Lemonade from Lemons, or, the Evolution of Our Diet

[Photo credit: Francesca Hotchen]

[Photo credit: Francesca Hotchen]

We've been dog-sitting this week, and it's hard not to feel sorry for the little critters and their boring culinary life. A quarter-cup of kibbles, mixed with a tablespoon of icky wet food, twice a day. Day in and day out. Every day of the year. Every year of their lives. Whew.

But it does make you wonder how that little bit of food suffices to meet all their nutritional needs and even makes them prone to gain too much weight. Dogs don't even need vegetables! All those ones pictured on the dog-food packages are for the owners' benefit, not the dogs'.

So why is that animals can supply all their nutritional needs so simply, while humans have a list as long as their arms of requirements? Fruits, vegetables, fiber, "essential" vitamins and minerals and fatty acids and amino acids. How do cows thrive on--basically--tufts of grass? And cats and dogs do just dandy on meat, thank you very much. Are human beings the only animals on the planet requiring such a princess diet?

I've come upon the answer in my recent reading.


This fast and fascinating book talks about the flip side of being the most amazing creatures the planet has yet produced, or, at least, the smartest. It turns out that there are plenty of not-so-amazing flaws we've developed along the way that are more or less survivable because we humans band together and apply cooperation and brainpower to our challenges.

Take, for example, our lameness with dietary requirements. Just about every danged animal on earth can produce its own vitamin C, for starters. In house! In their livers! Open mouth, insert food, generate vitamin C, whether the food contained any or not. But somewhere along the thousands and millions of years, some yahoo human underwent a mutation in gene GULO, which disabled the in-house vitamin C factory. But the human diet was already so varied, because we worked together and wandered about, gathering all kinds of food, that the food supply met the vitamin C needs, and the yahoo didn't even notice his defect. He didn't get scurvy and die before he could reproduce, so his dysfunctional gene wasn't skimmed from the gene pool. Instead the dope got married and had ten kids, and on it went. Now it's just humans, guinea pigs, and fruit bats who have to go outside for vitamin C.

Multiply that process times all the other essential micronutrients other animals can produce and which we can't. All the B vitamins. A. E. Nine amino acids. Linoleic and alpha-linolenic acids. Therefore, we discovered when it was far too late, if our diet didn't provide these items, we got sick. We developed scurvy or beriberi or protein deficiency or breakdowns in healthy cell membranes. Yikes. All without our knowing, we outsourced a few key processes in the factory and ran into trouble whenever the outside suppliers went out of business.

That's the bad news. Over the eons, humans become the lemons of the dietary-self-sufficiency world. The cow snickers into her tuft of grass. The dog smiles over his dry kibbles.

But the upside, of course, is that, since we're such princesses now and require our diets to provide so many things we can't provide ourselves, we get to enjoy a varied diet. As Lents puts it, 

While we eat plants and other animals mainly for their energy, consuming them also brings us all the proteins, fats, sugars, and even vitamins and minerals that those living things have in their bodies. We're not getting just energy when we eat, in other words; we're also getting various organic building blocks.

So there, cow and dog!

Even for vegans, who abjure the nutritional shortcuts that eating animals provides, "variety is the easiest way for vegetarians and vegans to ensure that they get enough of all the amino acids they need."

So pamper your princess side. Vary the foods you eat and make lemonade from the lemons our biology has handed us.