Submitted to: Lipids
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/1/2001
Publication Date: N/A
Interpretive Summary: Conjgated linoleic acid (CLA) is a naturally occurring mixture fatty acids found in diary products and cooked meat. It has been shown in animals studies that CLA is protective against some types of skin cancers. It also causes a reduction in body fat mass when fed to young, rapidly growing animals. Other studies in experimental animals has purported to show that CLA can enhance immune response, lower blood fats, and is protective against cardiovascular disease. These studies were done in laboratory animals. No studies were conducted in human volunteers to see if any of these beneficial effects were exhibited in people who consumed more CLA than is normally found in the human diet. Here we conducted a metabolic ward study with 17 healthy, normal women, 10 of whom were fed a diet that contained about ten times (3.9 grams per day) the normal amount of CLA for 63 days. The remaining seven volunteers ate a diet identical to the other ten except that it did not contain any CLA, and were used as controls subjects. The tendency of the the volunteers blood to clot was measured and the fats in the blood platelets, the cell that make blood clot, were analyzed. No differences in the clotting characteristics of the volunteers who consumed the CLA were detected although we did find that a small amount of CLA was incorporated into the platelets of the volunteers consuming the CLA diet. Thus, in short-term studies with healthy adults dietary supplementation with CLA at 10X the normal level has no effect of blood clotting. Thus, Cla may not provide the same benefits to humans that have been observed in animal studies. Whether, longer feeding periods or higher dosages of CLA would cause observable effects remains to be determined.
Technical Abstract: The effect of conjugated linoleic acid (CLA) on blood coagulation, platelet function and fatty acid composition was evaluated in normal females who were confined in a Metabolic Research Unit for 93 d. They were fed a low-fat diet (30 en% fat, 19 en% protein, and 51 en% carbohydrate) consisting of natural foods with the recommended dietary allowances for all known nutrients. After a 30-day stabilization period, subjects were randomly assigned to either an intervention group (n=10) whose diet was supplemented with 3.9 g/d of CLA or a control group (n=7) that received an equal amount of sunflower oil. Platelet aggregation (PA) was measured in platelet-rich plasma using ADP, collagen, and arachidonic acid agonists. No difference was detected between the amount of agonist required to produce 50% aggregation before and after the subjects consumed the CLA. The prothrombin time, activated partial thromboplastin time, and the antithrombin-III levels in the subjects were not significantly difference when pre- and post-CLA consumption values were compared. The in vivo bleeding times were also unaffected by CLA supplementation (10.4 + 2.8 min pre- and 10.2 + 1.6 min post- consumption). Platelets fatty acid composition was not influenced by the dietary CLA although there was a small increase in the amount of the 9 cis, 11 trans-18:2 isomer, normally present in platelets, after feeding CLA for 63 d. Small amounts of the 8 trans, 10 cis-18:2 and the 10 trans, 12 cis-18:2 isomers were detected. The blood clotting parameters and in vitro PA showed that adding 3.9 g/d of dietary CLA to a typical Western diet for 63 d produces no observable physiological changes in blood coagulation and platelet function in healthy adult females.