Canola-Mediterranean Diet Study in T2DM

The investigators plan to assess the effects of increasing both canola oil and plant protein foods while reducing carbohydrate intake in the context of a Mediterranean type diet on weight loss, glycemic control and cardiovascular risk factors in type 2 diabetes.

Obesity rates in Western nations have shown a dramatic rise in the last 20 years and diabetes rates have doubled, a trend which is predicted to be repeated over the next 20 years. In Canada the predicted cost to the healthcare system in only 7 years will rise to $17 billion. Weight loss diets (such as Atkins, Eddies, South Beach and Zone) emphasizing carbohydrate restriction have become increasingly popular for the prevention and treatment of diabetes. As a result, lower carbohydrate diets are being selected by health conscious members of the general population including those with diabetes. Because such diets in effect promote a high intake of protein from animal sources, even in the presence of weight loss, serum cholesterol levels rise due to increased cholesterol and saturated fat intake; and a further rise in serum lipids is likely to occur in the long term when weight loss has ceased. On the other hand, lower carbohydrate dietary patterns that are higher in plant rather than animal fat and proteins have been associated with improved blood lipids and reduced risk of heart disease and type 2 diabetes.

The investigators have therefore planned a study in which a weight reducing low carbohydrate, Mediterranean type diet that is high in plant proteins and canola oil will be compared to a weight reducing high cereal fibre diet in a 3 month study. 150 overweight and obese participants with type 2 diabetes will be randomized to one of 2 treatments.

Study visits will be as follows: weeks -2, 0 (for randomization), 2, 4, 8, 10 and 12. Body measurements, blood pressure and blood samples will be taken at each visit except week 2. The week 2 visit will be mainly for reinforcement of dietary advice; also body weight will be measured and blood drawn for fast glucose and HbA1c. Diet records will be reviewed at all visits. 24 hour urine samples will be collected at week 0 and week 12.

On completion of the 12 week study, participants will be given the option of continuing on the same diet or trying the opposite diet for a further 12 weeks. Visits will be every 4 weeks for a total of 3 visit. Body measurements, blood pressure and blood samples will be taken during these visits as in the initial 12 week study.

Inclusion criteria

• Men and women with type 2 diabetes diagnosed for more than 6 months
• BMI >27 (non-Asians); BMI >25 (Asians)
• HbA1c between 6.5% and 8.5% at screening, and at the preparation visit before starting diet
• on a stable prescribed dose of oral diabetes medication for at least 2 months
• on a stable dose of lipid medication for at least 2 weeks, if prescribed
• on a stable dose of blood pressure medication for at least 1 week, if prescribed
• have a family physician
• can keep written food records, with the use of a digital scale

Exclusion criteria

Individuals with the following characteristics/conditions will be excluded

• on insulin
• on steroids
• on warfarin (Coumadin)
• GI disease (gastroparesis, celiac, colitis, Crohn's disease, Inflammatory Bowel Syndrome)
• history of cancer, except non-melanoma skin cancer (basal cell, squamous cell)
• major cardiovascular event (stroke, myocardial infarction) in past 6 months
• major surgery in past 6 months
• major debilitating disorder
• liver disease (AST or ALT> 3x the upper limit of normal) except non-alcoholic fatty liver (NAFL) disease or non-alcoholic steatohepatitis (NASH).
• hepatitis B or C
• renal failure (creatinine > 150 mmol/L)
• serum triglycerides >4.5mmol/L
• acute or chronic infections (bacterial or viral)
• chronic inflammatory diseases (e.g. lupus, ulcerative colitis)
• blood pressure >145/90, unless approved by their family physician
• alcohol consumption >2 drinks/d
• food allergies to wheat, canola, or other study food components
• any condition determined by the investigators to make the subject unsuitable for the study