digestive health study

Fit, young woman holding a circle made out of vegetables over her abdomen

The process of digestion
Leaky gut and its causes
Major digestive enzymes and organs
Foods and teas that aid digestion
Common digestive complaints
Golden rules for Digestive Health
Foods that optimize Digestive Health
Digestion terms

The process of digestion

  1. Digestion begins in the mind with the Cephalic phase, whereby sensory awareness prepares the body for digestion by promoting release of digestive enzymes throughout the body.
  2. The second phase is chewing in the mouth, a mechanical process which breaks down the food and mixes it with enzymes in the mouth. Swallowing takes the food to the third stage of digestion – in the stomach, where food is mixed with Gastric Acid, a chemical process of breaking down the food into smaller parts ready for absorption.
  3. The third phase happens as chyme, the mixture from the stomach, passes into the Duodenum where it mixes with secretions from the Pancreas and Liver. These secretions both neutralise the high acid content of the chyme and also add in crucial digestive enzymes, as well as emulsifying agents.
  4. The fourth phase occurs as food passes through the Small Intestine where nutrients, now small enough, are absorbed.
  5. The fifth and final stage occurs as food passes through the Large Intestine, where food is processed for elimination.


Leaky gut and its causes

A leaky gut can occur when problems such as bacterial overgrowth cause the mucus membrane that lines the small intestine becomes more permeable to larger molecules. These molecules (such as complete proteins) are usually kept back from passing the mucus membrane, but when they do, they enter blood circulation triggering an immune response and causing allergies, inflammation, rashes, diarrhea, or joint pain, or chronic conditions such as asthma, inflammatory conditions such as rheumatoid arthritis or Crohn’s disease or skin conditions such as psoriasis. Possible causes include the use of NSAIDs (such as aspirin), infections with bacteria, yeast or viruses, parasitic organisms from polluted water (eg Giardia), alcoholism, food allergies, or environmental poisons. A leaky gut is common with the elderly as space between intestinal cells widens with age.

Major digestive enzymes and their functions

Proteases break down protein; lipases break down fat; amylases break down carbohydrate


Bile is manufactured in the liver and excreted into the duodenum either directly from the liver or from the gall bladder (where bile is stored). Bile is essential for absorption of fats, fatty acids, oils and fat soluble vitamins, and it also aids the action of enzymes. Bile works by emulsifying fats – breaking large fats into smaller pieces and mixing them with water ready for absorption. It also keeps the intestines free from micro-organisms and makes the stool soft by promoting the binding of water into stool.

Function of the Large Intestine (LI)

LI functions absorb water, salts and a few nutrients (nearly all absorption of nutrients occurs in the small intestine). It is home to countless bacterial microbes which are either beneficial or harmful – overgrowth of harmful bacteria leads to dysbiosis. The bacteria break down complex particles through fermentation as well as breaking down fiber to produce butyrate and other fatty acids that provide energy fuel for cells lining the LI tract.

Colon health

If the bacteria in the colon is out of balance, energy requirements for the cells that line the LI will be insufficient for the cells to stay healthy. The most important food sources of bacteria are lactobacillus acidophilis and bifidobacterium bifidum found in yogurt, cheese, miso and tempeh (probiotic foods) and probiotic supplements. Furthermore, the cells of the colon require fiber and water to stay healthy, both for energy (from breaking down fiber to produce butyrate and other fatty acids) as well to increase motility of food in the colon which both prevents build-up of harmful bacteria during fermentation and also prevents absorption of toxins (such as those secreted in bile from the liver). If food stagnates, fermentation will increase the presence of harmful bacteria that damage colon cells.

