Combination of L-lysine and L-arginine reduces stress and lowers cortisol levels
Supplementation with 2.34 g L-lysine and the same amount of L-arginine daily reduces psychological stress and lowers cortisol amounts in men's bodies. Researchers at the Japanese Ajinomoto amino acid manufacturers announced this in Biomedical Research.
Lysine, arginine & stress
Miro Smriga, the first author in the article that was published in Biomedical Research in 2008, has studied the effect of the lysine-arginine combination on anxiety and stress for years. He's observed the effect in mice [Nutr Neurosci. 2003 Apr;6(2):125-8.] subjected to a stressful situation in a laboratory, in pigs being transported [Nutr Neurosci. 2003 Oct;6(5):283-9.] and in humans with a stress-sensitive personality [Nutr Neurosci. 2005 Jun;8(3):155-60.].
At least part of the explanation for the stress-reducing effect of the lysine-arginine combination is probably that lysine interacts with the receptor for GABA. [Neurochem Res. 1995 Aug;20(8):931-7.] Sleeping pills and alcohol also work via the same receptor.
In the study that was published in Biomedical Research, the researchers gave a group of about one hundred healthy test subjects 2.34 g L-lysine and 2.34 g L-arginine daily for seven days. The subjects took the amino acids twice a day, at breakfast and the evening meal.
After the supplementation period the researchers got their subjects to complete a questionnaire, the State-Trait Anxiety Inventory. Psychologists use this to measure how sensitive you are to stress in daily life. The figure below shows that this sensitivity decreased in the subjects that had taken the lysine-arginine combination.
Cortisol is the main hormone associated with stress. The researchers measured the cortisol concentration in the subjects' saliva and saw that this did not decrease significantly in the women that had taken lysine and arginine supplements. In the men however this did happen, as the figure above shows.
The amino acids reduced the men's cortisol concentrations by 18 percent. The researchers took their measurements between 9 and 10 in the morning.
The Japanese also studied the effect of a stressful event – in this case exposure to noise - on the subjects. They noticed that lysine/arginine supplementation had no effect on the cortisol concentration in the women, but that in the men this speeded up the return of cortisol concentrations to normal levels.
Biomed Res. 2007 Apr;28(2):85-90.
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