Some of the intricately-folded sections of the small intestine secrete an amazing array of enzymes to digest the proteins, fats and carbohydrates we consume. The large intestine houses billions of beneficial bacteria that maintain the function of the entire intestine. They digest most forms of dietary fibre, producing essential fatty acids that feed the cells of the colon. They also make small amounts of some vitamins (mainly vitamin K, biotin, folate and B12). Research also shows that these amazing bacteria defend us against many infections and some types of cancer.
This article includes a brief general discussion of some gut problems. It is not intended to provide individual medical advice. That’s a task for your doctor.
Gas
Let’s start with something that is not usually a problem. As the bacteria in the large intestine go about their tasks, they produce gases. That is a normal and essential function of a healthy gut.
Some years ago, a gastroenterologist and I were concerned that many of our patients were reluctant to consume the high fibre diet we were prescribing because it increased gases, which they thought was a problem. We studied the frequency of gas emissions as there was little information about what was normal. On a typical Australian diet – which has less than the recommended 30g of dietary fibre a day – the average person passes gas 10-12 times a day. With a healthy high-fibre diet that may edge closer to 20 emissions. This normal and healthy function only requires a private place for the expulsion.
Lactose intolerance
Lactose is the naturally occurring sugar in milk, including human breast milk. Once they are weaned, many people’s tolerance to lactose slowly declines. This is not an allergy and a small amount of lactose (for example from a cup of milk spread over a few hours) actually helps some good gut bacteria survive. However, too much lactose from milk or ice cream can lead to passing gas 40 times a day, often with tummy pains. Most cheeses have very little lactose and will not cause problems. The bacteria that thicken yoghurt will also partially digest lactose and so natural yoghurt is unlikely to be a problem.
Coeliac disease
About 1-2% of people have an intestine that is damaged by gluten, a protein found in all types of wheat (including ‘ancient’ grains) as well as rye, barley and triticale. This is coeliac disease and sufferers must avoid every skerrick of gluten for life. Some also react to a similar protein in oats. A reaction to oats may also occur if the oats were processed in the same factory as gluten-containing grains.
Unfortunately, for those with genuine coeliac disease, it has become trendy for others to mistakenly think that they should also avoid gluten. As a result, many people serving in restaurants no longer take coeliac disease seriously. The trendiness of this issue has also led to many food companies producing a range of highly processed – and highly profitable – gluten-free foods. For most people, gluten is not a problem.
Irritable bowel syndrome (IBS)
Irritable bowel is a much more common problem. It is a non-specific condition with frequent pains in the tummy, constipation or diarrhoea (sometimes both, in an alternating pattern) and a general feeling of tummy discomfort. Some people also experience uncomfortable ‘bloating’ that isn’t just weak abdominal muscles. IBS is usually diagnosed once it’s clear other digestive diseases are not the problem. IBS is sometimes due to anxiety.
IBS is not dangerous, but can be unpleasant. For some people, it may be due to consuming too many foods containing FODMAPS (stands for Fermentable Oligosaccharides, Disaccharides, Monosaccharides And Polyols). The first three are natural carbohydrates. Polyols are sugar alcohols found naturally in some foods and also used as food additives. It’s the ‘fermentable’ bit that causes the symptoms.
Oligosaccharides occur in artichokes, asparagus, cauliflower, garlic, leeks, legumes, peas and onions. Wheat, rye, mushrooms, cashews and pistachios are also sources, as is inulin, often added to some yoghurts, cereals and drinks. The disaccharide that may cause problems is lactose, the natural sugar in milk. The monosaccharide is fructose, a sugar in fruit and honey and also produced during the digestion of sucrose (or regular sugar, which is made up of fructose and glucose). Polyols are found naturally in apples (apple juice is a major source), pears, cherries, lychees, mangoes, peaches and plums. Food additives sorbitol (420), mannitol (421), Isomalt (953), xylitol (967) and maltitol (965) are also sources.
Any reaction to FODMAPS is due to the quantity consumed. Small amounts are usually fine. Food processing can alter FODMAP content. For example, oligosaccharides in legumes pass into soaking and cooking water, so drained, rinsed canned legumes are less likely to cause problems. Genuine sourdough breads have lower levels of FODMAPS because the longer exposure to yeasts breaks down some of the fructans from the wheat.
NOTE: IBS is quite different from Inflammatory Bowel Diseases – which includes the serious conditions ulcerative colitis and Crohn’s disease.
Diverticulitis
Diverticula are small pouches that form in weak spots in the walls of the lower, slightly narrower, left side of the colon. They are rarely seen in countries where the diet is high in dietary fibre. A high meat diet may also be responsible.
The condition of having diverticula is called diverticulosis. Most people are unaware of it, unless the diverticula become infected or inflamed, which then causes diverticulitis. This may be accompanied by severe pain, fever and changes in bowel function, usually with small pellet-like stools. Mild cases usually settle with rest, a healthy diet, and possibly antibiotics. If the symptoms do not improve, hospitalisation with stronger antibiotics, and sometimes surgery, may be needed.
In the past, it was thought that people with diverticulosis should avoid foods such as nuts, seeds, corn, tomatoes, passionfruit, raspberries, figs and cucumbers. There is no evidence to back this belief. Diverticulosis is prevented and treated with a high fibre diet. Diverticulitis is treated with antibiotics to kill the bacteria that have caused the infection. Once the acute attack has passed, a high-fibre diet should be resumed. That means eating fruit, vegetables, legumes, wholegrains, as well as nuts and seeds. It makes sense for everyone to chew nuts before swallowing them.
Take home message
The greatest dietary deficiency in Australia is a lack of dietary fibre. Previously known as ‘roughage’, fibre was once thought to be simply ‘stringy’ waste that could not be digested and so was simply excreted. Nutritional science overturned that idea years ago. The many types of dietary fibre as well as starches known as resistant starch are digested by good bacteria and a truly healthy diet is always high in dietary fibre. As dietary fibre and resistant starches are found only in plant foods, this is yet another reason to give these foods the star role in our daily diet.
