wo ist vitamin d drin — can a DNA test help?

Vitamin D is primarily synthesized in the skin upon exposure to UVB sunlight. Dietary sources are limited: fatty fish (salmon, mackerel, herring), cod liver oil, egg yolks, and fortified foods (margarine, milk). A DNA test cannot tell you where vitamin D is found – that is a nutrition question. However, genetic tests can reveal variants (e.g., in VDR or GC genes) associated with lower vitamin D levels. Evidence is moderate: GWAS show associations, but effect sizes are small and not sufficient for individual prediction. A blood test for 25-hydroxyvitamin D remains the gold standard for deficiency diagnosis. DNA tests are complementary, not diagnostic. Caution: No genetic test replaces medical evaluation if vitamin D deficiency symptoms are present.