Shared genetic basis and causal relationship between nutrition, nutritional status and inflammatory bowel disease

• Vitamin D and appendicular lean mass show negative genetic correlations with inflammatory bowel disease and its subtypes. • Mendelian randomization reveals a positive causal effect of serum magnesium on inflammatory bowel disease and small intestine Crohn’s disease. • Cross-phenotype analysis identifies shared genetic loci, particularly in the HLA region, influencing both nutritional status and inflammatory bowel disease. • Targeted nutritional management may be crucial for slowing inflammatory bowel disease progression.