DFA: Conjugated Linoleic Acid (CLA) Supplementation and Intermediate Health Outcomes (2011)


Cornish SM, Candow DG, Jantz NT, et al. Conjugated lilnoleic acid combined with creatine monohydrate and whey protein supplementation during srength training. Int J Sport Nutr Exerc Metab. 2009 Feb; 19(1): 79-96. PMID: 19403955.

PubMed ID: 19403955
Study Design:
Randomized Controlled Trial
A - Click here for explanation of classification scheme.
Quality Rating:
Positive POSITIVE: See Quality Criteria Checklist below.
Research Purpose:
  • To determine the effects of the combination of CLA, creatine and whey protein on muscle mass and strength during a strength-training program
  • To determine whether the combination of CLA, creatine and whey protein affected markers of muscle protein and bone catabolism, oxidative stress and kidney function.
Inclusion Criteria:
  • Already performing regular strength training for at least 12 months
  • 18 to 30 years of age.
Exclusion Criteria:
  • History of nutritional supplementation for 12 or more weeks prior to the study
  • Disease or condition that prevented participation in high-volume strength training.


Description of Study Protocol:


RCT using double-blind repeated measures; subjects were randomized stratified by gender to one of three groups (CCP, CP or P). All subjects participated in strength training and supplementation. Three-day dietary records were kept during the first and last weeks of the intervention. Participants were instructed not to change their diet during the study.

Blinding Used

A research assistant who was not involved in any other parts of the study randomized subjects and coded the supplements to ensure all participant and investigators were blinded. Group coding was used to maintain blinding during data entry and analysis.


  • The CCP group received 6g per day CLA, 9g per day creatine and 36g per day whey protein. The CP group received 9g per day creatine, 36g per day whey protein, 6g per day placebo sunflower oil. The P group received 45g per day whey protein and 6g per day sunflower oil. The differences in the amount of whey protein were to maintain isonitrgenous supplementation and similar energy contents of the supplements. Supplementation was in powdered form. The CLA was composed of approximately 36% each of the c9t11 and t10 c12 isomers. Supplementation and exercise training occurred for five weeks. All subjects participated in the same high-volume, heavy-load periodized, free-weight strength-training program.
  • Compliance was measured by verbal communication and returned supplement containers.

Statistical Analysis

A three (group) x two (gender) x two (pre- and post-) ANOVA with repeated measures was used to assess changes in lean tissue mass, fat mass, muscle thickness, strength, 3 methylhistidine, NTx, 8-isoprostanes, and macronutrient intake over time. A two-way ANOVA was used to analyze baseline measurements between groups. Tests for body composition, strength, 3 methylhistidine, and NTx were one-tailed based upon a priori hypotheses. Significance was at P≤0.05.

Data Collection Summary:

Timing of Measurements

At baseline and after intervention (at five weeks).

Dependent Variables

  • Lean tissue and fat mass measured by air displacement plethysmography (BOD POD)
  • Muscle thickness measured using B-mode ultrasound
  • Leg-press and bench-press strength
  • Urinary indicators of 3 methylhistidine, N-telopeptides for bone resportion, 8-isoprostanes (oxidative stress), microalbumin (renal function) and NTx by ELISA (bone-collagen equivalents.

Independent Variables

  • CCP supplementation (CLA, creatine and whey protein)
  • CP supplementation (creatine and whey protein)
  • P supplementation (whey protein and sunflower oil).
Description of Actual Data Sample:
  • Initial N: 77
  • Attrition (final N): 69 (52 males); 10% attrition
  • Age (Mean±SD):
    • P group: Men 23.1±2.3 years; women 23.4±2.4
    • CP group: Men 22.6±2.4; women 21.8±2.6
    • CCP group: Men 22.4±2.4; women 22.0±2.8
  • Other relevant demographics: None other than regular strength trainers
  • Anthropometrics: Groups were not different at baseline for age, height, body mass, FFM, fat mass or percentage fat
  • Location: Canada.
Summary of Results:

Key Findings

  • There was a change from baseline to five weeks for lean tissue mass and and total body mass for all groups, P<0.01
  • There were no changes in fat mass or percent body fat over time
  • Contrast analysis (difference between groups) showed that the CCP group increased lean tissue mass more than the CP and P groups combined, P<0.05. Similarly, the CCP and CP groups increased lean tissue mass more than the P group, P<0.05.

Other Findings

  • Compliance was more than 98% for each group
  • No differences were found between groups from baseline to five weeks for intake of total energy and macronutrients
  • Bench press and leg press strength increased more in the CCP group than in the CP + P groups combined, P<0.05
  • All groups increased over time for muscle thickness, P< 0.05
  • There were no changes in 3 methylhistidine, NTx, and 8-isoprostanes over time in any group. However, in contrast analysis, the percent change scores for the CCP and CP groups combined were lower than the P group for 3 methylhistidine.
Author Conclusion:

The combined supplementation of CLA, creatine and whey protein was beneficial for increasing strength and lean-tissue mass during heavy resistance training. There were no indications of altered oxidative stress or altered kidney function with CLA or creatine supplementation.

Funding Source:
Government: The Natural Sciences and Engineering Research Council of Canada
Iovate Health Sciences
Other: equipment supplied by Saskatchewan Health Research Foundation
In-Kind support reported by Industry: Yes
Reviewer Comments:

The finding of the CCP group having greater increases in lean tissue mass than the other two groups combined would indicate an effect of CLA.  The finding that the CCP and CP groups combined increased lean tissue mass more than the P group would indicate an effect of creatine.  Thus, it appears that CLA enhanced the effect of creatine supplementation to increase lean tissue mass when combined with whey protein and strength training.

