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

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.

Inclusion criteria

• Men and women aged between 18 and 70 years
• Presenting a subclinical inflammation (Plasma CRP >2 and <10 mg/l)
• Abdominal obesity, waist girth >94 cm in men and >80 cm in women
• Consumption of dairy products fewer than 2 servings per day
• Pre-menopausal women with regular menstrual cycle for the last 3 months

Exclusion criteria

• Plasma CRP <2 or >10 mg/l
• Smokers (>1 cigarette/day)
• Body weight variation >10% for the last 6 months prior to the study baseline
• BMI >35 kg/m2
• Previous history of CVD, type 2 diabetes and monogenic dyslipidemia
• Subjects taking medications for hyperlipidemia, hypertension
• Post menopausal women who have initiated hormone replacement therapy within 6 months of study onset
• Endocrine or gastrointestinal disorders
• Smoking
• Food allergies, milk aversion or intolerant to lactose
• Clinical use of vitamin D or calcium supplements
• Vegetarianism