Conjugated Linoleic Acid
Reshapes Your Body,
Cardiovascular and Immune Systems, and More

n Woody Allen's movie Sleeper, a health-food "nut" from New York City's Greenwich Village - played, of course, by Allen - is transported 200 years into the future via cryonic suspension. When he awakens, the world is topsy-turvy, especially with regard to everything he thought he knew about health. In Sleeper's future, instead of tofu, alfalfa sprouts, and organic vegetables, the ideal health foods are hamburgers, french fries, and milkshakes. 

Well, here we are just into the 21st century, and at the doorstep of our health future is a genuine health food, conjugated linoleic acid (CLA), that breaks the old rules and makes new ones. Conjugated Linoleic Acid is a "good" fat found in shakes and burgers - and it's delivered to us in the here and now. Furthermore, Conjugated Linoleic Acid is especially found in - egad! - whole milk shakes and seared burgers, the least preferred forms of these foods, in terms of our health. Sometimes the facts are stranger than fiction . . . so here's how you can get significant added health protection from Conjugated Linoleic Acid.


Conjugated Linoleic Acid is a natural polyunsaturated fatty acid found in many foods, including milk, cheese, and meats; the meat that is richest in Conjugated Linoleic Acid is beef, but it is also found in lamb and veal and, to a lesser degree, in pork, chicken, and turkey.1

Conjugated Linoleic Acid is thought to be made in the bellies of ruminants, such as cows, from grain fermented with the help of certain bacteria. In a study in which the Conjugated Linoleic Acid content was examined under various feeding regimens, cows allowed to graze freely on the range, and not fed supplementally with corn silage or corn oil, had 500% more Conjugated Linoleic Acid in their milkfat than cows fed typical dairy diets.2

Evidence compiled over the last decade has led to the recognition that Conjugated Linoleic Acid possesses unique and potent antioxidant activity. In the body, it is taken up by phospholipids, a class of fats that serve as the principal structural components of cell membranes. Conjugated Linoleic Acid is now thought to represent a previously unidentified defense mechanism against membrane attack by oxygen radicals.3 It is also thought to help protect against atherosclerosis and cancer. It enhances body composition by helping to increase muscle while reducing fat. Moreover, in animal studies, Conjugated Linoleic Acid has been shown to increase bone mass and exert a positive effect on diabetes. Clearly, Conjugated Linoleic Acid is a serious health food.

Conjugated Linoleic Acid was discovered by Dr. Michael Pariza at the University of Wisconsin, where he and his colleagues isolated it in grilled ground beef. They were looking for a substance that could inhibit the formation of mutagens (compounds that can cause genetic mutations) in bacteria, the objective being to prevent cancer initiation in mice. They found such a substance, surprisingly, in fried ground beef in the form of Conjugated Linoleic Acid, a derivative of linoleic acid produced by the heating process.4 Conjugated Linoleic Acid is produced synthetically by heating linoleic acid (an essential nutrient found widely in plant oils and animal fats) in the presence of a base. It is produced naturally from linoleic acid by bacteria in the stomachs of herbivores (plant eaters), such as cows.

CLA helps protect against
atherosclerosis and cancer.

The mechanism by which Conjugated Linoleic Acid operates is unclear, but its concentration is increased when meats are cooked, thus increasing its potent antioxidant, anticarcinogenic (anticancer), and anticatabolic (helping to prevent metabolic destructiveness) effects. The benefits appear to increase with quantity, up to a point. Rats that were fed diets containing 0.5% or 1.5% Conjugated Linoleic Acid by weight had a total reduction of the number of breast-cancer tumors by 32% and 56%, respectively.5 It was also found that Conjugated Linoleic Acid inhibits the development not only of benign tumors, but of malignant ones as well. There was no significant dose-dependent increase in protection after reaching the 1% Conjugated Linoleic Acid level, and there were no adverse effects, even with chronic feeding of Conjugated Linoleic Acid.

An interesting property of Conjugated Linoleic Acid is its ability to suppress the formation of peroxides, which are exceptionally strong oxidizing agents. Optimal antioxidant protection was observed with only 0.25% Conjugated Linoleic Acid in the diet, whereas maximal tumor inhibition was achieved at about 1%. Hence, if there is no added antioxidant benefit beyond 0.25%, the anticarcinogenic effect must have some further explanation, suggesting that other mechanisms (besides antioxidant protection) might be involved in CLA's cancer-protective action.

