Tuesday 27 September 2016

How many hours would you have to walk to work off your Christmas dinner?

Emma Harper

Published 14/12/2015 | 16:29

Roast turkey on serving dish
Roast turkey on serving dish

For most, the Christmas dinner will feature the traditional roast turkey, ham, the occasional Brussels sprout and a mince pie or two for dessert — but after we have finished dining and have settled on the sofa ready to watch the telly, our digestive system has to get to work processing this delicious meal.

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In general, food contains five basic categories of nutrients: protein, fat, carbohydrates, vitamins and minerals.

For the body, the latter two, vitamins and minerals, are relatively straightforward; they are only present in tiny amounts, and are easily absorbed. The first three however, make up the vast majority of our diets, and therefore require the most attention from our bodies — especially if we over-indulge at Christmas!

Our main source of protein on Christmas day is the turkey and ham. All proteins are composed of a basic unit called an amino acid, and long chains of amino acids — called polypeptides — fold into a unique 3D structure. Then, enzymes in the digestive tract work together to break these structures down into shorter chains until they are small enough to be absorbed.

Although it can yield energy, protein has a much greater function — single amino acids can be rearranged into new proteins that then perform essential bodily functions, such as growth and repair.

The body’s favourite energy source is carbohydrates, which are plentiful in potatoes, stuffing and mince pies. Carbohydrates are made up of units called saccharides. Saccharides by themselves are called sugars, but they can also join together — for example, potatoes are made up of long chains called starch.

To release energy from starch, our body’s digestive enzymes needs to convert these chains back into single sugars so that they can be absorbed into the bloodstream. As sugar levels in our blood rise, a hormone called insulin is released. Insulin tells our body cells to absorb sugar, providing us with energy.

The third and final macronutrient, fats, can be found in most elements of your Christmas dinner, especially in sweet treats.

Fats are broken down into units called glycerol and fatty acids, and provide approximately twice as much energy as carbohydrates — despite this, they are more likely to be stored by the body, hence their bad reputation.

Our bodies do require a certain amount of fat from our diets, however, so don’t be afraid to spoil yourself over the Christmas holidays!

All of the energy we gain from our Christmas dinner — whether it be from protein, carbohydrates or fats — is measured in calories.

The average Christmas feast contains about 3,000 calories (including dessert!), and it would take us almost 12 hours to walk off this energy — add a little longer if you enjoy a second mince pie!

As food breakdown is a complex task involving multiple processes, spare a thought for how hard your body is working to provide energy on Christmas Day.

✱Emma Harper is an Irish Research Council scholar at Dublin City University researching type-2 diabetes and cardiovascular disease

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