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Conjugated Linoleic Acid (CLA)


BigJim77
(@bigjim77)
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Description:
Linoleic acid (LA) is a naturally occurring fatty acid found predominantly in beef and dairy products. LA is one of the two essential fatty acids (the other is linolenic acid). Linoleic acid is an omega-6 fatty acid, meaning that it is unsaturated, with a double bond occurring at the sixth carbon atom from the omega end of the molecule. Conjugated linoleic acid (CLA) is an isomer of LA - which refers to a slight rearrangement of the molecular structure (conjugation) - resulting in a fatty acid with altered chemical functions. The rearrangement in this case is a conjugated double bond occurring at carbons 10 and 12 or at carbons 9 and 11. Linoleic acid is found in the diet in vegetable oils, whereas the conjugated variety, CLA, is found primarily in meat and dairy products. The form of CLA found most commonly in dietary supplements is manufactured from vegetable oils such as sunflower oil or safflower oil. One of the leading brands of CLA (TonalinTM), and the one on which the majority of studies has been conducted, is derived from safflower oil.

Claims:

Builds muscle
Burns fat
Increases thermogenesis (calorie expenditure)
Fights cancer
Antioxidant

Theory:
The anti-tumor/anti-cancer properties attributed to CLA may be due to an antioxidant effect or to an undefined interaction between CLA and various carcinogens. CLA is also theorized to modulate the production of prostaglandins, which are derived from fatty acid molecules and have been linked to an elevated synthesis of growth hormone. Increased growth hormone levels are viewed as beneficial to both athletes and dieters as a way to promote enhanced muscle growth, strength and fat loss. Some prostaglandins may also increase blood circulation to the muscles and adipose tissue - an effect that has been suggested to improve muscle function and fat mobilization. Perhaps the more tantalizing effects of CLA when it comes to supplements, however, are those reported for the induction of weight loss, body fat loss and increased caloric expenditure.

Scientific Support:
The majority of research on dietary intake of CLA has been conducted in animals. Several studies have indicated an anti-tumor effect of CLA in normal doses (1-4 grams) - close to what an average person might consume daily from a "typical" intake of meat and dairy products. The potential anti-cancer effects of CLA (most notable the cis-9/trans-11 isomer) have been attributed to several possible mechanisms including its actions as an antioxidant.

The positive effects of CLA on body composition (less fat and more lean) have been shown in numerous animal studies (pigs, mice, rats, chicks), but the evidence in humans has been somewhat controversial. The joke around the scientific meetings has always been that CLA is a great weight loss supplement for mice, but not so good for humans. This view, however, is rapidly beginning to change based on recent results from several research groups.

In animals, adding CLA (primarily the trans-10/cis-12 isomer) to the diet consistently leads to the supplemented animals gaining less body fat, but more lean body mass (muscle), compared to control animals. As such, many of the studies show no change in total body weight - but that weight is made up of less fat and more muscle - good stuff! - but remember, these results are primarily being shown in rodents and livestock (very few of which are reading these web pages). In livestock studies (cattle, pigs, chickens), supplemental CLA has been shown to promote growth and prevent muscle wasting, whereas body fat accumulation and energy expenditure increased - so here you get a leaner stronger animal (isn't that what we're all looking for in terms of weight loss?). As a nice side benefit, CLA feeding also appears to reduce LDL cholesterol and triglyceride levels in rabbits with elevated cholesterol. So what does this picture look like? - A Happy Barnyard! The cattle, pigs and chickens are all low-fat, high-muscle machines - sort of like a barnyard version of Muscle Beach. Likewise, the CLA-supplemented lab animals (rats, rabbits, and mice) are slim and trim and are the envy of the guinea pigs who only seem to get recruited for the studies on carcinogens and tobacco-related studies.

But what does this all mean for you (the non-lab-rat human looking to shed a few pounds)? Based on a handful of recent studies, it means good news (maybe). Two recent studies have shown that CLA supplementation (3-4 grams/day) promotes a loss of body fat (2-4 lbs. extra in overweight subjects over 12 weeks) and reduces abdominal fat (by about 1 inch) in obese men. So does this mean that CLA is the answer to your weight loss prayers? Probably not - but it might help (keep reading).

Despite these recent positive findings on CLA, there are numerous earlier (but small) studies that have found no benefits of CLA for fat loss. One small study of weight lifters found no differences on measures of body weight, fat mass or fat-free mass following a month of CLA supplementation, but this study looked at subjects who already had a fairly low body fat percentage (14%). Another small study followed 10 subjects consuming 3-4 grams of CLA each day for three months and compared them to 10 subjects consuming a placebo. Results showed no difference in weight loss between CLA and placebo, but those talking CLA dropped somewhat more body fat (a good thing). In another study of 17 healthy women, CLA supplements (3 grams/day) or a sunflower oil placebo for 64 days, resulted in no change in body weight, fat-free mass, fat mass, or percentage of body fat. Likewise, CLA had no significant effect on energy expenditure, fat oxidation, or respiratory exchange ratio at rest or during exercise.