Animals fed a standard diet supplemented with 1% Conjugated Linoleic Acid not only displayed smaller tumors of the prostate compared with controls, but they were also found to have a drastic reduction in lung metastases (spreading of cancer).6 These results support the view that Conjugated Linoleic Acid may influence the prognosis of prostate cancer patients, thus opening the possibility of new therapeutic options.

Interestingly, Conjugated Linoleic Acid acts as an antioxidant outside the body as well as inside it, helping to arrest free radical oxidative damage in foods as well as in human tissue. This beneficial property holds up whether the Conjugated Linoleic Acid is produced naturally within foods (by bacteria within a cow, e.g.) or synthetically (by heat within a laboratory).6 Both forms have been shown to be effective agents in inhibiting the development of tumors.

In another study, Pariza et al. showed that Conjugated Linoleic Acid inhibits the initiation of tumors in the forestomachs of mice: the mice treated with Conjugated Linoleic Acid developed only about half as many cancers as did the controls.7 Under the conditions of the test, Conjugated Linoleic Acid was more potent than alpha-tocopherol (vitamin E) and almost as effective as butylated hydroxytoluene (BHT) in its antioxidant effect.

CLA also increases bone mass
and exerts a positive
effect on diabetes.  

CLA supplementation helps improve the ratio of lean body mass to fat, decreasing fat especially on the abdomen, and enhancing muscle growth. One explanation for this effect may be CLA's enhancement of insulin sensitivity, thereby allowing fatty acids and glucose to pass more easily through muscle-cell membranes and away from fat tissue. This results in an improved muscle-to-fat ratio.

Mice fed CLA-supplemented diets (0.5% CLA by weight) exhibited up to 60% lower body fat and up to 14% increased lean body mass compared to controls.8 Total energy availability was increased in both fat and muscle. These effects are due in part to reduced fat buildup and increased fat breakdown. It is also possible that CLA enhances fat burning in muscle cells as well as fat cells. These "body-styling" benefits of CLA are believed to be due to different molecular variations than the ones involved in enhancing immunity as well as protecting against atherosclerosis and cancer.9

To illustrate further its metabolic effects, mice given CLA - along with a high-fat diet - had reduced body-fat accumulation.10 CLA feeding produces a rapid, marked decrease in fat accumulation and an increase in protein accumulation, even at relatively low doses and independently of the amount of food consumed. A deficiency of CLA in the diet may be a major factor in Americans' tendency to gain so many fat pounds.

To assess the effect of CLA on atherosclerosis, 6 of 12 rabbits were fed a diet containing CLA. During and at the end of the study, their blood lipids (fats) were analyzed and were found to have lower LDL ("bad" cholesterol) and lower triglyceride levels than the controls.11 Interestingly, the ratio of LDL to HDL ("good" cholesterol) and the ratio of total cholesterol to HDL were significantly improved in the CLA-fed rabbits. Examination of the aortas (the largest artery in the body) of these rabbits showed less atherosclerosis than those of the controls.

A more recent study done at the University of Massachusetts confirmed lower total cholesterol levels for CLA-supplemented hamsters, plus better LDL and triglycerides, compared to controls.12 Noted also were improved nutrient potencies due to higher tocopherol (vitamin E)/cholesterol ratios, indicating that CLA has a tocopherol-sparing (conserving) effect, which leaves more vitamin E available for antioxidant protection.

CLA's antioxidant properties may also play a role in its ability to help keep the blood vessels clean. As a side note, CLA tends to be incorporated more abundantly into the cellular and mitochondrial membranes of the heart muscle. Since the heart relies on fatty acids rather than glucose as its energy source, a greater abundance of CLA in the heart muscle may improve the efficiency of fat transport and fat metabolism in the cardiac mitochondria. The result is likely to be a strengthened heart, more resistant to damage from stress as well as normal wear and tear.

In a Purdue University study that examined various rat-tissue cultures, including bone tissue, it was shown that supplemental CLA (at 1% of the diet by weight) modulated local factors that regulate bone metabolism.13 Despite a growing knowledge of the value of beneficial fats for bone health, the health press is so sour on fats in general that many women are unaware of their need to include adequate amounts of healthy fats in their diets in order to prevent bone loss.

