Digestion: Step 1

Putting food in your mouth:

If we want to talk food & performance, we must first understand what happens to food when we eat it. Talking Carbs, Proteins, and Fats is one thing, but is it really that simple?

No doubt all human beings (and mammals for that matter) use similar mechanisms to process food, but the speed these mechanisms work and their capacities vary among us all.

This post we will start to explore this, starting with what happens in our mouths. We'll follow up with the other major organs one by one, and try to gain a better understanding of how our body gets what it needs and how we do this differently from one another.

Step One: What Happens in Our Mouths?

Ultimately we have to get what's in the food into our bodies and to cells that can turn it into the things we need. This is the first step.

When we chew food in our mouths we are doing a few key things:

• Breaking up the food into smaller pieces so we can:

• so we can swallow without choking (important!)
• increase the exposed surface area of the food
• Allows soluble potions of the food to dissolve
• Increases exposure of the food to enzymes for breakdown

• Tasting the food

• Taste has got to count for something doesn't it? It stands to reason that flavour and survival (or perhaps propensity to get busy with someone of the opposite sex) is somehow related to good tasting things. That is a comforting thought. Just think: that satisfying poutine might just be helping you get some later.

• Disinfecting the food

• certain enzymes in saliva work to destroy bacteria in food

• Lubricating the food
• this keeps the food slippery for a smooth slide to the stomach

However we're more concerned with the metabolism aspects of chewing. The key mechanisms of action here are: dissolution of soluble nutrients, and breakdown of larger indigestible molecules into their digestible components via enzymes

Key catabolic (breakdown) enzymes in saliva:


Lipase: this is present in the saliva and although it doesn't work in the mouth (it requires the acidity of the stomach to work), this is a convenient place to get it into the nooks and crannies of the chewed up food.

Amylase: this works to break down certain starches into their component sugars for easier absorption downstream. Common foods processed via amylase are starches in corn, potato, wheat flour, etc. One really neat and important thing to know about amylase is that the number of duplicates of the amylase gene in a person's genome correlates directly with the amount of amylase expressed, and therefore the amount of starch that a person can break down.

Amylase works best when in the presence of ions such as chloride (think salt, sodium chloride) and at  a fairly neutral pH (6-7).  It becomes inactive at the low pH of the stomach (~ pH 4). Hence it seems the case that if a person eating pasta, but has a lower than average number of amylase genes, and chews and swallows faster than average, that person would have less than average sugar available for digestion, at least by the time food reaches the stomach. Does this mean that person would be converting less of the food into energy than another?  We need to follow the digestive trail all the way through to the end to find out.