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Celia Stewart Nutrition


Your digestive system is a tube that runs down the centre of your body. If you imagine yourself as a donut then your gut is the hole down the middle. Your gut is one of your main interfaces with the outside world and it has many functions. It is responsible for digesting and absorbing all the nutrients your body needs to function at its best. It serves as a physical barrier against invading organisms. It contains 70% of your immune system. It is one of the main routes for excreting toxins from your body. In short it is key to good health.

As well as the typical localised manifestations of heartburn, bloating, gas, indigestion, constipation and diarrhoea, a malfunctioning gut can cause symptoms throughout the body. These can include problems with your skin, poor energy levels and low mood, muscle and joint aches and pains, and symptoms of nutritional deficiency.

Digestion begins in the mouth. Chewing your food until it is reduced to pulp not only allows digestive enzymes in the mouth to do their job but also signals to the stomach that food is on its way which stimulates stomach acid production. The digestive juices of the stomach initiate the production of other digestive enzymes by the pancreas and the small intestine.

Stomach acid is required for the first step in protein digestion and to allow valuable minerals such as magnesium, calcium and iron to be made available for absorption.

The small intestine has a delicate lining with a very large surface area designed to digest food and then to absorb the end products. These are then distributed via the liver to the blood system and around the body to where they are needed. Undigested remains pass into the large intestine, or colon, where water is absorbed before excretion.


Low stomach acid
This will result in poor digestion in the stomach itself and also poor stimulation of other digestive enzymes and poor digestion further down the digestive tract. Poor digestion in the stomach can lead to nausea, heartburn and, belching, among a host of other symptoms.

Small intestinal bacterial overgrowth
Incomplete digestion in the small intestine can occur due to low stomach acid or to poor production of digestive enzymes. In either situation it can create further problems such as ‘small intestinal bacterial overgrowth’. If the small intestine does not fully digest the food we eat then something else will – in this case unwelcome bacteria and yeasts. Normally the small intestine contains fewer bacteria than the large intestine. In the small intestine these microbes have access, not to the remains of digestion, which are available to bacteria in the colon, but actually to an abundance of fresh food. This results in excessive fermentation and production of gas and toxins. Low stomach acid can contribute to this directly as normally it creates an acidic environment in the first part of the small intestine discouraging growth of bacteria and yeasts. Small intestinal bacterial overgrowth is thought to be a common reason for the symptoms of IBS (Pimental et al 2005).

Inflammation and increased intestinal permeability. The surface of the small intestine is equivalent in area to a tennis court. It is responsible for two very important functions – digestion and absorption. It is true that ‘you are what you eat’, but more importantly ‘you are what you absorb’. If the delicate surface of the small intestine is damaged then its efficiency will be reduced. Food allergens, such as gluten (Drago et al 2006), and some bacteria and yeasts or parasites, and NSAID painkillers can create inflammation in the small intestine. Inflammation can lead to increased intestinal permeability or leaky gut (Galland 1995). The lining of the small intestine, which normally produces enzymes and acts as a barrier to large molecules of food and toxins, and acts as an absorptive surface for digested foods, loses its ability to perform these functions effectively. Leaky gut can therefore lead to poor absorption of digested food, and vitamins and minerals, leading to symptoms of malabsorption and malnutrition. Furthermore a leaky gut allows the passage of bacterial and other toxins and inflammatory chemicals into the blood stream and the rest of the body. Diseases associated with leaky gut include acne, arthritis, autoimmune diseases, autism and cancer (Galland 1995).

Gut bacteria make up about 3 pounds of your body weight and 90% of the cells in our bodies. When an optimal mix, of ‘good’ and ‘bad’ bacteria are present the gut exists in a state of symbiosis. Dysbiosis describes a disruption of the normal bacterial microflora of the intestines due to a lack of beneficial or probiotic bacteria or an overgrowth of harmful bacteria or fungi. Many factors can disrupt the normal microflora such as antibiotics, which kill beneficial bacteria. Low stomach acid contributes to dysbiosis by failing to inactivate ingested harmful bacteria. Stress can influence the intestinal environment favoring harmful bacteria. Imbalanced diets containing too much fat or carbohydrate and sugar encourage the growth of unwelcome bacteria or yeasts. Intestinal bacterial or parasitic infections can upset the balance. Drugs such as NSAIDS which damage the intestinal lining or steroids which suppress the immune system and stimulate fungal growth lead to dysbiosis. Slow transit time, or constipation, encourages the proliferation of bad bacteria. Dysbiosis can result in gastrointestinal symptoms such as bloating and indigestion, malabsorption, diarrhoea, constipation or IBS or inflammatory bowel disease.

