Every once in a while I come across the phrase “but I digress,” which as it turns out, is just a nicer way of saying, “Gosh I strayed off topic; where was I?” Sometimes it’s entertaining, but usually it’s license for the writer to slip in an opinion, an experience, or another possibly related thought. An alternative definition of “digress” is “to wander from one’s path or main direction,” as in the following sentence: “I’m not exactly sure why I’m not as healthy as I would like to be, but I suppose it could be because of all the junk I eat, my sedentary lifestyle, my daily alcohol consumption, and the mass quantities of stupidity in politics these days; but I digress.”

Speaking of being healthy, in addition to addressing the above mentioned items of junk food, sedentary lifestyle and alcohol consumption, we could all greatly benefit from a clearer understanding of the human digestion system. For years now I have followed and been a satisfied customer of Natasha Trenev, the founder and CEO of Natren. I read her books, articles, and blog posts with great interest, and attempt to mentally digest everything she says about the relationship between gut health and wellness. So when this article came to my inbox last week, I quickly gobbled up every word, chewed carefully, and swallowed. Delicious! Thankfully, there was plenty left to share with you! Here’s Natasha:

Understanding the Human Digestive System By Natasha Trenev

The human digestive system has a unique design that uses mechanical and chemical processes that turn the food a person eats into energy and nutrients the body can use for energy, growth, and cell repair. The process of digestion has many stages in which several organs, tissues and body systems work together to achieve an end goal – in this case, breaking down large, complex molecules into smaller pieces for distribution and use throughout the body.

Digestive system organs fall into two main groups: the alimentary canal and accessory organs. Measuring up to 30 feet in length in the average adult, the alimentary canal is a series of hollow organs joined in a long, twisting tube that runs uninterrupted from the mouth to the anus. The liver, pancreas, and gallbladder, which are solid organs, act as accessories to the alimentary canal by adding secretions that aid digestion.

Other body systems participate in the digestive process. The autonomic nervous system largely controls digestion in that it stimulates a variety of functions, including salivary secretions, peristalsis that pushes food along the digestive tract, gastric acid production in the stomach, the opening and closing of sphincters, the release of hormones that aid digestion, and the storage of energy in the form of fat.

The circulatory system absorbs and distributes the nutrients produced by the digestive tract. Blood also carries chemical signals created by the endocrine system, which controls the speed of digestion.

The gastrointestinal tract (GI tract) contains bacteria, also known as gut microbiota, which help with digestion. Bacteria in the gut perform a variety of useful functions, including digestion of un-utilized energy substrates, stimulation of cell growth, suppressing pathogen growth, training the immune system to respond only to harmful pathogens, and defending against certain diseases.

Together, this combination performs the complex task of turning food and liquid into energy and useful nutrients.

The human body draws nutrients from food through four main processes: ingestion, digestion, absorption, and assimilation.

Ingestion introduces food into the system. The term ingestion includes a group of processes that take place in the mouth. These processes include chewing and grinding using the teeth, the release of saliva to lubricate and add chemicals to food, and swallowing of the food to send it to the next part of the digestive tract.

The processes of ingestion begin the breakdown of food. Chewing breaks down food through mechanical forces. Saliva contains two key enzymes, amylase and lipase, which break down food chemically. Amylase catalyzes the first step in the digestion of starch while lipase initiates fat digestion.

Digestion further breaks down food into particles small enough to be readily absorbed into the bloodstream. The body breaks down nutrients into macronutrients and micronutrients.

  • Macronutrients: Carbs, Fats, Proteins
    – Carbohydrates include sugar, starch and fiber. Depending on their chemical structure, carbohydrates can be simple (natural sugars from fruits, vegetables and dairy) or complex (starches, grains).
    – The body uses fat as a rich source of energy. Fat also helps the body absorb vitamins.
    – Meat, eggs, and beans contain protein, an important building block of bones, cartilage, muscles, skin, and blood. Digestion breaks down proteins into smaller amino acid molecules that easily move through the walls of the small intestine and into the bloodstream.
  • Micronutrients: Vitamins, Minerals
    Vitamins and minerals play a variety of roles in the bodys growth and health. Scientists categorize vitamins according to the fluid in which the vitamin dissolves. All of the B vitamins and vitamin C are water-soluble, while vitamins A, D, E, and K are fat-soluble. The body stores fat-soluble vitamins in fatty tissues and in the liver. The body cannot easily store water-soluble vitamins, however, and flushes any excess out in the urine.

The process of taking fluid and nutrients into the bloodstream, known as absorption, occurs primarily in the small intestine. This section of the alimentary canal is largely responsible for the absorption of water and soluble substances, such as simple sugars, salt, and alcohol.

The lining of the ileum has a thin epithelium that allows for the easy diffusion of nutrients and the sheer size of the small intestine provides a significant surface area on which absorption can take place. A human small intestine measures about 6 meters, or 20 feet, and its absorptive area measures 250 square meters (almost 2,700 feet), which is about the size of a tennis court.

