New research from Harvard University, in the U.S., has shown that cooked meat provides more energy than raw meat. The researchers claim their findings suggest cooking played a pivotal role in human evolution by increasing the energy content of some foods.

Conducted by Rachel Carmody, a student in Department of Human Evolutionary Biology at Harvard’s Graduate School of Arts and Sciences and published today in the Proceedings of the National Academy of Sciences (PNAS), the research also raises questions about the way modern humans eat.

Ms Carmody said that although earlier studies have examined aspects of what happens during the cooking process, surprisingly, none have ever fully examined whether cooking affected the energy value of food.

In her study, which took place over forty days, Ms Carmody fed two groups of mice a series of diets that consisted of either meat or sweet potatoes prepared in four ways: raw and whole, raw and pounded, cooked and whole, and cooked and pounded.

Over the course of each diet, researchers tracked changes in each mouse’s body mass, as well as how much they used an exercise wheel. The results, Carmody said, clearly showed that cooked meat delivered more energy to the mice than raw.

Study’s findings may shed light on human evolution

“Though early humans were eating meat as early as 2.5 million years ago, without the ability to control fire, any meat in their diet was raw, and probably pounded using primitive stone tools. Approximately 1.9 million years ago, however, a sudden change occurred,” Ms Carmody said. “The bodies of early humans grew larger. Their brains increased in size and complexity and adaptations for long-distance running appeared.”

Though earlier theories suggested the changes were the product of increased meat in their diet, Carmody’s research points to another possible hypothesis – that cooking provided early humans with more energy, allowing for such energetically-costly evolutionary changes.

Findings may help make food labels more accurate

Ms Carmody said her findings also lay bare the shortcomings in the Atwater system, a calorie-measurement tool commonly used to produce modern food labels.

“Atwater doesn’t discriminate between food that is digested by the human or the bacteria, and increasing evidence suggests that the bacteria take a pretty good portion of the food we eat,” she said. “In fact, research has shown that one of the ways to increase the value humans get, relative to the bacteria, is by processing food, and cooking is one way to do that.”

Implications for obesity prevention

Ms Carmody said her research could also inform how food scientists tackle one of the thorniest of dietary challenges – the prevalence of obesity in Western nations, and malnutrition in developing parts of the world.

She said, “This research illuminates that the way we’ve been thinking about food energy value historically have been based on the treatment of the human body as an efficient digestion machine, when, in fact, it’s not, and the degree to which it’s not is affected by food processing, including cooking.”

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