Causes of Irritable Bowel Syndrome

Irritable Bowel Syndrome (IBS) is a chronic Functional Disorder. IBS is not a bowel disease like Ulcerative Colitis, Crohns Disease or diverticulitis which are identified in a colonoscopy. However, in common with other non-communicable diseases, it is due to an interaction between genetic predispositions and environmental causes, such as nutrient deficiencies in what we eat and toxins in what we eat. 

  • Factors that predispose to Irritable Bowel Syndrome.
  • Factors that precipitate or trigger IBS symptoms.
  • Factors that perpetuate IBS over time.
  • Factors that are associated with IBS and which may share the same underlying mechanisms.

Factors that Predispose, Precipitate & Perpetuate IBS

A comprehensive reading of the literature suggests that the major predisposing factors to IBS may be interactions between genetic weaknesses, nutrient deficiencies and environmental toxins resulting in dysfunctional cellular structures and function, not only in the gut but quite possibly in the brain. Nutrigenomics is the scientific study of the interaction between the genetic code (genes) and Nutrients. Some of the Modern Diseases and Functional Disorders, including IBS, may only surface when genetic weaknesses, which have been in the family tree for hundreds if not thousands of years, interact with nutrient deficiencies in the modern diet and toxic substances in our food chain and environment.

Minor genetic weaknesses, poor dietary profile, low nutrient contents in food, inadequate nutrients absorbed from the diet, abnormal comensal bacteria profile, gut infections from enteric pathogens or viruses, environmental toxins can all conspire to cause, trigger or maintain IBS.

Genetic Weaknesses

The human genome contains countless variations, which accounts for the huge variability in personalities, looks, colour, height, weight and health states in the world population. There is substantial evidence that some indigenous people who have been examples of good health until 30-40 years ago (e.g. the Inuits and coastal Japanese) have developed all the modern diseases since changing their healthy indigenous diets and lifestyle to a western one. Professor Andrew Stoll, head of Psychiatric Pharmacology at Harvard Medical centre reviewed some of this evidence in his book "The Omega 3 connection".

Nutrient Deficiencies

When we say nutrients we don't mean diet. Diet is the food that we eat, while nutrients are what we are able to extract from our diet to feed the billions of cells that make up the body and its various systems. Food (e.g. meat, fruit and nuts) have complex structures that have to be broken down by digestive enzymes and intestinal bacteria and denatured into basic nutrients (e.g. amino acids, carbohydrates and sugars, fats, vitamins and nutritional minerals).

It took millions of years of evolution (the process of adapting to the environment through natural selection and survival of the fittest) for us to evolve into modern humans. By the end of the Paleolithic period (which ended 10,000 years ago) we were perfectly adapted to the Paleolithic diet and a natural environment. We harboured specific species of bacteria in our gut and kept them in a symbiotic homeostatic state that was suited to good intestinal and general health and longevity. During the middle ages, food supply to the cities was sparse, diseases were rife and life expectancy dropped to around 40 years. In the last 100 years since the industrial revolution, mass transportation and modern agriculture, our diet and conditions have changed drastically. Health has improved and longevity increased.

However, in the last 60 years we have escalated the introduction of chemical fertilisers that grow cell structures in plants and fruit without providing the micronutrients contents in the food. Apricots or most other fruits from a suburban backyard are usually much tastier these days than fruit from a supermarket. The lack of taste reflects the lack of nutrient contents (nutritional minerals and vitamins). This is probably because we have farmed the same soil and grown fruits from the same orchards for so long. We have also introduced food processing, packaging and storage methods that reduce the nutrient contents of foods. The 1995 Australian Bureau of Statistics Nutritional Survey found that most Australians do not get their recommended daily intake (RDI) of Zinc. Now Zinc is involved in over 300 biochemical pathways in the body and is as important as Iron. Dietary deficiency can lead to a multitude of functional deficiencies. Most Clinical Nutritionists believe that the RDI is too low anyway, as it is based on the minimum estimated requirements for disease prevention, not on requirements for optimum health.

The World Health Organisation and the NHMRC in Australia have published recommendations that the Omega 3 contents of our food intake is inadequate. Currently, on a typical good average western diet we consume a ratio between 20:1 to 40:1 Omega 6 to Omega3 fatty acids. Estimates in a Paleolithic diet are 1:1 to 2:1. Many studies indicate that Omega 3 fatty acids (which make up 40% of the dry volume of brain cells and is present in the protective membrane of every cell in our body) are severely lacking in our modern diet, due to a reduction in fish consumption.

Our modern diet contains high levels of grains, refined carbohydrates, sugar and dairy products. None of these were on the diet of Paleolithic hunter gatherers and none were on the diet of the indigenous people who were so healthy and devoid of modern diseases until they changed to a Western Diet.

USDA My Pyramid
USDA My Pyramid

The United States Department of Agriculture (USDA) originally designed the "Food Pyramid". According to US federal regulations, the panel that writes the dietary guidelines must include nutrition experts who are leaders in pediatrics, obesity, cardiovascular disease, and public health. Selecting the panellists is no easy task, and is subject to intense lobbying from organisations such as the National Dairy Council, United Fresh Fruit and Vegetable Association, Soft Drink Association, American Meat Institute, National Cattlemen's Beef Association and Wheat Foods Council.

Consequently, over the years Clinical Nutritionists have criticised the USDA Food Pyramid for pandering to Agricultural and Commercial interests. In 2005, the USDA revised the Food Pyramid, making several fundamental changes. However, the Harvard School of Public Health criticised the FDA for not having gone far enough and produced its own Food Pyramid.

Commensal Bacteria and Enteric Pathogens

Commensal bacteria are the community of bacteria that "normally"live in the gut in a symbiotic relationship with people as hosts. They break down and denature complex foods into amino acids, carbohydrates, sugars, fats, vitamins and nutritional mineral compounds that are essential and/or beneficial for our cells. Antibiotics, preservatives, some medications and toxins can alter the balance of commensal bacteria causing a condition known as Intestinal Dysbiosis. Intestinal Dysbiosis has been linked to IBS and Inflammatory Bowel Diseases (IBD), such as Crohn's Disease and ulcerative colitis. Some commensal bacteria produce amines and toxins. When these bacteria are in their normal numbers, the body's systems can handle these amines and toxins, as we have done for millions of years. However when the bacteria is overgrown sometimes a few thousand fold, these amines and toxins can cause cognitive deficits, depression, anxiety, physical and mental fatigue. They have been shown to invade the gut wall and trigger inflammation and autoimmune reactions.

Enteric pathogens are bacteria and parasites that do not normally reside in our gut and that can cause disease when they infest the gut. These are the pathogens that General Practitioners may test for when they order a faecal parasitology test (Multiplex PCR) following a bout of gastroenteritis.

Environmental Toxins

We have also added toxins to our food chain (herbicides, insecticides, antibiotics, preservatives, colourings and other additives). Nature locks away toxic heavy metals such as Lead, Cadmium, Mercury and Arsenic into rocks and compounds that are not bio-available. We mine them, extract them and use them in our daily lives, and they permeate the environment and our food chain. All of these did not exist in the food chain of our evolutionary ancestors. Consequently, those of us less genetically able to adapt to these changes get sick with the Modern Diseases and Functional Disorders, including IBS.