Question

Why do we r able to digest spinach even if we don't have the enzyme called present in our body?

Answer 1

Answer:

Explanation:

You can eat grass. Put it in a blender with water. Strain out the fibers and keep the liquid. Barley grass. Wheat grass. People eat these right now. You just need to separate the nutrients from the fiber. You can do the same with pine needles, and people have started doing this in some places. In the past, people boiled pine needles for tea rather than blending them. Sprouts and young growth in general is generally better than old.

For something to be edible it just needs to be non-toxic and to soften when cooked or for the nutrients to otherwise be made accessible, such as through blending or mashing. People can't digest cellulose, and tough old leaves make bad food. Ruminants like cows can digest cellulose, though, because of the archaebacteria in their stomachs.  One way to increase what you can eat is to feed it to a cow and then milk the cow. This is probably not what you're talking about, though. Digestion with microorganisms could be used to make certain foods more edible.

It'd be interesting to engineer lower-cellulose leaves for people to eat. That's probably what you were thinking about. Such leaves would be susceptible to disease and predators, since they'd rely on their toughness for protection. But maybe you could do it.

If you bred acorns to have lower tannin content, or took the time to extract the tannins, they're edible also. They were eaten in the past.

Taste is another matter entirely. Most of the food that you're used to has been bred for centuries to increase calorie content and reduce bitterness. Chimps are much less picky eaters than humans are, and can eat fruits that are far too astringent for humans.