what makes a leaf of lettuce more digestible than other leaves?


It’s clear that our stomachs can’t break down most greenery around us, like ruminants with 4 stomachs can. But what makes one leaf digestible to us and another not?

In: 27

Cellulose. Humans lack the enzyme cellulase thus leaving us unable to digest plants that are high in cellulose. However, a plant like lettuce has a relatively low amount of cellulose compared to other natural greens and leaves, and contains a higher amount of digestible material and our body just filters the cellulose through the stomach undigested which it is able to do since the amount is low.

Lettuce is a domesticated plant, genetically manipulated over centuries of selective breeding to produce leaves with a lot of water and not a lot of cellulose or wax.

Lettuce is 95% water by weight, higher than many fruits.

Most plants don’t shamelessly waste their moisture on leaves like this. Tree leaves are much lower in the 40-50% range, with the rest being indigestible cellulose fibers and protective waxes to retain moisture.

Lettuce is mostly water and fiber, we we cant realy digest it. We can not pull energy out of lettuce, that what makes people claim its healthy. There is not much protein, carbs or sugar that we can use in there so its low in calories.

Two things:

1. Cellulose. As other have mentioned this is the primary reason. No vertebrate can digest cellulose. Too much cellulose can cause bloating, indigestion, diarrhea, gas, etc. Its not good for us. Some vertebrate animals have formed symbiotic relationships to allow them to handle more, such as cows who have one stomach filled with bacteria that helps break it down. But didn’t go down that path.
2. Chemistry. Different leaves contain different chemicals that may serve a useful purpose to the plant, but are not so useful, and sometimes down right dangerous to us.

Plants like lettuce have been cultivated over centuries or millennial to produce more human friendly versions. Variants that have too much cellulose or dangerous chemicals were selected out in favor of more friendly versions over time. Wild cousins may still exist which we wouldn’t want to eat, but what you get in the market has been tamed by human agriculture over time.