Gut bacteria are now believed to influence weight gain. Two bacterial phyla, Firmicutes and Bacteroidetes, are the most predominant in the gut. Firmicutes are found to absorb more calories from food thereby leading to weight gain. Individuals with a greater proportion of Bacteroidetes are found to be slimmer than those with more Firmicutes. Current research into obesity is looking at ways to influence this balance to promote weight loss. For instance it is found that a diet higher in fibre increases the proportion of Bacteroidetes.

In a healthy gut beneficial, or friendly, probiotic bacteria such as Lactobacillus (predominantly in the small intestine) and Bifidobacteria (predominantly in the large intestine or colon) do us many favours. They physically crowd out unfavorable bacteria and yeasts by creating an acidic environment and by producing antimicrobial substances, which protect us from food poisoning and dysbiosis. They produce vitamins that we need and compounds that contribute to the health of colon cells. They aid digestion. Lactobacillus organisms produce an enzyme, lactase, which helps digest dairy products. Bifidobacteria produce substances which stimulate peristalsis in the colon helping with motility disorders. Probiotics also modulate the immune system (Pagnini et al 2009) and can increase your resistance to common infections and reduce the likelihood of allergy development (Johannsen & Prescott 2009). They also reduce inflammation in the digestive tract, which is believed to be the source of chronic inflammation associated with many diseases (Liu et al 2007).

  • Chew your food well and try to relax around mealtimes to encourage normal stomach acid and digestive enzyme release.
  • Increase your fibre intake from fruit and vegetables and wholegrains. Fibre feeds good bacteria, and stimulates healthy peristalsis.
  • Reduce saturated fats and animal produce which encourage the growth of unfavourable bacteria.
  • Avoid sugar and refined carbohydrates which also encourage the growth of bad bacteria and yeasts.
  • Drink 6-8 glasses of water a day to encourage elimination.
  • Avoid foods to which you are sensitive.

Digestive problems are many and varied. Nutritional therapists can help to unravel the root causes of your digestive symptoms and recommend solutions to improve them naturally.


Barbara G Stanghellini V De Giorgio R Corinaldesi, R (2006). Functional gastrointestinal disorders and mast cells: implications for therapy. Neurogastroenterology and motility 18(1): 6-17

Drago S El Asmar R Di Piero M Grazia CM Tripathi A Sapone A Thakar M Iacono G Carroccio A D’Agate C Not T Zampini L Catassi C Fasano A (2006) Gliadin, zonulin and gut permeability: Effects on celiac and non-celiac intestinal mucosa and intestinal cell lines. Scandinavian Journal of Gastroenterology 41(4):408-419

Galland L (1995) Leaky Gut Syndromes: Breaking the Vicious Cycles Townsend Letter for Doctors (online) Last accessed 22.02.2012 at

Johannsen H Prescott SL (2009) Practical prebiotics, probiotics and synbiotics for allergists: how useful are they? Clinical and Experimental Allergy 39(12):1801-1814

Liu Z Li N Neu J (2007) Tight juncions, leaky intestines, and pediatric diseases Acta Paediatrica 94(4):386-393

Pagnini C Saeed R Bamias G Arseneau KO Pizarro TT Cominelli F (2010) Probiotics promote gut health through stimulation of epithelial innate immunity Proceedings of the National Academy of the United States of America 107(1):454-459

Pimental M Evelyn J Chow BA Lin HC (2005) Normalization of Lactulose Breath Testing Correlates With Symptom Improvement in Irritable Bowel Syndrome: A Double-Blind, Randomized, Placebo-Controlled Study The American Journal of Gastorenterology 98(2):412-419

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