Is IgG useful for sleep?

Is IgG useful for sleep? From a scientific standpoint, the answer is no. IgG (immunoglobulin G) is an antibody involved in delayed immune responses and pathogen defense. There is no robust evidence that IgG levels or IgG tests directly help diagnose or improve sleep. Some companies market food-specific IgG tests claiming benefits for sleep via gut health, but the evidence is weak and largely based on marketing rather than science. Sleep quality is regulated by circadian rhythms, stress hormones (e.g., cortisol), melatonin, and lifestyle factors—none of which are captured by IgG testing. If you have sleep issues, consult a physician for validated assessments like sleep diaries, actigraphy, or polysomnography. The evidence level for IgG and sleep is best described as 'unclear' or 'marketing'.