Walnuts May Improve Lipid Profile in Type 2 Diabetes CME
News Author: Laurie Barclay, MD
CME Author: Charles Vega, MD, FAAFP
Release Date: December 1, 2004; Valid for credit through December 1, 2005
Dec. 1, 2004 — Adding walnuts to a low-fat diet improves lipid profile for patients with type 2 diabetes, according to the results of a randomized study published in the December issue of Diabetes Care.
"Walnuts are distinguished from other nuts by virtue of their higher polyunsaturated fat content (and importantly their a-linolenic acid [ALA] content) combined with antioxidants in the form of ?-tocopherol," write Linda C. Tapsell, PhD, from the National Centre of Excellence in Functional Foods, University of Wollongong in New South Wales, Australia, and colleagues. "There are mechanistic explanations for the influence of dietary polyunsaturated fatty acid (PUFA) on insulin action and energy metabolism, and cohort studies of women in the U.S. have demonstrated a reduced risk of developing type 2 diabetes with dietary PUFA replacing trans or saturated fatty acids (SFAs)."
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).
The three groups were similar in changes in body weight, percent body fat, total antioxidant capacity, and HbA1c levels.
Study limitations include open recruitment; participation of only 50% of volunteers, limiting generalizability of the results; and lower baseline cholesterol levels in the walnut group.
"Structured 'whole of diet' advice that included 30 g of walnuts/day delivering substantial amounts of polyunsaturated fatty acid improved the lipid profile of patients with type 2 diabetes," the authors conclude.
The Australian Research Council and the California Walnut Commission funded this study.
Diabetes Care. 2004;27:2777-2783
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