Study of the Impact of Low Fat Dairy and High Fat Dairy Consumption on Daytime Ambulatory Blood Pressure
Condition: Hypertension
MeSH terms: Hypertension
Study type: Interventional

Summary: 
      Market trends depicted by Agriculture and Agri-Food Canada suggest stagnation in cheese
      consumption, with potentially important impact on this key industry in Canada. This is in
      part due to the commonly accepted notion that saturated fat in the diet, of which cheese
      contributes significantly, increases the risk of heart disease. Yet, a rather large body of
      recent evidence suggests that saturated fat may have been unfairly demonized and that its
      impact on the risk of heart disease may in fact be less important than originally thought.
      This concept that dairy fat increases the risk of heart attacks therefore needs to be
      revisited.

      The proposed research is designed to investigate which risk factors for heart disease (e.g.
      cholesterol, blood pressure) are beneficially modified when low fat (milk) and high fat
      (cheese) dairy products are consumed.

      Our hypotheses are : (1) Consumption of low fat dairy (milk 1% fat) compared with a
      dairy-free control diet reduces daytime ambulatory systolic blood pressure and reduces
      inflammation; (2) Consumption of a high fat dairy (GABA-rich cheese) compared with a
      dairy-free control diet reduces daytime ambulatory systolic blood pressure and has favorable
      effects on LDL particle size, inflammation and HDL-C concentration.
    

Detailed description: 
      This is a single-center randomized crossover controlled feeding study. Briefly, adult men and
      women will be recruited based primarily on blood pressure criteria in the Quebec City
      metropolitan area through the media (newspaper, radio) and mailing lists (n=60).

      Participants will be randomized to 3 experimental diets of 6 weeks each: 1- CONTROL
      dairy-free diet, 2- low fat dairy (MILK, 1% fat, 3 servings/d), 3- high-fat dairy (GABA-rich
      cheddar cheese, approximately 32% fat, 1 serving (50g)/d). Usual energy intake will be
      estimated at the beginning of the study using validated tools. Experimental diets will be
      provided as part of a full feeding protocol under carefully controlled isocaloric conditions
      to maintain body weight constant. All meals and foods will be provided to participants so
      that control for energy and macronutrient intake will be optimized. The breakfast meal will
      represent approximately 30% of the daily energy intake whereas the lunch and dinner meals
      each will provide 35% of daily energy intake. Participants will be instructed to consume
      their entire meals. A seven-day cyclic menu will be used. We have opted to test the impact of
      dairy intake over a 6-week period (as opposed to 4 or 5 weeks) to maximize the chance to
      observe clinically meaningful changes in blood pressure. Diets will be separated by a 4 to 8
      week washout period. Randomization will be stratified by sex. Blood samples will be collected
      the day before each dietary phase and on 2 consecutive days after each dietary phase. The
      mean of the 2 consecutive measurements will be used in the analyses.
    

Intervention name(s): Control diet; Milk diet; GABA-rich cheese diet
Intervention type(s): Other; Other; Other
Allocation: Randomized
Intervention model: Crossover Assignment
Masking: Single (Outcomes Assessor)
Primary purpose: Prevention
Keywords: Cardiovascular disease; Blood pressure; Hypertension; Dairy products; Milk; Cheese