All healthy adult bodies process carbohydrates the same way, but not all carbs digest in the same manner. Some types of carbs break down quickly, others take a while and fibrous carbohydrates don’t break down at all. In some cases, certain digestive issues or nutritional deficiencies may contribute to an inability to digest carbohydrates. Because carbohydrates are your body’s main energy source, it is important to know how they digest and break down.
Simple carbohydrates are sugars and can be naturally occurring or added. For example, fruit contains natural sugar called fructose, while milk has its own naturally occurring sugar called lactose. Processed junk foods often have added sugar in the form of sucrose, dextrose or high fructose corn syrup. These simple carbohydrates all process in a similar manner in your body. After you chew and swallow the food, sugars quickly travel down into your small intestine. From there, enzymes convert the sugars directly into glucose, which is the main fuel source for every cell. Glucose molecules absorb through intestinal walls and immediately enter your bloodstream.
Complex carbohydrates are starches that have long branched chains. Your system has to work hard to deconstruct these molecules into simpler forms. When you chew food that has starch, such as potatoes, whole-grain foods or corn, saliva in your mouth goes to work. Saliva engulfs complex starch compounds and turns them into a type of simple carbohydrate called maltose. Once maltose molecules reach your small intestine, enzymes turn them into glucose and they enter your bloodstream in the same way as sugars.
Your body processes fiber in a completely different manner than sugars and starches. Although fiber is a complex carbohydrate, it does not break down into glucose. Fiber stays intact, for the most part, as it travels through your gut. Soluble fiber is the soft part of plants that holds onto water. It acts similarly in your gut by attracting water. When soluble fiber binds with water it forms a sludge or gel substance that slows digestion. Soluble fiber allows nutrients to absorb through intestinal walls, delays absorption of sugar and can help lower blood cholesterol by sticking to cholesterol and pushing it out through waste. Insoluble fiber is the rigid structural component of cell walls. This is the type of fiber that is difficult to chew and gets stuck in your teeth. Insoluble fiber speeds up digestion and makes it easy for you to have bowel movements. Most fibrous foods provide some of each type of fiber.
Even though everyone processes simple carbs, complex carbs and fiber the same way, certain issues may affect how efficiently your body uses carbohydrates. If you are lactose intolerant, your body does not make enough lactase, which is the enzyme that breaks down lactose in milk products. Lactose cannot digest and causes uncomfortable gas, bloating and diarrhea. Digestive issues, such as Crohn’s disease, or intestinal damage from anorexia nervosa or alcoholism, limit your body’s ability to absorb thiamine, or vitamin B-1. This vitamin is critical for digestion of carbohydrates. Without it, pyruvic acid builds up, causing difficulty breathing and heart damage. Diabetes is another issue that affects processing of carbohydrates. If you have diabetes, Type 1 or Type 2, your body either can’t produce insulin or doesn’t produce enough working insulin to help cells absorb glucose after carbohydrate digestion. Glucose reaches dangerously high levels, which can lead to heart disease, kidney failure or blindness.