Lipid of the Month

Each month we highlight a lipid of scientific interest. The LIPID MAPS® Lipid of the Month Archive lists lipids highlighted from 2015 - present.

December 2023

Lipid of the month Lycopene

It’s the time of year when theories regarding the famously red nose of Santa’s lead reindeer, Rudolf, come to the fore. Some suggest a dense network of blood vessels1, but a more lipid-centric cause seems to have been overlooked.

The carotenoid lycopene is a deep red colour and found in many vegetables, including carrots which children in some countries traditionally leave for Rudolf on Christmas eve.

Lycopene is a 40 carbon tetraterpenoid made up of eight isoprene units with 11 conjugated double bonds that absorb light to give the molecule its colour. In plants it is an accessory pigment to chlorophyll in photosynthesis, and in fruits such as tomatoes it signals the fruit’s ripeness to animals which eat the fruit and disperse the seeds. Lycopene is a precursor to other carotenoids such as carotene, for which carrots are more well known. Carotene is metabolised to make the visual pigment retinal, but the saying that eating carrots will help one see in the dark has little evidence to support it. Night-vision would undoubtedly be important for a nocturnally aviating cervid however.

Perhaps the many children leaving carrots for Rudolf don’t realise that carrots aren’t part of the natural diet of the reindeer. The carrot, Daucus carota, was domesticated in Asia2, but Rangifer tarandus the reindeer, is only partially domesticated3 and native to the Arctic region. The species may be unable to handle such an annual abundance of lycopene and one must consider that Rudolf may have a genetic condition whereupon the excess accumulates in his muzzle. Presumably this does not cause any health issues as he and his companions are over 80 years old and remain able to tour the globe in one evening. Indeed a navigational nose has clearly been advantageous to this particular individual!


  • Why Rudolph's nose is red: observational study
    DOI 10.1136/bmj.e8311
  • Population genomics identifies genetic signatures of carrot domestication and improvement and uncovers the origin of high-carotenoid orange carrots
    Nat Plants
    DOI 10.1038/s41477-023-01526-6
  • Investigating the domestication and early management of reindeer (Rangifer tarandus) in the Sámi archaeological context from teeth geometric morphometrics Sci Rep 2023 10.1038/s41598-023-33422-6.
    Sci Rep
    DOI 10.1038/s41598-023-33422-6

Lipid of the Month Archive