How to have a Happy Tummy - the process of digestion

If you are not feeling happy and contented after a meal perhaps your digestive system needs some support. Symptoms of bloating, colic, indigestion, nausea, constipation or diarrhoea can often be resolved through dietary changes and the use of natural supplements. 

It may help to understand the process the body goes through to utilize the energy obtained from food and allow a clearer understanding what can go wrong.

The digestive process

Digestion involves both a mechanical and chemical action and begins in the mouth with the process of chewing and enzymes. 

Chewing mixes foods making smaller particles and coating them with digestive enzymes which begin the digestive process of carbohydrates and fats. The mouth also contains active oral microbes which are important for digestion and overall health.[3] 

• Chew food completely to begin the digestive process.

The pharynx moves food (swallowing action) down the oesophagus tube which propels it into the stomach, lubricating it on the way. The oesophagus sphincter allow food to pass from mouth to oesophagus and then from oesophagus to stomach preventing backflow.

• A weak oesophagus spincter can lead to stomach acid leaking into the oesophagus - referred to as acid reflux 

The stomach adds gastric juices and mixes and churns food to form what is called chyme. Hydrochloric acid in gastric juice breaks down food and protein digestive enzymes cleave proteins. The acidic gastric juice also kills harmful bacteria. Intrinsic factor is secreted for the digestion of vitamin B12. Active microbes are present. The chyme is released into the duodenum (small intestine). The pyloric sphincter allows the passage of chyme from stomach to small intestine and prevents backflow. 

• Stomach acid is needed to breakdown food. Too little acid reduces this process. Aging, zinc deficiency and some medications can reduce stomach acid. 

The small intestine absorbs products of carbohydrate, protein, lipids and nucleic acids along with vitamins, mineral and water through much enzymatic activity. Chyme is propelled along by an involuntary process called peristalsis, a sequence of alternating waves of contraction and relaxation performed by smooth muscles of the alimentary wall, mixing chyme with juices as it moves along.

The pancreas manufactures enzymes to digest nutrients which provide energy. Bicarbonate is released which neutralizes acid which has entered the small intestine from the stomach.

• Insufficient enzymes can reduce food breakdown and result in digestive disorders. 

The liver manufactures bile salts (detergent-like substances) which are needed for the digestion of fats. Bile is stored in the gall bladder until needed. The Ileocecal valve (sphincter) allows passage of food from small into large intestine, preventing backflow.

• Insufficient bile flow can reduce the digestion of fats and absorption of fat-soluble vitamins – A, D, E and K. Improving bile flow can help reduce cholesterol levels.

The large intestine (colon) reabsorbs water and minerals and passes wastes (fibre, bacteria and unabsorbed nutrients) along with water to the rectum where it is stored until elimination.

Hormones are also involved in the digestive process

• Gastrin is the main digestive hormone of the stomach which is secreted in response to the presence of food and stimulates the secretion of gastric acid by parietal cells of the stomach mucosa.
• Secretin is produced by the duodenum which stimulates a watery solution of bicarbonate by the pancreas.
• Cholecystokinin (CCK) stimulates the secretion of pancreatic enzymes and bile from the liver – and bile release from the gallbladder.
• Gastric inhibitory peptide inhibits gastric secretion and slows gastric emptying and motility. [1],[2]

Common digestive disorders

• Diseases and disorders of digestion - hiatus hernia, gastritis, peptic ulcers
• Small intestinal disorders – duodenal ulcers, maldigestion, malabsorption
• Large intestinal disorders – constipation, diverticular disease, haemorrhoids
• Liver and pancreatic disorders can affect their ability to deliver pancreatic enzymes and bile to the small intestine – jaundice, acute pancreatitis and gallstones
• Leaky gut (intestinal permeability)
• Food allergies and intolerances
• Flatulence

Aging and the digestive process

Aging can pose its own set of problems when it comes to food. Aging can affect many parts of the digestive process resulting in concerns such as appetite suppression and constipation.

• Taste buds can become less sensitive reducing the taste of food - often noted when salt is used in excess due to a lack of taste. Deminished taste can take away the desire for food – leading to reduced appetite.
• Tooth loss, oral pain and reduced saliva production can make chewing and swallowing difficult.
• Digestion can be slowed due to reduced tone and strength of alimentary muscles.
• Sensory nerves are dampened slowing transmission of messages which are needed to release enzymes and hormones for digestion.

How to have a happy tummy

The diet should be attractive, desirable and healthy. The eating experience – anticipation, preparation, sight and aroma initiate the digestive process even before taste and texture are enjoyed – salivary and gastric secretion - that mouth-watering experience.

Swallowing food continues salivation, initiates peristalsis, and gastric receptive relaxation – readying the stomach for food. Solid food particles activate digestive activity.

