Impact of Dairy Consumption on Inflammation: a Clinical Study (PLI)

Overview

Inflammation and endothelial dysfunction are being increasingly recognized as key etiological factors in the development of atherosclerosis and subsequent cardiovascular disease (CVD). These pro-atherogenic states are strongly correlated and often found co-segregating among individuals with obesity and the metabolic syndrome. There is increasing evidence to support the use in clinical practice of these novel markers of atherosclerosis and CVD risk. Recent data from the JUPITER study (Justification for the Use of Statins in Primary Prevention: An Intervention Trial Evaluating Rosuvastatin) has provided undisputable evidence that treating patients with elevated plasma CRP concentrations, a marker of systemic subclinical inflammation, leads to marked reduction in the risk of CHD even in patients with highly desirable LDL-C levels. There is also accumulating evidence associating endothelial dysfunction, which is defined as incapacity of the arteries to vasodilate when required, to an increased risk of CVD. While there are more and more studies on how diet affects inflammation and endothelial function, the impact of dairy consumption per se on these novel risk factors for CVD has not been well characterized. The purpose of this study was to investigate the impact of dairy consumption on markers of inflammation and other risk factors in men and women with low grade systemic inflammation.

This research will be undertaken as a multicenter randomized cross-over controlled study. A total of 140 men and women with subclinical inflammation (plasma CRP 2-10 mg/l) but otherwise healthy will consume two diets, one rich in dairy and one without dairy, while consuming a diet low in saturated fat (\<10% energy), in trans fat (\<1% energy) and in cholesterol (\<200 mg/day). During the DAIRY diet, subjects will be asked to incorporate 3 servings of dairy (milk, yogurt, cheese) into their every day diet. During the CONTROL arm of the study, participants will be asked to consume energy equivalent replacement products. Each diet will be undertaken consecutively in random order and will have duration of approximately 28 days each (4 weeks).The primary analysis consists in comparing inflammation markers and related risk factors between the two treatments. The study is designed to detect a 12-16% difference in plasma CRP concentrations (the primary endpoint) between the control and the dairy diet. A 2-week stabilization run-in period will precede the randomization of participants. During this run-in period, participants will be asked and instructed to adapt their diet to a prudent dietary pattern low in saturated fat (\<10% energy), in trans fat (\<1% energy) and in cholesterol (\<200 mg/day). The total amount of fat in the diet will not be restricted, with recommendations ranging from 25-35% of energy. However, substitution of saturated for unsaturated fat will be advocated. Sodium intake \<2300 mg/d will also be recommended. Recommendations will also include advice on how to restrict the consumption of processed and energy dense foods. The run-in diet will not include specific recommendation on dairy products. Participants will have the choice to include/exclude dairy from their prudent diet, as long as they comply with the main dietary recommendations. This 2-week run-in period will allow participants to familiarize themselves with the dietary recommendations used during the intervention per se. The two diets will be separated by a 4-week wash out period and will also consist to the prudent dietary pattern recommended. It must be stressed that foods will not be provided during the run-in and wash-out periods. These periods are imposed to minimize the inter- and intra-individual variability before and between the experimental phases.