What do studies say about Vitamin D Genetik?

The provided context does not contain direct studies on vitamin D genetics. One entry mentions the rs4253778 SNP in the PPARA gene, for which no link to vitamin D is established. Overall, evidence for genetic testing regarding vitamin D is weak: variants in VDR, GC, CYP2R1, and DHCR7 have been associated with vitamin D levels in GWAS, but effect sizes are small and explain only a fraction of individual variation. Clinical utility for guiding supplementation remains unclear. Commercial tests like MyBody-X may analyze such SNPs, but results should not be used alone to determine dosing. Vitamin D status is best assessed via blood measurement of 25-hydroxyvitamin D. Based on the provided context, evidence is insufficient, hence rated 'unclear'. Caveat: marketing often overstates the role of single genes.