Why Can't We Live on Grass?
The other day I watched some cows contentedly chewing grass. They looked well nourished and healthy. Since humans can thrive on a totally vegetarian diet, I thought wouldn’t it be useful if we could also get some of our energy from digesting grass.
Grass, leaves, and other plant materials provide plenty of metabolic energy for cows, goats, sheep and other ruminants. However, this kind of plant material is indigestible for humans. It turns out we just don’t have the required digestive enzyme needed to break the grasses down.
The chemistry of life depends completely on enzymes which speed up and promote the chemical processes of life. Our enzymes make us omnivorous, capable of eating and digesting grains, meat, and vegetables. All the food we eat goes into the processing mill to translate it into the energy we require for movement and growth.
Our enzyme system converts virtually all the starches, sugars, fats and proteins we eat into useful energy, no matter what the original composition. But in order to digest the cellulose that forms a large part of the fibre in our diets, we need a specific enzyme called cellobiase which we don’t have. It’s produced, however, in the digestive system of animals like cows, which harbour the micro-organisms that are able to make it. Although we can’t digest cellulose, we still need to include foods rich in fibre because it seems to reduce the risk of some cancers.
So next time you enjoy a picnic, go easy on the wood chips and grass!
It’s probably a relief to hear that we couldn’t live on grass or trees. We don’t find it at all unpleasant or inconvenient that we aren’t designed to produce the cellobiase enzyme. We choose our diets instead on the basis of what can provide nourishment for us.
There are some diseases however which are marked by an inability to produce or distribute the necessary enzymes. Phenylketonuria (PKU) sufferers lack an enzyme to metabolize protein. People with Cystic Fibrosis (CF) can produce digestive enzymes but these can’t make their way into the intestine to function. Perhaps the more common disorder is milk intolerance wherein the enzyme lactase is lacking or in short supply. In these cases compensatory mechanisms are required - either you avoid the food or you take supplementary enzymes.
Often in the circles of family and friends we compensate for one another’s shortcomings. We see this among school friends as one serves as math coach while the other reciprocates in the social sciences. We observe this in the workplace in the sharing of computer knowledge and skills. It happens in the family too. Consider your own situation. Are you particularly strong in one area where a family member is weak (or vice versa)?
Today, consider using your strength in a random act of kindness for someone.
Consider the words of Solomon, ancient king of Israel, on the value of friends.
“Two are better than one because they have a good reward for their labor. For if they fall, one will lift up his companion. But woe to him who is alone when he falls, for he has no one to help him up. Again, if two lie down together, they will keep warm; but how can one be warm alone? Though one may be overpowered by another, two can withstand him. And a threefold cord is not quickly broken.”
While ancient literature like the Bible honours the ideas of friends, there is also the concept that God Himself can have friendship with His creation. When we open ourselves to the spiritual dimension, we can discover the One who tells us that “there is a friend who sticks closer than a brother.”
David Humphreys and Debbie Hughes
© August 2004
