What happens to this healthy apple and almond snack after we eat it?
What are the steps of digestion our body goes through when we eat?
Let’s begin in the mouth, where digestion begins. Actually, it begins in the brain. When you smell something delicious cooking or when you cut open an aromatic fruit, you often will begin to salivate or maybe your stomach will begin to growl. This is your mind giving messages to your mouth which will prepare you for the digestion that will begin when you take your first bite. Your mouth has salivary glands that produce a liquid that moistens and begins to digest your food. Starch digestion begins in the mouth with amylase.
Imagine the person (hopefully you!) who takes the time to sit down for their meal and takes the time to arrange it beautifully on the plate and takes the time to bless their food. Then they take the time to chew it carefully, enjoying its flavors and noticing how there are sour, sweet, bitter, pungent, salty, and umami flavors in the bite. The bolus or wad of food they create by chewing is thoroughly moistened with digestive juices and broken down as well by chewing it into tiny pieces.
Then imagine the person (we are probably all here occasionally) that realizes they have an appointment in 10 minutes and need to get some lunch. They bolt it down, barely remembering to taste it and chewing it only cursorily. That bolus has larger chunks and much less salivary amylase enzyme. The food that slides past the epiglottis and on down the esophagus is just that, still chunks of food, barely digested at all.
Either way, this bolus will pass through the LES, the lower esophageal sphincter, and enter into the stomach. So whether you are the person who chewed very thoroughly and liquefied your solids and chewed your liquids, as they say, or the food bolt-er, the food arrives into the stomach where the stomach acids begin the protein digestion (did you know that most every whole food has some protein in it?). That same stomach acid is also the guardian gate that kills foreign bacteria and does not allow them to get any farther down the gastrointestinal (GI) tract.
What problems can happen along the way?
Can you see some possible digestive problems already? YES! First of all, some people barely chew. Second of all, as we age, we produce less and less stomach acid. We need stomach acid to digest our proteins and to protect our bodies properly from invasive micro-organisms entering our bodies. We also need our stomach acid to digest our Vitamin B12 and our iron.
I want to back up here for a minute because you may see those invasive micro-organisms to be already inside our bodies. I want you to see our GI tract as the hole of a donut. Our body is the cake of the donut, and it is not until the digested particles pass through our small intestinal walls that they enter into our bodies. So the stomach acid is one of our first lines of defense, along with our skin, defense against anything that should not enter. A compromised stomach acid can be an issue here.
Continuing on down the GI: As the pepsin in the stomach (which causes chemical protein breakdown) and the churning of the stomach (which causes mechanical breakdown) turn the bolus into chyme, a step further in the digestion of both the starches and the proteins, the pyloric sphincter opens, dumping the chyme into the small intestine. The small intestine as you probably know is 20 feet long. It is made of the duodenum, the jejunum, and the ileum in that order.
When the chyme enters the duodenum, the pancreas sends digestive enzymes and the gall bladder sends bile, which was produced in the liver, to help with the digestion. It is here where the fats begin their digestion. The pancreas sends lipase and the bile emulsifies the fats so that they can become water soluble enough to go into the water-soluble bloodstream. So here we see some more red flags of what might go wrong. The pancreas may not be making enough enzymes (our raw foods are filled with enzymes, but many people eat only cooked foods, which puts all the work on the pancreas) or the liver or gall bladder may not be working well enough to produce and store enough bile to break down the fats so they are digestible and usable in our bodies (not enough bile limits the fat digestion).
The duodenum specializes in the digestion of fats. It also continues the breakdown of the proteins begun in the stomach. We continue on to the jejunum where the carbohydrates broken into simple sugars and the proteins are absorbed. Here we see another possible problem. If we are short on stomach acid, the proteins may only break down into peptides rather than amino acids. Peptides are chains of amino acids, linked together. It is when these won’t break down any farther into individual amino acids that they begin to create havoc in our small intestinal wall.
The peptides that are not supposed to get through the tight junctions in our gut wall may cause damage to the gut wall, loosening the links so they make a big enough space to get through. Once in the bloodstream, the peptides are marked by the immune cells as foreign invaders because only the proteins broken down into amino acids are supposed to be let through. The tagged peptides then may be attacked by the immune cells, causing inflammation.
These peptides also happen to be similar to peptides of proteins found in our organs. An example here is the peptides from gluten are very close to ones found in our thyroids. The immune cells may attack these as well, believing them to be invaders, and causing a step towards auto-immunity. Also, back at the enlarged gaps in the wall, other food not yet digested enough, may also get through. This is what is known as leaky gut. This is also why once someone gets sensitive to one major peptide, maybe from gluten or dairy, we may also become sensitive to others, if they are getting through the loosened junctions.
The arrows below show what the macronutrients are broken down into:
Proteins -> peptides-> amino acids
Carbohydrates-> simple sugars, which are glucose or fructose or galactose
Fats-> fatty acids or glycerols