Bottom line = the scientific evidence is overwhelmingly positive in the animal studies, but about evenly split between positive and no-effect studies of humans (see more in the Value section).

Safety:
No adverse side effects are reported with CLA supplementation - but at least one of the more recent human trials reported that about 30% of subjects reported gastrointestinal symptoms associated with recommended doses (3-5 grams/day).

Value:
Confused yet? What we're left with is a supplement that has scientific evidence on both side of the fence (like almost every supplement) - which side of the CLA fence should you be on? In considering the overall "value" of CLA for fat loss, we need to consider some of the metabolic differences between animals (where almost all of the CLA data is positive for lowering body fat and increasing lean tissue) and humans (where we have a split). Rodents, for example, have a metabolic rate that is about 7 times higher than that of a human - which translates, after normalizing rodent and human data to the same scales, to a reduction of body fat that is 7 times greater in rodents than in humans following CLA supplementation. In the rodent studies, CLA supplementation has also been shown to increase daily energy expenditure by nearly 8% - but in humans this effect may only be a bit over 1% (too small to be detected in anything but the largest study using the most sensitive equipment). So this leaves you to make our own judgement call - to supplement with CLA or not. Our recommendation is that if you're looking for a non-stimulant method for slightly increasing energy expenditure and promoting body fat loss, then CLA is worth a try (perhaps combined with green tea extract).

Dosage:
Most people ingest less than 1 gram per day from meat and dairy foods. Typical dosage recommendations are 3-5 grams per day and the 2 most recent studies on CLA have shown benefits using doses of 3.4g and 4.2g per day. Because most of the studies showing a positive effect of CLA have used the TonalinTM brand of CLA (a 50/50 blend of the cis-9/trans-11 and trans-10/cis-12 isomers), SupplementWatch recommends that you look for products that include TonalinTM.