Spices that aid digestion

  • Umbelliferae family seeds (Anise, Caraway, Dill, Fennel): help expel gas (carminative) and relax intestinal spasms (antispasmodic)
  • Cardamom: carminative, digestant, stimulant, treats indigestion and flatulence
  • Cayenne pepper and paprika: contains capsaicin which acts as digestive and anti-ulcer aid, treats indigestion, stimulates salivary flow and increase secretion of digestive fluids in stomach
  • Cinnamon: sedative for smooth muscle (eg that lines GI tract and enacts peristalisis), carminative, digestant, diuretic, antibiotic, anti-ulcerative, stimulates weak digestion
  • Cloves: contains eugenol (and other components) which prevent digestive tract cancers and helps liver function (detoxification environmental toxins), are anti-bacterial
  • Coriander: carminative and digestive aid; stimulates conversion of cholesterol to fat digesting bile acids in liver
  • Cumin: stimulates secretion of pancreatic enzymes; digestive aid and effective for flatulence; anti-bacterial; anti-fungal; enhances liver’s detoxification enzymes
  • Dill and Fennel: Monoterpenes  (including carvone, limonene, anethofuran) activate liver enzyme glutathione-S-transferase (helps glutathione attach to toxic molecules). Flavonoids assist with carminative and sedative properties
  • Ginger: carminative, alleviates symptoms of gastrointestinal distress, promotes elimination of intestinal gas, promotes intestinal spasmolytic (substance that relaxes and soothes the intestinal tract)
  • Nutmeg: Carminative; Anti-diarrheal actions including improving intestinal tone and inhibiting intestinal contractions stimulated by irritating agents; food preservative, disinfectant and antiseptic of animal and plant pathogens and food poisoning and spoilage bacteria
  • Pepper (Black): Carminative and stimulates taste buds to prompt secretion of stomach acids; Anti-bacterial and Anti-oxidant; contains Peperine which increases absorption of nutrients such as selenium, B vitamins and beta-carotene, supports and enhances the liver’s detoxification processes

Liver support / teas:

  • Milk thistle: helps protect liver from toxic damage
  • Licorice: helps protect liver from toxic damage; helps protect intestinal walls through anti-inflammatory and anti-bacterial action
  • Dandelion, artichoke and turmeric: increase bile flow, thus helping liver to detoxify, as well assisting fat digestion
  • Goldenseal and garlic: digestive cleansers – help body get rid of toxic bacteria and yeasts in GI tract. Goldenseal kills harmful bacteria and shuts down enzymes found in bacteria (often bacteria not toxic but it the substances their enzyme systems produce are), increase GI tone, stimulate bile secretion and digestion
  • Gentian and Ginger: both are digestive bitters that act. Gentian is a gastric stimulant that can increase digestive function. Ginger also stimulates GI function and tones intestinal muscles, improves bile flow, helps in digestion of fats, lessens risk of inflammation along lining of intestines
  • Nettle and burdock: diuretic effects on kidneys and urinary cleansers of toxins from body.


Common digestive complaints

  • Gas: caused by fermentation of foods by bacteria in the large intestine due to excess transit time caused by low fiber, excess fiber (causing more fermentation), excess simple sugar in diet, bacterial overgrowth in colon
  • Constipation: occurs when stool remains in bowel too long and primarily depends on having adequate fiber in diet. Other solutions are to drink enough water and get regular exercise. Causes include:
    • use of diuretics, reducing body fluid levels
    • use of medications containing codeine, which slow down the muscle and nerve activity needed to pass stools
    •  hypothyroidism
    • bowel obstruction (eg from polp or tumor)
  • Diarrhea: excess water and undigested / unabsorbed food matter in stool resulting from impaired digestive processes, infection, inflammation, stress, allergies
  • Heartburn: excess acid in stomach that flows back up the esophagus causing burning sensation resulting from a stomach that is too full, weakness of the sphincter valve of the stomach and esophagus, obesity, smoking, consumption of chocolate, fried foods, soft drinks, alcohol and coffee, stress (which produces more acidity and also stops / slows digestion) 


Four R’s of digestive health

Removing or restricting – pathogens, allergens and toxins from the patient’s food intake

  • Allergens (eg gluten)
  • Xenobiotics
  • Endotoxins and exotoxins
  • Bacteria, pathogens, parasites, fungi
  • Oxidative stress
  • Supplements – excessive use or that are not bioavailable
  • Processed food products
  • Foods prepared outside home: what is in it? How much is known about ingredients or cooking methods / cleanliness?