We have already learned that CLA improves insulin sensitivity and can thus help to control insulin levels. And because elevated insulin can promote atherosclerosis, CLA may be able to counteract this disease. Additionally, as we have already mentioned, CLA increases protective fats and decreases fats that are more easily oxidized in the bloodstream, while conserving vitamin E and thus optimizing its effects. These actions may provide antiatherogenic benefits.

When the body's process of breaking down large molecules into smaller ones (catabolism) is not balanced properly through the rebuilding process known as anabolism, the result is a loss of tissue, and hence muscle-wasting and weakness. CLA can help counteract this imbalance. In studies with experimentally induced catabolism in rats, CLA stopped or reduced its negative effects. Anecdotally, CLA supplementation has been reported to be a simple and safe intervention in patients experiencing appetite loss or weight loss associated with a viral or inflammatory disease or surgery.

Reports of better health with fewer colds and flu have come from people taking CLA; this is partly attributable to its potent antioxidant properties. Other mechanisms thought to be responsible include CLA's ability to stimulate the production of key immune system cells and to inhibit the release of an immunoglobulin associated with allergies.14,15

By reducing the production of certain immune-suppressing compounds (leukotrienes and prostaglandins) and by improving insulin sensitivity (elevated insulin leads to loss of immune-system sensitivity), CLA further enhances immune function. And because studies have shown no toxicity of CLA, it appears to be a safe and effective substance that can be consumed in relatively high doses.16 If the doses of CLA used to help reduce mammary, colon, skin, and other tumors in rodents and other laboratory animals are extrapolated to a 70-kg person (155 lbs), the daily dose needed would be in the range of 3 grams.

Chicks fed a diet containing 0.5% CLA were found to have stronger immune systems than those that were not. They had improved seek-and-destroy capabilities for targeting invading bacteria.17 Catabolic agents were unable to stunt the growth of these chicks.

It has been estimated that in the United States, average nonvegetarians consume about 1 gram of CLA per day if they eat beef, lamb, and cheese, the three best sources of this substance. The optimal daily dosage for immune-system enhancement and the anticatabolic effect is 2-4 g.

CLA supplementation helps
improve the ratio of
lean body mass to fat. 

There is compelling evidence that CLA operates to produce a wide range of benefits, including tumor shrinkage, the promotion of youthful metabolic function, the lowering of body fat, and the lessening of arteriosclerosis. Yet, how CLA accomplishes all that it does is still not known. But, as Durk Pearson & Sandy Shaw® suggest in Durk Pearson & Sandy Shaw Life Extension News - Vol. II, No. 6 - December 1999, the mechanisms of CLA's actions may involve nothing less than the regulation of gene expression. Indeed, conjugated linoleic acid has been found to regulate the gene expression for the synthesis of  adhesion molecules, which possess the ability to attract or draw different molecules together.18 Adhesion molecules, for example, are implicated in coronary disease and play a vital role in immune function.

In posing the question of whether CLA is a nutrient, scientist Michael Pariza writes, "The conclusion that the average dietary intake of CLA today may be lower than in the past is an important consideration. We should ask if this reduction has had negative effects, for example contributing to the increasing incidence of obesity in the U.S. and Europe. Understanding the biochemical mechanism(s) of CLA's action will be crucial to fully using the potential of this interesting class of fatty acids to improve human health."19

The American public has been misguided by the federal government and the medical profession in their national campaign against eating cholesterol-laden foods - a campaign that has also spilled over to encompass fat consumption in general. Cholesterol consumption is not the problem (see Dr. Kilmer McCully's letter in Now You Can Add 9.5 Years to Your Life - Editorial - February 2000). There are both "good" and "bad" fats in the diet: among the good ones are monounsaturates, high-oleic oils, medium-chain triglycerides (MCTs), and CLA, as well as the omega-3 fatty acids. Bad fats include some saturated fats along with trans-fatty acids, the worst of the polyunsaturated fats. In balance, fats are a necessary and vital part of every diet, in proper measure and when selected intelligently.

The result of the national campaign has been to lower total fat consumption, the good with the bad, and has made it difficult to choose fats wisely in the absence of the best information.

So it has been with the cholesterol/fat campaign, which has thrown the baby out with the bathwater, or, to resume Woody Allen's Sleeper metaphor, put us all into cryonic suspension, without reasonable hope of success. It's time to wake up and end the antifat hysteria that has contributed to a net gain of more than seven pounds of weight per average American (see Melt Fat Away with Ephedrine and Caffeine, and Stay Healthy - February 2000). Considering all the benefits of the good fatty acid, CLA, it's smart to increase your intake. The unique mechanisms by which CLA can improve immune function and help protect us from free radicals and age-related degeneration make it a valuable addition to any life extension program.


