The First Cross-Canada Trial of the Nutrition Trialists' Network--Enhanced Dietary Portfolio and Exercise on Arterial Damage (MRI-Enhanced Dietary Portfolio Plus Exercise on Cardiovascular Risk)

Presently in Canada, 29% of deaths are due to cardiovascular disease (CVD), costing $20.9 billion annually. The investigators have, therefore, brought together an unique network of investigators at different stages in their careers with a range of disciplines (nutrition, cardiology, diabetes, exercise physiology, imaging, physics, clinical trials, statistics, laboratory medicine, primary care, genetics, psychology, knowledge translation (KT), epidemiology), and with international recognition, experience and connections, to undertake a Canada-wide, multi-centre study which will test the ability of an effective cholesterol-lowering diet (dietary portfolio) and an exercise program, developed at Laval University, over 3 years to reduce the progression of plaque build-up in the carotid artery as assessed by Magnetic Resonance Imaging (MRI) in individuals with hypercholesterolemia and or type 2 diabetes. The dietary portfolio which has been proven in many of our studies to be an effective cholesterol-lowering diet will be enhanced to include features from other dietary strategies which the investigators have tested or developed; such as high monounsaturated fat (from Mediterranean diet) (CMAJ 2010) and low glycemic index foods (JAMA 2008). The investigators plan to recruit194 (approximately 200) men and postmenopausal women, who have measurable thickening (as assessed by ultrasound) due to plaque build up in the carotid arteries, in a 1.5 year period for this 3 year study. Ultrasound selection will be of individuals with intima-media thickness (IMT) >/=1.2mm as relevant arterial thickening to ensure a relatively low risk for the majority of the group, yet with some measurable arterial thickening.

Those selected will be randomly assigned to receive advice in one of four experimental arms: 1) Portfolio Plus diet and intensive increased physical activity program, 2) Portfolio Plus diet and a copy of Health Canada Physical Activity Guidelines with advice to increase physical activity, 3) DASH-like diet and an intensive increased physical activity program and 4) DASH-like diet and a copy of Health Canada Physical Activity Guidelines with advice to increase physical activity. The results of the study will have a major influence on dietary and exercise guidelines for coronary heart disease (CH risk reduction and provide evidence for the larger international trial that will focus on hard endpoints, myocardial infarction (MI) and CHD events). It is hoped that this cohort of participants will continue on and form part of the planned 9 year hard end point (MACE) study if funded.

Prior to starting treatments, participants will undergo screening ultrasound examination of both right and left carotids to enable selection of those individuals whose intima-media thickness (IMT) would be 5-30% below the cut point considered by the Mannheim Consensus as relevant arterial thickening to ensure a relatively low risk group, yet with some measurable arterial thickening.

It will be emphasized at the outset that both the dietary portfolio and the DASH-like diets have been associated with benefits in terms of cholesterol reduction to provide equal encouragement for all study arms. Portfolio and DASH-like dietary advice will consist of half hour individual sessions with the dietitian at baseline, and at 3-month intervals throughout the trial except for the first month when dietary advice will be reinforced, every 2 weeks, by telephone call to the participant or participant visit to the clinic. Prior to starting each diet, instruction will be given on achieving the dietary goals. At follow-up visits, the participants' completed 7-day diet records will be discussed and the original advice reinforced.

For the treatments with intensive increased physical activity the standardized physical activity/exercise component will be supervised by trained kinesiologists (exercise physiologists) for the 4 visits followed by monthly phone calls for the first year for the exercise component, when the major exercise training is provided. 7-day Exercise diaries will be collected at each visit. Using well-established procedures standardized across centers by the Quebec Heart and Lung Institute, the baseline visit will be used to provide a broad qualitative assessment of participants' lifestyle habits and preferences. Standardized physical activity questionnaires will be completed and participants will be asked to wear a pedometer for seven days prior to the intervention to quantify baseline physical activity (daily step count Cardiorespiratory fitness (CRF) is assessed using a submaximal treadmill test adapted from a progressive submaximal power output test performed on a cycle ergometer. The protocol begins with a warm-up workload of 2.5 mph with a 0% slope. The second stage is performed at a speed of 3.5 mph with a 2% slope. The third stage is adjusted in an attempt to reach 75% of the age-estimated maximal heart rate (HR). If necessary, a 4th stage is performed. Estimated VO2max is predicted by extrapolation to age-predicted maximal heart rate at a standardized submaximal treadmill stage (3.5 mph, 2% slope) and estimated maximal oxygen consumption (VO2max) are the variables considered as indicators of CRF in the present study.