What is CSID?
Congenital sucrase-isomaltase deficiency (CSID) is a genetic condition that affects the body’s ability to digest certain sugars.
Sucrase and isomaltase are enzymes produced in the lining of the small intestine to break down sucrose and maltose/isomaltose (starches). But with this condition, there is a relative deficiency of these enzymes. Therefore, when a person with CSID consumes sucrose or maltose they may experience unpleasant gastrointestinal symptoms.
The most common symptoms are loose bowel movements or diarrhea and bloating. Although some people may experience vomiting as well.
A familiar way to think about CSID would be to compare it to lactose intolerance. Lactose intolerance occurs because of a lack of lactase enzyme in some people which reduces their ability to break down lactose and digest it without symptoms.
In fact, lactose intolerance can often occur alongside sucrase-isomaltase deficiency.
CSID usually becomes apparent in infancy when someone is first introduced to fruits and grain foods. After ingestion of sucrose or maltose, there will be a fairly quick reaction leading to cramps, bloating, flatulence, and/or diarrhea.
These symptoms can lead to malnutrition in infants and a failure to thrive so having a diagnosis and management strategy as soon as possible is incredibly important.
Diagnosis of CSID can be done using a disaccharidase assay. This involves taking a small tissue biopsy from the small intestine to test the levels of sucrase, maltase, and lactase present.
As people with CSID approach adulthood, they are more likely to be able to tolerate sucrose and maltose.
CSID Treatment & Management
CSID cannot be cured. Therefore, nutritional management is often the first-line strategy. Hopefully, as a person gets older, their body will produce more of these enzymes but that is not always the case.
There is no one size fits all approach to CSID. This is because everyone with CSID will have differing levels of enzymatic deficiency and therefore different tolerance levels.
Sucrose, maltose, and isomaltose are found in such a wide variety of foods that it would be almost impossible to completely eliminate them from your diet. However, they can be limited to stop symptoms from occurring.
Sucrose is often found in the form of table sugar which can be added to foods such as soft drinks, biscuits, and yogurt. There is also naturally occurring sucrose found in fruit. Typically, a person with CSID will have the hardest time digesting sucrose, particularly in low fiber, processed foods with added sugar.
Maltose and isomaltose are predominantly found in starchy foods. This includes grains such as rice and bread as well as starchy vegetables like potatoes and corn. Some individuals with CSID will be able to tolerate a regular amount of starchy foods, some will have to limit these foods and others may have to completely eliminate these foods from their diet.
Approximately 60% to 80% of starch digestion in the small intestine is regulated by sucrase-isomaltase. But 20% to 40% is regulated by maltase-glucoamylase. So for the most part, many people can tolerate some amount of starchy foods.
How To Evaluate Your Sucrose & Starch Tolerance
The frustrating thing about CSID treatment is that there is not a set process for determining your tolerance to certain foods.
CSID is rare, so unlike something like FODMAP-related IBS, it is less well documented online and has far fewer resources available.
So I am going to run you through my personal approach as a dietitian which I use with my clients.
STEP 1: Disaccharide Free Diet
I often start with a strict disaccharide-free diet which eliminates most sucrose, starch, and lactose from one’s diet.
This is followed for a minimum of two weeks but can be up to four. Basically, it should be done until symptoms have resolved.
Note that if you know that you do not have any issues digesting lactose, higher lactose dairy foods can remain in your diet during this process.
|FOOD GROUP||FOODS RECOMMENDED||FOODS TO AVOID|
|Fats||Pure vegetable oil − Canola, Corn, Flaxseed, Olive, Safflower, Sunflower|
Margarine or diet spreads without whey or milk solids
Lard, meat drippings
|Butter Margarine with whey or milk solids|
|Milk and Milk Products||Hard cheeses such as cheddar|
Unsweetened soy or nut milk
Unsweetened lactose free milk
|All except those listed to the left|
|Fruits||Fresh, frozen, canned in own juice: |
Berries: blackberry, blueberry, cranberry, gooseberry, loganberry
|All except those listed to the left including:|
|Vegetables||Fresh, frozen, canned with additives, added sauces, or added butter or margarine:|
Parsnip Peppers (green & red)
Asian green eg. Bok Choy
|All except those listed to the left including:|
All legumes (black beans, chickpeas, lentils etc)
Potato (all types)
Squash (all types)
|Grains||None||Flours made with grains |
|Meat and Meat Substitutes||Lamb |
Poultry: chicken, duck, turkey
|Meats that are: Processed, Breaded, Smoked, Cured, Canned |
Eggs with added milk, flour, or sugar
|Nuts & Seeds||None||All, including: |
|Sugars & Sweeteners||Glucose |
Fructose (fruit sugar)
Sugar substitutes (if lactose free, in moderation): Aspartame, Cyclamate, Saccharine
|Sucrose (table sugar) |
Lactose (milk sugar)
Maltose (grain sugar)
Foods with added sugars Syrups
*Spices and herbs can be enjoyed freely
STEP 2: Reintroduction & Testing
There are many ways to go about the testing phase, however, my recommended process would be to introduce one food every other day in a small, moderate, and high quantity or until symptoms occur.