Quality Criteria Checklist: Primary Research
Relevance Questions
  1. Would implementing the studied intervention or procedure (if found successful) result in improved outcomes for the patients/clients/population group? (Not Applicable for some epidemiological studies) Yes
  2. Did the authors study an outcome (dependent variable) or topic that the patients/clients/population group would care about? Yes
  3. Is the focus of the intervention or procedure (independent variable) or topic of study a common issue of concern to dieteticspractice? Yes
  4. Is the intervention or procedure feasible? (NA for some epidemiological studies) Yes
Validity Questions
1. Was the research question clearly stated? Yes
  1.1. Was (were) the specific intervention(s) or procedure(s) [independent variable(s)] identified? Yes
  1.2. Was (were) the outcome(s) [dependent variable(s)] clearly indicated? Yes
  1.3. Were the target population and setting specified? Yes
2. Was the selection of study subjects/patients free from bias? Yes
  2.1. Were inclusion/exclusion criteria specified (e.g., risk, point in disease progression, diagnostic or prognosis criteria), and with sufficient detail and without omitting criteria critical to the study? Yes
  2.2. Were criteria applied equally to all study groups? ???
  2.3. Were health, demographics, and other characteristics of subjects described? Yes
  2.4. Were the subjects/patients a representative sample of the relevant population? Yes
3. Were study groups comparable? Yes
  3.1. Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT) Yes
  3.2. Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline? Yes
  3.3. Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.) Yes
  3.4. If cohort study or cross-sectional study, were groups comparable on important confounding factors and/or were preexisting differences accounted for by using appropriate adjustments in statistical analysis? N/A
  3.5. If case control study, were potential confounding factors comparable for cases and controls? (If case series or trial with subjects serving as own control, this criterion is not applicable.) N/A
  3.6. If diagnostic test, was there an independent blind comparison with an appropriate reference standard (e.g., "gold standard")? N/A
4. Was method of handling withdrawals described? Yes
  4.1. Were follow-up methods described and the same for all groups? Yes
  4.2. Was the number, characteristics of withdrawals (i.e., dropouts, lost to follow up, attrition rate) and/or response rate (cross-sectional studies) described for each group? (Follow up goal for a strong study is 80%.) ???
  4.3. Were all enrolled subjects/patients (in the original sample) accounted for? Yes
  4.4. Were reasons for withdrawals similar across groups? ???
  4.5. If diagnostic test, was decision to perform reference test not dependent on results of test under study? N/A
5. Was blinding used to prevent introduction of bias? Yes
  5.1. In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate? Yes
  5.2. Were data collectors blinded for outcomes assessment? (If outcome is measured using an objective test, such as a lab value, this criterion is assumed to be met.) Yes
  5.3. In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded? N/A
  5.4. In case control study, was case definition explicit and case ascertainment not influenced by exposure status? N/A
  5.5. In diagnostic study, were test results blinded to patient history and other test results? N/A
6. Were intervention/therapeutic regimens/exposure factor or procedure and any comparison(s) described in detail? Were interveningfactors described? Yes
  6.1. In RCT or other intervention trial, were protocols described for all regimens studied? Yes
  6.2. In observational study, were interventions, study settings, and clinicians/provider described? N/A
  6.3. Was the intensity and duration of the intervention or exposure factor sufficient to produce a meaningful effect? Yes
  6.4. Was the amount of exposure and, if relevant, subject/patient compliance measured? Yes
  6.5. Were co-interventions (e.g., ancillary treatments, other therapies) described? N/A
  6.6. Were extra or unplanned treatments described? N/A
  6.7. Was the information for 6.4, 6.5, and 6.6 assessed the same way for all groups? Yes
  6.8. In diagnostic study, were details of test administration and replication sufficient? N/A
7. Were outcomes clearly defined and the measurements valid and reliable? Yes
  7.1. Were primary and secondary endpoints described and relevant to the question? Yes
  7.2. Were nutrition measures appropriate to question and outcomes of concern? Yes
  7.3. Was the period of follow-up long enough for important outcome(s) to occur? Yes
  7.4. Were the observations and measurements based on standard, valid, and reliable data collection instruments/tests/procedures? Yes
  7.5. Was the measurement of effect at an appropriate level of precision? Yes
  7.6. Were other factors accounted for (measured) that could affect outcomes? Yes
  7.7. Were the measurements conducted consistently across groups? Yes
8. Was the statistical analysis appropriate for the study design and type of outcome indicators? Yes
  8.1. Were statistical analyses adequately described and the results reported appropriately? Yes
  8.2. Were correct statistical tests used and assumptions of test not violated? Yes
  8.3. Were statistics reported with levels of significance and/or confidence intervals? Yes
  8.4. Was "intent to treat" analysis of outcomes done (and as appropriate, was there an analysis of outcomes for those maximally exposed or a dose-response analysis)? N/A
  8.5. Were adequate adjustments made for effects of confounding factors that might have affected the outcomes (e.g., multivariate analyses)? Yes
  8.6. Was clinical significance as well as statistical significance reported? Yes
  8.7. If negative findings, was a power calculation reported to address type 2 error? No
9. Are conclusions supported by results with biases and limitations taken into consideration? Yes
  9.1. Is there a discussion of findings? Yes
  9.2. Are biases and study limitations identified and discussed? Yes
10. Is bias due to study's funding or sponsorship unlikely? Yes
  10.1. Were sources of funding and investigators' affiliations described? Yes
  10.2. Was the study free from apparent conflict of interest? Yes