Randomized Crossover Trial

A - Click here for explanation of classification scheme.

POSITIVE: See Quality Criteria Checklist below.

To compare the effects of conjugated linoleic acid (CLA) and safflower oil (SAF) on changes in body weight, body composition and adipose distribution among obese post-menopausal women with type 2 diabetes (T2DM).

• Female
• 70 years or more of age
• Post-menopausal (absence of menses for one year or more)
• Obese (BMI higher than 30kg/m²)
• HbA1c 6.5% or higher and less than or equal to 14%
• Normal hepatic enzyme activity.

Tobacco use, renal or liver disease, malignant tumors, impaired cognitive function, insulin or hormone replacement therapies or placement of a pacemaker or defibrillator.

Recruitment 

Subjects were recruited from the Columbus, Ohio area over a 2.9-year period.

Design

• After obtaining written consent, subjects reported to the Clinical Research Center (CRC) at the Ohio State University for a screening visit to document and assess demographic information, medical history, HbA1c, hepatic enzyme concentrations, height and weight to determine BMI, cognitive function with the use of an Orientation-Memory-Concentration test and willingness to comply with the study protocol
• Eligible subjects were randomly assigned in block fashion to two groups based on their BMI and HbA1c concentrations at screening
• All subjects received CLA and SAF treatments in the crossover design. Subjects reported to the CRC in the early morning (before 1,000) to control for diurnal variations in hormone concentrations. Subjects fasted overnight for a minimum of 10 hours before each study visit and were asked to abstain from taking their prescribed diabetes medications and treatment capsules the morning of each study visit. The initial diet period (diet period one) was 16 weeks in  duration, followed by a four-week washout period and a second 16-week period (diet period two). A four-week washout period is typical of feeding trials with fatty acid supplementation.

Blinding Used

Subjects were assigned to a treatment order and allocated dietary supplements that were in coded and numbered containers.

Intervention

• Subjects consumed eight dietary oil capsules daily, with instructions to take two capsules with each meal and two capsules at night for a total of 8.0g dietary oil daily. Each CLA capsule contained 1.0g CLA-80 oil. The CLA treatment capsules provided 6.4g CLA isomers and 1.6g oil composed primarily of oleic and palmitic acids per day.
• Each SAF capsule contained 1.0g SAF. The fatty acid composition of oils were periodically analyzed for composition throughout the duration of the study (every six months) and did not change
• SAF contained 5.8% of 16:0 (palmitic acid), 2.0% of 18:0 (stearic acid). 12.0% of 18.1n-9 (oleic acid), 78.4% of 18.2n-6(linoleic acid)
• CLA contained 1.5% of 16:0 (palmitic acid), 1.6% of 18:0 (stearic acid), 13.1% of 18.1n-9 (oleic acid), 41.6% of c9t11-CLA and 40.4% of t10c12-CLA
• Dual-energy X-ray absorptiometry (DEXA) was used to determine body composition
• Height was measured to the nearest 0.1cm with use of calibrated, wall-mounted stadiometer at screening visit
• Weight was assessed with a calibrated digital scale at each study visit and recorded to nearest 0.1kg
• Sagittal abdominal diameter (SAD) was measured as a surrogate marker of visceral adiposity. Measurements were recorded to the nearest 0.1cm at the level of the iliac crest.
• Fasting blood samples were analyzed at each study visit for glucose, insulin, leptin, adiponectin, serum concentrations of alanine transaminase (AST), aspartate transaminase (AST) and serum fatty acids. The homeostasis model assessment for insulin resistance (HOMA-IR) was used as a proxy measurement of insulin sensitivity.
• Diet and activity records were kept for three consecutive days (two weekdays and one weekend day) for four occasions during the study period. Data were analyzed for energy, distribution of macronutrients and fatty acids. For physical activity, subjects recorded all occupational and leisure activity in 15-minute increments. Physical activity was calculated according to established energy expenditure to estimate daily average energy cost of physical activity and metabolic equivalents per day.

