Infrared vision with vitamins

Posted August 25, 2005

Although I've mostly been interested in sensory augmentation by means of technology, there was an interesting third-hand report of augmentation through diet and biochemistry. The military during WWII (there are mentions of both US and British forces) evidently experimented with putting people on diets that replaced the normal form of vitamin A with a slightly different chemical, in the hopes that the red-sensitive photopigment in the retina constructed from it would be changed to a chemically similar form, present in other animals, with spectral sensitivity extending into the near infrared. The idea, of course, was to be able to see signal lights and so forth that were invisible to enemy soldiers.

I did some quick checking on this, and though I couldn't find any references to military research, there were some examples in the regular civilian literature. Yoshikami, Pearlman, and Crescitelli (Vision Research 9:633-646 1969) did a similar experiment on rats, putting them on a diet which was deficient in vitamin A and supplementing it with additions of either vitamin A1 (the normal form) or A2 (the altered one). No behavioral studies were done, but they did extract the retinas and perform some spectral analysis, with the result that there was indeed some alteration of the photopigments, specifically the addition of a second form with sensitivity shifted redward by about 20nm.

That study cited Millard and McCann (Journal of Applied Physiology 1:807-810 1949) which was an experiment on humans, albeit with fairly loose controls on diet. They found that behaviorally the group taking A2 supplements had slightly improved red sensitivity, but didn't provide any detailed spectral response curves.

So it seems to be the case that this effect is real, but small: the best you can hope for is a shift of about 20nm, which is not really enough to be of military significance or even detectable without careful testing. Still, it's an interesting "hack" on human biochemistry.