Study of the Impact of Dairy Fat on Cardiovascular Health.

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, and this is one of the key objectives of this proposed research program.

The proposed research is designed to investigate for the first time if dairy fat improves the levels of the so-called "good cholesterol", a protective risk factor that has been essentially ignored in the arguments supporting the reduction of saturated fat for heart health.

Our hypothesis is that consumption of SFA from dairy (cheese) compared with a low fat diet and diets rich in MUFA and PUFA leads to favorable changes in plasma HDL-C concentrations and functional characteristics. Consumption of SFA from dairy (cheese) also increases LDL particle size, reduces inflammation and has no deleterious impact on plasma LDL-C and apolipoproteins B (apoB) concentrations compared with a low fat diet.

This is a multi-center randomized crossover controlled feeding study. Briefly, adult men and women will be recruited in the Quebec City and Winnipeg metropolitan area through the media (newspaper, radio), local lipid clinics and mailing lists (n=90).

Participants will be randomized to a series of 5 experimental diets of 4 weeks each: 1- Cheese diet, 2- Butter diet, 3- Carbohydrate (CHO) diet, 4- MUFA diet, 5- PUFA diet. 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. The diets will be separated by washout periods of 4 weeks. Blood samples will be collected on two consecutive days before and after each dietary phase. The mean of the two consecutive measurements will be used in the analyses.

Eligibility Criteria:
Inclusion Criteria:

* Men and women age between 18 and 65 years
* Waist circumference \>80.0 cm for women and \>94.0 cm for men
* Plasma concentration of triglycerides \>1.70 mmol / L
* Stable weight for 6 months before the start of the study (+/- 5lbs)

Exclusion Criteria:

* Men or women aged under 18 years or over 65 years
* History of CVD, type 2 diabetes or dyslipidaemia monogenic
* Endocrine disorders
* Smoking
* Lipid lowering medications or hypertension medications
* Food allergies and aversions to any food in the composition of experimental menus
* Subjects with special dietary habits (e.g. vegetarianism)
* Subject with a calculated Framingham risk of cardiovascular disease (CVD) \> 20%