Conjugated Linoleic Acid
Also indexed as: CLA
Conjugated linoleic acid (CLA) is a slightly altered form of the essential fatty acid linoleic acid.
Where is it found?
CLA is found mainly in dairy products and also in beef and poultry, eggs, and corn oil. Bacteria that live in the intestine of humans can produce CLA from linoleic acid, but supplementation of a rich source of linoleic acid did not produce increases in blood levels of CLA in one human study.1 CLA is available as a supplement.
CLA has been used in connection with the following conditions (refer to the individual health concern for complete information):
| Science Ratings | Health Concerns |
|---|---|
 |
Athletic performance (body composition and strength) Cancer prevention (lung, colon, breast) |
 Reliable
and relatively consistent scientific data showing a substantial health benefit. Contradictory, insufficient, or preliminary studies
suggesting a health benefit or minimal health benefit. For an herb, supported by traditional use but minimal
or no scientific evidence. For a supplement, little scientific support and/or minimal health
benefit. |
|
Who is likely to be deficient?
No deficiencies of CLA are reported or believed to occur, since it is not an essential nutrient.
How much is usually taken?
Animal research uses very large amounts, equivalent to several grams per day for humans. Until human research is conducted with CLA, the appropriate amount to take of this nutrient remains unclear.
Are there any side effects or interactions?
Overweight volunteers who took 4.5 grams of CLA per day for one year had an increase in their blood levels of lipoprotein(a), a risk factor for heart disease.2 In a double-blind study of human volunteers, supplementation with 4.2 grams per day of a mixture of cis-9,trans-11 CLA and trans-10,cis-12 CLA for three months increased the concentration of C-reactive protein, another risk factor for heart disease.3 In a study of healthy volunteers, supplementing with 4.5 grams of CLA per day for 12 weeks caused an impairment of blood vessel function (endothelial dysfunction), which is believed to be associated with an increased risk of heart disease.4 Taken together, these findings suggest that long-term use of CLA could increase the risk of developing heart disease.
In a double-blind study of people with type 2 diabetes, supplementing with 3 grams of CLA per day for eight weeks significantly increased blood glucose levels by 6.3% and decreased insulin sensitivity.5 A reduction in insulin sensitivity was also seen in a study of overweight men without diabetes after treatment with 3 grams of CLA per day for three months.6 However, in another study of obese men and women, supplementation with 6 grams of CLA per day for 24 weeks had no significant effect on blood glucose levels or insulin sensitivity.7 Moreover, in a study of young sedentary men, 4 grams of CLA per day for eight weeks improved insulin sensitivity.8 Although the studies are conflicting, it would be prudent for people who have, or are at risk of developing, diabetes to monitor their blood sugar levels during long-term use of CLA. One unpublished human trial reported isolated cases of gastrointestinal upset.9
At the time of writing, there were no well-known drug interactions with conjugated linoleic acid.
References
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The information presented in Healthnotes is for informational purposes only. It is based on scientific studies (human, animal, or in vitro), clinical experience, or traditional usage as cited in each article. The results reported may not necessarily occur in all individuals. For many of the conditions discussed, treatment with prescription or over the counter medication is also available. Consult your doctor, practitioner, and/or pharmacist for any health problem and before using any supplements or before making any changes in prescribed medications. Information expires September 2008.