Effie Viguiliouk: This systematic review and meta-analysis of the totality of evidence from 12 randomized clinical trials in 450 participants with type 2 diabetes found that eating about 1/2 a cup of tree nuts per day (equivalent to about 60 g or 2 servings) significantly lowered the two key markers of blood sugar, HbA1c and fasting glucose, in comparison to calorically matched control diets without tree nuts.
Medical Research: Were any of the findings unexpected?
Effie Viguiliouk: We found that the greatest reductions were seen when tree nuts replaced refined carbohydrates (high-glycemic index carbohydrates) rather than saturated fats.
Medical Research: What should clinicians and patients take away from your report?
Effie Viguiliouk: Given that people in North America consume on average less than 1 serving of tree nuts a day, this is one way they can adapt their diets to take advantage of the metabolic benefits. One serving of tree nuts is about ¼ cup or 30 grams. Inclusion of about 1/2 a cup of tree nuts (which includes such things as almonds, Brazil nuts, cashews, hazelnuts, macadamia nuts, pecans, pine nuts, pistachios and walnuts, but not peanuts) as part of a healthy diet can help with lowering and stabilizing blood sugar levels in individuals with type 2 diabetes.
Medical Research: What recommendations do you have for future research as a result of this study?
Effie Viguiliouk: In order to address the sources of uncertainty in our analyses, there is a need for longer, higher quality trials that use tree nuts to lower the glycemic load of the diet by displacing high-glycemic index carbohydrates with a specific focus on glycemic endpoints as a primary outcome. The inclusion of such trials in future meta-analyses will help guide the development of nutrition recommendations and health claims, as well as the planning of future trials.
Effie Viguiliouk, Cyril W. C. Kendall, Sonia Blanco Mejia, Adrian I. Cozma, Vanessa Ha, Arash Mirrahimi, Viranda H. Jayalath, Livia S. A. Augustin, Laura Chiavaroli, Lawrence A. Leiter, Russell J. de Souza, David J. A. Jenkins, John L. Sievenpiper. Effect of Tree Nuts on Glycemic Control in Diabetes: A Systematic Review and Meta-Analysis of Randomized Controlled Dietary Trials. PLoS ONE, 2014; 9 (7): e103376 DOI: 10.1371/journal.pone.0103376