Amino Acid Helps Fight Fatigue

OSAKA, Japan— Researchers found L-ornithine, a free amino acid, has an anti-fatigue effect by increasing the efficiency of energy consumption and promoting the excretion of ammonia (Nut. Res. 2008;28(11):738-43). In a double blind, placebo-controlled, two-way crossover study, 17 healthy volunteers were randomized to L-ornithine (2000 mg/d for seven days and 6000 mg/d for one day as L-ornithine hydrochloride) or placebo for eight days. L-ornithine administration promoted lipid metabolism and activated the urea cycle from serum triacylglycerol, ketone bodies, free fatty acids and blood ammonia level changing. L-ornithine significantly attenuated the subjective feeling of fatigue compared with postload (P<0.01). Moreover, in female subjects, the subjective feeling of fatigue was significantly lower compared with the placebo group (P<0.05). In the physical performance test in female subjects, the decrease in mean speed for 10 seconds maximum pedaling from 0.5- to 3.5-hour trials in the group receiving L-ornithine was smaller than that in the group receiving placebo (P<0.05). Researchers “recommend L-ornithine intake as a nutritional supplement in cases of physical fatigue.”