Walnuts and Glucose Variability

The Effect of Walnuts on Glucose Variability in Adults With Type-2 Diabetes Mellitus: a Dose-response Metabolic Feeding Study

Persons with type 2 diabetes mellitus (T2DM) have swings in their blood sugar levels that may lead to a higher risk of developing heart disease. An important part of diabetes management involves eating a diet to prevent large swings in blood sugar levels. Walnuts contain fat, protein and fiber that may reduce the swings in blood sugar. The purpose of this study is to compare the effects of a walnut-free American Diabetes Association (ADA) diet versus 2 levels of walnut-enriched ADA diets on blood sugar swings. Eighteen male and female adults with T2DM will participate in the study. Subjects will be randomized to consume an ADA diet with or without walnuts for 3 consecutive days every other week. Subjects must test their blood sugar twice daily and wear a continuous glucose monitor during the three 72-hour study periods. Subjects will be between 40 and 70 years of age and will be recruited from the surrounding community using flyers and public service announcements. Consent will take place in the Department of Nutrition at Loma Linda University by the study investigators. In total, subject participation will last 5 weeks and all meals will be provided during the 3 study periods.

The primary objective is to evaluate the effect of two isocaloric walnut-enriched meal plans versus a walnut-free ADA meal plan on within-day glucose variability in adults with diabetes by assessing: a) the overall standard deviation (SD) around the sensor glucose calculated for each day and then averaged over the 3-day study periods; b) the mean amplitude of glycemic excursions (MAGE) over the 3-day study periods.

A secondary objective will be to test for a dose-response effect, i.e. the more walnuts (full-dose versus half-dose) the lower the glucose variability.

The effect of the three isocaloric ADA meal plans (full-dose, half-dose, walnut free) on the mean of the daily differences(MODD) will be recorded as a measure of between-day glycemic variability

Glucose levels will be measured before and after breakfast, lunch and dinner for each of the three isocaloric ADA meal plans (full-dose, half-dose, walnut free)

The mean of the glucose for the range captured on each sensor (sensor maximal glucose level minus minimal glucose level will be recorded

The duration of hypoglycemia will be measured as hours per day for each of the three isocaloric ADA meal plans (full-dose, half-dose, walnut free)

The duration of hyperglycemia will be measured as hours per day for each of the three isocaloric ADA meal plans (full-dose, half-dose, walnut free)

Inclusion Criteria: adults between age 40 and 70 years with type 2 diabetes duration of type 2 diabetes more than 6 months but less than 10 years HbA1c 6.0-8.0% BMI 25-40 kg/m2 diet controlled or stable dose of metformin for at least 3 months willing to test blood glucose with personal meter twice a day during study test days Exclusion Criteria: using oral hypoglycemic agents or insulin history of ischemic heart disease or congestive heart failure history of severe diabetic complication (neuropathy, renal failure, stroke) taking medication affecting glucose levels (i.e. corticosteroids) active infectious disease active malignancy pregnant or breast feeding woman smoker history of daily caffeine or alcohol intake known allergy to nuts lactose or gluten intolerance