Effect of Isoflavone and Vitamin D Supplementation on Serum Vitamin D Levels, Body Composition, Inflammatory Markers, and Quality of Life in Patients With Inflammatory Bowel Disease

Inflammatory bowel disease (IBD), including ulcerative colitis (UC) and Crohn's disease (CD), has emerged as a growing global health problem. Although historically more prevalent in Western countries, the incidence and prevalence of IBD have substantially increased throughout Asia over the past decade. The disease is characterized by chronic relapsing inflammation resulting from dysregulated interactions among genetic susceptibility, environmental factors, gut microbiota, and the immune system. Several lifestyle and dietary factors have been implicated in disease pathogenesis. High-fat and refined-carbohydrate dietary patterns may promote pro-inflammatory responses, impair intestinal barrier function, alter mucus production, and contribute to gut microbial dysbiosis. Many patients experience recurrent disease activity despite clinical remission, highlighting the need for adjunctive strategies that may support long-term disease management. Malnutrition is a common complication of IBD that encompasses a broad spectrum of nutritional disturbances. Patients may experience lean body mass loss, micronutrient deficiencies, protein depletion, altered hydration status, and reduced physical performance. Conversely, excessive adiposity and changes in fat distribution may also occur and can contribute to ongoing immune activation. Therefore, nutritional status assessment and composition measurements may provide a comprehensive evaluation than body mass index (BMI) alone. Isoflavones are naturally occurring phytoestrogens found in soy-based foods. Fermentation of soybeans into tempeh increases isoflavone bioavailability by converting glycoside forms into more biologically active aglycones while reducing antinutritional factors. Emerging evidence suggests that isoflavones may modulate inflammatory pathways and influence cytokine production, including tumor necrosis factor-alpha (TNF-α), a key mediator involved in intestinal inflammation. Vitamin D has important functions beyond skeletal health and participates in immune regulation through its effects on both innate and adaptive immune responses. Vitamin D deficiency is frequently observed in patients with inflammatory bowel disease and has been associated with poorer clinical outcomes. Previous studies have reported improvements in disease activity scores, quality of life, and vitamin D status following supplementation, although data regarding its effects on inflammatory cytokines remain limited. The balance between proinflammatory and anti-inflammatory cytokines is central to the pathogenesis of IBD. TNF-α promotes inflammatory signalling, leukocyte recruitment, epithelial injury, and immune dysregulation. In contrast, interleukin-10 (IL-10) is a major anti-inflammatory cytokine that suppresses excessive immune responses and contributes to intestinal immune homeostasis. The evaluation of both cytokines may provide insight into the immunologic effects of nutritional interventions. Quality of life is an important patient-centred outcome in IBD because the disease burden extends beyond gastrointestinal symptoms to include fatigue, emotional well-being, and social functioning. The validated Inflammatory Bowel Disease Questionnaire-9 (IBDQ 9) offers a practical assessment of health-related quality of life and has demonstrated good reliability in Indonesian patients. This study aimed to investigate the effects of an 8-week nutritional intervention consisting of tempeh powder providing approximately 50 mg of isoflavones per day combined with vitamin D3 supplementation at a dose of 4,000 IU per day in patients with IBD. The study will assess changes in serum vitamin D levels, body composition indicators, inflammatory biomarkers (TNF-α and IL-10), and quality-of-life scores using the IBDQ-9. The findings of this study are expected to contribute to the development of evidence-based nutritional strategies that complement standard medical therapy and support the overall management of patients with IBD.