In particular, the improvements were more significant in adults aged 45 to 54.
The peptide studied is β-lactolin, also known as glycine–thereonine–tryptophan–tyrosine tetrapeptide.
Abundant in fermented dairy products such as camembert cheese, it could also be released from whey protein digestion using specific enzymes.
The peptide could improve spatial working and episodic memory by inhibiting monoamine oxidase-B (MAO-B) – the enzyme which breaks down “happy hormones” such as dopamine, as previously reported in a mice study.
According to the study, the inhibition of MAO-B has also led to an increase in dopamine levels in the brain and the activation of dopamine D1-like receptors.
Writing in Scientific Reports, the researchers said that the daily intake of β-lactolin has shown to improve various aspects of mood states, especially trait anxiety and subjective stress.
Aside from Kirin, researchers from Kobe University Graduate School of Medicine, Tokyo’s Medical Station Clinic, Keio University, and National Center for Geriatrics and Gerontology were also involved in the study.
Studying the effects of of β-lactolin in humans for the first time, they conducted a six-week study on 60 subjects between 45 to 64 years old.
The subjects were randomised to receive either whey peptide containing 1.6mg of β-lactolin per day or placebo.
Changes in their mood states were evaluated using self-reporting questionnaires. Changes in the levels of their salivary stress markers, such as cortisol, were also measured.
Findings showed that as compared to the placebo, the intervention group saw significant improvements to their trait anxiety and subjective stress, based on the State–Trait Anxiety Inventory and Perceived Stress Scale questionnaires respectively.
In this case, trait anxiety in the intervention group dropped 6.0 ± 5.8 – significantly higher than 3.6 ± 3.3 recorded in the placebo.
Perceived Stress Scale in the intervention group also went down by 4.5 ± 4.8, also a significant difference as compared to the placebo’s reduction of 2.1 ± 4.2.
“These results indicate that the daily intake of β-lactolin improves several aspects of mood state, such as state anxiety and perceived stress,” said the researchers.
Further analysis based on age groups found that reduction in Perceived Stress Scale was more significant in subjects aged 45 to 54 taking β-lactolin.
In contrast, in subjects aged 55 to 64, the beneficial effects of β-lactolin on Perceived Stress Scale was not significant.
Immunoglobulin A levels
Aside from questionnaires, the researchers also studied changes in the subjects’ salivary immunoglobulin A (lgA), which was found to be significantly higher in the intervention group by the end of the study.
This is a type of antibody that mainly functions in the mucosal immune system and serves as the first line of defence in protecting the oral cavity and upper respiratory tract.
Findings showed that in the placebo group, IgA levels were significantly decreased – down -45.51 ± 95.35 – by the end of the study.
In contrast, that of the intervention group had increased 1.29 ± 74.03, which the researchers said was a finding showing that β-lactolin might be able to maintain IgA levels.
However, there were no statistically significant differences in the changes between the two groups in other stress markers, such as cortisol and α-amylase.
“In conclusion, supplementation with β-lactolin improves trait anxiety, subjective stress, and psychological QOL, which may be associated with immunologic responses detected via salivary analysis,” said the researchers.
Source: Scientific Reports
Supplementation with whey peptide rich in β-lactolin improves trait anxiety and subjective stress in healthy adults: a randomized, double-blind, placebo-controlled study.
https://doi.org/10.1038/s41598-024-73780-3
Authors: Ayabe, T., Shinohara, M., Kita, M. et al.