Effect of lowering the glycemic load with canola oil on glycemic control and cardiovascular risk factors: a randomized controlled trial

Jenkins DJA, Kendall CWC, Vuksan V, et al. Effect of lowering the glycemic load with canola oil on glycemic control and cardiovascular risk factors: a randomized controlled trial. Diabetes Care. 2014. DOI:10.2337/dc13-2990.

This parallel design, randomized trial assessed effect of ALA and MUFA as part of a low-glycemic-load diet on glycemic control, lipid parameters, and CVD risk factors. Subjects had type 2 diabetes with A1C 6.5% to 8.5% and were receiving oral antihyperglycemic therapy. Subjects had no significant CV, renal, or hepatic disease at baseline.

Interventions over 3 months:

  • Low-glycemic-load diet with a canola oil-enriched bread supplement containing ALA and MUFA (31 g canola oil; 500 kcal/day of 2,000 kcal/day diet) (n=70)
    • Emphasis on low glycemic-index foods (eg, legumes, barley, pasta, parboiled rice, fruit)
     
  • High wheat-fiber diet with whole-wheat bread supplement (500 kcal) (control; n=71)
    • Advised avoidance of white-flour products; to be replaced with whole-wheat breakfast cereals, study breads, brown rice, etc
     
  • Subjects asked to keep exercise constant; no specific exercise advice provided

The primary outcome was change in A1C. Secondary outcomes included Framingham CVD risk score and reactive hyperemia index ratio (marker of flow-mediated vasodilation)  

Click on slide thumbnail to view larger. Slide available for download in the slide library.
Effects of Canola Oil-Enriched Low-Glycemic-Load Diet on Glycemic Control and CVD Risk Factors Design  
Effects of Canola Oil-Enriched Low-Glycemic-Load Diet on Glycemic Control and CVD Risk Factors: Design 

Primary outcome
Mean A1C change (absolute A1C units), %:*

  • Low-glycemic-load diet with canola oil-enriched bread supplement (n=70): -0.47 (-5.15 mmol/l) (95% CI, -0.54 to -0.40; P<0.001)
  • High wheat-fiber diet with whole-wheat bread supplement (control; n=71): -0.31 (-3.44 mmol/l) (95% CI, -0.38 to -0.25; P<0.001)

Relative A1C reduction for the low-glycemic-load diet was -0.16 (-1.71 mmol/l) (95% CI, -0.25 to -0.06; P=0.002); this change remained significant after adjustment for change in body weight, which showed similar reductions in both treatment groups (-2.1 kg in in the low-glycemic-load diet and -1.6 kg for the control diet).

Click on slide thumbnail to view larger. Slide available for download in the slide library.
Effects of Canola Oil-Enriched Low-Glycemic-Load Diet on Glycemic Control and CVD Risk Factors Change in A1C  
Effects of Canola Oil-Enriched Low-Glycemic-Load Diet on Glycemic Control and CVD Risk Factors: Change in A1C 

Change in lipids, CVD risk factors 
Low-glycemic-load diet vs control:

  • Significant decreases in TC, LDL-C, TG, TC:HDL-C ratio, LDL-C:HDL-C ratio with low-glycemic-load diet relative to control
  • Reduction in Framingham Risk Score seen in both groups; more significant reduction with low-glycemic-load diet vs control (-1.16 [95% CI, -1.49 to -0.82] vs
    -0.53 [95% CI, -0.84 to -0.22] ; -0.63 [95% CI, -1.09 to -0.17] change between diets; P=0.008)
  • No significant between-group differences in BP, heart rate
  • Nonsignificant reduction in vascular reactivity with low-glycemic-load diet – but nearly significant increase for control, resulting in increase in reactive hyperemia index for control diet (-0.12 [95% CI, -0.24 to 0.01] vs 0.13 [95% CI, 0.00 to 0.25] ; -0.24 [95% CI, -0.42 to -0.06] change between diets; P=0.009)

Click on slide thumbnail to view larger. Slide available for download in the slide library.
Effects of Canola Oil-Enriched Low-Glycemic-Load Diet on Glycemic Control and CVD Risk Factors Change in Lipids CVD Risk  
Effects of Canola Oil-Enriched Low-Glycemic-Load Diet on Glycemic Control and CVD Risk Factors: Change in Lipids, CVD Risk 

Change in A1C in subjects with elevated systolic BP
When data were examined to assess the impact of the dietary interventions among subjects with higher vs lower baseline measurements for CVD and metabolic syndrome:

  • The only significant treatment difference seen was for subjects with systolic BP ≥130 mm Hg vs those with systolic BP >130 mm Hg.
  • A substantial A1C reduction was seen among subjects with systolic BP >130 mm Hg who consumed the low-glycemic-load diet vs the control diet (-0.62%
    [-6.79 mmol/l] [95% CI, -0.77% to -0.47%]; P<0.001).
  • Among subjects with systolic BP >130 mm Hg, the treatment difference was over five-fold greater than the treatment difference observed among those with systolic BP <130 mm Hg. (-0.41% [-4.45 mmol/l] [95% CI, -0.62% to -0.19%]; P=0.001 vs -0.07% [-0.81 mmol/l] [95% CI, -0.20% to 0.06%]; P=0.253) 


*Baseline n values are shown. At Weeks 8, 10, and 12, n=54 in low-glycemic-load diet group; n=64, 60, and 59 in control group. 

ALA=alpha-linolenic acid; HDL-C=high-density lipoprotein cholesterol; LDL-C=low-density lipoprotein cholesterol; MUFA=monounsaturated fatty acid; TC=total cholesterol; TG=triglycerides

  


June 2014 

This overview was created by KnowledgePoint360 Group, LLC, and was not associated with funding via an educational grant or a promotional/commercial interest.  

Previous Article
Improved glucose control with weight loss, lower insulin doses, and no increased hypoglycemia with empagliflozin + MDI insulin 

Next Article
Incretin based drugs and risk of acute pancreatitis in patients with type 2 diabetes: cohort study 

Back to
Recent Diabetes Articles 

BG Footer

 

 

Last Modified: 8/4/2014