Replace or replenishing – digestive enzymes in the pancreas and other digestive factors, such as stomach wall (Gastrin, HCl) and bile secretions

Reinoculate or reintroduce – friendly bacteria, using prebiotics and probiotics

  • Probiotics: lactobacilli, bifidobacteria
  • Prebiotics: inulin

Repair – involving direct nutritional support to intestinal cells via nutrients critical for intestinal wall structure and function

  • L-Glutamine
  • Clean, low irritant diet
  • Adequate protein
  • Anti-oxidants: Vitamins E, C, A, Glutathione
  • Vitamin support: B vitamins, Vit K


Healing Foods

  • Fibers:
    • decrease intestinal transit time (longer transit time that prolonged exposure to cancer causing compounds)
    • increase stool weight
    • delay gastric emptying resulting in reduced after-meal blood sugar levels
    • increase satiety, increase pancreatic secretion
    • increase beneficial intestinal microflora
    • decrease serum lipids
    • make bile soluble
  • Types of fiber
    • Fructooligosaccharides (FOS): eg Inulin in Jerusalem artichoke, burdock, chicory, dandelion root, leeks, onions, asparagus; and Galactooligosaccharides (GOS) in soybeans
      • Food for friendly bacteria in colon: increase number of friendly bacteria and reduce numbers of harmful bacteria
      • Increase production of fatty acids such as butyrate
      • Increase absorption of calcium and magnesium
      • Improve elimination of toxic compounds
      • Lower blood cholesterol and triglyceride levels
    • Gamma oryzanol: Gamma oryzanol may be useful for various digestive disorders such as stomach ulcers, gastritis, and irritable bowel syndrome. Gamma oryzanol’s beneficial effects appear to be due to its ability to reduce the secretion of gastric acid and normalize the nervous system control of digestive secretions. The best dietary sources include the bran portion of grains such as rice, wheat, barley, and oats. Other food sources include vegetables (esp. asparagus, tomatoes, and peas), citrus fruits, berries, and olives.”[1] It also “increases the conversion of cholesterol to bile acids and inhibits the absorption of cholesterol” (Murray, 2005, p. 94)
    • Pectins: found in plant cell walls and outer skin and rind of fruits and vegetables. Has gel forming properties responsible that have cholesterol lowering effects by binding cholesterol and bile acids and promoting their excretion
    • Guar gum: a mucilage found inner layer of seed portion of most legumes that has the most potent cholesterol lowering agents. Also reduces fasting and after meal glucose and insulin levels in healthy and diabetic peoples, and decreases body weight and hunger ratings in obese people
    • Psyllium: has the most potent cholesterol lowering agents. Also reduces fasting and after meal glucose and insulin levels in healthy and diabetic peoples, and decreases body weight and hunger ratings in obese people
    • Oat bran: contains hemicelluloses that promote regular bowel movement by increasing hydration of stool, and are digested by gut bacteria, increasing the number of beneficial bacteria and creating Short Chain Fatty Acids (SCFAs) used by colon cells for fuel. Also binds cholesterol in gut, preventing its absorption
    • Slippery elm: or marshmallow. “Slippery elm contains mucilage, a substance that becomes a slick gel when mixed with water. It coats and soothes the mouth, throat, stomach, and intestines. It also contains antioxidants that help relieve inflammatory bowel conditions. Slippery elm also causes reflux stimulation of nerve endings in the gastrointestinal tract leading to increased mucus secretion. The increased mucus production may protect the gastrointestinal tract against ulcers and excess acidity.” [3]
  • Artichoke: Caffeoylquincic acids and flavonoids treat digestive problems including nausea, bloating, loss of appetite and abdominal pain (largely by increasing the flow of bile from the liver by up to 150%, and bile also attracts water, allowing softer, easily passed stools); Inulin content high in Fructooligosaccharides that act as prebiotic fuel for beneficial bacteria in colon, and source for fatty acid fuel for colon cells such as butyrate
  • Dandelion: Root – liver remedy: enhances bile flow, improves liver congestion, bile duct inflammation, hepatitis, gallstones, jaundice due to direct effect on liver, causing increased bile production and flow to gallbladder and direct effect on gallbladder, causing contraction and release of stored bile
  • Bitters: made from plant and root extracts (such as gentian root) and useful for increasing production of gastric fluids in stomach [2] 
