Supplementation with 2.34 g of 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.
Miro Smriga, the first author of 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 subjected to a stressful situation in a laboratory, in pigs being transported, and in humans with a stress-sensitive personality.
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. 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 of L-lysine and 2.34 g of 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 a person is 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 confirmed that this had not decreased significantly in the women who had taken lysine and arginine supplements. In the male subjects 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 researchers 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.