welche nährstoffe fehlen bei haarausfall — can a microbiome test help?

The question about nutrient deficiencies in hair loss is relevant, but the provided context contains no specific studies or recommendations on this topic. Commonly, iron, zinc, vitamin D, vitamin B12, and biotin are linked to hair loss. A microbiome test (e.g., gut or scalp microbiome) is currently not supported by strong evidence as a diagnostic tool for hair loss. The given contexts discuss other genetic variants (MTHFR, CYP2C19, SOD2, ESR1, FTO) and their metabolic implications, but not hair loss or microbiome. Therefore, based on the provided material, there is no evidence that a microbiome test can help identify nutrient deficiencies causing hair loss. For diffuse hair loss, a physician should first check standard blood markers (ferritin, vitamin D, TSH, zinc). Microbiome testing remains experimental in this context.