The Potential Effect of Conjugated Linoleic Acid on Endurance Exercise: A Mechanistic Review

Research Article

Austin Sports Med. 2021; 6(1): 1044.

The Potential Effect of Conjugated Linoleic Acid on Endurance Exercise: A Mechanistic Review

Tavakoli-Rouzbehani OM1,2*, Rezaei AM1, Safaei E1,2, Iranshani AM1,2 and Amirpour M1,2

¹Tabriz University of Medical Sciences, Student Research Committee, Iran

²Department of Clinical Nutrition, Tabriz University of Medical Sciences, Iran

*Corresponding author: Omid Mohammad Tavakoli-Rouzbehani, Department of Clinical Nutrition, Faculty of Nutrition and Food Sciences, Tabriz University of Medical Sciences, Tabriz, Iran

Received: December 29, 2020; Accepted: January 29, 2021; Published: February 05, 2021


Introduction: The purpose of the present study was to appraise the results from disseminated human, animal and in vitro studies, and evaluate the possible effect along with the mechanism of CLA supplementation on endurance exercise.

Methods: Related articles were searched on PubMed, Web of Science, Scopus, Embase, and Cochrane databases with defined keywords. Articles were assessed through their titles and abstracts. Finally, 11 articles were included based on inclusion and exclusion criteria.

Results: Most of the studies were conducted on animals, and CLA was often supplemented along with training. Dosage and study duration vary for a broad range. Results showed various possible pathways on the effect of CLA supplementation on endurance exercise and related factors.

Conclusions: It was indicated that CLA supplementation could prolong endurance performance by improving oxidant status, mitochondrial biogenesis, testosterone biosynthesize, fat oxidation, and change in body composition. Although CLA is being used in many countries and numerous studies have shown its safety, its long-term supplementation and effect need to be investigated. Also, further studies are required to identify the molecular mechanism in the human body.

Keywords: CLA; Endurance Exercise; Conjugated Linoleic Acid; Resistance Exercise; Oxidant Status; Mitochondrial Biogenesis; Testosterone


Exercise is generally divided into two groups: aerobic/endurance and power/strength [1]. Endurance exercise such as running, swimming and cycling and is classically performed against a relatively low load over a long duration, whereas strength exercise like bodybuilding is performed against a relatively high load for a short period [1,2]. However, a pure type of each exercise type is rare, and exercises are usually a mixture of both types that have been termed concurrent exercise. In response to exercise, our body can adapt to either endurance or strength exercise. Low-intensity training for long periods can enhance individuals’ endurance performance adaptations, resulted from improved cardiovascular system function [1].

The power and velocity maintained for a duration of 30 minutes to four hours evaluate the endurance performance typically [3]. Accumulation of hydrogen ion (i.e., lactic acidosis) and heat (i.e., hyperthermia) are the main by-products of extreme and prolonged oxidative metabolism come along with endurance exercise [3]. It is also suggested that oxidative stress can be induced during exercise, especially when training is of high intensity. In fact, oxygen-containing free radicals such as the hydroxyl ions, superoxide, hydroperoxyl, and lipid peroxyl are the metabolites generated after exercise. Whenever the production of these radicals exceeds the antioxidant capacity of the tissue, the radicals quickly react with cellular components. As a result, this oxidant system leads to reduced contractile function, arrhythmias, and muscle fatigue [4]. Whether the body has the potency to supply enough oxygen and glucose is another crucial determinant of endurance exercise [3].

Conjugated Linoleic Acid (CLA) is a term used to describe a group of positional and geometrical isomers of conjugated dienoic octadecadienoate fatty acids produced from linoleic acid by rumen bacteria [5]. CLA contains two double bonds separated by a single bond in either a configuration of cis or trans [6]. All physiological effects are induced by cis-9, trans-11, and trans-10, cis-12 (c9:t11 and t10:c12, respectively) isomers which are among the most common isomers of CLA [7]. These double bonds are commonly positioned between carbon molecules 8 and 13, but they can be located in any position on the carbon chain [8]. Also, the effect was reported to be dose-dependent in the range of dietary CLA levels between 0 and 1.5% weight to accomplish desired health benefits [6]. The two major sources of CLA in human diets are dairy products (milk and cheese) and ruminant meats (beef and lamb) [9]. The fat in meat and milk contains about 4.3 and 5.5 mg CLA/g of fat respectively with almost 9-cis and 11-trans isomers [6]. The potent biological effect of CLA such as anti-carcinogenic, anti-inflammatory, anti-obesity, anti-diabetic, immunomodulatory, anti-atherosclerotic, reduction of whole-body fat and bone formation promoting properties have been suggested in previous studies [10]. Also, studies demonstrate the effects of CLA supplementation on the energetic metabolism, promoting significant changes in the lipid metabolism and in body composition [11]. Studies suggest that CLA supplementation may also help resynthesize of glycogen and improve fatty acid b-oxidation in skeletal muscle [11]. Therefore, we have conducted this review to evaluate the possible effect and the mechanism of CLA supplementation on endurance exercise.


Articles evaluating “the effect of CLA and its isomers on endurance exercise” were searched on PubMed, Web of Science, Scopus, Embase, and Cochrane. The title and abstract of each article were assessed to delete duplication data. Any irrelevant articles were excluded. The remaining articles were reviewed to determine compatibility with the inclusion criteria. Searching was limited to articles with the English language. Review articles, case reports, letters, editorials, abstracts in symposium and congress, and unpublished studies were excluded. Studies meeting the following inclusion criteria were included: 1. English articles; 2. evaluated the effect of CLA isomers on endurance exercise. The following data were collected from each study: publication data (i.e., first author’s name, publication year and study location), study design, sample size and specifications, intervention data (i.e., duration of intervention, intervention substance and it’s dosage, type and amount of placebo) and results related to our primary objective. Characteristic of studies have been summarized in (Table 1).

Citation:Tavakoli-Rouzbehani OM, Rezaei AM, Safaei E, Iranshani AM and Amirpour M. The Potential Effect of Conjugated Linoleic Acid on Endurance Exercise: A Mechanistic Review. Austin Sports Med. 2021; 6(1): 1044.