Lactose tolerance is determined by introducing dairy products and milk. Sucrose tolerance is determined by introducing fruits, nuts and seeds, and finally sugars. Maltose tolerance is determined by introducing grains, especially “white” grains and flours, legumes, and starchy vegetables.
Below is an example testing schedule:
|Food Being Tested||Day 1||Day 3||Day 5|
|Week 1: Lactose||½ cup of cow’s milk||1 cup of cow’s milk||2 cups of cow’s milk|
|Week 2: Naturally occurring sucrose (part 1)||½ banana||1 banana||1 banana & a small apple|
|Week 3: Added sugars||⅓ cup sugar-sweetened soda||⅔ cup sugar-sweetened soda||1 cup sugar-sweetened soda|
|Week 4: Whole Grain/high fiber starches||1/2 slice of high fiber, whole grain bread||1 slice of high fiber, whole grain bread||2 slices of high fiber, whole grain bread|
|Week 5: Low fiber starches||¼ cup cooked white rice||½ cup cooked white rice||1 cup cooked white rice|
It is unlikely for weeks 2-5 that a person with CSID will make it to day 5 without symptoms. Typically symptoms will occur after the small or moderate serving size. In this case, you would cease testing of that food and move to the next item on the testing schedule.
I also recommend keeping a food and symptom diary during the testing phase so that you are able to look back on it down the road.
You don’t necessarily need to follow a rigid testing schedule. You can reintroduce foods sporadically and just see how you go and develop a better understanding of your tolerance over time. However, this process is a quicker way of going about that.
STEP 3: Personalisation Of Diet
Step 3 is simply all about finding something that works for you. Based on what you now know about sucrose and starches in foods and your own personal tolerance, you can hopefully follow a much less strict version of a disaccharide-free diet.
At this stage, everyone will have a different dietary pattern. Although, if you are finding that your diet still needs to be quite restrictive to avoid symptoms, it would be a good idea to see a dietitian to ensure you are meeting your nutrient requirements. That is if you hadn’t already consulted with one during the above process.
Medication For CSID
Similar to using lactase enzymes when you are lactose intolerant, there are products that contain the sucrase enzyme.
At this point, it seems that the only enzyme replacement therapy available for CSID is a product called Sucraid.
When Sucraid is taken with high sucrose foods it can help break them down to avoid symptoms.
However, it does not work for starchy foods. Unfortunately, there are no isomaltase enzymes available at this time.
Sucraid is also not available in Australia.
Other Tips For Dietary Management of CSID
Outside of limiting foods rich in sucrose and starches, there are a few other strategies that can improve one’s tolerance to these foods.
Chew Foods Well
Digestion doesn’t start in the stomach. It actually begins in the mouth. This is great news for people with CSID because simply chewing foods really well can improve the digestion of higher starch foods.
There is an enzyme in saliva called amylase, which helps break down starches. When you chew foods for an extended period of time, the starches are exposed to the amylase enzyme for longer and require less of the enzymes in the small intestine to be broken down completely.
Aim to chew these foods 30 times before swallowing or until it is the consistency of applesauce.
Go For High Fiber Starch Foods & Combine With Higher Fat Foods
Both fiber and fat slow digestion. The more food remains in the digestive tract, particularly the small intestine, the more the starch will be able to be broken down.
Some examples of this would include:
- Cheese sauce with starchy vegetables
- Adding peanut butter & psyllium husk to porridge
- Avocado and feta on wholegrain toast
These strategies alone likely won’t stop symptoms from occurring but they could allow you to have larger portions of starchy foods without symptoms.
Congenital sucrase-isomaltase deficiency is a rare genetic condition. Often this condition is identified when an infant is first being introduced to solid foods.
Typically the introduction of grains, fruits, and vegetables will trigger symptoms such as gas, bloating, and diarrhea.
Over time, most people with CSID are able to better tolerate sucrose and starches but may still need to have a modified diet in adulthood.
If you are really unsure about what foods you are able to tolerate and in what portion sizes, it would be best to consult with a dietitian and/or go through an elimination and reintroduction process.
In my experience, those with mild symptoms are able to often tackle this process on their own and only have a slightly restricted diet. Perhaps just having a lower to moderate carbohydrate diet, avoiding added sugars, and using the extra tips above could do the trick.
However, chronic diarrhea seen in people with a more severe enzyme deficiency (particularly if this is resulting in nutrient deficiencies and unintentional weight loss), should see a dietitian for swift management of the condition.