The intestines are the longest organ in the human body at 26 feet in total length, 21ft of small intestine and 5 of colon. The  multiple coils increase the surface of absorption. The intestines are hypersensitive, with 100 000 000 neurons linked to the brain, it makes the gut  a sensitive transmitter and receiver of emotions... Giving you the gut feeling.

Each part of the intestine absorbs selective vitamins and minerals, and if that section is troubled, it doesn't absorb as well or at all.

Starting at the mouth it only absorbs a small amount of vitamins B6, B12, C and folate and the mineral zinc depending on the time you chew and your saliva composition.

The stomach absorbs very little. 

Now for the intestines. The small intestine can be described in sections, 'the first section the part of the intestine closest to the stomach (called the duodenum) and the middle part of the small intestine (called the jejunum) specialize in the absorption of most minerals. The vitamins are also spotlighted in these areas, with the exception of vitamin B12, whose primary absorption site is the very last segment of the small intestine, called the ileum. Literally hundreds of nutritive substances are absorbed from the small intestine.

The last part of the digestive tract—the large intestine—is particularly important for the absorption of vitamin K, biotin, and the electrolyte minerals (sodium, chloride, and potassium).'* These need the bacteria in the colon, as it is the bacteria that digests the elements which are then excreted and absorbed by the body.

 if the small intestine isn't functioning properly, it doesn't churn the food enough times and doesn't break it down. Therefore, it is left for the large intestine to produce more bacteria and ferment a larger quantity of food than it is designed to do and flatulence is a side effect. The main indication is that you have to loosen off your belt in the afternoon, due to gas build up.

Another few symptoms of poor functioning intestines are difficulty getting out of bed in the morning and once up, just wanting to go back to bed a little while later and bad mood disappearing as the day goes on. Mental irritation might be present with the long muscle of the intestine in spasm, which decreases the circulation and makes it hard to absorb minerals. 

Spasmophilia, which occurs in 18% of the population ( women) characterized by cramps, restlessness, back spasm, indicates a serious magnesium deficiency. If related to hypoglycemia the symptoms include anxiety, hunger, accelerated heart beat, numb hands and feets, cramps in the calves, feet, back  as well as spasms in the stomach, gallbladder and colon.  You are easily irritated, nervous, all of this can be attributed to stress and come near or at a season change. Also lack of Vitamine D and minerals ( cal, mag, potassiumm, phosphorus) can lead to this , so can a hormonal disorder related to the thyroid, parathyroid or suprarenals.  .

Joint Pain in the lumbar vertebrae, feet and knees, connection with hallus vlagus and the intestins the connection might be throughthe femoral nerve.

striated nails- might be due to the lack of calcium, magnesium or zinc

Fecal matter that stagnates and hardens ( constipation) is sometimes due to compressed veins or improper blood or lymph circulation, compressed veins can sometimes dilate which can cause hemorrhoids. ( the liver and pancreas can help to stimulate the system.)

As for diarrhea , over emotionality stimulates your SNS increasing the speed of digestion. Digestion has to move at a very specific speed, not too fast nor too slow.

if black stool is present go see a dr

The other player in good digestion is the bile and pancreas secretions

Most frequent intestinal problem is linked to hormones especially in women.: 


**Most of this information is taken from the book "Understanding the messages of your body by Jean-Pierre Barral"  if you need more information I suggest you buy the book!**