The idea of food processing these days conjures up images of excess sugar and unhealthy fats, but humans and our ancestors have been processing food for millions of years.
In fact, as DNews' Jennifer Viegas reports today, food processing plays an important role in our evolution, according to new research from Harvard University published in the journal Nature.
Between 2 million and 3 million years ago, human ancestors worked with stone tools to process their meals, pounding or slicing their food to break it down before chewing. Around this time, early humans began adding meat to their diets, a high-calorie food difficult to chew effectively when it's raw or in big chunks. Processing food -- even just cutting it into smaller pieces -- outsources some of the work of digestion so more energy can be extracted from meals.
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Thanks to cooking and other means of food preparation, it's easy to take for granted just how much time and energy food processing saves us.
Consider the efforts other mammals go through simply to chew their food. Our closest relatives, chimpanzees, spend much of their day chomping away at their food, and with much greater bite force at that. Most mammals eat a lower-quality diet and take their time with their meals. Other animals, like reptiles, put even more work into each meal because they swallow their food whole.
Testing how much of a difference in effort was required with chewing raw vs. primitively processed food proved a decidedly unappetizing challenge for the study's participants. Volunteers sampled a small buffet of foods inspired by Paleolithic Era cuisine, which included raw, sliced, pounded and cooked goat as well as a selection of vegetables. Goat was chosen by the researchers because of its similar texture to game. With special devices meant to measure the effort involved, the volunteers chewed until they would normally swallow and then spat each morsel out.
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According to the researchers' data, the muscular effort and number of chews required by processed food was almost 20 percent less than its raw counterparts over the course of an entire day.
Time and energy expenditure aside, cooking or otherwise processing food comes with other benefits as well. Processed food can be consumed in smaller, more digestible pieces, providing an extra nutrition boost thanks to a higher surface area to volume ratio.
Over time, food processing began to have an impact on human physiology. "Eating meat and using stone tools to process food apparently made possible key reductions in the jaws, teeth and chewing muscles that occurred during human evolution," study author Katie Zink said in a statement.
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When metabolically expensive organs don't require as much energy to do their jobs, they shrink in size. Smaller guts, for example, are only compatible with diets rich in high-quality, easy-to-digest food. This extra resource bandwidth can then be taken up by other organs, specifically the brain. This trade-off is known as the "expensive-tissue hypothesis," first proposed in 1995.
Food processing allowed for larger brains and the ability to communicate through speech, according to paleoanthropologist Daniel Lieberman, who worked on the Harvard study. "We are partly who we are because we chew less."