Table 1 Randomized clinical trials using CLA as intervention on putative benefits

BACHMAIR et al., 2015 [55]

Forty-three healthy adults at low to moderate risk of cardiovascular disease

Double-blind, placebo controlled study

Sample received 4 g/day of CLA80:20 or placebo for two weeks

No clear evidence was found for inhibition or activation of platelet function as well as inflammation by CLA80:20 in a low to moderate cardiovascular risk group.

JENKINS et al., 2014a [56]

Thirty-four untrained to moderately trained men

Double-blind, placebo controlled study

Randomly assigned to either a CLA (Clarinol A-80; n = 18) or placebo (PLA; sunflower oil; n = 16) group Prior to and following 6 weeks of aerobic training (50 % VO₂peak for 30 min, twice per week) and supplementation (5.63 g of total CLA isomers [of which 2.67 g was 9-cis, 11-trans and 2.67 g was 10-trans, 12-cis] or 7.35 g high oleic sunflower oil per day)

Serum triacylglycerol concentrations were lower (p < 0.05) in the CLA than the PLA group. For VO₂peak and glucose, there were group × time interactions (p < 0.05). However, post-hoc statistical tests did not reveal any differences between the CLA and PLA groups.

JENKINS et al., 2014b [57]

Thirty-four untrained to moderately trained men

Double-blind, placebo controlled study

Randomly assigned to either a CLA (Clarinol A-80; n = 17) or placebo (PLA; sunflower oil; n = 16) group. Before and after 6 weeks of aerobic training (50 % VO₂peak for 30 min, twice per week) and supplementation (8 ml CLA or PLA per day), each subject completed an incremental cycle ergometer test, maximal number of sit-ups in 1 min, and the standing long jump

There were no differences between the CLA and PLA groups for the analysis of covariance-adjusted post-test mean values for physical working capacity, sit-ups, or standing long jump. The physical working capacity increased from pre- to post-training in the CLA (p = 0.003) and PLA (p = 0.003) groups. There were no differences from pre- to post-training for sit-ups and standing long jump in either the CLA or PLA groups. There was no effect of CLA on physical working capacity, maximum number of sit-ups or standing long jump.

ARYAEIAN et al., 2014 [58]

Seventy eight adults with active rheumatoid arthritis

Double-blind clinical trial

Four groups receiving one of the following daily supplement for 3 months; group C: 2.5 g CLAs, group E: 400 mg Vitamin E, group CE: CLAs plus Vitamin E, group P: Placebo. Cytokines, matrix metalloproteinase (MMP-3) and citrullinated antibody (CCP-A)

Co-supplementation CLAs and Vitamin E may be effective in the level of inflammatory markers in rheumatoid arthritis patients.

EFTEKHARI et al., 2014 [59]

Ninety atherosclerotic patients

clinical randomized trial

Patients were classified into 3 groups receiving 3 g/d CLA or 1 920 mg/d ω3 or placebo for 2 months.

Although CLA did not appear to have a significant effect on triglycerides, ω3 supplementation significantly reduced triglycerides level. Consumption of CLA and ω3 supplementation did not significantly affect HDL cholesterol, LDL cholesterol, and total cholesterol.

MOHAMMADZADEH et al., 2013 [60]

Thirty four volunteers patients with rectal cancer

Randomized, double-blind, placebo-controlled pilot

CLA group (n = 16), receiving 3 g CLA/d, and placebo group (n = 18) receiving placebo capsules (sunflower oil) for 6 weeks

CLA supplementation improved inflammatory factors, MMP-2, and MMP-9 as biomarkers of angiogenesis and tumor invasion. It seems that CLA may provide new complementary treatment by reducing tumor invasion and resistance to cancer treatment in patients with rectal cancer.

PENETO et al., 2013 [61]

Twenty nine healthy adult volunteers (nineteen women and ten men, aged twenty two to thirty six years)

Double-blind clinical trial

CLA depletion was achieved through an 8-week period of restricted dairy fat intake (depletion phase; CLA intake was 5.2 ± 5.8 mg/day), followed by an 8-week period in which individuals consumed 20 g/day of butter naturally enriched with 9-cis, 11-trans CLA (repletion phase; CLA intake of 1020 ± 167 mg/day)

The intake of a 9-cis, 11-trans CLA-enriched butter by normal-weight subjects induces beneficial changes in immune modulators associated with sub-clinical inflammation in overweight individuals.

