Conjugated linoleic acid and exercise

I have written several blogs about the health benefits of conjugated linoleic acid (CLA), a fatty acid or fat in plain English, found primarily in foods of ruminant origin, such as the milk and meat products from cows, buffaloes, sheep, goat, etc. While I have also written several peer reviewed scientific articles on the topic in many international journals, this is based on an invited book chapter I did not submit eventually. Here I discuss a few things about the potential relationship of CLA with exercise.

There have been some studies over the past several years about the effect of CLA on exercise. In a study with growing mice over a period of 10 weeks, the maximum running time in CLA-fed (1% of the diet) animals was significantly longer, by 26%, compared to that of the control mice, while also decreasing the serum concentrations of triglycerides, nonesterified fatty acids, and urea nitrogen and significantly reducing the consumption of liver glycogen (Kim et al., 2010). It demonstrated that dietary CLA enhanced the endurance capacity of mice by increasing fat utilization and reducing the consumption of stored liver glycogen as substrates for energy metabolism. When five-week-old male BALB/c mice were fed a control diet containing 1.0% linoleic acid or a diet containing 0.5% CLA that replaced an equivalent amount of linoleic acid for 1 wk, the maximum swimming time until fatigue was significantly higher in the CLA-fed group than in the control group (Mizunoya et al., 2005). In the same experiment, the respiratory exchange ratio was significantly lower in the CLA-fed group during treadmill running, but oxygen consumption did not differ between groups, suggesting that fatty acids contributed more as an energy substrate in the CLA-fed mice. The muscle lipoprotein lipase activity was significantly higher in the CLA-fed group than in the control group (Mizunoya et al., 2005). These results suggested that CLA ingestion increases endurance exercise capacity by promoting fat oxidation during exercise. However, when given at 0.5% of the diet there was no effect of CLA on swimming endurance of mice (Zhang et al., 2009).

In an experiment with forty-four healthy female young subjects subject to exercise, exercise with CLA (3.6 g/d) or supplemented with CLA without exercise for six weeks and compared to control subjects, fat ratio, fat mass, waist and hip girths were reduced in all experimental groups and fat-free mass increased in and CLA groups and body weight reduced in the CLA group when compared to baseline levels (Colakoglu et al., 2006). While endurance performance significantly increased in animals subject to exercise + CLA, CLA alone was not effective in doing the same even though it seemed effective on serum glucose and insulin concentrations (Colakoglu et al., 2006). Similarly, waist and hip circumferences were reduced significantly by addition 1.6 g/d of CLA to healthy overweight humans before and after exercise that were supplemented with lysine, proline, alanine and arginine or their mixtures at 0.76 or 1.52 g/d (Michisita et al., 2010). Taken together, effects of CLA on endurance capacity in humans appears to be cumulative with other factors that increase it, but its independent ability to do the same, if any, needs further investigation.

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