The mucosal folds on the inner surface create even more surface area for absorption.
Each villus has a network of capillaries and fine lymphatic vessels, known as lacteals, close to its surface. Amino acids and carbohydrates move into capillaries while lipids move into lacteals. Villi is Latin for shaggy hair. These villi are in constant motion, absorbing nutrients as food moves through the ileum.

The villi and microvilli of the ileum contain a large number of capillaries that absorb fatty acids and glycerol. The ileum also plays an essential role in the absorption of vitamin B12 and other bile salts. Additionally, the ileum secretes protease and carbohydrate enzymes that complete the breakdown of protein and carbohydrates. Specialized cells in the ileum absorb materials into the bloodstream or lymphatic systems, which transport the molecules to the liver, kidneys and other parts of the body.

Undigested food, older cells from the GI tract lining and other waste products move through the large intestine, which absorbs water, vitamin K and the remaining B vitamins, and nutrients. The absorption of water turns liquid waste into stool.

Assimilation is the uptake of nutrients into body cells and tissues, and the reassembly of absorbed nutrients into complex substances. The small intestine absorbs most digested food molecules, as well as water and minerals, during assimilation those molecules are passed on to other parts of the body for storage or further chemical change. Simple sugars, glycerol, amino acids, and some vitamins and salts move through the bloodstream to the liver. The lymphatic system absorbs fatty acids and vitamins.

Bacteria are essential to the operation of the human digestive system. Friendly bacteria in the digestive system, known collectively as the microbiota, live primarily in the colon and ileum. The esophagus, stomach, and duodenum also house bacteria, but generally in lower numbers due to the strong stomach acid and digestive enzymes that are at work here.

Bacteria enjoy a symbiotic relationship with their host. Bacteria have a safe place to live and provide a number of benefits in return. Friendly flora help maintain an optimal pH level, stimulate the immune system, get rid of hormones no longer needed by the body, and reduce potential toxic and carcinogenic substances. One of the most significant contributions of probiotic bacteria in the gut is that they provide protection against harmful pathogens that try to invade the cells lining the internal intestinal wall.

Bacteria can also help the host body metabolize food. The body easily breaks down simple carbohydrates into energy-rich adenosine triphosphate (ATP), which stores and releases energy as required. It takes more effort to use complex carbohydrates, as the body needs to break down complex carbohydrates into their component simple sugars before it can process them.

Bacteria use carbohydrate-active enzymes (CAZymes) to break down complex carbohydrates. There are several different kinds of CAZymes and each is specialized in the complex carbohydrate molecules it breaks down. The human body does not make the enzymes that degrade many plant structures so, without beneficial bacteria, it would waste much of the nutritional value of vegetables. Some bacteria species living in the digestive tract can make vitamin K and some B vitamins. The human body cannot make these vitamins and has trouble absorbing them from food. An imbalance in the gut flora, or dysbiosis, is associated with the pathogenesis of many intestinal and extra-intestinal disorders. Dietary supplementation may restore balance to the gut flora.

The human digestive system is a complex process that turns whole foods into molecules tiny enough for absorption into the cells of the body and g­­­ets rid of the waste. It is truly a marvel that, given the right intake, will serve to nourish, sustain, and protect the host for decades. Of course, even the most well-designed system will break down every so often. As hosts, it is our responsibility to maintain the health of our digestive system – after all, we cannot live without it! A healthy gut requires a healthy, balanced diet that contains the raw nutrients, vitamins and minerals necessary for life.

The balance of bacteria in the system also needs to be maintained. Back in the days before processed foods, chemicals, GMOs and a nutritionally sparse diet, this was a little easier. For generations, regular consumption of fermented foods was sufficient to maintain digestive health – however, that is rarely enough nowadays, and most of us should consider some sort of supplemental probiotic as part of our daily diet to ensure a healthy and diverse gut microbiota. [End of article].

OK, so that’s a lot of big words! Yeah, I don’t quite understand all of it either. Is digestion complicated? Absolutely. So what’s the take away?

Very simple. Do you have a car? Do you want it to run properly? Then put GOOD FUEL in your car’s gas tank. Do you want it to last a while? Then maintain it with regular service check ups. Do you want to enjoy it? Then keep it clean with quality products. Do you want to keep it out of the local police lock-up? Then drive responsibly and obey the law.

Do you have a body? Then put GOOD NUTRITION in your mouth. Do you want to live a long and healthy life? Then schedule regular medical checkups and follow your doctor’s suggestions. Use chemical-free products for personal hygiene and in your home. And use common sense, as my father would say. Exercise, eat healthfully, meditate, and take care of yourself. Because if you don’t, someone else will have to.

I’m fairly confident you take as good a care of your body as you do your car, right?

To Your Digestive Health and Mine,

Dr. Hank