Fiber offers a piddling two calories because enzymes in the human digestive tract have great difficulty chopping it up into smaller molecules.Įvery calorie count on every food label you have ever seen is based on these estimates or on modest derivations thereof. Fats provide approximately nine calories per gram, whereas carbohydrates and proteins deliver just four. We calculate the available energy in all foods with a unit known as the food calorie, or kilocalorie-the amount of energy required to heat one kilogram of water by one degree Celsius. Our cells use the energy stored in the chemical bonds of these simpler molecules to carry on business as usual. Digestive enzymes in the mouth, stomach and intestines break up complex food molecules into simpler structures, such as sugars and amino acids that travel through the bloodstream to all our tissues. Although it did not occur to me at the time, I later realized that humans, too, engage in a kind of tug-of-war with the food we eat, a battle in which we are measuring the spoils-calories-all wrong.įood is energy for the body. Whereas the birds want to get as many calories from fruits as possible-including from the seeds-the plants are invested in protecting their progeny. Eventually, little jungles grew.Ĭlearly, the plants that emus eat have evolved seeds that can survive digestion relatively unscathed.
My colleagues and I planted thousands of collected seeds and waited.
I was trying to figure out how often seeds pass all the way through the emu digestive system intact enough to germinate. At one particularly strange moment in my career, I found myself picking through giant conical piles of dung produced by emus-those goofy Australian kin to the ostrich.
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