Nuts May Lower Risk of Diabetes

Laurie Barclay, MD

June 18, 2002

June 19, 2002 -- New data presented June 16-17 at the 62nd Scientific Sessions of the American Diabetes Association suggest that eating nuts helps prevent the development of diabetes and that zinc supplementation in obese, insulin-resistant women improves insulin sensitivity, even in the absence of zinc deficiency.

"Major constituents of nuts (unsaturated fatty acids, magnesium and fiber) have been inversely associated with risk of type 2 diabetes; however, the overall effects of nut consumption on risk of type 2 diabetes are not available," write Rui Jiang and colleagues from Brigham and Women's Hospital in Boston. "Our results suggest that frequent nut consumption is associated with lower risk of type 2 diabetes in women."

In this offshoot of the Nurses' Health Study, the authors analyzed data from validated dietary questionnaires completed in 1980 by 83,818 women, aged 34 to 59 years, without a history of cardiovascular disease, cancer, or diabetes. During 16 years of follow-up, 3,206 women developed type 2 diabetes.

After adjustment for age, body mass index (BMI), smoking, physical activity, family history of diabetes, alcohol, and total energy intake, nut consumption was inversely associated with risk of diabetes. Compared with women who almost never ate nuts, multivariate relative risk (RR) among women who ate nuts less than once weekly was 0.93 (95% confidence interval [CI], 0.86-1.01). RR was 0.84 (95% CI, 0.76-0.93) among those who ate nuts one to four times weekly, and RR was 0.72 (95% CI, 0.60-0.88) among those who ate nuts more than five times weekly (P<.0001 for trend).

The protective effect of nuts did not vary after further controlling for dietary factors, including intake of vegetables, fruits, and whole grain, and a composite diet score composed of trans fat, cereal fiber, glycemic load, marine omega-3 fatty acids, folate, and polyunsaturated fat-to-saturated fat ratio.

"The inverse association persisted within strata defined by levels of family history of diabetes, body mass index, smoking, alcohol use, physical activity, and dietary variables," the authors write.

In a separate study by Dilina N. Marreiro and colleagues from Universidade de Sao Paulo-SP in Brazil, zinc supplementation enhanced insulin sensitivity in obese women who were not zinc-deficient.

In this prospective, double-blind, clinical interventional study, 56 obese women with normal glucose tolerance were randomized to treatment with zinc, 30 mg daily, or placebo for four weeks. At baseline, age was 25 to 45 years, mean BMI was 36.2 +177; 2.3 kg/m 2, and both groups were similar in clinical and laboratory parameters.

Insulin resistance as measured by a homeostasis model assessment did not change in the placebo group, but it decreased from 5.8 +177; 2.6 to 4.3 +177; 1.7 (P<.05) in the zinc-supplemented group. Insulin decreased from 28.8 +177; 14.1 to 21.2 +177; 8.1 mU/mL (P<.05) in the zinc group but was unchanged in the placebo group.

"A short time of zinc supplementation improved insulin sensitivity in obese insulin [resistant] women without zinc deficiency," the authors write. "Although the mechanism concerning the effect of zinc supplementation is not completely understood, further studies are recommended to address the possible role of zinc therapy in insulin resistance states such as [diabetes]."

ADA Annual Meeting: Abstracts 1644-P, 569-P. June 16-17, 2002.

Reviewed by Gary D. Vogin, MD

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