  • Carob: tanins in carob have astringent or drying effect in GI system and inhibit growth of bacteria bacteria and bind to and inactivate toxins. Useful for treating diarrhea 
  • Peppermint: as oil in enteric-coated capsules, are prevented by the capsules from being released in the stomach and instead released in small and large intestines where it relaxes muscles, thus helping with improving rhythmic contractions of intestinal tract and relieving intestinal spasm, and helping with IBS 
  • Beets: Liver health – stimulates liver detoxification process possibly due to high content of nutrient Betaine 
  • L-glutamine: amino acid that is useful in intestinal repair due its function in providing fuel for rapidly dividing cells (such as those of the mucosal lining of the intestines) and also being a precursor for the anti-oxidant and liver detoxifying Glutathione (Murray, Healing Foods, p. 64). In addition, it is the preferred respiratory fuel for GI mucosal cells and immune cells. (Bland et al. , 2004, p. 51). It also has anti-inflammatory properties and helpful with colitis and IBS possibly due to lowering levels of interleukins, inflammatory messaging molecules, in the intestines (Hass, 2006, p.256). Present in most foods, but highest in high protein foods especially eggs and whey protein.
  • DGL: “Deglycyrrhizinated licorice, also known as de-glycyrrhizinated licorice, or commonly referred to by the acronym DGL, is an herbal supplement typically used in the treatment of gastric and duodenal ulcers. It is made from licorice from which the glycyrrhizin has been removed.” [4]
  • Licorice root: anti-inflammatory, anti-arthritic, anti-toxic (ie supporting and protecting the liver), anti-biotic, anti-cancer and laxative. Also softens and soothes intestinal tissues and mucus membranes. Helps with stomach and intestinal problems such as indigestion, nausea, constipation.
  • Garlic: has anti-inflammatory properties by altering “immune system messages and quieting of molecule NF-kappa B […] with likely application to conditions like inflammatory bowel disease” (Haas, 2006, p. 255)
  • Boswellia: herb that has anti-inflammatory properties as well as being used to treat GI problems. [5]
  • Fermented foods: contain bacteria that is beneficial to GI health. Examples include yoghurt, miso, and fermented vegetables such as tempeh and sauerkraut
  • Healing teas: Mint, Ginger, Umbelliferae family seeds, Cardamom, Cinnamon, Licorice
  • Chlorophyll: Green pigment in plants that is either fat-soluble or water soluble. Anti-cancer and anti-oxidant effects. Natural form in plants is fat-soluble and can stimulate red blood cell production (water soluble form often present in shops cannot). Water soluble form is not readily absorbed but has soothing effect on GI tract due largely to astringent qualities: abilities to attract water and also stimulate wound healing. Dietary sources include green leafy vegetables, broccoli, wheat grass juice and algae such as spirulina and chlorella 
  • Aloe vera: intestinal purgative that helps stimulate colon activity (without cramping). Useful remedy or preventative for constipation
  • Bioflavonoids: Phytonutrients. Primarily function as anti-oxidants with direct anti-tumor effects and immune enhancing properties. “Natures biological response modifiers” (Murray, 2005, p. 143). Actions in body are anti-inflammatory, anti-allergenic, anti-viral, anti-cancer properties, primarily working as anti-oxidants to protect cells. Food sources include: Fruits, especially darker fruits such as berries, cherries, citrus fruits; vegetables: including tomatoes, peppers, broccoli, onions, greens, parsley; legumes; green tea and red wine; ginkgo bilboa.
    • Flavonoid functions:
      • Save plants from environmental stress
      • Biological response modifiers, altering body responses to allergens, viruses, carcinogens
      • Anti-allergenic compounds modify and reduce all phases of allergenic response, inhibiting formation and secretion of inflammatory compounds that produce allergenic response
      • Protect against GI problems due to blocking formation of cancer causing chemicals (eg nitrosamines)
      • Increase Vit A levels within cells, decrease leakiness and breakages of small blood vessels, protect against free-radical damage, support joint structures
      • Prevent release and synthesis of inflammatory compounds (eg histamine) especially quercertin
        • Quercetin (in many foods and high in onions)
          • Anti-oxidant
          • Anti-inflammatory and promotes activity of hormones such as insulin
          • Useful in treating allergies


