T Nation

CLA--Health Warning

If you go to Udo Erasmus’s home page:

and click on current news flashes you can read that:

The Norwegian food-authorities are now warning the following groups about the dangers of CLA:

Pregnant Mothers
Breast Feeding Mothers
High Cholesterol
Overweight and Diabetes 2

There is an article on CLA by Udo who does not think much of CLA either.

I wouldn’t put stock in anything Udo says. CLA is good for you healthwise but there seems to be different isonomers of CLA for supplement on market. Grass fed animals generally have higher amount of CLA in the muscles. UDO who used to be salesman for some companies selling cold pressed vegetable oils. He’s bit misguided over the health benefits of saturated fat. For some reason he thinks saturated fat is bad for you. Erasmus neglects to tell that dietary saturated fats are very important for the proper utilization of essential fatty acids, especially for the omega-3 fatty acids in flax oil that he has promoted so heavily. Udo’s blended oil porduct is good though in moderate amount.

Maybe he just wants to sell more of his oil… Can’t wait till he starts putting CLA in it:)


I respect you as one of the more knowledgable people on the forum, and I hope you are correct about CLA as I have 3 bottles of Jarrow tonalin in my fridge. However:

The health advisory was from “The Norwegian food-authorities” Udo was only reporting on it (and agreeing with them) and it was based on reports like these:

Riserus U, Arner P, Brismar K, Vessby B. Treatment with dietary trans10cis12 conjugated linoleic acid causes isomer-specific insulin resistance in obese men with the metabolic syndrome.
Diabetes Care. 2002 Sep;25(9):1516-21.

OBJECTIVE: Conjugated linoleic acid (CLA) is a group of dietary fatty acids with antiobesity and antidiabetic effects in some animals. The trans10cis12 (t10c12) CLA isomer seems to cause these effects, including improved insulin sensitivity. …

In a randomized, double-blind controlled trial, abdominally obese men (n = 60) were treated with 3.4 g/day CLA (isomer mixture), purified t10c12 CLA, or placebo. … Unexpectedly, t10c12 CLA increased insulin resistance (19%; P < 0.01) and glycemia (4%; P < 0.001) and reduced HDL cholesterol (-4%; P < 0.01) compared with placebo, whereas body fat, sagittal abdominal diameter, and weight decreased versus baseline, but the difference was not significantly different from placebo. The CLA mixture did not change glucose metabolism, body composition, or weight compared with placebo but lowered HDL cholesterol (-2%; P < 0.05).

CONCLUSIONS: These results reveal important isomer-specific metabolic actions of CLA in abdominally obese humans. A CLA-induced insulin resistance has previously been described only in lipodystrophic mice. Considering the use of CLA-supplements among obese individuals, it is important to clarify the clinical consequences of these results, but they also provide physiological insights into the role of specific dietary fatty acids as modulators of insulin resistance in humans.

Riserus U, Vessby B, Arnlov J, Basu S.
Effects of cis-9,trans-11 conjugated linoleic acid supplementation on insulin sensitivity, lipid peroxidation, and proinflammatory markers in obese men.
Am J Clin Nutr. 2004 Aug;80(2):279-83.

BACKGROUND: We recently showed that trans-10,cis-12 (t10,c12) conjugated linoleic acid (CLA) causes insulin resistance in obese men. However, metabolic effects of the c9,t11 CLA isomer are still unknown in obese men. Because c9,t11 CLA is the predominant CLA isomer in foods and is included in dietary weight-loss products, it is important to conduct randomized controlled studies that use c9,t11 CLA preparations. …

In a randomized, double-blind, placebo-controlled study, 25 abdominally obese men received 3 g c9,t11 CLA/d or placebo (olive oil). Before and after 3 mo of supplementation, we assessed insulin sensitivity (hyperinsulinemic euglycemic clamp), lipid metabolism, body composition, and urinary 8-iso-prostaglandin F(2alpha) (a major F(2)-isoprostane) and 15-keto-dihydro-prostaglandin F(2alpha), markers of in vivo oxidative stress and inflammation, respectively.

