dsfacts logo

Get the Facts on Duodenal Switch.


A sugar molecule is the basic building block of every carbohydrate. The body uses carbohydrates to make glucose (blood sugar) to use for energy for your cells, tissues and organs. The glucose can be used immediately or stored in your liver and muscles for when it's needed. The most common forms of carbohydrates are sugars, starches and fibers.

food high in carbohydrates Sugar carbs are found in a range of natural food, including milk (containing lactose, or milk sugar), fruits (containing fructose, or fruit sugar) and sugar beet (containing sucrose).

Starch carbs are found in all cereal grains, as well as roots and tubers. Starchy foods include: bread, pasta, rice, noodles, couscous, tapioca, potatoes, sweet potatoes and yams.

Dietary fiber carbs are found in most plant foods, like fruits and vegetables, legumes and whole grain cereals.

Your digestive system handles all carbs in the same way - by breaking them down into single sugar molecules so they are small enough to absorb into the bloodstream. Fiber is an exception because it can't be broken down into sugar molecules and as a result passes through the body undigested. Simple carbs are digested very quickly whereas complex carbs take longer to digest and are usually packed with fiber, vitamins and minerals.

A quick note on dietary fiber. There are two types: soluble (dissolves in water) and insoluble (doesn't dissolve in water). Soluble fiber binds to fatty substances in the intestines and carries them out as a waste and insoluble fiber helps push food through the intestinal tract, promoting regularity and helping prevent constipation.

Soluble fiber is found in the following: oatmeal, oat bran, nuts and seeds, most fruits (e.g., strawberries, blueberries, pears, and apples), dry beans and peas.

Insoluble fiber is found in the following: whole wheat bread, barley, brown rice, couscous, bulgur or whole grain cereals, wheat bran, Seeds, most vegetables, Fruits.

Digestible or Net Carbs
It is common to see the phrase "Digestible Carbs" or "Net Carbs". This refers to the total amount of carbs in a particular food that can be absorbed and digested in the intestinal tract. It excludes dietary fiber as they cannot be digested. Sugar alcohols are carbs that we do not completely absorb. The most common ones are sorbitol, xylitol, mannitol, and maltitol. The easiest way to calculate the net carbs in a food is to subtract the dietary fiber and sugar alcohol content from the total carb content.

Total Carbs: 30g
    Dietary Fiber: 5g
    Sugars: 1g
    Sugar Alcohol: 15g
Net Carbs: 10g (30 - 5 - 15 = 10)

A final note on carbs. Do not eat carbs before bedtime as it triggers insulin and initiates fat storage which we sure don't want!

A DS Carb Primer

By Kelly L.

All carbs begin digesting in the mouth when it comes in contact with the enzyme amylase. Even complex carbs begin the process of breaking down into simpler types at this point. Since monosaccharides need no further digestion to be absorbed, you begin absorbing them as soon as they hit your mouth.

Enzyme activity continues in the stomach but, it is slowed by contact with stomach acids.

When the carbs hit the intestines is where the DS may assist in preventing some absorption of the more difficult to digest polysaccharides (starches). A type of amylase is secreted by the pancreas into the duodenum that cuts carbs down into simple sugars. As it passes further, more enzymes break the carbs down into even smaller bits until they are eventually converted to glucose and absorbed by the villi in your intestinal walls.

Because of the switch portion of the DS, the amount of time that a polysaccharide is in contact with pancreatic enzymes is reduced. Enough to stop some of the digestive process? Likely. This is probably why many people have gastrointestinal issues when eating starches. No gas or runs? You're likely digesting them more efficiently and, therefore, absorbing more.

Also, since glucose is absorbed by the villi in the intestine, those with shorter common channels and those earlier out will also absorb less. As your body adjusts to the DS, you grow more villi to counteract the malabsorption, so more villi equals' greater absorption of glucose.

It's possible that that's where your surgeon came up with the 30-60% malabsorption of carbs figure. But, for anyone who is not losing or maintaining their weight effortlessly, that 30-60% guesstimate is just too wide a margin to mess with. I'd avoid or severely limit all starches, too.

Sugar alcohols are technically carbs, too, like fiber. But, because they aren't completely digestible by the body, they aren't absorbed the way that regular sugar is absorbed. Some of it is absorbed, though, so (besides the unpleasant bathroom side effect) you shouldn't eat a whole bag of sugar free candy, either.

Carbs and Gas

By Diana C.

Fruits comprise simple carbs (primarily fructose, which is a monosaccharide and doesn't have to be digested at all) and so are fully absorbed in the small intestine, and fiber, which is indigestible by both our guts and our bacterial symbionts.

Flour products contain starches, which are made up of long chains of monosaccharides -- thus, polysaccharides -- which are only partially digestible by our rearranged guts with the diminished contact with digestive enzymes. This results in some of the starch ending up in the colon where it is digested by our bacterial symbionts to produce gas. The more whole grain-y the complex carbs we put in our guts, the higher the fiber (indigestible) to starch ratio, and the less likely to cause issues.

Other things that cause gas are specific starches that are indigestible in our guts, but which our colon bacteria are happy to process, such as raffinose and inulin (the offensive starches in beans, broccoli, etc.) and retrograded starch, caused by cooking and then cooling of amylose, the primary starch in white flour products, which process produces a form of amylose that is indigestible in our small intestine, but can be digested by our colon bacteria. This of course is a worse problem for DSers, who digest starches even less well than others.

For more information on gas and flatulence-producing foods:
Natural Gas: Myths and Facts

More Information on Carbohydrates

Artificial Sweeteners and Cancer: Questions and Answers
Artificial Sweeteners: A Safe Alternative to Sugar Carb Calculator
Carbohydrate Content of Selected Foods
Choose Carbohydrates Wisely

Now that you know about Carbohydrates
NEXT: More from Life After Duodenal Switch