Digestion terms

  • Mechanical Digestion: function = to increase surface area of food for digestive enzymes and chemicals to work on
    • Chewing in mouth
    • Peristalisis of smooth muscle from esophagus to colon that moves food along the digestive tract
    • Churning action of stomach muscles that break down food into chime with the consistency of cream
  • Chemical Digestion: function = to break the bonds between large food molecules to make them small enough for absorption
    • Chemical mixing: HCl (Hydrochloric Acid) produced by parietal cells of the stomach breaks down food and activated digestive enzymes (pepsin which breaks apart protein) and assists in killing bacteria
    • Acid neutralization: Bicarbonate produced by mucosa cells of stomach protect stomach from HCl corrosion; Bicarbonate produced by Pancreas neutralizes chime thus protecting small intestine
    • Enzymes: secreted by Pancreas into Duodenum break apart bonds of carbohydrates (enzyme amylase splits them down to simple sugars), proteins (protease which digests links to leave simple amino acids), fats (lipase breaks them down to fatty acids and glycerol); brush border enzymes released by microvilli of small intestine complete the digestion of proteins and carbohydrates
    • Bile: secreted by liver either directly into duodenum or from the gallbladder (where it is stored and concentrated) emulsifies fats, cholesterol and fat soluble vitamins, breaking them into tiny globules with a larger surface area for fat splitting lipase enzymes to act on during digestion
    • Bacteria: living in large intestine ferment and break down food (fiber) and create vitamins in the process; they also produce fatty acids from fiber that provide fuel for intestinal cells of the colon as they absorb water and vitamins in stool
  • Hydrochloric acid: production by parietal cells of stomach as result of parasympathetic nervous reflexes in response to sight, smell or taste of food; also released due to physical stimulus of food entering stomach; rising HCL stimulates release of hormone gastrin that stimulates release of more HCl and protein digesting enzymes (pepsin). HCl functions are detailed above 
  • Chyme: mixture with the consistency of cream that is the result of mechanical and chemical digestion in stomach. Chyme exits the duodenum and enters the duodenum. Increased chyme in the duodenum and jejunum slows release of chyme from the stomach (as well as digestive processes in the stomach) 
  • Peristalsis: the wave like action of smooth muscle in the entire intestinal tract (from the esophagus to the rectum) that in involved in food propulsion 
  • Malabsorption: resulting from problems in breaking down food into absorbable molecules due to stress or activation of sympathetic nervous system that disrupts chemical and mechanical digestion, lack of chemical production of either HCl, enzymes or bile in chemical digestion, or lack of chewing. Furthermore, incompletely digested foods may cross intestinal lining leading to immune response, in turn causing inflammation and disrupted absorptive function of villi of intestine 
  • IBS (Irritable bowel syndrome): large intestine dysfunction associated with abdominal pain and distention, more frequent bowel movements, pain during bowel movements or relief of bowel movements, constipation or diarhea, excessive production of mucus in the colon, flatulence, nausea, loss of appetite, anxiety, depression. Causes include excessive stress and allergies (to foods such as mild and dairy products, corn, wheat, eggs, peanuts, chocolate) 
  • Probiotics: health promoting “friendly” bacteria in colon, as well as substances that promote growth and proliferation of these bacteria 
  • Dysbiosis: balance of bacteria in colon becomes wrong and unfriendly bacteria outnumber friendly bacteria (nb both are needed thus the need for balance). Dysbiosis may be caused by:
    • Putrefaction: low fiber and high fat diet causes bacteroides to flourish which stimulate enzymes to break down bile causing increase in tumor-causing particles and estrogen levels, and cancer of colon and breast (due to increased hormone levels: hormones in bile)
    • Deficiency: numbers of friendly bifidobacteria, lactobacilli and Escherichia coli dwindle contributing to IBS (Irritable Bowel Syndrome) and food intolerance
    • Fermentation: excess activity of friendly bacteria due to excess carbohydrate consumption leading to gas production and abdominal distention, flatulence, diarrhea, constipation
    • Sensitization: body develops allergic immune response to friendly bacteria leading to inflammatory bowel disease, connective tissue diseases and skin disorders
  • Yeast overgrowth: similar to dysbiosis – overgrowth of candida albancans in Large Intestine resulting in symptoms that effect all of body including genitourinary, endocrine, nervous and immune systems. Involves overgrowth of yeast and immune depletion or if normal lining of cells in colon are damaged leading to absorption of yeast cells. More common in women due to effect of estrogen, birth control pills, and use of anti-biotics. Characterised by flu like symptoms and malaise, as well as fatigue, immune system malfunction, depression, chemical insensitivities, digestive disturbances. Increased fiber and decreased sugar are preventative measures
  • H Pylori: bacteria that 50% of the world’s population are infected with. Infection may be person to person, via food contamination of restaurant cooks, or contamination of animals and animal meats
  • GALT (Gut Associated Lymphoid Tissue): 705 of immune system tissue in lining of GI tract and intestinal mucus. M-cells carry antigens to Peyer’s patches which enhance B and T cell proliferation, attachment of them to antigens, and activation of macrophages. Secretory IgA act as sentinels whose arousal by foreign substances signals cytokines to begin inflammatory process (to rid body of antigens) 

