wo ist selen enthalten — what are common causes?

The provided context contains no information about selenium. Therefore, the following answer is based on general medical and nutritional knowledge, not on the given sources. Selenium is an essential trace element found in: Brazil nuts (1–2 nuts meet daily requirements), tuna, sardines, eggs, meat (especially liver), whole grains, and mushrooms. The selenium content of plant foods depends on soil levels. Common causes of selenium deficiency include: inadequate intake (e.g., restrictive diets or living in low-selenium regions like parts of Europe and China), malabsorption disorders (e.g., Crohn's disease, celiac disease), dialysis, HIV infection, and certain medications. Severe deficiency can lead to cardiomyopathy (Keshan disease) and osteoarthropathy (Kashin-Beck disease). Caution: Overconsumption from Brazil nuts or supplements can cause selenosis (hair loss, nail changes, nausea). The evidence for these statements is well-established, but since the context does not provide specific studies, the evidence level is marked as 'unclear'.