Proteins and fats and their digestion

Proteins and fats and their digestion

By
Dale Pinnock
Contains
0 recipes
Published by
Quadrille Publishing
ISBN
978 184949 541 7

OK, so it is probably less necessary to know the ins and outs of the digestion of these two macronutrients for the needs of this book, but a little overview will be useful to strengthen the understanding of some of the concepts that appear later on.

Stomach

The stomach is perfectly geared up for protein digestion. It is a highly acidic environment. The hydrochloric acid in the stomach combines with something called pepsinogen to form pepsin, which begins to break the bonds that hold the protein together. Some of the more simple proteins can begin to be broken into their individual amino acids (the building blocks that combine to make proteins) at this stage. Most, however, have to move on to the small intestine to be broken down.

Fats are only marginally affected by stomach secretions. Enzymes called lipases begin to break fats down to a degree but, in the most part, fat digestion takes place within the small intestine.

Both proteins and fats cause the stomach to work quite hard to break them down and so they can stay in the stomach for some time. Their presence slows down the movement of food from the stomach to the intestine (in comparison to more simply composed meals), which is an important point to remember. When you eat a meal that has good-quality protein and fat sources in it, their complexity means that the food will leave the stomach at a slower rate.

Small intestine

Once the food has left the stomach (which can really take some time with high-quality proteins and fibre), protein digestion is undertaken by two enzymes: trypsin and chymotrypsin. These enzymes break proteins down into their individual building blocks: amino acids. These are sent into circulation. Some will go straight to specific tissues, but most will be sent to the liver where they are strung together in sequence to make specific proteins that are needed for the body.

Fat digestion really happens predominantly in the small intestine. Bile that is secreted into the small intestine from the gall bladder breaks large globules of fat into smaller droplets that are easier for the body to deal with. The smaller they are, the more surface area they have and the more enzymes can work on them. Once these smaller droplets are formed, lipases act on them and break them down into small particles that are ready for absorption.

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