Statistical Analysis

• A mixed model design including the effects of week and treatment and interactions between week and treatment was used to fit the data from week zero to week 36
• PROC MIXED procedure (SAS 9.1) was used to conduct the analysis
• Measurements from each subject were treated as repeated measures, taking into account that measurements from the same subject were correlated
• Compound symmetry variance-covariance structure was used to estimate the error variance and covariance among weeks for each subject to account for correlation within subjects
• Orthogonal contrasts are used in the mixed model to evaluate change of BMI over time
• All data are reported at a 5% level of significance
• Data were not subjected to intent-to-treat analysis.

 

Timing of Measurements

• A screening visit documented and assessed demographic information, medical history, HbA1c, hepatic enzyme concentrations, height and weight, cognitive function with the Orientation-Memory-Concentration test and willingness to comply to the protocol
• Initial diet period (diet period one) was 16 weeks in duration, followed by a four-week washout period and a second 16-week diet period (diet period two)
• Subjects were seen monthly at the Clinical Research Center
• Weight was recorded at the initial visit and at monthly intervals
• Body composition, waist and hip circumferences, skinfolds, SAD and biochemical indices were measured at the beginning and end of each diet period
• Diet and activity records were assessed at the beginning and end of each diet period.

Dependent Variables

• BMI (kg/m²)
• Adipose tissue (g)
• Trunk adipose tissue (g)
• Lean tissue (g)
• Waist circumference (cm)
• Waist-hip ratio
• Hip circumference (cm)
• Sagittal abdominal diameter (SAD)
• Triceps skinfold thickness (mm)
• Subscapular skinfold thickness (mm)
• Fasting glucose (mg per dL)
• Fasting insulin (μU per ml)
• HOMA-IR
• Leptin (ng per ml)
• Adiponectin (mcg per ml)
• Alanine aminotransferase (U per L)
• Aspartate aminotransferase (U per L)
• Energy (kcal)
• Carbohydrate (g)
• Protein (g)
• Fat (g)
• PUFA (g)
• Linoleic acid (g)
• MUFA (g)
• SFA (g)
• Activity (Met ea).

Independent Variables

• CLA treatment
• SAF treatment.

Control Variables

A four-week washout period between diet periods.

 

• Initial N: 55 females
• Attrition (final N): 35 females
• Age: 60.1±7.9 years
• Ethnicity: Seven African Americans, 26 White, one American Indian, one Asian
• Other relevant demographics:
  • Time since diagnosis of diabetes: 9.71±6.24 years
  • Medication users:
    • Sulfonylureas: 23
    • Biguanides: 19
    • Thiazolidinediones: 13
    • Incretin mimetic: Zero
    • α-Glucosidase inhibitor: One
    • Combination therapy: Five
• Anthropometrics: No differences were observed for age, ethnicity, BMI, duration of diabetes, and HbA1c between groups at baseline
• Location: Columbus, Ohio.

Key Findings

• A significant decrease in BMI was observed over the course of both diet periods with CLA supplementation; however, supplementation with SAF did not alter BMI
• Total adipose mass measured by DEXA was significantly decreased by CLA supplementation; SAF had no effect on total adipose mass but was significantly related to reduced trunk adipose mass and increased lean tissue mass
• Neither SAF nor CLA supplementation significantly altered waist circumference, waist-hip ratio, SAD or skinfold thickness measurements during the study
• CLA had no significant effect on fasting glucose or insulin
• SAF significantly decreased fasting glucose
• HOMA-IR analyses showed a significant improvement of insulin sensitivity with SAF supplementation
• Supplementation with CLA had no effect on change of the adipolines adiponectin or leptin. Supplementation with SAF significantly increased adiponectin but did not alter leptin concentrations.
• No significant differences were observed between the groups for food sources of energy or for intakes of total fat, carbohydrate and protein; saturated fat; polyunsaturated fatty acids, linoleic acid; or monounsaturated fatty acids
• Physical activity was unchanged throughout the course of the study.

