Saliva. Spit. Digestion.

This post isn't much of a debunking since Hutchinson's Handbook of Health by Woods Hutchinson, published in 1911 actually got the saliva and digestion thing right. I guess chemistry was already advanced enough back then to understand this. I will just outline the basic steps and maybe supplement with some new information.

According to Dr. Hutchinson, the process of digestion begins before we even eat anything.  That delicious and sometimes annoying sensation when your mouth begins to 'water' at the sight and/or smell of food...that's the beginning of digestion, and that's all due to your saliva!

Saliva is produced in the mouth by salivary glands and its primary function is to aid in digestion. The saliva not only prepares the digestive system to break down the food, but also "brings word to the juices [in the stomach] to be ready." Hutchinson also says that the saliva initiates a cascade to innervate the stomach nerves so the stomach can prepare its digestive juice, also known as "appetite juice."

I am now always going to refer to what is going in my stomach before I eat as my "appetite juices." Anyway, one point of contention that Hutchinson mentions is that the attractive appearance of food and a good appetite are important in food, because if our "appetite juices" are not secreted, "the food may lie in the stomach for hours before the proper process of digestion, or melting, begins."

First of all, food doesn't really melt. And secondly, even if food isn't attractive, I still get hungry, and I think that, unless you have some serious GI problems, even if you don't have a good appetite or think your food looks pretty, you will still digest it.

However, this may be why we feel more bloated or heavy when we eat when we're not actually hungry-- because the juices aren't secreted and we don't have a "good appetite," so the food seems to sit in the stomach longer before it is digested. 

One thing that I learned from reading this chapter is that saliva is meant to break down the starches in food. Saliva contains ptyalin, a "ferment, or digestive substance" (now known as a protein/enzyme) that breaks down the starch in food, which is a polysaccharide (a long chain of sugars) and turns it into glucose, which can be more easily broken down by the body. (This information is courtesy of wisegeek.org).

Hutchinson also says that particularly starchy foods, like bread, biscuits, crackers, and pastries require "thorough and elaborate chewing," so that the ptyalin has time to break down the food.  However, the ptyalin actually continues to act on the chewed-up food even after it enters the stomach, AND the pancreas and acids in the stomach finish the job that the saliva started.  So you really don't need to chew your bread any more than your meat or eggs, since your body has a mechanism to prevent you from looking like a cow every time you eat your toast.

I couldn't find any scholarly articles to support this next claim, but wisegeek.org also mentions that ptyalin amounts in humans vary based on ethnic origin, and since Asian cultures consumed more starch, they typically have more of the enzyme than people with Northern European ancestry. This was found from "genetic studies" but I couldn't find any specific ones, although there are lots of genetic studies involving ptyalin if you want to learn more about this really cool enzyme.

More on digestion next time! And now a joke to end this week's post...

What is half of a digestive system?

*(Scroll down for the answer)*


































a semi-colon!