CARVALHO et al., 2013 [62]

Fourteen women diagnosed with metabolic syndrome

Randomized clinical trial, placebo-controlled

Participants received strawberry jam enriched or not with microencapsulated CLA (3 g/day) as a mixture of 38.57 % 9-cis, 11-trans, and 39.76 % 10-trans, 12-cis CLA isomers associated with a hypocaloric diet for 90 days

There were no significant effects of CLA on the lipid profile or blood pressure. Mean plasma insulin concentrations were significantly lower in women supplemented with CLA, did not alter the waist circumference, but there was a reduction in body fat mass detected after 30 days, and had a reduced waist circumference

BULUT et al., 2013 [63]

Eighteen sedentary male volunteers

Randomized double blind experiment

Volunteers were randomly divided into CLA and placebo supplementation groups; both groups underwent daily supplementation of either 3 g CLA or 3 g placebo for 30 days and performed exercise on a bicycle ergometer 3 times per week

CLA is not more effective than exercise alone.

LÓPEZ PLAZA, et al., 2013 [64]

Thirty eight volunteers (29w, 9 m)

A prospective, placebo-controlled, randomised double-blind, parallel clinical trial

Volunteers consumed 200 ml/day of skimmed milk with 3 g of CLAs or 3 g olive oil (placebo).

The consumption of skimmed milk enriched with 3 g of a 1:1 mixture of 9-cis, 11-trans and 10-trans, 12-cis for 24 weeks led to a decrease in body weight and total fat mass in healthy, overweight subjects who maintained habitual diets and exercise patterns. No adverse effects were observed

ENGBERIN et al. 2012 [65]

Sixty-one healthy volunteers

Double-blind, placebo controlled study

The diets were identical except for 7 % of energy (18.9 g in a diet of 10 MJ/day) that was provided either by oleic acid, by industrial trans fatty acids or by 9-cis, 11-trans CLA.

The effect of the CLA diet compared with the oleic acid diet was 0.11 mm Hg (95 % confidence interval: −1.27, 1.49) systolic and −0.45 mm Hg (−1.63, 0.73) diastolic. Short-term high intakes of 9-cis, 11-trans CLA do not affect blood pressure in healthy volunteers.

JOSEPH et al., 2011 [66]

Twenty seven volunteers with overweight, borderline hypercholesterolemic,

Double-blinded, 3-phase crossover trial

Participants consumed under supervision in random order 3.5 g/d of safflower oil (control), a 50:50 mixture of 10-trans, 12-cis, and 9-cis, 11-trans CLA:Clarinol G-80, and 9-cis, 11-trans isomer CLA

Compared with the control treatment, the CLA treatments did not affect changes in body weight, body composition, or blood lipids. In addition, CLA did not affect the β-oxidation rate of fatty acids or induce significant alterations in the safety markers tested.

MICHISHITA et al., 2010 [67]

Forty-one healthy subjects

Single-centre, randomized, double-blind, placebo-controlled trial

Subjects were randomized to receive either placebo or one of three test supplements: amino acid mixture 0.76 g/day; amino acid mixture 1.52 g/day; or amino acid mixture 1.52 g/day coadministered with conjugated linoleic acid 1.6 g/day and exercises for a period of 12 weeks

The results suggest that ingestion of these supplements might enhance the fat-burning effects of exercise.

WANDERS et al., 2010 [68]

Sixty-one healthy women and men

Double-blind, placebo controlled study

It was provided either by oleic acid, by industrial trans fatty acids or by a mixture of 80 % 9-cis, 11-trans and 20 % 10-trans, 12-cis CLA.

High intakes of an 80:20 mixture of 9-cis, 11-trans, and 10-trans, 12-cis CLA raise the total to HDL cholesterol ratio in healthy volunteers. The effect of CLA may be somewhat less than that of industrial trans fatty acids.

SLUIJS et al., 2010 [69]

Four hundred and one

Double-blind, randomized, placebo-controlled and parallel-group trial

Subjects receive either 4 g CLA/d (2.5 g 9-cis, 11-trans CLA/d and 0.6 g 10-trans, 12-cis CLA/d) or placebo supplements for 6 months

There was no effect of 9-cis, 11-trans CLA supplementation on blood pressure, body composition, insulin resistance, or concentrations of lipid, glucose, and C-reactive protein.

SYVERTSEN et al., 2007 [70]

One hundred and eighteen volunteers

Randomized, double-blind, placebo-controlled trial

Supplementation with either placebo (olive oil) or CLA (Clarinol) for 6 months

CLA does not affect glucose metabolism or insulin sensitivity in a population of overweight or obese volunteers.