Differential Effects of Conjugated Linoleic Acid (CLA) and Safflower Oil (SAF) on Total and Central Adipose Mass and Lean Mass¹

	Diet Period One		Diet Period Two		P for Trend	P for Comparison of Treatments
	Baseline (Week Zero)	Δ Weeks Zero to 16	Baseline (Week 20)	Δ Weeks 20 to 36
Body weight (kg)						0.032
SAF	99.16±3.29	-0.11±0.55	97.18±4.14	0.90±0.79	0.415
CLA	98.86±4.13	-1.25±0.71	98.78±3.30	-0.86±0.59	0.024
BMI						0.000
SAF	36.3±1.2	0.1±0.2	36.4±1.4	0.5±0.2	0.054
CLA	37.1±1.4	-0.5±0.2	36.4±1.2	-0.4±0.2	0.002
Adipose tissue (g)						0.074
SAF	42,994±2,272	80±667	43,203±2,877	135±906	0.849
CLA	44,656±2,872	-1,076±849	42,150±2,281	-1,591±721	0.019
Trunk adipose   tissue (g)						0.039
SAF	24,391±1,227	-1,203± 852	25,680±1,674	-1,943±1,267	0.042
CLA	25,506±1,655	1,075±1,184	23,587±1,267	314±942	0.361
Lean tissue (g)						0.193
SAF	45,149±1,615	1,402±594	46,390±2,046	654±808	0.043
CLA	46,489±2,040	-412±756	46,513±1,625	599±642	0.851
Waist circumference (cm)						0.904
SAF	111.3±2.3	-1.0±0.7	110.8±2.9	1.0±1.0	0.949
CLA	112.0±2.9	-0.7±0.9	110.1±2.3	0.6±0.7	0.915
Waist:hip ratio						0.190
SAF	0.91±0.01	0.00±0.00	0.92±0.02	-0.01±0.01	0.874
CLA	0.90±0.02	0.01±0.01	0.91±0.01	0.02±0.01	0.084
Sagittal abdominal diameter (cm)						0.449
SAF	27.3±0.6	0.1±0.4	27.6±0.9	0.7±0.5	0.239
CLA	27.7±0.8	0.3±0.5	27.0±0.7	-0.2±0.4	0.900
Triceps skinfold thickness (mm)						0.629
SAF	41.7±1.8	0.2±1.0	40.8±2.3	0.8±1.4	0.550
CLA	41.3±2.2	-0.6±1.2	41.7±1.8	0.5±1.0	0.940
Subscapular skinfold thickness (mm)						0.184
SAF	45.9±1.7	-3.5±1.2	43.2±2.3	1.5±1.8	0.366
CLA	43.1±2.2	43.1±2.2	42.1±1.8	1.4±1.4	0.328

¹ All values are means ± SEMs.

Effect of Dietary Oils on Serum Metabolites and Adipokines¹ 

	Diet Period One		Diet Period Two		P for Trend	P for Comparison of Treatments
	Baseline (Week Zero)	Δ Weeks Zero to 16	Baseline (Week 20)	Δ Weeks 20 to 36
Fasting glucose (mg per dL)						0.011
SAF	148±8	-19±8	159±11	-11±11	0.034
CLA	145±10	5±10	138±9	11±9	0.137
Fasting insulin (μU per ml)						0.462
SAF	19.9±2.1	-1.7±1.8	13.3±2.8	-1.1±2.6	0.186
CLA	15.4±2.6	-1.1±2.3	17.8±2.2	1.4±2.0	0.763
HOMA-IR						0.050
SAF	7.1±0.9	-1.3±0.8	5.3±1.2	-0.8±1.2	0.027
CLA	5.4±1.1	0.1±1.0	6.2±1.0	1.3±0.9	0.592
Leptin (ng per ml)						0.053
SFA	30±4	1±1	27±5	3±2	0.134
CLA	29±5	0±2	31±4	-2±1	0.215
Adiponectin (ng per ml)						0.059
SAF	7.3±1.1	0.8±0.6	7.9±1.3	2.4±0.8	0.005
CLA	9.5±1.3	-0.3±0.8	8.3±1.1	0.8±0.6	0.878
Alanine aminotransferase (U per L)						0.059
SAF	28.6±1.6	-2.2±1.4	25.1±2.1	-2.4±2.0	0.063
CLA	25.2±1.9	-1.1±1.8	24.8±1.7	3.0±1.6	0.430
Aspartate aminotansferase (U per L)						0.034
SAF	31.4±2.0	-4.5±2.0	27.2±2.7	-2.5±2.8	0.043
CLA	28.2±2.4	-1.7±2.5	26.8±2.1	4.8±2.1	0.347

