Конъюгированная линолевая кислота (CLA) син. c9,t11-CLA and t10,c12-CLA Описание: Конъюгированная линолевая кислота (CLA) относится к смеси двух или более изомеров двойной связи незаменимой жирной кислоты омега-6 – линолевой кислоты. Обычные пищевые источники CLA включают молочные продукты и мясо.240 Конъюгированная линолевая кислота считается как цис-кислотой, так и транс-жирной кислотой, хотя она не считается транс-жиром на этикетках питания и не оказывает такого же вредного воздействия на метаболизм.241 Хотя конъюгированная линолевая кислота не считается важным питательным веществом в рационе, она, по-видимому, оказывает биологическую активность на человека. Она широко используется в форме добавок в качестве антиоксиданта для поддержания общего состояния здоровья и снижения уровня липидов в сыворотке крови.242 Считается, что принцип применения CLA в спортивном питании оказывает положительное влияние на состав тела при некоторых условиях использования. imageИсследования показывают, что конъюгированная линолевая кислота обладает несколькими потенциальными защитными свойствами в организме.243 Для начала она обладает сильными антиоксидантными свойствами, которые опосредуются (по крайней мере частично) повышением антиоксидантных ферментов каталазы и глутатионпероксидазы. CLA также может проявлять противораковые (регрессирующие) свойства. Хотя ее точный способ действия здесь все еще является предметом многих исследований, было показано, что он усиливает подавляющий опухоль ген, известный как PTPRG (протеин-тирозинфосфатаза, тип рецептора, G). Также было показано, что CLA снижает уровни интерлейкинов IL-6 и IL-1, которые являются медиаторами воспаления. Это может привести к противовоспалительному эффекту. Это питательное вещество может также улучшить периферическую чувствительность к инсулину 244 и увеличить минеральную плотность кости.245 Conjugated-linoleic acid may also have positive effects on fat and energy metabolism.246 This may be mediated in part via increases in acyl-CoA oxidase, which is an enzyme involved in fatty acid oxidation, polyunsaturated fatty acid synthesis, and increased PPAR (peroxisome proliferator-activated receptors) signaling.247 CLA may also increase uncoupling protein-2 (UCP-2) mRNAexpression, which is a protein found largely in skeletal muscle tissue, and involved in mitochondrial energy production. Some studies with animals suggest the supplementation of CLA can lower body fat levels and increase lean body mass.248,249 Human studies with sedentary subjects do appear to support such activities, although conclusive ergogenic effects in training-experienced individuals have not yet been demonstrated. It is of note that the effects of conjugated-linoleic acid appear to be isomer dependant.250,251 The two most abundant isomers in CLA have been identified as c9,t11-CLA and t10,c12-CLA. In some cases, the isomers may have conflicting effects. For example, studies suggest that the t10,c12-CLA isomer is responsible for increasing fat oxidation and lean mass retention, but also contributes to insulin resistance.252 One the other hand, the c9,t11-CLA isomer appears to reduce insulin resistance. Commercial CLA supplements, and often those used in studies showing positive metabolic benefits, tend to contain a balanced mixture of these two isomers. Promoted Benefits: Conjugated-linoleic acid is promoted to increase lean muscle mass and reduce body fat retention. Clinical Studies: This ingredient has been shown to improve body composition and gender specific performance in placebo-controlled studies with untrained adults. It has a Clinical Support Rating of 4 (4/5). One placebo-controlled study examined the effects of conjugated-linoleic acid supplementation on body composition, strength, and markers of muscle degradation in a group of sedentary (inactive) men and women.253 Subjects took 5 grams of CLA per day for a period of seven weeks, and followed a controlled resistance training program. The use of CLA was shown to produce a slight but statistically significant increase in lean body mass compared to placebo (+1.4 kg versus +.2 kg). There was also a greater loss of fat mass (-.8 kg versus +.4 kg). Additionally, male subjects taking CLA noticed a greater increase in bench press strength than those taking placebo. The use of CLA was also associated with a lower catabolic effect of training, as measured by 3-methylhistidine (a marker of muscle fiber breakdown). A second placebo-controlled study examined the effects of CLA on body composition, strength, and markers of catabolism in a group of experienced resistance- trained male athletes.254 Subjects consumed 6 grams of CLA per day for four weeks, during which time they continued a resistance training program. The supplementation of conjugated-linoleic acid was not shown to produce any statistically significant changes in performance, fat or lean mass, or markers of muscle breakdown compared to placebo. There were some statistically strong trends of improvement, however, suggesting that CLA may have exerted some ergogenic effect in a majority of subjects. It remains unknown if a higher dosage, longer period of intake, or different methodologies would have yielded statistically significant results. Some other studies have failed to report statistically significant or statistically strong findings. While conflicting, the data on CLA does support ergogenic action. Further research is needed, however, to determine if conjugated-linoleic acid exhibits consistent performance-enhancing properties in exercise experienced adults. Empirical Evidence: Conjugated-linoleic acid is widely available as a stand-alone nutritional supplement. The feedback on its use as a sport supplement tends to be positive. Most reports support its ability to reduce fat mass retention. For this purpose, bodybuilders commonly use CLA during bulking phases of training in an effort to better partition nutrients towards the gain of lean mass, or at least to limit the retention of fat when increasing calories. Less common are reports of significant muscle gain, strength increases, or improved exercise or sports performance as a result of CLA supplementation. A minority of users fail to notice any body composition or performance benefits with the use of this supplement. Whether this is due to an individual insensitivity to CLA, or particular instances in which it can impart positive metabolic effects, remains unknown. Conjugated-linoleic acid has an Empirical Evidence Rating of 4 (4/5). Effective Dosage: Based on clinical studies, a dosage of 5-6 grams per day (mixed isomers) is recommended. Side Effects / Safety: Conjugated-linoleic acid was well tolerated during clinical studies, with no health-significant side effects reported. A small percentage of users appear to notice minor gastrointestinal disturbance (upset stomach, diarrhea).255
