- Click here for explanation of classification scheme.

Comparison of the effects on plasma lipoproteins and body composition of the consumption of a modified butter naturally enriched with CLA (CLA-B: 4.22g CLA per 100g butter fat) by the addition of sunflower oil to the diet of dairy cows with the consumption of a control butter (CON-B) that was low in CLA (0.38g CLA per 100g butter fat).

• Men
• BMI>26 and waist circumference>90cm
• Good health
• Non-smokers
• Between 18 and 55 years of age.

• Presence of a monogenic dyslipoproteinemia
• Use of medication known to affect lipid metabolism
• Chronic, metabolic or acute disease
• Significant weight change in the six months before the experiment
• Regular alcohol intake (more than one drink per day or more than seven drinks per week)
• Unusual dietary habits such as vegetarianism, food allergies or a dislike of foods included in the experimental diets.

Recruitment

Recruited from the Quebec City area 

Design

• Randomized cross-over trial
• Eight subjects were randomly assigned to the CLA-B diet for the first four-week period and to the CON-B diet for the second four-week period. The other eight subjects were assigned to the nutritional treatment sequence in reverse.

Blinding used

Double-blind

Intervention

• Both butters were manufactured from milk produced by dairy cows from a Laval University dairy herd. Cows were initially fed the same diet, then after three weeks, milk samples were obtained and the CLA content measured.
• Cows with the lowest concentration of CLA were identified, their milk was collected to make the control
• Once the production of CON-B was completed, the same cows were fed a similar diet to which 5% sunflower oil was added. Milk samples were taken after three weeks, and cows with the greatest concentration of CLA continued consuming the diet for the purpose of milk collection and the manufacture of the CLA-B.
• The butters were incorporated into two experimental diets
• Figure 1 shows relative isomeric distribution of CLA isomers in the butters; the percentages below were estimated by the reviewer from the figure
• Control butter (CON-B): 0.38g CLA per 100g fatty acids: About 52% cis-9, trans-11; cis-10, trans-11 undetectable; about 15% trans-10, cis-12+21:0
• CLA-B: 4.22g CLA per 100g fatty acids; About 80% cis-9, trans-11; less than 5% cis-10, trans-11; less than 5% trans-10, cis-12+21:0
• Each intervention period for was four-weeks. Experimental periods were separate by an eight-week washout period, during which the subjects resumed their usual diets.

 Statistical Analysis

• Repeated-measures analysis of variance, adjusted for cross-over designs, using the general linear model was performed to identify differences between experimental treatments 
• In the analysis of variance model, the carryover effects for each of the variables studied were tested by introducing a term referring to the sequence in which the dietary treatments were given. Although no significant sequence effect was found, a significant interaction was observed between treatment and sequence for VLDL-triacylglycerol and LDL apo B, which suggested a different response to the two diets across time. Therefore, only the results of the first period were analyzed for those two variables.
• Paired T tests were used to identify differences within the experimental diets only when significant differences were found between dietary treatments
• Group averages are reported as means ± SDs
• CRP values were logarithmically transformed before statistical analysis to achieve normal distribution. Two subjects who were found, during the course of the study, to have CRP concentrations >10mg/L, which suggested the presence of bacterial infection or inflammation, were excluded from statistical analysis for that variable.
• Differences were considered significant at P<0.05.

Timing of Measurements

• Food intake over three days was measured prior to the start of the study to estimate subject's usual energy intakes and thereby set proper energy levels for the experimental period
• Body weight taken every weekday before lunch
• On weekdays, subjects came to the metabolic kitchen daily to consumer their lunch meal, and they were then given their next dinner and breakfast meals in a package to take home
• At the beginning (day one) and at the end (day 28) of each experimental period, waist circumference was measured
• In the week after each experimental period (day 30 or 31), visceral adipose tissue accumulation was measured
• Fasting blood samples were collected on days one and 28 of each experimental period  
• Experimental periods were separated by an eight-week washout period, during which the subjects resumed their usual diets to remove the residual effects of the preceding experimental diet on the tested variables.

