Conjugated linoleic acid

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Conjugated linoleic acid (CLA) refers to a family of many isomers of linoleic acid (at least 13 are reported), which are found primarily in the meat and dairy products of ruminants. As implied by the name, the double bonds of CLAs are conjugated.

Conjugated linoleic acid is a trans fat, though some researchers claim that it is not harmful in the same fashion as other trans fatty acids, but rather is beneficial.[citation needed] CLA is a conjugated system, and in the United States, trans linkages in a conjugated system are not counted as trans fat for the purposes of nutritional regulations and labeling. Unlike most trans fatty acids found in the human diet, CLA occurs naturally, produced by microorganisms in the fore-stomach of ruminants. Non-ruminants, such as humans, may be able to produce some isomers of CLA from non-conjugated ruminant fats. One such example is vaccenic acid, which could be converted to CLA by delta-9-desaturase.[1]

CLA comes in two isomers: the c9,t11 isomer (rumenic acid) which appears responsible for improving muscle growth,[citation needed] and the t10,c12 isomer which primarily prevents lipogenesis (storage of fat in adipose tissue). Most supplements sold in stores contain a 50/50 mix of both isomers. [2]

Various antioxidant and anti-tumor properties have been attributed to CLA, and studies on mice and rats show promising results; however, it is suspected that sufficient concentrations to achieve anti-inflammatory effects within human tissues may not be attainable via oral consumption.[citation needed]

Many studies on CLA in humans show a tendency for reduced body fat[3], particularly abdominal fat, changes in serum total lipids and decreased whole body glucose uptake. The maximum reduction in body fat mass was achieved with a 3.4 g daily dose[4].

CAS registry number: 2420-56-6, Molecular Formula: C18H32O2

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[edit] Other benefits

CLA may be beneficial in other aspects, including prevention of breast and colon cancer.[citation needed]

Additional potential benefits include a reduction in food-induced allergic reactions, as well as the overall enhancement of the immune system. [1]

[edit] Possible Side Effects

There are concerns that the use of CLA may actually cause insulin resistance, leading to an increased risk for developing diabetes.[5]. [2]

A recent study (2006) conducted in mice by the US Department of Agriculture gives account of some highly concerning effects of CLA: it can dramatically induce essential fatty acid redistribution (DHA and AA) in various organ tissues. The same study raises the concern that it might pose significant risks, especially regarding cardiovascular health and inflammatory diseases. DHA content in heart tissue for instance was found to be reduced by no less than 25% by certain CLA isomers, while spleen DHA increased 6-fold and spleen AA was reduced to only 5% of its normal levels in that tissue. [3]. Another study (2005) of CLA supplementation of hatching chicks showed high mortality and low hatchability rate among the CLA-supplemented groups, and also a decrease in brain DHA levels of CLA-incubated chicks. [4]

[edit] Dosage

CLA is available commercially in doses of about 500mg to 1300mg (or .5 g to 1.3 g). The optimal dosage is about 3.4 g, with larger doses showing little or no improvement.[citation needed]

CLA should be taken with protein-rich food to prevent side effects, including diarrhea, nausea, and stomachache.[citation needed]

[edit] Dietary Sources

Kangaroo meat may have the highest concentration of CLA when compared with other foods.[6] Food products of grass-fed ruminants (eg lamb, beef) are good sources, and contain much more CLA than those from grain-fed animals. [7] In fact, products of grass fed animals can produce 300-500% more CLA that cows fed the typical diet of 50% hay and silage with 50% grain. [8]

[edit] See also

[edit] References

  1. ^ Banni S, Angioni E, Murru E, Carta G, Melis M, Bauman D, Dong Y, Ip C (2001). "Vaccenic acid feeding increases tissue levels of conjugated linoleic acid and suppresses development of premalignant lesions in rat mammary gland". Nutr Cancer 41 (1-2): 91-7. PMID 12094634. 
  2. ^ Lowery: Poison or Gift? 2001 International CLA Conference Report.
  3. ^ Thom E, Wadstein J, Gudmundsen O. (Sep-Oct 2001). "Conjugated linoleic acid reduces body fat in healthy exercising humans.". The Journal of International Medical Research 29 (5): 392-396. PMID 11725826. Retrieved on 2006-05-27. 
  4. ^ Blankson H, Stakkestad JA, Fagertun H, Thom E, Wadstein J, Gudmundsen O. (December 2000). "Conjugated linoleic acid reduces body fat mass in overweight and obese humans.". Journal of Nutrition 130 (12): 2943-2948. PMID 11110851. Retrieved on 2006-05-27. 
  5. ^ Ulf Risérus, MMed; Samar Basu, PhD; Stefan Jovinge, MD, PhD; Gunilla Nordin Fredrikson, PhD; Johan Ärnlöv, MD; Bengt Vessby, MD, PhD (September 2002). "Supplementation With Conjugated Linoleic Acid Causes Isomer-Dependent Oxidative Stress and Elevated C-Reactive Protein.". American Heart Association Journals. 01.CIR.0000033589.15413.48v1. Retrieved on 2007-02-19. 
  6. ^ Commonwealth Scientific and Industrial Research Organisation (CSIRO) (2004-04-23). Kangaroo meat - health secret revealed. Press release. Retrieved on 2007-01-23.
  7. ^ T. R. Dhiman, L. D. Satter, M. W. Pariza, M. P. Galli, K. Albright, and M. X. Tolosa (May 2000). "Conjugated Linoleic Acid (CLA) Content of Milk from Cows Offered Diets Rich in Linoleic and Linolenic Acid". Journal of Dairy Science 83 (5): 1016-1027. PMID 10821577. Retrieved on 2006-05-27. 
  8. ^ T. R. Dhiman (2001). "Role of diet on conjugated linoleic acid content of milk and meat.". Journal of Animal Science 79. Retrieved on 2007-03-09. 
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