Nutrients 2023 , 15 , 3466
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included active IBS (according to the Rome IV criteria), any chronic intestinal disease, immunodeficiency disorders or immunosuppressive treatment, any known food allergies or celiac disease, intake of antibiotics within four weeks before the screening visit or any previous psychiatric illness (within five years), consumption of systemic psychotropics, rheumatoid drugs, steroid drugs, regular asthma medications or use of creams containing cortisone within the previous four weeks before the screening visit. Subjects who had been included in any other clinical study with an intake of any investigational product, who were pregnant or had plans to change their current diet and/or exercise regime during the participation of the trial, had any malignant disease or other end-organ diseases that were judged to interfere with the study, or those with a history of heavy caffeine consumption (>400 mg/day) were also excluded. Any intake of antibiotics, and/or intake of other probiotic supplements or other food supplements which could interfere with the study was also prohibited. Subjects were informed that deviating from the study procedures would lead to premature withdrawal. 2.3. Study Product The subjects were randomly assigned to one of two treatment arms: LPHEAL9 or placebo (1:1). The randomization list was computer-generated with a block size of four by an external statistician. The probiotic treatment arm received one capsule daily consisting of Lactiplantibacillus plantarum HEAL9 (LPHEAL9, HEAL9™, DSM 15312) at a dose of 10 10 CFU (10B CFU) per day, maize starch, maltodextrin (bulking agents), and magnesium stearate (processing and anti-caking aid). The placebo arm received one capsule per day with an identical appearance containing only maize starch and magnesium stearate. Both capsules were white vegetable capsules (hydroxypropyl methylcellulose and titanium dioxide). The study product was packed externally, and specific personnel not involved in the study were responsible for the labeling. Study products were handed out at baseline, week 4, and week 8, with a four-week supply on each occasion. The study was double- blind, and the subjects and personnel involved in the study did not know which product (LPHEAL9 or placebo) was distributed. The subjects were asked to return any unused study product at the next visit, which was used to assess compliance. The subjects were asked to refrain from using supplements and foods containing probiotics, supplements with dietary fiber or known to affect cognition (e.g., Vitamin B12, fish oil, etc.) during their participation in the study. 2.4. Assessment of Stress, Mood, Cognition, and Sleep Cohen’s Perceived Stress Scale (PSS) was used to assess the subjective feelings of stress throughout the study [11]. The PSS is composed of 10 questions on feelings and thoughts during the past month and measures the degree to which situations in one’s life are assessed as stressful. The individual scores can range from 0 to 40 with higher scores indicating a higher perceived stress. For cut-off values, levels below 13 are considered as low stress, 14–26 as moderate stress, and 27–40 as high perceived stress [12]. Cohen’s PSS was evaluated at all five visits of the study. For the assessment of mood states, the short form of the Profile of Mood State (POMS) questionnaire was used [13]. It is a psychological rating scale that assesses transient and distinct mood states, based on seven different subscales (Tension–Anxiety, Depression– Dejection, Anger–Hostility, Vigor–Activity, Fatigue–Inertia, and Confusion–Bewilderment, and Friendliness). A higher total score indicates a worse outcome for mood disturbance, whereas a lower score indicates little or no mood disturbance. Both the total score and the different subscales were evaluated at visits 2 through 5 during the study. The Pittsburg Sleep Quality Index (PSQI) questionnaire assesses sleep quality over a one month period [14]. It is composed of 10 questions, the answers to which provide both a composed score and five different sub-scores (duration of sleep, sleep disturbance, sleep latency, daytime dysfunction, and overall sleep efficiency). Subjects were considered
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