References:
1. Azain MJ, Hausman DB, Sisk MB, Flatt WP, Jewell DE. Dietary conjugated linoleic acid reduces rat adipose tissue cell size rather than cell number. J Nutr. 2000 Jun;130(6):1548-54.
2. Banni S, Angioni E, Casu V, Melis MP, Carta G, Corongiu FP, Thompson H, Ip C. Decrease in linoleic acid metabolites as a potential mechanism in cancer risk reduction by conjugated linoleic acid. Carcinogenesis. 1999 Jun;20(6):1019-24.
3. Bee G. Dietary conjugated linoleic acid consumption during pregnancy and lactation influences growth and tissue composition in weaned pigs. J Nutr. 2000 Dec;130(12):2981-9. 4. Benito P, Nelson GJ, Kelley DS, Bartolini G, Schmidt PC, Simon V. The effect of conjugated linoleic acid on plasma lipoproteins and tissue fatty acid composition in humans. Lipids. 2001 Mar;36(3):229-36.
5. Cook ME, Miller CC, Park Y, Pariza M. Immune modulation by altered nutrient metabolism: nutritional control of immune-induced growth depression. Poult Sci. 1993 Jul;72(7):1301-5. 6. 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.
7. DeLany JP, West DB. Changes in body composition with conjugated linoleic acid. J Am Coll Nutr. 2000 Aug;19(4):487S-493S.
8. Devery R, Miller A, Stanton C. Conjugated linoleic acid and oxidative behaviour in cancer cells. Biochem Soc Trans. 2001 Apr;29(2):341-4.
9. Gavino VC, Gavino G, Leblanc MJ, Tuchweber B. An isomeric mixture of conjugated linoleic acids but not pure cis-9, trans-11-octadecadienoic acid affects body weight gain and plasma lipids in hamsters. J Nutr. 2000 Jan;130(1):27-9.
10. Guthrie N, Carroll KK. Specific versus non-specific effects of dietary fat on carcinogenesis. Prog Lipid Res. 1999 May;38(3):261-71.
11. Ip C, Scimeca JA, Thompson HJ. Conjugated linoleic acid. A powerful anticarcinogen from animal fat sources. Cancer. 1994 Aug 1;74(3 Suppl):1050-4.
12. Ip C, Singh M, Thompson HJ, Scimeca JA. Conjugated linoleic acid suppresses mammary carcinogenesis and proliferative activity of the mammary gland in the rat. Cancer Res. 1994 Mar 1;54(5):1212-5.
13. Kelley DS, Taylor PC, Rudolph IL, Benito P, Nelson GJ, Mackey BE, Erickson KL. Dietary conjugated linoleic acid did not alter immune status in young healthy women. Lipids. 2000 Oct;35(10):1065-71.
14. Kritchevsky D, Tepper SA, Wright S, Tso P, Czarnecki SK. Influence of conjugated linoleic acid (CLA) on establishment and progression of atherosclerosis in rabbits. J Am Coll Nutr. 2000 Aug;19(4):472S-477S.
15. Lee KN, Kritchevsky D, Pariza MW. Conjugated linoleic acid and atherosclerosis in rabbits. Atherosclerosis. 1994 Jul;108(1):19-25.
16. Li Y, Seifert MF, Ney DM, Grahn M, Grant AL, Allen KG, Watkins BA. Dietary conjugated linoleic acids alter serum IGF-I and IGF binding protein concentrations and reduce bone formation in rats fed (n-6) or (n-3) fatty acids. J Bone Miner Res. 1999 Jul;14(7):1153-62.
17. Martin JC, Gregoire S, Siess MH, Genty M, Chardigny JM, Berdeaux O, Juaneda P, Sebedio JL. Effects of conjugated linoleic acid isomers on lipid-metabolizing enzymes in male rats. Lipids. 2000 Jan;35(1):91-8.
18. Miner JL, Cederberg CA, Nielsen MK, Chen X, Baile CA. Conjugated linoleic acid (CLA), body fat, and apoptosis. Obes Res. 2001 Feb;9(2):129-34.
19. Moya-Camarena SY, Belury MA. Species differences in the metabolism and regulation of gene expression by conjugated linoleic acid. Nutr Rev. 1999 Nov;57(11):336-40.
20. Pariza MW, Park Y, Cook ME. The biologically active isomers of conjugated linoleic acid. Prog Lipid Res. 2001 Jul;40(4):283-98.
21. 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.
22. Park Y, Albright KJ, Storkson JM, Liu W, Cook ME, Pariza MW. Changes in body composition in mice during feeding and withdrawal of conjugated linoleic acid. Lipids. 1999 Mar;34(3):243-8.
23. Ryder JW, Portocarrero CP, Song XM, Cui L, Yu M, Combatsiaris T, Galuska D, Bauman DE, Barbano DM, Charron MJ, Zierath JR, Houseknecht KL. Isomer-specific antidiabetic properties of conjugated linoleic acid. Improved glucose tolerance, skeletal muscle insulin action, and UCP-2 gene expression. Diabetes. 2001 May;50(5):1149-57.
24. Sisk MB, Hausman DB, Martin RJ, Azain MJ. Dietary conjugated linoleic acid reduces adiposity in lean but not obese Zucker rats. J Nutr. 2001 Jun;131(6):1668-74. 25. Stangl GI. Conjugated linoleic acids exhibit a strong fat-to-lean partitioning effect, reduce serum VLDL lipids and redistribute tissue lipids in food-restricted rats. J Nutr. 2000 May;130(5):1140-6.
26. Szymczyk B, Pisulewski PM, Szczurek W, Hanczakowski P. Effects of conjugated linoleic acid on growth performance, feed conversion efficiency, and subsequent carcass quality in broiler chickens. Br J Nutr. 2001 Apr;85(4):465-73.
27. Thiel-Cooper RL, Parrish FC Jr, Sparks JC, Wiegand BR, Ewan RC. Conjugated linoleic acid changes swine performance and carcass composition. J Anim Sci. 2001 Jul;79(7):1821-8. 28. Watkins BA, Seifert MF. Conjugated linoleic acid and bone biology. J Am Coll Nutr. 2000 Aug;19(4):478S-486S.
29. West DB, Blohm FY, Truett AA, DeLany JP. Conjugated linoleic acid persistently increases total energy expenditure in AKR/J mice without increasing uncoupling protein gene expression. J Nutr. 2000 Oct;130(10):2471-7.
30. West DB, Delany JP, Camet PM, Blohm F, Truett AA, Scimeca J. Effects of conjugated linoleic acid on body fat and energy metabolism in the mouse. Am J Physiol. 1998 Sep;275(3 Pt 2):R667-72.
31. Yamasaki M, Mansho K, Mishima H, Kasai M, Sugano M, Tachibana H, Yamada K. Dietary effect of conjugated linoleic acid on lipid levels in white adipose tissue of Sprague-Dawley rats. Biosci Biotechnol Biochem. 1999 Jun;63(6):1104-6.
32. Yang M, Pariza MW, Cook ME. Dietary conjugated linoleic acid protects against end stage disease of systemic lupus erythematosus in the NZB/W F1 mouse. Immunopharmacol Immunotoxicol. 2000 Aug;22(3):433-49.
33. Zambell KL, Keim NL, Van Loan MD, Gale B, Benito P, Kelley DS, Nelson GJ. Conjugated linoleic acid supplementation in humans: effects on body composition and energy expenditure. Lipids. 2000 Jul;35(7):777-82.

Copyright 2001, SupplementWatch, Inc. - www.supplementwatch.com


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Ripped-Babe
(@ripped-babe)
New Member
Joined: 2 weeks ago
Posts: 2
 

Thank you, nice information. I would also like to see something on ALA if you have it.


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