Association between walnut consumption and diabetes risk in NHANES

Background: Dietary interventions and cohort studies relating tree nut consumption to blood glucose levels suggest a possible effect of walnuts.

Objective: To examine the associations between walnut consumption and diabetes risk using data from the National Health and Nutrition Examination Survey.

Methods: National Health and Nutrition Examination Survey data on adults conducting 24-hour dietary recall was pooled across the years 1999 through 2014. Diabetes status or risk was based on self-report, medication use, fasting plasma glucose levels, and haemoglobin A1c (HbA_1c ) levels. Individuals were characterized based on reported consumption of walnuts, mixed-nuts, or no nuts.

Results: After adjustment for covariates, walnut consumers showed lower risk for diabetes compared with non-nut consumers based on self-report (odds ratio of 0.47, 95% confidence interval [CI] 0.31-0.72) as well as fasting blood glucose (relative risk ratio 0.32, CI 0.17-0.58) and HbA_1c (relative risk ratio 0.51, CI 0.27-0.99). For each standard deviation of increase in walnut intake, prevalence of diabetes dropped 47%. The gender by walnut interaction suggests that the effect may be more potent among women than men (dose response P = .061).

Conclusions: Both among individuals with known diabetes and those diagnosed based on elevated diabetes blood markers, the prevalence of individuals with diabetes was significantly lower among the walnut consumers. A possible gender-specific effect invites further attention.