Effects of Walnuts on Endothelial Function in Overweight Adults with Visceral Obesity: A Randomized, Controlled, Crossover Trial
Complete Project
Title:
Effects of Walnuts on Endothelial Function in Overweight Adults with Visceral Obesity: A Randomized, Controlled, Crossover Trial
Status:
Completed
Topic:
Cardiovascular Health / Endothelial Function*
Funding Source:
The California Walnut Commission
Funding Period:
2009-2011
Study Design:
Randomized controlled crossover trial
Purpose:
This study explored the effects of daily walnut intake among overweight adults who had at least one risk factor for metabolic syndrome, a cluster of conditions (high blood pressure, high fasting glucose, high triglycerides, and/or low HDL cholesterol) that occur together and raise the risk of Type 2 diabetes and cardiovascular disease. Walnuts are a rich source of omega-3 fats, other healthful nutrients, and antioxidants, and have been shown to benefit cardiovascular health.
Further Study Details:
Participants took part in an 8-week walnut phase and an 8-week control phase, with a 4-week washout period between phases. We randomly assigned half of the study group to start first with the control phase, and the other half to start first with the walnut phase. The control phase consisted of following their typical eating habits. The walnut phase consisted of following their typical eating habits, with the exception of eating 2 ounces of walnuts per day and adjusting for the 350 extra daily calories from the walnuts to maintain a daily caloric intake consistent with the control phase. We compared the effects of both phases on endothelial function (ability of blood vessel walls to constrict and dilate properly), blood pressure, body weight, waist circumference, dietary intake, fasting glucose, and fasting lipids (total cholesterol, HDL cholesterol, LDL cholesterol, and triglycerides).
Findings:
A total of 40 participants completed the study. During the walnut phase, endothelial function improved significantly from baseline compared to during the control phase. During the walnut phase, body weight and waist circumference remained stable, and there was a beneficial trend in reduction of systolic blood pressure. Dietary intake of polyunsaturated fats, omega-3 fats, omega-6 fats, and total fat increased significantly during the walnut phase while dietary intake of other nutrients remained stable. There were no significant changes in glucose or lipid levels during the walnut phase. Results provide evidence of a role for walnuts in protecting against diabetes and heart disease in at-risk individuals.
Eligibility:
Overweight men and women age 25 to 75 years who had not been diagnosed with diabetes or cardiovascular disease, but who had at least one risk factor for metabolic syndrome.
Yale-Griffin Prevention Research Center