In article ,
Jeff Layman wrote:

We can digest cellulose to some extent, but it does vary between
individuals. Surprisingly, the older we are the more we can digest it!
https://gut.bmj.com/content/gutjnl/25/8/805.full.pdf

It's actually more whether we can break the cell walls that matters.
For some reason, we can do that for leaf vegetables like kale but
not grass (leaves).

But isn't the cell wall made (mainly) of cellulose in green plants? I
always assumed that chewing the cud was just an additional stage in the
mechanical breakdown of cell walls, particularly for animals which
depend on the breakdown of cellulose for a good part of their
nutrition.It's an interesting point, though; would we be able to digest
more cellulose - in the absence of specific bacteria for that purpose -
if we chewed the green plants more thoroughly?

Certainly if it is raw, which is why the invention of cooking was so
important. But my point was that we don't get significant nutrition
from the cell walls, unlike cattle.


Regards,
Nick Maclaren.