Dependent Variables

• Waist circumference, height and weight
• Visceral adipose tissue accumulation was measured by computed tomography, which was performed on a Siemens Somatom DRH Scanner
• Plasma lipoproteins: Plasma and lipoprotein cholesterol, triacylglycerols
• LDL apolipoprotein (apo) B and HDL apo A-I were measured by rocket immunoelectrophoresis
• LDL particle size was quantified by densitometric scanning of Sudan Black-stained gels
• Plasma leptin concentrations were determined with the use of a highly sensitive, commercial, double-antibody radioimmunoassay.
• Plasma CRP concentrations were measured by using a commercially available, highly sensitive immunoassay.

Independent Variables

• CON-B
• CLA-B.

Control Variables

Throughout the study, participants were asked to maintain usual level of physical activity, which was evaluated by a weekly questionnaire completed by the subjects.

• Initial N: 17 men
• Attrition (final N):
  • 16 men completed the study
  • One subject withdrew before the second phase of the study due to a job relocation
• Age: 36.6±12.4 (20-55)
• Ethnicity: All were white
• Other relevant demographics: Most were Canadian
• Anthropometrics:
  • Weight (kg): 94.6±13.3 (71.2-119.5)
  • BMI (kg/m²): 31.2±4.4 (26.2-44.4)
  • Waist circumference (cm): 105.8±9.8 (92.5-129.5)
• Location: Subjects were free living but came to the metabolic kitchen at Laval University for their lunch meal, to pick up their remaining food and for measurements. 

 Key Findings

• The 16 participants were overweight or obese, but their mean blood lipid profiles were within the normal range at baseline
• Table 1 of the article compares the subjects usual diet with the nutritional composition of the experimental diets. That some subjects lost weight despite the fact that their experimental energy intake was higher than their reported habitual energy intake suggested that, on average, subjects underestimated their energy intake. 
• The diet-induced variations in body weight, waist circumference, and plasma leptin concentrations did not differ significantly between the two groups
• No significant difference was found in the accumulation of visceral and subcutaneous adipose tissue between the diet groups.

Table 1. Body weight

	CON-B	CLA-B	P (between diets)
Body weight (kg)
Day 1	94.4±13.4	94.3±13.3
Day 28	93.1±13.0	92.5±12.9
Change (day 28-day one)	-1.31±1.23	-1.77±1.46	0.18

Other Findings

• When compared with the CON-B diet, the CLA-B diet resulted in significantly smaller reduction in plasma total cholesterol (-0.02 vs. -0.26mmol/L), but the changes in VLDL, LDL and HDL cholesterol and HDL subfractions did not differ significantly between the two diets. The greater reduction in total cholesterol after the CON-B diet was accompanied by a significantly greater decrease in total:HDL and LDL:HDL cholesterol after the CON-B diet than after the CLA-B diet.
• The CON-B diet resulted in a significantly greater reduction in plasma apo B concentrations than did the CLA-B diet
• Neither diet affected the LDL peak particle diameter or the concentration of plasma CRP.

• The results indicate that, in overweight or obese men with only a slight deterioration of their lipid profile, a 10-fold CLA enrichment of butter fat via the addition of sunflower oil to the feed of dairy cows does not induce significantly greater metabolic effects than are observed with the consumption of a control butter diet low in CLA.
• Further human studies are needed to evaluate the individual effects of different CLA isomers on lipoprotein metabolism and in persons with a more detrimental lipid profile at study onset.

Government:	Natural Sciences and Engineering Research Council of Canada; FCAR fund; Quebec Ministry of Agriculture; Canada Research Chair in Nutrition
Industry:	Novalait Inc,; Dairy Farmers of Canada Food Company: Commodity Group:

I think the author's recommendations for future studies is key to the effect of CLA. It appears most of the studies have been with relatively healthy people, maybe CLA has an effect in people who are not as healthy and showing effects of metabolic syndrome etc.