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 diarrhoea, along with bloating, although some people may also experience vomiting.
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.
Diagnosing CSID
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 diarrhoea.
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.
Nutritional Management
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 yoghurt. There is also naturally occurring sucrose found in fruit. Typically, a person with CSID will have the hardest time digesting sucrose, particularly in low fibre, 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 Cherry Damson plums Figs Guava Grapes Kiwi fruit Lemon/Lime Passion fruit | All except those listed to the left including: Apple Apricot Banana Dates Grapefruit Mango Melons Papaya Peach Pear Pineapple Raspberry Strawberry |
| Vegetables | Fresh, frozen, canned with additives, added sauces, or added butter or margarine: Avocado Celery Chives Cucumber Garlic Green onion Kale Lettuce Mushroom Parsley Parsnip Peppers (green & red) Radish Spinach Swiss chard Tomato Turnip Watercress Broccoli Cabbage Brussel sprouts Eggplant 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) Carrot Beetroot Green peas Corn Pumpkin Okra |
| Grains | None | Flours made with grains Wheat Amaranth Barley Buckwheat Bulgur Corn Couscous Millet Oats Quinoa Rice Rye Spelt Triticale |
| Meat and Meat Substitutes | Lamb Beef Pork Wild game Poultry: chicken, duck, turkey Fish Shellfish Eggs (plain) Tofu Tempeh | Meats that are: Processed, Breaded, Smoked, Cured, Canned Corned beef Eggs with added milk, flour, or sugar Edamame Legumes |
| Nuts & Seeds | None | All, including: Almond Brazil nut Cashew Hazelnut Macadamia Pecan Pistachio Pumpkin seeds Sesame seed Sunflower seed Walnut |
| Sugars & Sweeteners | Glucose Dextrose Fructose (fruit sugar) Levulose Honey 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 fibre starches | 1/2 slice of high fibre, whole grain bread | 1 slice of high fibre, whole grain bread | 2 slices of high fibre, whole grain bread |
| Week 5: Low fibre 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.
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 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.
For starch foods, there is a product called Starchway available. It is taken at the time of the meal or drink and contains the enzymes Invertase and Glucoamylase.
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 Fibre Starch Foods & Combine With Higher Fat Foods
Both fibre and fat slow digestion. The longer food stays in the digestive tract, especially in the small intestine, the more time starch has 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.
Conclusion
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 diarrhoea.
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 diarrhoea 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.
Looking For 1-on-1 Help?
CSID or sucrose isomaltase deficiency can be difficult to manage on your own. Like many intolerances, it can be super frustrating to figure out what you should and shouldn’t be eating for symptom management.
What makes it even harder is the complete lack of helpful resources online and even many health professionals being unfamiliar with the condition. Hence why I have written this blog post!
I came across this condition several years ago as a new grad dietitian when a client of mine who thought they had a bad case of IBS but he was finally diagnosed with CSID in his 40s! It was incredibly rewarding being able to solve his constant, lifelong gut issues in just a matter of months through the above management strategies. So I continued practicing in this area and helping many more people with CSID.
Hopefully, I will be able to produce some more free content in the future as time permits.
But if you would like some help managing CSID, our dietitians at Ideal Nutrition off one on one consults specifically for this condition & other complex gut issues!
