Vitamin D in Nature: A Product of Synthesis and/or Degradation of Cell Membrane Components.
Level 5 - mechanism / opinion, no new human data
Narrative review of non-human biochemistry and mechanism-based literature
PubMed 30482146 · doi:10.1134/S0006297918110056
What was done
Narrative literature review surveying published evidence on the synthesis, accumulation, and degradation pathways of vitamin D precursors (7-dehydrocholesterol [7-DHC] and ergosterol) into vitamin D3 and D2 across land animals, plants, fungi, algae, lichens, and aquatic organisms.
What was found
The abstract reports no pooled quantitative figures or statistical metrics. It describes comparative biosynthetic pathways: - Land animals: 7-DHC via lanosterol (vitamin D3) - Plants: 7-DHC via cycloartenol (vitamin D3) - Fungi: ergosterol via lanosterol (vitamin D2) - Algae: 7-DHC or ergosterol (vitamin D3 or D2) In many non-animal organisms (e.g., algae, fungi, lichens), vitamin D forms spontaneously via UV irradiation of membrane sterols and accumulates as an unmetabolized degradation product due to an absence of clearance enzymes. Zooplankton and fish obtain vitamin D from dietary sources and store it without evident metabolic utilization. Notable exceptions include rainbow trout and at least four plant species that synthesize active calcitriol in quantities high enough to induce enzootic calcinosis in grazing animals. Atypical conversions in the dark, under blue light, or at low temperatures (<16°C in the lichen Cladonia rangiferina) were also noted.
Why it matters
Demonstrates that vitamin D across phylogenetic kingdoms often functions as an incidental membrane sterol degradation byproduct rather than an active endocrine regulator.
Limits
Narrative design without systematic search criteria, quality appraisal, or quantitative meta-analysis. The abstract reports no sample sizes or effect magnitudes, and all findings describe comparative bench/ecological biochemistry rather than human clinical outcomes.
Cited by
- supports Lichen species synthesize vitamin D3 and can be utilized as a vegan source of vitamin D3.