Blog Post

CSID: How To Manage Sucrase-Isomaltase Deficiency

Sucraid CSID

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.

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 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. 

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 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. 

CSID high starch 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. 

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 ProductsHard cheeses such as cheddar
Unsweetened soy or nut milk 
Unsweetened lactose free milk
All except those listed to the left
FruitsFresh, frozen, canned in own juice: 

Berries: blackberry, blueberry, cranberry, gooseberry, loganberry
Damson plums 
Kiwi fruit 
Passion fruit
All except those listed to the left including:

Vegetables Fresh, frozen, canned with additives, added sauces, or added butter or margarine:

Green onion 
Parsnip Peppers (green & red)
Swiss chard 
Brussel sprouts 
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)
Green peas
GrainsNoneFlours made with grains 
Meat and Meat SubstitutesLamb 
Wild game
Poultry: chicken, duck, turkey 
Eggs (plain)
Meats that are: Processed, Breaded, Smoked, Cured, Canned 
Corned beef 
Eggs with added milk, flour, or sugar
Nuts & SeedsNoneAll, including: 

Brazil nut 
Pumpkin seeds
Sesame seed
Sunflower seed 
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 TestedDay 1Day 3Day 5 
Week 1: Lactose ½ cup of cow’s milk1 cup of cow’s milk2 cups of cow’s milk
Week 2: Naturally occurring sucrose (part 1)½ banana1 banana1 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 starches1/2 slice of high fiber, whole grain bread1 slice of high fiber, whole grain bread2 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

Sucraid 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 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. 

CSID friendly meal


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. 

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 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 1-on-1 help managing CSID, I do offer a 12-week CSID symptom management coaching package. Feel free to book a free 15-minute discovery call here to learn more and to see if we are a good fit or you can email me for more details at

By Leah Higl

Leah is an accredited practising dietitian from Brisbane. She also competes as an under 75kg powerlifter with Valhalla Strength Brisbane. As both an athlete and dietitian, she spends much of her time developing her knowledge and skills around sports nutrition, specifically for strength-based sports. Although, she works with a range of athletes from triathletes to combat sports and powerlifting. Leah also follows a plant-based diet and her greatest passion is fuelling vegan/vegetarian athletes and proving that plant-based athletes can be just as competitive as their non-vegan counterparts.​