Inclusion Criteria:
* Female at birth
* You are aged 45-60 years and in perimenopause (determined by changes in menstrual bleeding patterns (such as changes in cycle length of 7 days or longer in either direction from what is normal for you), AND vasomotor symptoms (e.g., hot flushes and sweats) AND mild to moderate mood or cognitive disturbances, or joint and muscle pain over the previous 12 months)
* You are willing and able to give informed consent for participation in the study
* You are sufficiently fluent in English to understand and complete tasks
* You are at least 12 months post-natal
* Willing to withhold from having grapefruit juice
Exclusion Criteria:
* Currently receive or seek treatment for any mental health condition
* Have a BMI \>=30 OR \<=18.5
* Have lost or gained more than 10% of body weight in a short period (e.g., 6 months), as this can affect mood and cognition
* Currently using hormonal contraception or have used hormonal contraception in the last 6 months
* Have had gender reassignment surgery or gender-affirming hormone therapy
* Had a head injury causing concussion or unconsciousness in the past 6 months
* Participated in other studies that may influence mood, cognition, or gut health in the last three months
* Are currently diagnosed with and/or treated for psychiatric or neurological disorders
* Are on perimenopausal hormone replacement therapy (HRT) (e.g., estrogen, progesterone, testosterone) or other hormone-modulating medications (e.g., GLP-1 agonists, thyroxine replacement), as these can impact mood and cognitive functions
* Currently use statins or have used statins in the last 6 months, as these may impact mood and cognitive functions
* Participated in any other study with the same tasks in the last year
* Currently use medications that influence cognition or mood, such as antidepressants, anxiolytics, antipsychotics, stimulants, mood-stabilizers, or cognitive-enhancing drugs
* Have chronic or severe gastrointestinal diseases (e.g., inflammatory bowel disease, Crohn's disease, celiac disease, or severe acid reflux; treatment with e.g., corticosteroids, antacids), as these conditions and treatments can affect the gut microbiota and immune responses differently from healthy individuals
* Have a compromised immune system
* Currently smoke, vape, or use any other nicotine products
* Have a current diagnosis of cognitive impairment or neurodegenerative disorders (e.g., mild cognitive impairment, dementia), as these conditions could confound cognitive assessments.
* Have severe medical conditions requiring ongoing medication that may independently affect cognition or mood (e.g., diabetes)
* Currently or recently used antibiotics (last 3 months), as antibiotics may alter gut microbiota and interfere with probiotic effects
* Currently or recently used probiotics or prebiotics or consumed fermented products (e.g., kimchi, kombucha, sauerkraut, kefir, etc.) on a regular basis (last 3 months), which might interfere with the study intervention
* Have known allergies or intolerances to probiotics or components in the probiotic supplement.
* Have substance abuse or dependence (e.g., alcohol, recreational drugs) that may affect mood and cognition.
* Have Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (Long COVID)
* Have had a hysterectomy
* Are pregnant or lactating, as hormonal changes associated with these states could confound results.
* Score of 20 or above on PHQ-9 depression questionnaire, indicating severe depression
* Score of \>1 on PHQ-9 suicidality item, indicating significant suicidality (as assessed by medical on-site professionals
