Which lifestyle factors change Vitamin D 25-OH?

The 25-hydroxyvitamin D (25-OH D) level is primarily influenced by sunlight exposure (UV-B radiation), which varies by skin pigmentation, latitude, season, and sunscreen use. Dietary intake from fatty fish, cod liver oil, fortified foods, and UV-exposed mushrooms contributes modestly. Supplementation is the most reliable way to raise levels, especially in deficiency. Body weight matters: obesity reduces bioavailability due to sequestration in adipose tissue. Physical activity outdoors may increase synthesis indirectly. Smoking and heavy alcohol use are associated with lower levels, likely due to altered metabolism. The evidence is strong (RCTs, meta-analyses), but individual factors like genetics (e.g., VDR, GC), liver/kidney function, and medications (e.g., anticonvulsants) also affect levels. A blood test is necessary for accurate assessment.