Evidence check: Zink in the context of Schlaf

The provided context does not contain specific information on zinc and sleep. In general, zinc is an essential trace element involved in melatonin synthesis and neurotransmitter regulation, both of which can influence sleep. Some observational studies suggest a link between low zinc status and sleep disturbances, but robust randomized controlled trials supporting zinc supplementation for sleep improvement in healthy individuals with normal levels are lacking. Consumer DNA tests that claim to predict zinc needs often rely on single SNPs (e.g., in SLC30A8) with weak evidence; clinical relevance is unclear. High-dose zinc (e.g., >40 mg/day long-term) can cause copper deficiency and neurological issues. Therefore, without a confirmed deficiency, zinc supplementation for sleep is not evidence-based. Given the absence of relevant context, the evidence level is marked as 'unclear'.