4 Steps for Strong Small Intestine Digestion

Small intestine health highlights:

Small Intestine Function:

  • Break down and absorption of fat, protein, carbohydrate and nutrients
  • Immune system barrier

When Things Go Wrong:

  • Small intestinal bacteria overgrowth (SIBO)
  • Leaky gut
  • Food sensitivities

Supporting the Small Intestine:


Def. Small Intestine: 

The small intestine is a 20-foot muscular tube responsible for digesting and absorbing macro- and micronutrients.

4 Steps for Strong Small Intestine Digestion
4 Steps for Strong Small Intestine Digestion

The small intestine connects the stomach to the large intestine and is divided into 3 sections: duodenum (1 foot long), jejunum (8 feet long) and the ileum (11 feet long).

The small intestine is a delicate barrier, keeping toxins out and allowing nutrients in to the body.

The duodenum is largely responsible for nutrient digestion.

The jejunum and ileum are mainly responsible for nutrient absorption. 

Digestion and Absorption Function: Small Intestine


The duodenum is largely responsible for nutrient digestion. The duodenum is fairly acidic due to the presence of hydrochloric acid from the stomach, however upon the release of bicarbonate from the pancreas and bile from the gallbladder, the acid level decreases. The pancreatic enzymes and bile are able to further break down chyme..

Rhythmic contractions, called peristalsis, move chyme down the length of the intestine toward the jejunum and ileum.



Protein Absorption:

Proteins (long chains of amino acids) are broken down in the stomach by HCl and pepsin, then in duodenum by pancreatic enzymes trypsin and chymotrypsin, and finally in the small intestine by brush border cells in the small intestine called aminopeptidase and dipeptidase,. These peptidases split protein peptides into individual amino acids. The single, free amino acids are transported and absorbed into the blood, carried to the liver, then reassembled for use.

Carbohydrate Absorption:

Carbohydrates begin to be broken down in the mouth by salivary amylase and then in the pancreas by pancreatic amylase. The small intestine brush border enzymes lactase, maltase and sucrase break down disaccharides (two-sugar molecules) into monosaccharides (one-sugar molecules) for transport across the intestinal lumen and into the blood.

Fat Absorption:

Fats are mainly digested in the small intestine by bile from the liver and gallbladder and pancreatic lipase from the pancreas. Triglycerides are broken down into free fatty acids and monoglycerides and enter circulation.

Micronutrient, Mineral and Water Absorption:

  • Water-soluble vitamins (B & C) are absorbed in the small intestine.

Finger-like folds called villi and microvilli line the small intestine. These villi and microvilli are one-cell thick, and play a complicated role: they both block the absorption of bad, foreign substances and allow the good, nourishing nutrients to pass into the bloodstream.

In sum, absorption is the name of the small intestine game. We are what we absorb. We can eat all the nourishing foods in the world, but if we can't absorb the macro- and micronutrients, we're losing out on all their benefits.


When Things Go Wrong:

1. Small intestinal bacteria overgrowth (SIBO)

  • In a healthy small intestine, there are relatively few bacteria (less than 10,000 bacteria per milliliter of fluid). The large intestine contains the majority of bacteria (at least 1,000,000,000 bacteria per milliliter of fluid). In a small intestine overrun with bacteria, there is an increased number of bacteria present in the small intestine that should normally be found in the large intestine.

The increased number of small intestinal bacteria interferes with the digestion of food and absorption of nutrients, primarily by damaging the cells lining the small intestine.


2. Leaky gut

  • Condition in which the lining of the intestine becomes damaged and leads to a development of small gaps between the cells that line the intestinal wall. These gaps allow substances, like undigested food and bacteria, to escape into the bloodstream. When these larger undigested protein molecules enter the bloodstream, the body produces an immune response and attack to these foreign proteins.

Our immune system is upregulated and can produce irritation, inflammation, and even autoimmunity.

4 Steps for Strong Small Intestine Digestion
4 Steps for Strong Small Intestine Digestion

3. Food sensitivities, allergies, intolerance

  • Damaged microvilli from leaky gut, SIBO, medications (NSAIDS, antibiotics), inflammatory foods and pathogens can result in digestive intolerance and symptoms of such, including bloating, gas, and malabsorption.

A 4-R protocol in conjunction with an elimination protocol can help repair the lining and allow for food reintroduction.


Supporting the Small Intestine:

  1. Mindful eating and lots of chewing readies your body to fully break down the incoming meal and allow for optimal nutrient absorption.
  2. 4-R Protocol: Remove inflammatory foods, Replace for proper digestion, Repair gut, Reinoculate with healthy bacteria.
  3. Digestive Enzymes + HCl +PepsinIn working with a nutritionist or practitioner, try taking a supplement to break down food for improved absorption.
  4. Protocols like FODMAPSSCD, and GAPS focus on types of carbohydrates. Consider trying one of these carbohydrate-sensitive protocols to help remove bacterial overgrowth.

The small intestine is a delicate barrier, keeping toxins out and allowing nutrients in to the body.

One of the best ways to support the small intestine is to not overburden it with food allergens and support it with plenty of nutrient-dense foods and mindful eating practices.