  1. Pariza MW, Ha YL. Conjugated dienoic derivatives of linoleic acid: a new class of anticarcinogens. Med Oncol Tumor Pharmacother 1990;7(2-3):169-71.
  2. Dhiman TR, Anand GR, Satter LD, Pariza MW. Conjugated linoleic acid content of milk from cows fed different diets. J Dairy Sci 1999 Oct;82(10):2146-56.
  3. Pariza MW, Ha YL. Newly recognized anticarcinogenic fatty acids. Basic Life Sci 1990;52:167-70.
  4. Ha YL, Grimm NK, Pariza MW. Anticarcinogens from fried ground beef: heat-altered derivatives of linoleic acid. Carcinogenesis 1987 Dec;8(12):1881-7.
  5. Ip C, Chin SF, Scimeca JA, Pariza MW. Mammary cancer prevention by conjugated dienoic derivative of linoleic acid. Cancer Res 1991 Nov 15;51(22):6118-24.
  6. Cesano A, Visonneau S, Scimeca JA, Kritchevsky D, Santoli D. Opposite effects of linoleic acid and conjugated linoleic acid on human prostatic cancer in SCID mice. Anticancer Res 1998 May-Jun;18(3A):1429-34.
  7. Ha YL, Storkson J, Pariza MW. Inhibition of benzo(a)pyrene-induced mouse forestomach neoplasia by conjugated dienoic derivatives of linoleic acid. Cancer Res 1990 Feb 15;50(4):1097-1101.
  8. Park Y, Albright KJ, Liu W, Storkson JM, Cook ME, Pariza MW. Effect of conjugated linoleic acid on body composition in mice. Lipids 1997 Aug;32(8):853-8.
  9. Park Y, Storkson JM, Albright KJ, Liu W, Pariza MW. Evidence that the trans-10,cis-12 isomer of conjugated linoleic acid induces body composition changes in mice. Lipids 1999 Mar;34(3):235-41.
  10. DeLany JP, Blohm F, Truett AA, Scimeca JA, West DB. Conjugated linoleic acid rapidly reduces body fat content in mice without affecting energy intake. Am J Physiol 1999 Apr;276(4 Pt 2):R1172-9.
  11. Lee KN, Kritchevsky D, Pariza MW. Conjugated linoleic acid and atherosclerosis in rabbits. Atherosclerosis 1994 Jul;108(1):19-25.
  12. Nicolosi RJ, Rogers EJ, Kritchevsky D, Scimeca JA, Huth PJ. Dietary conjugated linoleic acid reduces plasma lipoproteins and early aortic atherosclerosis in hypercholesterolemic hamsters. Artery 1997;22(5):266-77.
  13. Li Y, Watkins BA. Conjugated linoleic acids alter bone fatty acid composition and reduce ex vivo prostaglandin E2 biosynthesis in rats fed n-6 or n-3 fatty acids. Lipids 1998 Apr;33(4):417-25.
  14. Wong MW, Chew BP, Wong TS, Hosick HL, Boylston TD, Shultz TD. Effects of dietary conjugated linoleic acid on lymphocyte function and growth of mammary tumors in mice. Anticancer Res 1997 Mar-Apr;17(2A):987-93.
  15. Sugano M, Tsujita A, Yamasaki M, Noguchi M, Yamada K. Conjugated linoleic acid modulates tissue levels of chemical mediators and immunoglobulins in rats. Lipids 1998 May;33(5):521-7.
  16. Pariza MW. A new approach to evaluating carcinogenic risk. Proc Natl Acad Sci USA 1992 Feb 1;89(3):860-1.
  17. Cook ME, Miller CC, Park Y, Pariza MW. Immune modulation by altered nutrient metabolism: nutritional control of immune-induced growth depression. Poult Sci 1993 Jul;72(7):1301-5.
  18. Wahle KW, Rotondo D. Fatty acids and endothelial cell function: regulation of adhesion molecule and redox enzyme expression. Curr Opin Clin Nutr Metab Care 1999 Mar;2(2):109-15.
  19. Pariza MW. Conjugated linoleic acid, a newly recognized nutrient. Chem Indust June 16, 1997.

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