¹ All values are means ± SEMs.

Diet and Physical Activity¹

	Diet Period One		Diet Period Two		P for Trend	P for Comparison of Treatments
	Baseline (Week Zero)	Δ Weeks Zero to 16	Baseline (Week 20)	Δ Weeks 20 to 36
Energy (kcal)						0.500
SAF	1,746±75	-154±92	1,547±14	141±144	0.938
CLA	1,925±96	-395±126	1,527±86	222±102	0.287
Carbohydrate (g)						0.612
SAF	197±10	-20±12	180±14	4±17	0.453
CLA	200±12	-28±15	184±10	-2±13	0.129
Protein (g)						0.267
SAF	78±4	-2±4	71±5	7±6	0.541
CLA	85±5	-10±6	74±4	3±5	0.333
Fat (g)						0.578
SAF	77±5	-10±6	63±7	15±9	0.606
CLA	85±6	-19±8	62±5	16±6	0.791
PUFA (g)						0.448
SAF	15±1	-2±2	12±2	4±2	0.594
CLA	18±2	-5±2	12±1	4±2	0.587
Linoleic acid (g)						0.619
SAF	13±1	-2±1	10±2	4±2	0.315
CLA	15±1	-3±2	11±1	4±2	0.739
MUFA (g)						0.658
SAF	30±2	-4±2	25±3	4±4	0.923
CLA	33±3	-9±3	24±2	6±3	0.589
SFA (g)						0.891
SAF	26±2	-3±2	21±3	7±3	0.386
CLA	26±2	-3±3	20±2	5±2	0.565
Activity (Met eq)						0.475
SAF	158±5	9±8	166±7	-3±13	0.706
CLA	161±7	-2±10	162±6	-7±9	0.516

 ¹ All values are means ± SEMs.

• A significant reduction of BMI with 6.4g CLA supplementation per day was observed, which is supported in other studies. This weight loss may be attributed to reduction of adipose tissue mass.
• SAF reduced trunk adipose mass in both diet periods and increased total body lean tissue mass and decreased trunk adipose obesity as assessed with DEXA
• Supplementation with CLA and SAF exerted different effects on BMI, total and trunk adipose mass and lean tissue mass in obese post-menopausal women with type 2 diabetes
• Supplementation with these dietary oils may be beneficial for weight loss, glycemic control or both.

Government:	National Center fo Research Resources (UL1RR025755) and the Clinical Research Center at The Ohio State University (M01-RR00034) from the NIH, the Caroline Kennedy Endowment.
Industry:	Cognis Pharmaceutical/Dietary Supplement Company:
University/Hospital:	The Ohio State University

• Interactions between SAF and specific macronutrients were not tested
• Although anthropometric measurements  (waist circumference and SAD) did not show a significant reduction in abdominal adipose, the use of DEXA found a decreased trunk adipose during SAF supplementation
• Study population was obese post-menopausal women; therefore, the possibility to generalize results to non-obese men and women or to pre-menopausal women is limited
• Energy and nutrient intakes were assessed with a repeated three-day diet record that may not reflect subtle changes in calories that may have occurred with the addition of 72kcal of oil per day
• 16-week crossover interventions may not provide adequate time to show maximum results on changes in outcomes measured
• There are limitations that occur in a free-living population that could be better measured in a controlled environment.