Sorbitol breath test (sorbitol malabsorption)

Sorbitol (E 420) is a sugar alcohol. It occurs naturally in pears, apples, plums, cherries and dried fruit and is used as a sweetener in sugar-free chewing gum, sweets and diabetic products. In the sorbitol breath test, a fixed amount of sorbitol dissolved in water is drunk on an empty stomach; breath samples are then collected over several hours and analysed for hydrogen (H₂) and methane (CH₄). The combination with fructose is assessed by the fructose-sorbitol combined breath test. The breath gases themselves as well as the fructose and lactose breath tests are explained on their own pages.

What sorbitol does in the body

There is no dedicated transporter for sorbitol in the small intestine. It passes through the lining only slowly and incompletely, probably between the cells. What is absorbed is converted into fructose by the liver via the enzyme sorbitol dehydrogenase. The unabsorbed portion remains in the gut contents and osmotically holds water there. In the colon, bacteria ferment the sorbitol into short-chain fatty acids, carbon dioxide and hydrogen. Part of the hydrogen passes into the blood and is exhaled; methane-producing archaea such as Methanobrevibacter smithii use it to make methane. How much sorbitol is tolerated depends strongly on the amount. Sorbitol eaten at the same time also hampers the absorption of fructose.

Raised sorbitol breath test – what happens in the body?

If hydrogen or methane rises clearly after the drink, part of the sorbitol has reached the colon undigested and has been fermented there. The resulting gases stretch the gut – bloating, abdominal pain and wind are the consequence. The water bound in the gut makes the stool softer or even liquid. If methane predominates, gut transit is often slower; studies have linked methane with constipation. A very early rise in gas may also indicate that bacteria are already fermenting the sorbitol in the small intestine. Because the capacity to absorb sorbitol is limited, a rise is also observed in studies in many people without symptoms. What matters is therefore whether symptoms occur during the test.

Unremarkable sorbitol breath test – what does it mean?

If hydrogen and methane remain low during the measurement period, the sorbitol drunk was largely absorbed in the small intestine or fermented only slightly. Sorbitol malabsorption as the reason for symptoms is then less likely. Note that some people produce hardly any hydrogen because their gut flora quickly uses it up – this is why methane is always measured as well. Recent antibiotics, laxatives or a colonoscopy can temporarily reduce the number of bacteria and influence the result. Symptoms after foods containing sorbitol may also stem from the fructose contained in the same types of fruit.

The interpretation is given in your report.