Ground Beef and Cardiovascular Disease
Condition: Lipoprotein Metabolism Disorder
MeSH terms: Cardiovascular Diseases; Metabolic Diseases
Study type: Interventional

Summary: 
      This study tested the hypothesis that ground beef high in monounsaturated fat (MUFA) and low
      in saturated fat (SFA) would increase the high-density lipoprotein-cholesterol concentration
      and low-density lipoprotein particle diameter. In a crossover dietary intervention, 27
      free-living normocholesterolemic men completed treatments in which five 114-g ground beef
      patties/week were consumed for 5 weeks with an intervening 4-week washout period. Patties
      contained 24% total fat with a MUFA:SFA ratio of either 0.71 (low MUFA, from pasture-fed
      cattle) or 1.10 (high MUFA, from grain-fed cattle).
    

Detailed description: 
      Participants and study design Healthy, nonsmoking males between the ages of 23 and 60 years
      were screened for eligibility. The 30 participants selected were not consuming restrictive
      diets or medications. Family histories were obtained as part of a complete physical
      examination that included a treadmill exercise test with an electrocardiogram. Baseline blood
      chemistries were analyzed by a local laboratory and all blood chemistries were within normal
      ranges as defined by the testing laboratory. All participants were free living and were
      instructed to maintain routine activities and body weight (62.2 kg of entry weight). Exercise
      and physical activities were not restricted, but participants were requested not to change
      their habitual level of physical activity. Twenty-seven of the initial 30 participants
      completed the study.

      Of the 3 non-completers, 1 had a re-occurrence of a previous illness, another relocated, and
      data from the 3rd was omitted following baseline samples that showed high triglyceride
      concentrations (.5 mmol/L). A 2-period, randomized cross-over design was used. Each
      participant completed two 5-wk diet interventions in a randomly assigned order with a 4-wk
      washout period between the test diet interventions. The men consumed 5 ground beef patties
      per week for 5 wk during each dietary intervention (25 patties of each type for each ground
      beef intervention). The 2 interventions were low-monounsaturated fat ground beef and
      high-monounsaturated fat ground beef. To facilitate product distribution and blood sampling,
      participants were assigned to 1 of 2 groups, which were balanced with regard to age, body
      weight, and total cholesterol concentration at the initial screening. Group 1 began the study
      2 wk before group 2. Both groups rotated through both test diets, but the pattern in which
      they crossed over differed between groups. Therefore, crossovers included all possible
      rotation sequences. Body weights were recorded weekly.

      Collection and analysis of blood samples Prior to the initiation of the dietary treatments
      and at the end of each diet phase and after 5 minutes of seated rest, blood was collected
      from the participants into vacutainers from a vein in the antecubital fossa using standard
      phlebotomy procedures. Plasma was harvested from the blood collected with EDTA and
      lipoproteins preserved in plasma prior to lipoprotein separation using density gradient
      ultracentrifugation employing human density intervals. Determination of LDL lipoprotein
      diameters was by non-denaturing gradient gel electrophoresis. Particle diameters were
      determined by comparison with migration distances of standard proteins of known hydrated
      diameter. Plasma total lipoproteins isolated as the d < 1.2 kg/L fraction of plasma were
      separated on the basis of diameter with a gel-filtration chromatographic system to determine
      the relative distribution of plasma total cholesterol among very low-density lipoproteins
      (VLDL), LDL, and HDL lipoprotein classes. Concentrations of total cholesterol, triglycerides,
      and glucose in plasma were determined by separate enzymatic assays. Concentrations of serum
      insulin and serum C-reactive protein (CRP) were assayed using commercially available ELISA
      kits according to the manufacturers' instructions.

      Statistical analysis We compared nutrient and dietary exchange data and final plasma glucose,
      lipids, insulin, CRP, and lipoprotein particle diameters to their corresponding baseline
      values by paired t test. Data were tested for unequal variance by the Breusch-
      Pagan/Cook-Weisberg test for heteroscedasticity to test the null hypothesis that the error
      variances were all equal. Values for changes from baseline for the low- and high-MUFA
      treatment groups were compared by 1-way analysis of variance, with ground beef type as the
      treatment effect. Associations among plasma analytes were assessed using Pearson correlation
      coefficients. P-values were considered significant at P < 0.05.
    

Intervention name(s): Ground beef
Intervention type(s): Dietary Supplement
Intervention description(s): Ground beef naturally low in monounsaturated fatty acids or naturally high in monounsaturated fatty acids
Allocation: Randomized
Intervention model: Crossover Assignment
Intervention model description: A 2-period, randomized cross-over design was used. Each participant completed two 5-wk diet interventions in a randomly assigned order with a 4-wk washout period between the test diet interventions.
Masking: Single (Participant)
Primary purpose: Basic Science
Keywords: ground beef; lipoprotein cholesterol; cardiovascular disease