The un-absorbed residue from food (fibre) serves as nutrients for microbiota in the colon supporting digestive function and health.  

Circadian rhythms regulate digestion, absorption and motility. Any disruption of circadian rhythms can lead to the promotion of and/or exacerbation of gastrointestinal disorders and diseases.

• Eat at the same times every day to follow the body's natural rhythm [4]
• Don't eat late 
• Chew food slowly and thoroughly
• Relax while eating [5]
• Eat when hungry - avoid snacking
• Don't eat too much

Foods which support digestive function

Fruit contains compounds such as fibre, vitamins and minerals which can aid digestion. For example:

• Papaya contains papain a digestive enzyme which helps the digestion of protein.
• Apples are rich in a soluble fibre called pectin.
• Bananas are rich in fibre and a substance called inulin that stimulates the growth of good bacteria in the gut.
• Avocado is a superfood packed with fibre and essential nutrients to promote healthy digestive function. 

Vegetables and salads provide vitamins, minerals, plant enzymes and fibre.

Wholegrains and legumes add fibre which add bulk to the stool reducing constipation and offer prebiotic food for healthy gut bacteria. [6]

Fibres – such as chia and flaxseeds, work like prebiotics supporting the growth of healthy bacteria. Fibre promotes regular bowel function and healthy stools. [7]

Fermented foods such as yoghurt, sauerkraut, kefir, kombucha, kimchi, natto and miso contain probiotics help to increase healthy gut bacteria. [8]

Don't forget the water to keep things flowing. 

Add some Spice not only do spices add to the aroma and taste of food, but many spices aid digestion. For example:

• Ginger helps digestion by speeding up the process that moves food from the stomach into the upper small intestine.
• Turmeric helps with bile flow.
• Chilli promotes digestion.
• Cinnamon helps reduce blood sugar.

Supplements

Supplements which aid digestion.

Zinc helps the production of digestive enzymes. A deficiency of zinc can result in loss of taste or smell, reduced appetite, and diarrhoea. [9]

Digestive enzymes can assist with the breakdown of foods when the body's own production of enzymes is lacking.

Ginger (Zingiber officinalis) - the warming action of ginger helps speed up the digestive process. 

Milk thistle (Silybum marianum) - supports the action of the liver. 

Globe artichoke (Cynara scolymus), Dandelion (Taraxacum radix) roots, Turmeric (Curcuma longa) are beneficial for liver and gallbladder function, promoting the flow of bile and reducing symptoms of indigestion. 

Psyllium husks, slippery elm, chia seeds, linseeds are good fibres to support bowel function.

Probiotics and prebiotics enable the process of digestion and increase the assimilation of the nutritional components. [10]

Digestive upsets

Ginger (Zingiber officinalis) for nausea and vomiting; flatulence, colic, dyspepsia and anorexia (loss of appetite).

Peppermint (Mentha x piperita) is helpful for flatulence, indigestion, colic, nause and symptoms of irritable bowel (IBS). Peppermint can help the gallbladder for cholecystitis (gallbladder inflammation) and cholelithiasis (gallstones). Peppermint oil capsules are reduce spasms and symptoms of IBS by relaxing the intestines. 

Chamomile (Matricaria recutita) can help with nervous dyspepsia, constipation and diarrhoea, IBS, gastric ulcers, indigestion, colic and flatulence.

Liquorice (Glycyrrhiza glabra)  is beneficial for its soothing and healing action on the mucosa. It aids the healing of gastric and duodenal ulcers, reduces spasms and gastritis and prolongs the life of stomach surface cells (antipepsin effect). [11]

The information provided is not intended to be used for diagnosis or treatment. If you are experiencing any health concerns, please consult your doctor for advice.

References

1. Whitney, Eleanor Noss; Cataldo, Corinne Balog; Rolfes, Sharon Rady; 2002, Understanding Normal and Clinical Nutrition 6th Edition, Wadsworth/Thompsons Learning, Australia
2. Food, Eating, and the Gastrointestinal Tract https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7231022/
3. Oral microbiome and health https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6605021/
4. Circadian rhythms: a regulator of gastrointestinal health and dysfunction https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6533073/
5. Mindful Eating: A Review of How The Stress-Digestion-Mindfulness Triad May Modulate And Improve Gastrointestinal And Digestive Function https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7219460/
6. Prebiotic Potential of Cereal Components  https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8535731/
7. Fiber and Prebiotics: Mechanisms and Health Benefits https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3705355/
8. Microbiological, technological and therapeutic properties of kefir: a natural probiotic beverage https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3833126/
9. Zinc and its importance for human health: An integrative review https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3724376/
10. Probiotics: Versatile Bioactive Components in Promoting Human Health https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7560221/
11. Fisher, Carole; 2009, MATERIA MEDICA OF WESTERN HERBS, Vitex Medica, New Zealand