Friday, March 14, 2014

Amazing journey!

Photos are of food we have encountered either in the Bay Area or in our travels to other countries.  How many can you identify? All of the foods shown are useful to us for their carbohydrates, fats, proteins, and vitamins.

Once I have eaten my hamburger and fries, I think I am finished - but I am only beginning.  It is an amazing story of what is yet to come!  

So now I have enjoyed the flavor of each bite as I chewed my food into small fragments.  My salivary glands have released a protein enzyme called ptyalin, which mixes with the starch of the bun and the potatoes and starts to break long carbohydrate molecules into two 6-carbon sugars called disaccharides.  Down the esophagus it goes.  

When you reach up and touch your throat, you feel the cartilage rings of the Trachea (windpipe) - the esophagus (gullet) lies behind that, parallel with the spine.  There is a special door at the entrance to the stomach called a sphincter (ring shaped) muscle that must open to allow the food to pass.  It also prevents stomach acid from splashing up into the gullet (except when you have 'heart burn'.)

In the stomach gastric juice is pouring from the stomach lining walls.  It does only one thing - Protein molecules are large and difficult to break down- before they can do you any good they must be broken all the way down into their amino acid building blocks - it only starts here with the release of a protein enzyme called pepsinogen which only breaks the big protein molecules into somewhat smaller pieces.  (Other than this, no other food digestion occurs in the stomach). Hydrochloric acid is also added to activate the pepsinogen.  

But these is a problem... the wall of the stomach is made of protein.  To avoid digesting itself it has to coat the stomach wall with thick layers of sticky mucus, which is also secreted by the stomach wall.  The walls of the stomach churn and mix the food with the juices to reduce it all to a uniform paste.  Additional fluid is added from the blood.

Finally the food is released in small 'burps' through another sphincter into the small intestines - this is the length of a 20-foot garden hose - wound back and forth in the lower abdomen.  This is where most of the real digestion happens.

If there is protein present in the food mixture, the pancreas is stimulated to release protein-digesting enzymes (also made of protein), also special enzymes to break down any remaining starch and complex sugars, and if fats are present, the gall bladder is signaled to release bile.  Bile has the effect of a detergent, breaking the fat particles into tiny particles that can be acted on by another enzyme from the pancreas. So the pancreatic excretions are essential for the breakdown of fats, proteins, and carbohydrates!  It also released natural antacids to counteract the acid coming from the stomach.

Finally the semifluid food mass must travel through the 20 foot + length of the small intestines, with millions of tiny projections (called villi) extending inward, providing a huge surface area through which the tiny molecules of digested food and some fluid can enter into the blood steam.  

It's interesting to note that while many mammals can digest cellulose as an energy food, humans can not... we don’t have the enzymes for that piece of work.  We have a small vestigial organ at the end of the small intestines that is at the same location of the cellulose digesting organ of other mammals - but ours is inoperative... it is our appendix!

You will notice one important category missing in the list of digestible foods - and that is fruits, salads, and vegetables - While it’s true that fruits contain some sugar, vegetables do not.  Vegetables and salads are high in cellulose... but also high in those trace nutrients that we call vitamins.  We cannot produce most of our own vitamins and they are essential to our health.  Plus these foods taste good.

If we lived close to nature, eating those foods that came naturally from the farm we would not have one problem.  With modern processing and transport systems, concentrated sugar and corn syrup are ubiquitous! Whenever sugar enters the blood steam, the pancreas responds by releasing insulin, which permits the cells to absorb food out of the bloodstream.  If more sugar enters the cells than can be used for energy the excess is stored as fat.  So the presence of sugar is a stimulus to the cells to store food as fat.  A person with a low sugar diet will release less insulin, and the body's food will be routed for energy use.  Think of this as a 'disease' of civilization. In nature sugar is quite rare in most foods.

At the end of the small intestines is another sphincter muscle that controls flow into the large intestines. This starts on the lower right side of the abdomen - travels up, across the top of the abdomen, then down the left side.  The main function of the large intestine is to reabsorb water out of the food mass and return it to the blood.  The remaining material in the large intestines is home to a myriad of microorganisms... most are either neutral or beneficial to us - some produce vitamins that are absorbed into the blood.  

Our bacterial 'garden' lives on any left over food and cellulose in the large intestines.   Some beans contain a carbohydrate that we dont have the enzymes to digest.  This carbohydrate  passes through to the large intestines where the bacteria receive it as a treat! As they process it, a side effect is the  production of excess gas!  

Our bacteria are harmless to us - But if we travel to a country where sewage water contaminates food - we can pick up a variety of bacteria that can make us sick.  This is also the primary reason that food handlers here are urged to wash after they have visited the restroom!

High Sierra Picnic

Cream pies sitting out at room temps, the juice from raw chicken, things that have been in the refrigerator too long... all can contain 'strange' bacteria that move into our system and cause serious gastric disruptions.  What is commonly called 'stomach flu' is almost always caused by some sort of  contaminated food... Be especially careful of which foods you select from a potluck meal where some dishes may have been unrefrigerated for hours before eating!

Finally the end of the line - the last sphincter is the anus - which controls the release of the accumulated waste from the last part of the large intestines called the rectum.  If waste remains in the rectum too long before excretion, excess water will be removed back to the blood and the mass becomes too dry and constipation occurs - the solution eat more fiber to give something for muscles to push against, and drink more water...  If the waste is passed on before fluid can be reabsorbed out of it the condition is diarrhea.