The Citrus-Primate Connection

Around 5000 species of mammals inhabit the Earth today, and almost all make their own Vitamin C from simple sugar. Your dog doesn’t need orange juice to live a scurvy-free life.

Human ancestors, and most other primates, lost the genetic ability to perform this impressive biochemical feat around 61 million years ago [1]. How did they/we survive?

Short answer – don’t know (yet).  It’s accepted that these primate ancestors were insectivores. Insects, in general, do not contain high levels of Vitamin C [2]. But, insects do like hanging around flowers, fruits, and leaves. An insect could be noshing on some C-rich fruit (insects do require Vitamin C for development and reproduction) when the primate ate it. Or the primate could accidentally eat plant material while aiming for the insect.

What about other Vitamin C deficient mammals – Guinea pigs and bats? Guinea pigs… and fruit bats… certainly get plenty of Vitamin C in their diet. What about insect-eating bats? Well, maybe they aren’t as Vitamin C inept as we thought [3]. And, we deficients may be able to survive on less Vitamin C and/or recycle the little we do ingest [4].

 

1.  Lachapelle M.Y. and G. Drouin. 2011. Inactivation dates of the human and guinea pig vitamin C genes. Genetica 139:199–207. 
2. Kourimska L. and A. Adamkova. 2016. Nutritional and sensory quality of edible insects. NSF Journal. 4:22-26.
3. Cui J., Y.H. Pan, Y. Zhang, G. Jones, and S. Zhang. 2011. Progressive pseudogenization: vitamin C synthesis and its loss in bats. Mol Biol Evol. 28(2): 1025-31. 
4. Troadec, M. and J. Kaplan. 2018. Some vertebrates go with the GLO. Cell. 132(6)921-922.

Limes & Science Go Together

In 1740, an English commodore led an ill-fated squadron of ships out to sea, prepared to circumnavigate the world (and attack some Spanish holdings along the way). Of over 1800 men starting the voyage, only 500 survived. The main killer was not war or weather, but  nutrition.

Just a few years after the flotilla returned, a naval doctor conducted one of the most famous experiments in the history of science. After a few months at sea, sailors on Dr. James Lind’s ship began exhibiting signs of scurvy. The doctor treated sick sailors with random supplements to their regular diet. Some shipmen received vinegar, or sea water, or barley water. They made no improvement. Sailors who were given citrus fruits, though, made quick and full recoveries.

Unfortunately, dogma and a small sample size caused many (including Dr. Lind) to underestimate the power of citrus. It wasn’t until the mid-1790s, as scurvy-free anecdotes and experiences grew, that ships rationed out citrus juice to prevent the disease. Enjoy some lemons, limes, or oranges in celebration of science!