Inclusion Criteria:

• Adults, male or female, aged 20 to 70 years
• Body mass index of 25 kg/m2 or more and less than 30 kg/m2
• Meeting the Rome IV criteria for diarrhea-predominant irritable bowel syndrome (IBS-D), defined as Bristol Stool Form Scale type 6 or 7 in 25% or more of bowel movements from 2 weeks before screening through the day of the screening visit
• No inflammatory bowel disease or malignancy
• Provided written agreement to refrain from consuming kimchi-containing foods for the duration of the study (approximately 2 months)

Exclusion Criteria:

• Drug-induced constipation
• Constipation secondary to another condition, such as diabetes mellitus or thyroid disease
• History of intra-abdominal surgery other than appendectomy (including gastrectomy, gastric bypass, gallbladder or biliary tract surgery, pancreatectomy, bowel resection with particular reference to the ileum, and colorectal surgery or insertion procedures)
• Uncontrolled hypertension (resting blood pressure 160/100 mmHg or higher)
• Uncontrolled diabetes mellitus (fasting blood glucose 160 mg/dL or higher)
• Uncontrolled hypothyroidism or hyperthyroidism
• AST or ALT concentration 3 times or more the upper limit of the reference range of the testing laboratory
• Creatinine concentration 2 times or more the upper limit of the reference range of the testing laboratory
• Severe cardiovascular or cerebrovascular disease or malignancy within the previous 6 months
• Psychiatric disorder such as severe affective disorder, schizophrenia, or substance use disorder, or current use of related psychiatric medication (intermittent use for sleep disturbance is permitted)
• Severe alcohol use disorder
• Heavy smoking (20 cigarettes per day or more)
• Hypersensitivity to the main ingredient or components of the study food
• Severe gastrointestinal symptoms such as heartburn or dyspepsia
• Use of medications or foods that may affect the study results, including kimchi and probiotics
• For female volunteers, suspected pregnancy, lactation, or plan to become pregnant during the study period
• Participation in another drug clinical trial within one month prior to the screening date, or planned participation
• Judged unsuitable for participation by the principal investigator for reasons other than those listed above