RESULTS: … Compared with placebo, c9,t11 CLA decreased insulin sensitivity by 15% (P < 0.05) and increased 8-iso-prostaglandin F(2alpha) and 15-keto-dihydro-prostaglandin F(2alpha) excretion by 50% (P < 0.01) and 15% (P < 0.05), respectively. The decreased insulin sensitivity was independent of changes in serum lipids, glycemia, body mass index, and body fat but was abolished after adjustment for changes in 8-iso-prostaglandin F(2alpha) concentrations. There were no differences between groups in body composition. CONCLUSIONS: A CLA preparation containing the purified c9,t11 CLA isomer increased insulin resistance and lipid peroxidation compared with placebo in obese men. Because c9,t11 CLA occurs in commercial supplements as well as in the diet, the present results should be confirmed in larger studies that also include women.

Riserus U, Basu S, Jovinge S, Fredrikson GN, Arnlov J, Vessby B.
Supplementation with conjugated linoleic acid causes isomer-dependent oxidative stress and elevated C-reactive protein: a potential link to fatty acid-induced insulin resistance.
Circulation. 2002 Oct 8;106(15):1925-9.

In a double-blind placebo-controlled trial, 60 men with metabolic syndrome were randomized to one of 3 groups receiving t10c12 CLA, a CLA mixture, or placebo for 12 weeks. Insulin sensitivity (euglycemic clamp), serum lipids, in vivo lipid peroxidation (determined as urinary 8-iso-PGF(2alpha) [F2-isoprostanes]), 15-ketodihydro PGF(2alpha), plasma vitamin E, plasma C-reactive protein, tumor necrosis factor-alpha, and interleukin-6 were assessed before and after treatment. Supplementation with t10c12 CLA markedly increased 8-iso-PGF(2alpha) (578%) and C-reactive protein (110%) compared with placebo (P<0.0001 and P<0.01, respectively) and independent of changes in hyperglycemia or dyslipidemia. The increases in 8-iso-PGF(2alpha), but not in C-reactive protein, were significantly and independently related to aggravated insulin resistance. Oxidative stress was related to increased vitamin E levels, suggesting a compensatory mechanism.

CONCLUSIONS: t10c12 CLA supplementation increases oxidative stress and inflammatory biomarkers in obese men. The oxidative stress seems closely related to induced insulin resistance, suggesting a link between the fatty acid-induced lipid peroxidation seen in the present study and insulin resistance. These unfavorable effects of t10c12 CLA might be of clinical importance with regard to cardiovascular disease, in consideration of the widespread use of dietary supplements containing this fatty acid.

Larsen TM, Toubro S, Astrup A.
Efficacy and safety of dietary supplements containing CLA for the treatment of obesity: evidence from animal and human studies.
J Lipid Res. 2003 Dec;44(12):2234-41.

Dietary supplements containing conjugated linoleic acid (CLA) are widely promoted as weight loss agents available over the counter and via the Internet. In this review, we evaluate the efficacy and safety of CLA supplementation based on peer-reviewed published results from randomized, placebo-controlled, human intervention trials lasting more than 4 weeks. We also review findings from experimental studies in animals and studies performed in vitro.

CLA appears to produce loss of fat mass and increase of lean tissue mass in rodents, but the results from 13 randomized, controlled, short-term (<6 months) trials in humans find little evidence to support that CLA reduces body weight or promotes repartitioning of body fat and fat-free mass in man. However, there is increasing evidence from mice and human studies that the CLA isomer trans-10, cis-12 may produce liver hypertrophy and insulin resistance via a redistribution of fat deposition that resembles lipodystrophy. …

In conclusion, although CLA appears to attenuate increases in body weight and body fat in several animal models, CLA isomers sold as dietary supplements are not effective as weight loss agents in humans and may actually have adverse effects on human health.


Thanks for the heads up! This is one of the things that makes this site hands down the best–I can count on my fellow T-men and women to be looking for the latest information.

I have to say that was a very through and convincing recap. I have used CLA in the past. I experminted with various dosages, getting up to around 6-7g./day for periods. I have to say that I noticed no real benefit from CLA usage. I stoped using CLA years ago.

Again, thanks for the heads up,