Diet quality may improve with daily walnut intake
Among those at high risk for diabetes, overall diet quality and certain cardiovascular risk factors may be improved with a daily intake of walnuts, according to recent study findings published in BMJ Open Diabetes Research & Care.
“We found that daily walnut ingestion improved overall diet quality, and vascular health as measured by endothelial function, in adults at risk for type 2 diabetes,” David L. Katz, MD, MPH, FACPM, FACP, FACLM, director of Yale University Prevention Research Center, told Endocrine Today. “When walnut ingestion was combined with advice about overall calorie intake, daily walnut intake was associated with a decline in waist circumference as well.”
David L. Katz
Katz and colleagues evaluated 112 adults aged 25 to 75 years (31 men) at high risk for diabetes randomly assigned to a diet with or without dietary counseling to adjust calorie intake. The two groups were further assigned to either daily inclusion of 56 g of walnuts or complete avoidance of walnuts for 6 months. After 3 months, the intervention arms were reversed.
Researchers sought to determine the effect of walnut intake on diet quality.
After 6 months, diet quality as assessed with the Healthy Eating Index 2010 was significantly improved with the walnut-included diet compared with the walnut-excluded diet. Participants in the walnut-included diet also had significantly improved endothelial function and total and LDL cholesterol compared with baseline; however, no significant differences were found between the walnut-included diet, with or without dietary counseling for calorie intake adjustment, compared with the walnut-excluded diet.
No significant improvements were seen in BMI, percent body fat, percent body water or visceral fat with the walnut-included diet for 6 months, with or without dietary counseling, compared with the walnut-excluded diet (P > .05).
Significant increases were found for percent body fat and visceral fat relative to baseline with the walnut-included diet without dietary counseling. Significant improvements from baseline were found for waist circumference with dietary counseling regardless of walnut intake.
“The health benefits of walnuts are already rather robustly established,” Katz said. “This study suggest benefits over an extended timeline with routine intake by adults at risk for diabetes. That population numbers in the many tens of millions. The study also reaffirms prior research suggesting that walnut intake, and nut intake in general, has favorable effects on appetite and satiety, and thus may lead to improvement in body composition and/or weight control despite the high energy density of nuts.”
According to Katz, many questions still remain, including those about the optimal dose and frequency of intake of walnuts for maximum health benefits.
“In particular, we are interested in the potential contributions of walnut intake to weight-loss efforts, and the potential for improvements in body composition of clinical significance when routine walnut intake is combined with dietary counseling to help make ‘room’ for those added calories,” Katz said.
Disclosure: Katz reports receiving compensation from the California Walnut Commission.