How does the food we eat travel through the body?

The road a mouthful takes can be described in one sentence: once digested, foods are broken down into their smallest building blocks, absorbed from the small intestine and carried by the blood to tissues and organs, and turned into energy in the cells together with oxygen. All of these events together are called metabolism.

Below we take the links of that road in order: where carbohydrate, fat and protein break down to, where fiber stands along the road, what the speed varies with, and where this account gets used wrongly.

The general line of the road

The guideline defines three words separately. The breaking down of foods or tissues into their smallest components is called catabolism, the joining of those smallest components into new structures anabolism, and the sum of the two metabolism.

The components that break down come together again to build new structures; the repair of tissues, growth and the maintenance of health are provided this way. So the road is not a one-way consumption but continuous dismantling and building.

The work that starts in the mouth

The road starts not on the plate but in the mouth. The one recommendation the guideline gives for this stage is behavioral: food should be chewed well and eaten slowly.

What chewing amounts to along the road is that it makes the later links easier. In the section on older age the same recommendation is repeated to make digestion easier: eating small amounts frequently and chewing food well.

The source gives no duration or number of chews for this stage; the measure it gives is the pace itself.

Where carbohydrate breaks down

Complex carbohydrates are broken down during digestion into simple sugars such as glucose. As glucose passes into the blood, insulin is released from the pancreas, and the glucose that enters the cells with the help of insulin is used there to provide energy.

The normal glucose value in the blood is given as 70-100 mg/100 mL, and it is also written that this value changes according to whether you are hungry or full. So this link of the road is in motion throughout the day; it is not interpreted by looking at a single moment.

The surplus does not go to waste: carbohydrates are stored as glycogen in the liver and muscles, and once stored, what is left is converted into fat and kept.

The road of fat

Fats are made up of fatty acids and provide the highest energy among the macronutrients; 1 gram gives 9 kcal. For carbohydrate and protein, 1 gram gives 4 kcal.

The distinguishing feature of fat along the road is its speed: fat leaves the stomach slowly and gives a feeling of fullness. Fat-soluble vitamins and certain chemical structures important for the body are also taken in and carried along with fat.

The road of protein

Proteins are made up of amino acids, and digestion breaks them down into those building blocks. The job of these components is not only to give energy; the repair of tissues and the building of new structures draw on the same pool. So protein is not thought of only as an item of energy.

That is why the guideline recommends spreading protein across the day rather than piling it into one meal. The sentence it writes for older age is clear: taking in sufficient protein at every meal is important in preventing loss of muscle mass.

Where fiber stands along the road

Dietary fiber is in the class of carbohydrates but does not turn into energy like other carbohydrates; it passes through the digestive system without undergoing any essential change and is excreted from the body.

Even so it intervenes in the road. Soluble fiber delays gastric emptying and, by slowing the digestion of carbohydrates, prevents a rapid rise in blood sugar. Insoluble fiber holds water within its structure and increases the movement of waste matter through the intestine.

It also contains the prebiotics needed by the bacteria beneficial to the intestine. We covered what fiber amounts to in meals in the fiber guide.

What the speed of the road varies with

Three variables can be listed. The first is the content of the meal: fat and fiber slow gastric emptying. The second is the pace of eating; the guideline recommends that food be chewed well and eaten slowly.

The third is age. With aging, physiological changes occur such as a fall in stomach acid secretion, a delay in the rate of gastric emptying and a reduction in the absorption of nutrients from the small intestine.

Part of what is felt after a meal has to do with that speed too; we wrote the details in this tip.

Where this account gets used wrongly

Digestion is not a cleaning job. The road the guideline describes is food being broken down and turned into new structures; no claim that a single food puts the digestive system right on its own appears in this source.

The second wrong use is focusing on a single component. The guideline puts variety of foods at the foundation of healthy eating; the road works not with a single component but with the components that arrive together.

In short: the road starts in the mouth, continues with absorption in the small intestine and turns into energy in the cell; its speed is set by the content of the meal, the pace of eating and age. We covered what the components amount to on the plate in this guide.