What is Sucrase Isomaltase Deficiency?
Backstory - How are Carbohydrates Digested?
Did you know that around 50% of the Western diet is made up of carbohydrates?
Carbohydrates are macronutrients that are bodies use for energy, and they can be considered either simple or complex.
Simple carbohydrates, often called simple sugars, are monosaccharides or disaccharides. Monosaccharides have one single carbohydrate unit, which can include glucose or fructose, and disaccharides have two unites, which can include sucrose, maltose, or lactose.
Complex carbohydrates are made up of multiple glucose (simple sugar) molecules and various structures and bonds, which can be referred to as polysaccharides. These can include starches, glycogen, and fibers.
Disaccharides and polysaccharides have to be broken down into monosaccharides for proper absorption, in order to give the body energy. In the final step of digestion, there are enzymes located in the brush border of the small intestine that break down these carbohydrates into single units, either glucose or fructose. Two of these enzymes are sucrase and isomaltase.
Sucrase is responsible for breaking down sucrose (aka table sugar) into glucose and fructose. Isomaltase is responsible for breaking down branched-chain dextrins (aka starches) into two glucose molecules. The sucrase-isomaltase enzyme complex helps our bodies break down sugar and the majority of starches for proper absorption.
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Sucrase-isomaltase Deficiency
The absence of sucrase-isomaltase, in cases of congenital sucrase isomaltase deficiency (CSID) and sucrase isomaltase deficiency (SID), can lead to poor breakdown and absorption of sugars and many starches.
CSID is known as “an inherited primary defect of sucrase-isomaltase caused by variants in the sucrase-isomaltase (SI) gene” (Chey et al.). This lead to either the absence of or reduced effectiveness of the sucrase-isomaltase enzyme complex. CSID is most commonly found in children.
SID refers to the non-genetic form of poor sucrase-isomaltase activity, whether from a reduced amount or reduced effectiveness of the enzyme. Typically, SID is found in adults and is due to intestinal damage, which can be caused by various conditions including villous atrophy (seen in inflammatory states), infection, and/or rapid transit.
The most common symptoms seen with CSID and SID include diarrhea (especially after a meal with sugars or starches), bloating, pain, and gas. For children, failure to gain weight and diaper rash may also occur.
What’s interesting about CSID and SID is that it can be commonly misdiagnosed as IBS-D, and many of the therapies for IBS-D won’t work fully for those with CSID/SID. As we standardize the diagnosis process for CSID/SID, we may be able to differentiate these diagnoses earlier, or see how prevalent an overlap is between these conditions.
Take Action
Do you think your symptoms could be due to CSID or SID? The first step to take is to talk to your gastroenterologist. Getting a diagnosis can be tricky, but they will be able to work with you on this.
If you’re a fellow dietitian, healthcare provider, or just interested in learning more about this condition, how it’s diagnosed, how it’s treated, and the role of the dietitian… join Dietitian Deep Dive for a 2 part SID Series November 2 and 9 here! This is a project I run alongside GI nutrition expert Kate Scarlata MS, RD.
Are you frustrated with your IBS symptoms? Do you desire to be confident in your food choices? Do you want to have a healthier relationship with your body and diet? Are you ready to take control of your IBS?
