Display Settings:


Send to:

Choose Destination
See comment in PubMed Commons below
FASEB J. 2012 Mar;26(3):971-5. doi: 10.1096/fj.11-195859. Epub 2011 Dec 9.

Immediate pigment darkening: its evolutionary roles may include protection against folate photosensitization.

Author information

  • 1Department of Radiation Biology, Institute for Cancer Research, Norwegian Radium Hospital, Oslo University Hospital, Montebello 0310 Oslo, Norway.


The evolution of dark human skin colors in tropical areas is possibly related to photoprotection of folates. However, natural folates absorb mainly UVB radiation, and too little UVB can penetrate down to folates in dermal vessels to cause serious damage. However, endogenous photosensitizers, like riboflavin and uroporphyrin, absorbing UVA and visible light, can cause photosensitization of folates. Immediate pigment darkening (IPD), generated by UVA, has an absorption spectrum covering those of the endogenous photosensitizers. IPD is most prominent for darker skin types, which were typical for populations living under tropical solar fluences. We here propose that the biological role of IPD is protection of folates against photodegradation, which would be of large evolutionary importance for early hominids.

[PubMed - indexed for MEDLINE]
Free full text
PubMed Commons home

PubMed Commons

How to join PubMed Commons

    Supplemental Content

    Icon for HighWire
    Loading ...
    Write to the Help Desk