to those of participants following a standard diet, which was either a healthy diet or typical American diet in the majority of the studies. The analysis showed that there was no significant difference between the two groups in ten controlled trials (n=826) on FBG and eight trials (n=760) on HOMA-IR. However, the authors found that the diet had an insulin lowering effect of 0.15 µU/mL (95% CI [0.22 –0.08], p<0.001). The evidence for FBG was determined to be low-quality and contain substantial inter-study heterogeneity, but the evidence for HOMA-IR and insulin were of moderate quality with non-significant inter-study heterogeneity. When looking at the effect of the DASH diet on HbA1c in their own low-quality meta-analysis of two trials (n=65), the authors found that there was a significant reduction in HbA1c of 0.53% (95% CI [0.62 – 0.43], p<0.001). However, these latter studies were exclusively focused on adults with type 2 diabetes mellitus (T2DM), limiting the generalizability of this finding.
As the Chiavaroli et al. umbrella review found,3 there may be a beneficial reduction in blood sugar among those with T2DM.7,8 Azadbakht et al. investigated the effect of the DASH diet on 31 patients with T2DM through a randomized crossover clinical study.7 After a three week run-in period, the patients were randomized to a DASH diet or a control diet (50 – 60% carbohydrates, 15 – 20% protein, 30% total fat, and 5% of caloric intake from simple sugars) for eight weeks with an additional four week wash-out period between treatments. When comparing the mean changes during the DASH diet versus the control diet, the authors found that FBG was significantly reduced (29.4 ± 6.3 mg/dL vs 12.8 ± 6.7 mg/dL, p=0.04) and A1c was significantly reduced (1.7 ± 0.1% vs 0.5 ± 0.02%, p=0.04) to a greater extent on the DASH diet.
Overall, while there may be a potential benefit of blood glucose reduction in diabetic individuals, many studies demonstrate that the DASH diet is ineffective at reducing blood sugar in more healthy populations. Nonetheless, more randomized control trials need to be conducted in order to make more substantial conclusions.
References
- Shirani F, Salehi-Abargouei A, Azadbakht L. Effects of Dietary Approaches to Stop Hypertension (DASH) diet on some risk for developing type 2 diabetes: a systematic review and meta-analysis on controlled clinical trials. Nutrition. 2013;29(7-8):939-947.
- Razavi Zade M, Telkabadi MH, Bahmani F, Salehi B, Farshbaf S, Asemi Z. The effects of DASH diet on weight loss and metabolic status in adults with non-alcoholic fatty liver disease: a randomized clinical trial. Liver Int. 2016;36(4):563-571.
- Chiavaroli L, Viguiliouk E, Nishi SK, et al. DASH Dietary Pattern and Cardiometabolic Outcomes: An Umbrella Review of Systematic Reviews and Meta-Analyses. Nutrients. 2019;11(2).
- Siervo M, Lara J, Chowdhury S, Ashor A, Oggioni C, Mathers JC. Effects of the Dietary Approach to Stop Hypertension (DASH) diet on cardiovascular risk factors: a systematic review and meta-analysis. Br J Nutr. 2015;113(1):1-15.
- Martin CL, Siega-Riz AM, Sotres-Alvarez D, et al. Maternal Dietary Patterns are Associated with Lower Levels of Cardiometabolic Markers during Pregnancy. Paediatr Perinat Epidemiol. 2016;30(3):246-255.
- Ghorabi S, Salari-Moghaddam A, Daneshzad E, Sadeghi O, Azadbakht L, Djafarian K. Association between the DASH diet and metabolic syndrome components in Iranian adults. Diabetes Metab Syndr. 2019;13(3):1699-1704.
- Azadbakht L, Fard NR, Karimi M, et al. Effects of the Dietary Approaches to Stop Hypertension (DASH) eating plan on cardiovascular risks among type 2 diabetic patients: a randomized crossover clinical trial. Diabetes Care. 2011;34(1):55-57.
- Asemi Z, Tabassi Z, Samimi M, Fahiminejad T, Esmaillzadeh A. Favourable effects of the Dietary Approaches to Stop Hypertension diet on glucose tolerance and lipid profiles in gestational diabetes: a randomised clinical trial. Br J Nutr. 2013;109(11):2024-2030.
- Kucharska A, Gajewska D, Kiedrowski M, et al. The impact of individualised nutritional therapy according to DASH diet on blood pressure, body mass, and selected biochemical parameters in overweight/obese patients with primary arterial hypertension: a prospective randomised study. Kardiol Pol. 2018;76(1):158-165.
- Tiong XT, Nursara Shahirah A, Pun VC, et al. The association of the dietary approach to stop hypertension (DASH) diet with blood pressure, glucose and lipid profiles in Malaysian and Philippines populations. Nutr Metab Cardiovasc Dis. 2018;28(8):856-863.
- Weyer C, Hanson R, Tataranni P, Bogardus C, Pratley R. A high fasting plasma insulin concentration predicts type 2 diabetes independent of insulin resistance: evidence for a pathogenic role of relative hyperinsulinemia. Diabetes. 2000;49(12):2094-2101.
