Grant: Project Grant

Heart diseases remain a leading cause of death, disability, and healthcare costs. Two of the most important ways to prevent heart disease are a healthy diet and cholesterol-lowering medications, the most used being statins. Both can meaningfully improve blood cholesterol and also benefit blood pressure and inflammation. However, statins also slightly raise blood sugar, which increase long-term risk of type 2 diabetes, and diabetes itself increases long-term heart disease risk. A healthy diet, in contrast, improve blood sugar. Yet, it remains unclear how much additional benefit a healthy diet provides when someone is already taking a statin, whether these benefits differ by statin dose, and whether diet can offset statin-related worsening of blood sugar. Addressing this gap is urgent because real-world evidence suggests that starting preventive medication may reduce motivation to improve diet. This study will quantify the benefits of combining a healthy diet with a statin at three different doses, focusing on heart disease risk and statin-related changes in blood sugar. Ninety adults will take part. All meals will be provided to participants during the study. Each participant will complete four 4-week diet/medication interventions: a standard Canadian diet or a plant-rich diet aligned with Canada's Food Guide, each combined with either rosuvastatin or a placebo. Participants will be randomly assigned to one of three rosuvastatin dose groups (5, 10, or 20 mg/day; same dose across the study). At the end of each 4-week period, we will measure blood cholesterol, inflammation, blood pressure, and blood sugar. This trial will generate readily usable, dose-specific evidence on how dietary improvements add to statin therapy, including whether diet can mitigate statin-related worsening of blood sugar. The findings will support sustained dietary change alongside medication and inform guideline-relevant shared decision-making about statin dosing and side-effect management.