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Cooking increases the bioavailable calories of food

26 February 2015

Emily Groopman and colleagues at Harvard University devised an experiment to investigate the effect of heating on foods containing a high proportion of fat, after she found only studies investigating heating foods rich in either starch or protein. The research into cooking carbohydrate or protein dense foods showed that the heating process does increase the calories available from the food, and so Groopman aimed to investigate whether this was the same across all three macronutrients.

Peanuts were chosen as the fatty source, as they are on average 50% fat, and mice were the experimental subject. Four different diets were prepared – raw and whole peanuts, raw and blended peanuts, roasted and whole peanuts, and roasted and blended peanuts. 20 mice were fed each of the diets and by considering the consumption and exercise of the mice, Groopman was able to conclude that the cooked peanuts had more bioavailable energy.

It was found that the mice consumed less of the cooked peanuts, however their body mass increased at a similar percent of the mice consuming (more of the) raw peanut. Groopman hypothesized that the structures surrounding the oil bodies in peanuts are broken down when heated, making the fats inside more easily digestible. This was supported by microstructural studies of the peanut cell walls.

The study supports existing research that the cooking process increases the energy one can obtain from food, more so in light of the fact that the fat food group has an average of 9kcals per gram compared to 4kcals per gram on average from carbohydrate or protein. Such findings can have implications for forming high energy diets and also provides an interesting perception to explain the evolutionary concept behind human programming to crave fatty foods, and the human practice of cooking.

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