Who, what, where and when-influences on cutaneous vitamin D synthesis.
Level 5 - mechanism / opinion, no new human data
Narrative review of physical and biological mechanisms without original human data or systematic review methodology.
PubMed 16766240 · doi:10.1016/j.pbiomolbio.2006.02.004
What was done
This review evaluated the environmental, physical, and personal factors that influence the two-stage synthesis of previtamin D in human skin following ultraviolet (UV) irradiation of 7-dehydrocholesterol.
What was found
The abstract reports no numerical values or quantitative thresholds. It identifies astronomical factors governing the solar zenith angle (SZA), local atmospheric state, skin pigmentation, age, and individual behavioral exposure as primary drivers. SZA is the only unequivocally determinable factor; at large SZAs, available solar UV radiation is insufficient for significant synthesis, while at smaller SZAs, exposure requirements can only be estimated using idealized models.
Why it matters
It highlights that standardizing sun exposure advice for vitamin D is challenging because most influencing factors beyond solar angle are variable and individual-dependent.
Limits
The abstract contains no empirical patient data, clinical trial outcomes, or exact quantitative values, relying entirely on mechanistic and theoretical reasoning.
Cited by
- contradicts Light entering the eyes stimulates the body to produce vitamin D after about 15 minutes.