In addition, immune-related indicators (such as immunoglobulin A, immunoglobulin G, immunoglobulin M, C-reactive protein (CRP), tumor necrosis factor α, etc.)were related to prebiotics/probiotics/synbiotics [47,48,49,50], but in patients with liver disease or rheumatoid disease or human immunodeficiency virus (HIV), adult athletes, kidney disease patients, healthy elderly individuals aged > 60 years, or obese adults (age ≥ 18 years) who had undergone bariatric surgery, correlations are no longer proven [42,44,51,52,53,54,55,56]. Here, CRP is linked to liver disorder.