Adapted from:

Marieb, E.N. (2009). The essentials of human anatomy and physiology. San Francisco, C.A.: Pearson Education

Murray, M. (2001). Total body tune-up. Chapter 2. New York, N.Y.: Bantam Press

Murray, M. (2005). Encyclopedia of Healing Food. New York, N.Y.: Atria Books

Murray, M. (1998). The complete book of juicing. Roseville, CA: Prima publishing

Haas, E. (2006). Staying Healthy with Nutrition. Berkeley, Ca. Celestial Healing Arts.

Bland, J., Costarella, L., Levin, B., Liska, D., Lukaczer, D., Schlitz, B., Schmidt, M., Lerman, R., Quinn, S., Jones, D. (2004). Clinical Nutrition: A Functional Approach, Second Edition. Gig Harbor, WA: The Institute for Functional Medicine.

Lipski, L. A voyage through your digestive system


[1] Retrieved 4/15/2012 from http://www.supplementnews.org/wiki/gamma_oryzanol

[2] Adapted from: http://www.guidetohealth.com/library/herbs-for-health-and-healing/indigestion/

[3] Retrieved 4/15/2012 from: http://www.umm.edu/altmed/articles/slippery-elm-000274.htm#ixzz1s86Uawwr

[4] Retrieved 4/15/2012 from: http://en.wikipedia.org/wiki/Deglycyrrhizinated_licorice

[5] Adapted from: http://en.wikipedia.org/wiki/Boswellia

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