Sugar and Starch Free, No Problem

IBS impacts more than 10 percent of the general population, and it’s not just a lifestyle burden; but it is also a major economic burden on patients who experience it. They will pay a median of $13,288 for their healthcare, compared to $5,999 for patients without it, according to a 2024 study published in PubMed.

People diagnosed with CSID are often originally misdiagnosed as IBS patients, when in actuality, medical professionals should be targeting their patients’ inability to digest sucrose and certain starches, such as maltose and isomaltose.

In my own experience, what happened was I was misdiagnosed as an IBS patient and then placed on a low-FODmap diet, which did not target any of my issues; instead, I was eating foods that were making my symptoms worse. The primary therapeutic strategy should have been to eliminate sucrose and starches, and then ensure I was getting the right alternative carbohydrate to bypass my defective enzymes. It wasn’t until a physician’s assistant, fresh out of college, actually tested me for CSID because she had just finished learning about it in her required nutrition course. That diagnosis was the first time I actually found relief through working with a dietician and doing the elimination diet.

What is the Low-FODmap diet?

It was developed for irritable bowel syndrome to help target short-chain carbohydrates, so anything fermentable and poorly absorbed in the small intestine: oligosaccharides, disaccharides, monosaccharides, and polyols. The diet helps reduce the osmotic load and bacterial fermentation in the colon for patients by restricting foods like wheat, onions, garlic, certain fruits, dairy, and artificial sweeteners. It doesn’t specifically limit sucrose or the starches that can trigger CSID, so a patient could still consume foods rich in sugar and starch, such as rice and potatoes. And some low-FODmap staples, like nuts, gluten-free breads, and lactose-free dairy products, might still contain hidden sucrose and starches that are problematic for those individuals with CSID.

Another point of the low-FODmap diet is that it’s intentionally a short-term solution. You would complete an initial elimination phase, then reintroduce foods, identifying personal tolerances for each new addition. For CSID, however, enzyme deficiency is permanent, and therefore a patient will need to follow essentially a lifelong safe dietary pattern, which requires consistent avoidance of sucrose and specific starches. A low-FODmap plan can be nutritionally off-balance; it’s low in fiber, calcium, and certain vitamins if it’s not carefully managed, and CSID patients already frequently have limited carbohydrate options, which would add yet another restriction and risk for more deficiencies, especially in children and teens who need a diet to help support their growth.

The Bottom line: Both diets might share a similar goal of helping with symptom relief, but a low-FODmap regimen is not going to address the core issue of an enzymatic defect in a patient with CSID. They need a diet tailored to their nutritional needs: a low-sugar, low-starch plan supplemented with enzyme replacement therapy.

Disclaimer: This post is for educational purposes only and doesn’t replace any personalized medical advice. If you think you have CSID, consult a gastroenterologist or a registered dietitian experienced in metabolic disorders before making major dietary changes.