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.

Fatty Fortitude

Is Fat really the best fuel for endurance?

The latest Atkins diet, the Primal diet, the 4 hour body, all of these contend that fat is the fuel that we should choose.

This does make sense in a few ways:

1. We store seemingly unconstrained amounts of energy as fat. 
2. Our bodies take sugars and make them into fat really quickly
3. Our bodies tend to metabolize more fat for energy during activities of moderate intensity

But what about the 'carbing up' activities of countless, and skinny (read : fat free) marathoners. Can people really be burning fat as fuel when trouncing out a 7 minute mile?

Without knowing the rough biochemical pathway they each of these substances has to travel to ultimately end up as ATP (adenosine triphosphate - the fuel that is ultimately employed by muscles to contract) we are a bit in the dark. I will be addressing this in some future posts so that we might be able to tell if using fat is good for endurance, or if its good for everyone.

Precipititous Pessimism Pervades Primalism

or: the primal diet, worth following?

I've recently perused some of the 'Primal Diet' information, primarily my sources have been Mark's Daily Apple and Nerd Fitness, two blogs I quite enjoy.

The premise is this:

If human beings have existed (and, presumably, evolved) for a really long time, and we've been hunter gatherers for all but the last 10,000 years or so, then our biology is tuned to consume hunter gatherer foods, not farmed foods. 

It's supposed that many of our first world problems (think obesity, diabetes, cancer, heart disease) are resulting from our propensity to eat 'nutrient poor' carbohydrate heavy, grain derived foods.

I'm inclined to agree with this for the most part. Eating shallow root vegetables, fruit/berries, and nuts  with little bits of lean meat thrown in seems like a great idea. Certainly it sounds healthy.

However where I'm not sure I agree is when primal proponents vilify grains.

Unfortunately proponents seem to discount any natural selection that may have happened since we practiced farming. It's not hard to conceive of a hypothetical small tribal population 3000 years ago during a famine having nothing but grains to subsist on, resulting in many of those who aren't able to digest it properly dying before they could pass on their genes to the next generation.  It stands to reason that this (natural selection) must have been happening consistently over the past 10,000 years.

There are vegetarian populations that have thrived (think many Indian Hindus/Hare Krishnae). Certain Italian and Japanese populations live long & fulfilling lives with pasta and rice forming the better part of their caloric intake. This has gone on for generations and during quite a few lean years. It might very well be the case that people  descended from rice & wheat rich regions  could be better suited for grain consumption than someone descended from Inuit or Viking Populations.

Does this mean that if I'm Irish I'm better off eating potatoes than pasta? If I'm Japanese then fish and rice instead of potatoes or oatmeal? If I'm a first nations person from Northern Russia I'm better off sticking with seal meat? Maybe that's the case. However there's been so much inter-racial mixing that we might never know.

There are many methods to identify the types (alleles) and levels of expression of key genes that aid us in digesting these foods. Perhaps in the near future a simple test at the clinic will let us know if we should eat that or meat or not worry about it?

 It may be the case that there's a co-occurence of fat people and over-servings of corn syrup, but correlation is not causation. In my opinion there's not one answer for everybody, but presumably science will offer up better ways that we can tell what's best for each of us.