Causes cluster into four groups: (1) inadequate intake (low variety, highly processed diet, low legumes/vegetables/protein); (2) malabsorption (celiac disease, IBD, chronic gastritis, post-bariatric surgery); (3) increased needs (pregnancy, lactation, growth, intense training, infection); and (4) increased losses or medication effects (prolonged diarrhea, heavy sweating, blood loss, diuretics, long-term acid suppressants). Alcohol use, poor sleep, and chronic stress can also indirectly worsen diet quality. Taking a multivitamin does not guarantee adequacy—dose, absorption, and nutrient interactions matter. The best path is diet history + risk assessment + targeted labs with a personalized plan.\n\nSource note: NIH ODS mineral fact sheets (risk groups and interactions).