In this case, the genetic element is believed to play a major role in the proper function of the 'innate' immune system in primates -- an ancient, first line of defence against bacteria, viruses and other pathogens, in which the body recognises something that probably doesn't belong there.

'Many people are familiar with the role of our adaptive immune system, which is what happens when we mount a defence against a new invader and then retain antibodies and immunity in the future,' Gombart said, according to an OSU release.

In primates, this action of 'turning on' an optimal response to microbial attack only works properly in the presence of adequate vitamin D, which is actually a type of hormone that circulates in the blood and signals to cells through a receptor.

The study was published in the BMC Genomics.