>Rats are opportunistic omnivores, just like us. So metabolism is very
>similar.

'Fraid not, old boy. The reason rats are so widely used in experiments
is that they are *cheap* to breed and dispose of. Also they have been
bred to a bland, pink-eyed uniformity, useful in eliminating genetic
variations that cause bothersome kinks in researchers' pretty curves.

But mostly R. rattus synthesizes the ascorbate ion ("vitamin C"), either
in its liver or adrenals (not sure which). This is THE major difference
in biochemistry between rats and humans and it's very significant.
Humans seldom get enough ascorbate in their diet; rats don't have to.

In transitioning from Paleo to Neolithic, grains etc displaced
major sources of dietary ascorbate. So up went disease rates etc.,
especially frank and chronic subclinical scurvy. Rats don't
get scurvy, nor do cats, dogs etc. that so many people try to
draw parallels with to support their opinion.