Effect of Nuts on Glycemic Control and Cardiovascular Disease Risk in Type 2 Diabetes
The investigators wish to study the effect of nuts on glycemic control and to confirm their
lipid lowering effects in type 2 diabetes. The consumption of nuts with their high
unsaturated fat, vegetable protein (arginine) and fiber contents will decrease the glycemic
load of the diet and improve glycemic control. The investigators anticipate that the
favorable fatty acid profile of nuts along with the vegetable protein will improve the blood
lipid profile in type 2 diabetes and thereby establish a cardiovascular risk reduction
associated with nuts in this population.
Furthermore, flavonoids and vitamin E present in high concentrations in nuts, and known to
have antioxidant activity may help to counter the elevated oxidative stress and inflammation
experienced by diabetics. The investigators will therefore determine the effect of nut
feeding on measures of oxidative stress (including oxidized low-density lipoprotein
cholesterol (LDL-C), considered to be of direct relevance to coronary heart disease),
inflammation (C-reactive protein, serum amyloid A and interleukin-6) and nitric oxide
metabolism (blood nitric oxide and nitrotyrosine levels). These data would further add to
interest in nuts in relation to cardiovascular disease risk reduction and diabetic
complications.
Background Diet: A diet conforming to the American Diabetes Association (ADA) and National
Cholesterol Education Program (NCEP) Adult Treatment Panel III guidelines. Nuts, soy and
dietary supplements (vitamins, minerals, herbal remedies) will be excluded in the background
diet during all phases of the study.
Treatment diets:(1) Full-Dose Nut Diet: Raw nuts will be added as supplements to the
subject's usual diet. Subjects with calorie needs of 2,400 kcal or greater, assessed by
Lipid Research Clinic (LRC) tables, will receive the full-dose supplement (100 g/d of nuts,
approximately 600 kcal). Subjects requiring between 1,600-2,400 kcal daily will receive 75%
of the full-dose supplement (75 g/d of nuts, approximately 450 kcal). Subjects requiring
less than 1,600 kcal daily will receive 50% of the full-dose supplement (50 g/d of nuts,
approximately 300 kcal). (2) Half-Dose Nut Diet: Raw nuts will be added as supplements to
the subject's usual diet. Subjects with calorie needs of 2,400 kcal or greater, assessed by
LRC tables, will receive half of the full dose of the nut supplement (50 g/d of nuts,
approximately 300 kcal) with the rest of the calories provided by the muffin (2 muffins are
300 kcal) for a total of 600 kcal. Subjects requiring between 1,600-2,400 kcal daily will
receive 75% of the half-dose supplement (37.5 g/d of nuts and 1.5 muffins, approximately 450
kcal). Subjects requiring less than 1,600 kcal daily will receive 50% of the half-dose
supplement (25 g/d of nuts and 1 muffin, approximately 300 kcal). (3): The full-dose control
supplement will be four 150 kcal muffins. Control supplements will be matched with the
energy content of the nut supplements, i.e. either 600 kcal/d (4 muffins); 450 kcal/d (3
muffins); 300 kcal/d (2 muffins). The macronutrient composition of the muffins will conform
to an NCEP Step 2 diet with 25% total fat, <7% saturated fat by use of corn oil as the oil
commonly used in healthy baked goods, with 18% protein (the average for our subject
population) using added skim milk powder, and zero cholesterol. Muffins will be made with
whole wheat flour.
Diet History: one-week weighed diet histories will be obtained prior to the start and at
weeks 4, 8 and 12 of the study for assessment of macronutrients, dietary fiber and fatty
acids.
Palatability/Satiety: for palatability and satiety, subjects will record their ratings using
a 7-point bipolar semantic scale at monthly intervals during each study phase.
Anthropometry and Blood Pressure: height at recruitment and body weight, blood pressure,
waist and hip circumference, and body composition will be taken immediately prior to and at
each clinic visit (wk 0, 2, 4, 8, 10, 12) during the study.
Interventional
Allocation: Randomized, Endpoint Classification: Efficacy Study, Intervention Model: Parallel Assignment, Masking: Single Blind (Outcomes Assessor), Primary Purpose: Treatment
Markers of glycemic control: Fasting serum fructosamine
From prestudy and week 0, to end of treatment weeks 8, 10, 12
Yes
David JA Jenkins, MD, PhD
Principal Investigator
University of Toronto, St. Michael's Hospital
Canada: Health Canada
REB 06-274
NCT00410722
December 2006
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