In this parallel design trial, 58 adults with type 2 diabetes were randomized to one of three dietary advice groups, each with 30% energy as fat: low fat, modified low fat, and modified low fat inclusive of 30 g of walnuts per day. Mean age was 59.3 ± 8.1 years.

Patients received dietary advice at baseline, with monthly follow-up and telephone calls bimonthly for support. All groups were advised to consume fish and five daily portions of fruits and vegetables. Body weight, percent body fat, blood lipids, glycosylated hemoglobin (HbA1c), total antioxidant capacity, and erythrocyte fatty acid levels were measured at baseline and at three and six months, and analysis was by intent-to-treat.

Erythrocyte biomarkers of dietary intake confirmed higher dietary polyunsaturated fat-to-saturated fat ratio and intakes of ?-3 fatty acids in the walnut group. Compared with the two other treatment groups, the walnut group had a significantly greater increase in high-density lipoprotein (HDL) cholesterol-to-total cholesterol ratio (P = .049) and in HDL (P = .046). The walnut group also had a 10% reduction in low-density lipoprotein (LDL) cholesterol, reflecting a significant effect by group (P = .03) and time (P = .04).