Carbohydrate Malabsorption

Malabsorption of any dietary sugar in a person with IBS, IBD or any functional gut disorder results in fermentation of the sugar with associated gas production and a potential laxative effect.

These processes may lead to abdominal symptoms including pain, flatulence, bloating, and altered bowel habits.

Other less common symptoms may include fatigue, nausea, heartburn, and urgency with bowel movements.

If you are suffering from these common gastrointestinal symptoms you should be screened for sugar malabsorption to determine dietary restrictions that will improve symptoms and quality of life. This is the important role of breath testing in diagnosing malabsorption

All patients undertaking breath testing benefit from seeing a specialist dietitian to receive instructions on how to best manage their symptoms through diet whilst maintaining nutritional adequacy.

carbohydrate malabsorption

Lactose Intolerance

Lactose, often described as the ‘milk sugar’, is present in many dairy foods. Digestion and absorption of lactose requires the enzyme, lactase, which resides in the brush border of the stomach. Lactase is reduced in many gastrointestinal conditions, such as Crohn’s disease and Ulcerative Colitis. Production of lactase also decreases with age, usually starting from early childhood. This is called lactase deficiency and it is a normal physiological process otherwise known as weaning. Adults who continue to have lactase activity are called lactase persistent. Certain ethnic groups are known to be at high risk of lactose intolerance as they produce low levels of lactase, including those of Asian, African and Mediterranean backgrounds.

Diagnosis of lactose intolerance does not necessarily require a dairy free diet. Depending on the severity of your condition, you may only need to reduce your intake of these foods, or you may require further restriction. This should be discussed with your dietitian. With the increasing availability of lactose free dairy products and the naturally low level of lactose in many dairy foods, managing lactose intolerance is easy and it doesn’t have to affect calcium intake.

Fructose Malabsorption

Fructose is known as the ‘fruit sugar’, but it is also found in some vegetables and honey. Fructose malabsorption is likely to occur due to an impairment of absorption in the small intestine. It is not fully understood why some people malabsorb the sugar, but if you have an underlying gastrointestinal condition such as IBS, Crohn’s disease or suffer symptoms of bloating, wind, abdominal cramps and altered bowel habits, breath testing for fructose will help to identify whether this is a trigger for your symptoms.

Diagnosis of fructose malabsorption does not necessarily require a fruit free diet. There are many fruits you can have such as bananas and kiwifruit, although the overall quantity of fruit may need to be adjusted. Patients with fructose malabsorption can absorb fructose in certain conditions, e.g. if there is glucose present in a food. Your tolerance to fructose and the degree of dietary restriction you require can be defined by your dietitian. Many people are now searching the internet for food lists in this area, but be aware that the research into this condition continues, with food lists changing frequently. As such we recommend specialist dietetic advice.

Sucrose Malabsorption

Sucrose is traditional table sugar used most commonly in Australian commercial products and in the household. Malabsorption of sucrose is caused by a reduced production of sucrase enzyme (sucrase-isomaltase deficiency) which is required to digest sucrose.

A low sucrose diet aims to reduce dietary sucrose and sucrose loading in soft drinks, cordials and sweets. The degree of restriction required will depend on your symptoms and the level of sucrose in your current diet. This can be assessed by consulting your dietitian.

Sorbitol Malabsorption

Sorbitol is a type of sugar found naturally in fruits such as stone fruits, and also used as an artificial sweetener in sugar free gums and mints. Sorbitol is poorly absorbed in the small intestine by everyone, and a sorbitol breath test will determine your ability to absorb a small load of sorbitol which will then determine whether dietary restriction of the sugar is required to improve gastrointestinal symptoms.

It is very useful to undertake a sorbitol breath test in conjunction with a fructose test. Many of the fruits safe on a low fructose diet are high in sorbitol, for example stone fruits, so it is important to understand your tolerance to both sugars. 

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