Dairy foods and meat contain conjugated linoleic acid (CLA) 123. It is also available as a dietary supplement. CLA contains a mixture of different chemical forms -- or isomers -- of linoleic acid, a type of fat your body needs to function properly. Preliminary findings, based largely on animal studies, suggest that CLA may have both beneficial and harmful effects with respect to diabetes, as well as other diseases. Because of the inconsistent data, anyone with diabetes should consult their doctor before using this supplement.
Sources of CLA
CLA is found naturally in milk fat and the meat of ruminants -- animals that chew their cud, like cows and sheep. The amount of CLA in these foods depends on what the animal has eaten. For example, according to an October 1999 article in the "Journal of Dairy Science," the CLA content of milk from grass-fed cows is five times higher than that from grain-fed cows 1. CLA is also sold as a dietary supplement. The supplements are not derived from ruminants, but are instead made by chemically altering vegetable oils. Because of this, the two sources have slightly different chemical structures.
- CLA is found naturally in milk fat and the meat of ruminants -- animals that chew their cud, like cows and sheep.
The Evidence -- Animal Research
L-Carnitine & Diabetes
The effect of CLA on diabetes is mixed 2. For example, studies of rats with diabetes published in the July 2003 issue of the "American Journal of Physiology -- Endocrinology and Metabolism" and the May 2001 issue of "Diabetes" have demonstrated that CLA makes cells more responsive to insulin -- the hormone that lowers blood glucose -- and improves how the body handles glucose 4. However, studies of mice published in the September 2000 issue of "Diabetes" and the September 2002 issue of the "Journal of Lipid Research" suggest that CLA supplementation impairs the action of insulin, and also increases fat accumulation in the liver, both of which may increase the risk of diabetes.**
The Evidence -- Human Research
CLA studies in humans also report conflicting results. For example, one group of researchers found that CLA supplementation was associated with lower blood glucose levels in people with diabetes, as reported in the January 2003 issue of the "Journal of Nutrition." Others have reported that CLA had no effect on insulin sensitivity, and may actually worsen insulin action and increase blood glucose levels, as published in the October 2004 issue of the "American Journal of Clinical Nutrition" and the September 2002 issue of "Diabetes Care. 8"
- CLA studies in humans also report conflicting results.
- For example, one group of researchers found that CLA supplementation was associated with lower blood glucose levels in people with diabetes, as reported in the January 2003 issue of the "Journal of Nutrition."
The Fine Print
The Disadvantages of High Saturated Fat Levels
In addition to the fact that some studies were completed on rodents, and the human studies were small in sample size, there are other barriers to interpreting and applying these research results. For example, the CLA supplements used in the research protocols varied with respect to dosage and exact chemical structure. There were also study differences in terms of the length of time the supplement was administered and the health of the participants. Some had an established diagnosis of diabetes, whereas others had signs of pre-diabetes. These factors further complicate analysis, and larger scale human studies are needed to obtain accurate answers on CLA supplementation in diabetes.
- In addition to the fact that some studies were completed on rodents, and the human studies were small in sample size, there are other barriers to interpreting and applying these research results.
Warnings and Precautions
Because of the mixed study results, CLA should be used only if approved by your primary diabetes doctor, after a discussion about potential medication interactions or other side effects. For example, in addition to the potential worsening of blood glucose control, CLA supplements may also cause mild to moderate nausea, diarrhea, bloating and flatulence. Given the lack of evidence regarding the safety of CLA supplements, they are not recommended for women who are pregnant or breastfeeding.
The U.S. Food and Drug Administration regulates dietary supplements as foods rather than medications, which means manufacturers do not have to prove that their products are safe or effective before selling them.
- Because of the mixed study results, CLA should be used only if approved by your primary diabetes doctor, after a discussion about potential medication interactions or other side effects.
- The U.S. Food and Drug Administration regulates dietary supplements as foods rather than medications, which means manufacturers do not have to prove that their products are safe or effective before selling them.
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- Journal of Dairy Science: Conjugated Linoleic Acid Content of Milk from Cows Fed Different Diets
- Journal of Nutrition: The Conjugated Linoleic Acid (CLA) Isomer, t10c12-CLA, Is Inversely Associated with Changes in Body Weight and Serum Leptin in Subjects with Type 2 Diabetes Mellitus
- American Journal of Health-System Pharmacy: Conjugated Linoleic Acid
- American Journal of Physiology. Endocrinology and Metabolism: Isomer-specificctions of Conjugated Linoleic Acid on Muscle Glucose Transport in the obese Zucker Rat.
