The probiotic strain HN001 improved total happiness and perceived stress score (PSS) in a four-week RCT in New Zealand, which was funded by Fonterra Cooperative Group.
“This study sheds light on the impact of probiotics on happiness. Lactobacillus rhamnosus HN001 showed promising results in this current controlled clinical trial, consistent with a previous open-label consumer study,” wrote researchers in Nutrients.
HN001 is a probiotic strain widely studied for its potential to improve human health. Previous studies have demonstrated promising results for HN001 in the improvement of mental well-being, particularly in terms of increased happiness and support for stress management in healthy adults.
“In three different clinical and two preclinical studies, HN001 was selected to explore its potential effects on mental well-being and brain health. HN001 showed a positive effect on social functioning and anxiety in prediabetes patients, lowered anxiety and depression postpartum, and improved total happiness scores in a consumer experience study carried out in 2022,” said researchers.
To further explore these findings, researchers conducted a double-blind, placebo-controlled trial.
The study
There were 120 participants aged 18 years and above recruited for this RCT. They were diagnosed with mild to high stress as measured by the PSS.
Overall, the median age was 48 years, with an approximately equal distribution of male and female participants.
The mean age for the probiotic group was 46.6 years, which was similar to that of the placebo group with a mean age of 45.3 years.
There were 61 participants in the probiotic (HN001) group and 59 participants in the placebo group.
Participants were instructed to consume the assigned capsules daily for over 28 days with a 3-day window, where participants were given a flexible time frame of three days to either start or complete a particular phase of the intervention.
The probiotic group was given three Nutiani HN001 capsules a day, supplied by Fonterra Cooperative Group. This provided a dose of 6 × 109 CFU day−1 of HN001.
The control group received a placebo, maltodextrin, with the same number of capsules per day.
Psychological assessments, including the Oxford Happiness Questionnaire (OHQ), were completed at baseline (T0), day 14 (T1), and day 28 (T2).
Increased happiness and less stress
HN001 showed improvements in both happiness and PSS scores.
The total happiness score increased from 107.1 at T0 to 121.8 at T2 in the probiotic group.
For the placebo group, the total happiness score increased from 106.6 at T0 to 116.5 at T2 – this was relatively lower than the probiotic group.
The probiotic group also showed more improvement than the placebo group in stress level scores.
The PSS for the probiotic group dropped from 24 at T1 to 14.9 at T2.
For the placebo group, the PSS dropped from 24.6 at T1 to 16.6 at T2.
Although this difference was not statistically significant, the percentage of participants taking HN001 who reported lower stress levels at the end of the study was 47%, which was higher than those in the placebo group at 39%.
HN001 showed better effects in men than women
HN001 supplementation also increased happiness with significant sex-specific effects.
The study revealed that HN001 significantly improved happiness scores in men compared to the placebo group, with noticeable effects emerging after two weeks and continuing to increase until the end of the study.
“This aligns with research indicating that probiotics often require over four weeks to impact mental health. While no significant changes were observed in the female subgroup, men experienced a greater boost in happiness scores, particularly between days 14 (T1) and 28 (T2),” said researchers.
The difference may be due to the female participants’ mean age of 46, which included premenopausal and menopausal women who are more prone to stress, depression, and anxiety during this life stage.
However, 70% of females in the probiotic group reported moving from "not happy" to "happy" – 13% more than the females in the placebo group.
“These findings suggest that HN001 has the potential to improve mental well-being, especially in men, and may require a longer intervention for women, given the biological and social factors at play,” said researchers.
The effects of HN001 on increasing happiness and reducing stress in men, while considered small, are comparable to the effect of some antidepressants like ACE inhibitors.
Although the placebo group also showed improvements in happiness, stress, anxiety, and depression, the changes were less significant than those in the HN001 group. This highlights the psychological impact of placebo interventions and suggests that larger study sizes may be needed to detect statistically significant differences.
Further research is necessary to understand how HN001 works, but its known ability to strengthen the immune system across all age groups may play a role. It’s possible that the strain reduces subclinical inflammation, which helps regulate the overactive stress response often seen in individuals with higher stress levels.
“We observed an improvement in total happiness and PSS scores over time after the 4-week intervention.
“Interestingly, the sex subgroup analysis showed statistically significant differences in both total happiness and PSS scores over time, emphasising the need for larger and longer intervention studies to reach statistical significance, as well as the need for subgroup analyses to investigate sex-specific effects of probiotic intervention outcomes,” concluded the researchers.
Source: Nutrients
DOI: https://doi.org/10.3390/nu16172936
“Effects of Lacticaseibacillus rhamnosus HN001 on Happiness and Mental Well-Being: Findings from a Randomized Controlled Trial”
Authors: Imad Al Kassaa and Maher Fuad.
