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Vitamin C Loss

February 25, 2008

A listener asks: If vitamin C is essential to our survival, why can’t our bodies produce it?


Behind a vitamin deficiency. I’m Bob Hirshon and this is Science Update.

Listener Neill Curtis of Baltimore, Maryland wrote to ask why humans don’t produce our own vitamin C, if the nutrient is essential to our survival. We turned to evolutionary biologist Herb Schellhorn of McMaster University in Canada. He says most mammals can produce vitamin C themselves. But humans and other primates have a mutation in the gene that codes for the enzyme gulonolactone oxidase, which is essential to the last step of vitamin C biosynthesis.

HERB SCHELLHORN (McMaster University):
Our ancestor and the ancestor of all primates lost this function we think about 40 million years ago.

No one knows why they lost this ability. Perhaps our ancestors didn’t need it, because fruit was so abundant. There’s also a theory that not having the enzyme actually helps primates resist malaria. If you have a science question, call us at 1-800-why-isit. I’m Bob Hirshon for AAAS, the science society.