- Diabetes: Isomer-Specific Antidiabetic Properties of Conjugated Linoleic Acid. Improved Glucose Tolerance, Skeletal Muscle Insulin Action, and UCP-2 Gene Expression.
- Diabetes: Conjugated Linoleic Acid Supplementation Reduces Adipose Tissue by Apoptosis and Develops Lipodystrophy in Mice
- Journal of Lipid Research: Dietary Trans-10,Cis-12 Conjugated Linoleic Acid Induces Hyperinsulinemia and Fatty Liver in the Mouse
- American Journal of Clinical Nutrition: Conjugated Linoleic Acid supplementation, Insulin Sensitivity, and Lipoprotein Metabolism in Patients with Type 2 Diabetes Mellitus
- Diabetes Care: Treatment With Dietary trans10cis12 Conjugated Linoleic Acid Causes Isomer- Specific Insulin Resistance in Obese Men With the Metabolic Syndrome
- Nutrition and Metabolism: Pros and Cons of CLA Consumption: An Insignt from Clinical Evidences
- U.S. National Library of Medicine. Linoleic acid. National Center for Biotechnology Information. PubChem Compound Database.
- Benjamin S, Prakasan P, Sreedharan S, Wright AD, Spener F. Pros and cons of CLA consumption: an insight from clinical evidences. Nutr Metab (Lond). 2015;12:4. Published 2015 Feb 3. doi:10.1186/1743-7075-12-4
- Chen SC, Lin YH, Huang HP, Hsu WL, Houng JY, Huang CK. Effect of conjugated linoleic acid supplementation on weight loss and body fat composition in a Chinese population. Nutrition. 2012;28(5):559-65. doi: 10.1016/j.nut.2011.09.008
- Whigham L, Watras A, Schoeller D, Efficacy of conjugated linoleic acid for reducing fat mass: a meta-analysis in humans, The American Journal of Clinical Nutrition, Volume 85, Issue 5, May 2007, Pages 1203–1211, doi: 10.1093/ajcn/85.5.1203
- Kamphuis MM, Lejeune MP, Saris WH, Westerterp-plantenga MS. The effect of conjugated linoleic acid supplementation after weight loss on body weight regain, body composition, and resting metabolic rate in overweight subjects. Int J Obes Relat Metab Disord. 2003;27(7):840-7. doi: 10.1038/sj.ijo.0802304
- Li X, Thomason PA, Withers DJ, Scott J. Bio-informatics analysis of a gene co-expression module in adipose tissue containing the diet-responsive gene Nnat. BMC Syst Biol. 2010;4:175. Published 2010 Dec 27. doi:10.1186/1752-0509-4-175
- Kasiappan R, Rajarajan D. Role of MicroRNA Regulation in Obesity-Associated Breast Cancer: Nutritional Perspectives. Adv Nutr. 2017;8(6):868–888. Published 2017 Nov 15. doi:10.3945/an.117.015800
- Smedman A, Vessby B. "Conjugated linoleic acid supplementation in humans--metabolic effects." Lipids August 2001.
- Allison Dilzer, Yeonhwa Park. "Implication of Conjugated Linoleic Acid (CLA) in Human Health." Critical Reviews in Food Science and Nutrition Volume 52, Issue 6, 2012
- Arion Kennedy, Kristina Martinez, Soren Schmidt, Susanne Mandrup, Kathleen LaPoint, Michael McIntosh. "Antiobesity mechanisms of action of conjugated linoleic acid." The Journal of Nutritional Biochemistry Agust 2009.
- gho J. Onakpoya, Paul P. Posadzki, Leala K. Watson, Lucy A. Davies, Edzard Ernst. "The efficacy of long-term conjugated linoleic acid (CLA) supplementation on body composition in overweight and obese individuals: a systematic review and meta-analysis of randomized clinical trials." European Journal of Nutrition March 2012.
- Shama V. Joseph, Hélène Jacques, Mélanie Plourde, Patricia L. Mitchell, Roger S. McLeod, Peter J. H. Jones. "Conjugated Linoleic Acid Supplementation for 8 Weeks Does Not Affect Body Composition, Lipid Profile, or Safety Biomarkers in Overweight, Hyperlipidemic Men." The Journal of Nutrition May 18, 2011.
William Gamonski is a graduate of St. Francis College, where he earned a Bachelor of Science degree in health promotion and sciences. He was a dietetic intern at Rivington House and has been a personal trainer for the past two years. He is currently pursuing a Master of Science degree in nutrition.