Not All Carbs Are Created Equal: Simple and Complex Carbohydrates

What do table sugar, milk, and high-fructose corn syrup have in common?

By Roberta H. Anding, MS, Baylor College of Medicine and Texas Children’s Hospital
Edited by Kate Findley and proofread by Angela Shoemaker, Wondrium Daily

Rather than avoiding bread at all costs, consider the type of bread you’re eating. Professor Anding breaks down carbohydrates by type and also explains the difference between whole grains and refined.

Whole grain bread slices
For complex carbohydrates, it takes longer physiologically to break these molecules down into their component parts than for a simple carbohydrate. Photo by Luis Camarasa / Shutterstock

Simple Carbohydrates

Carbohydrates are made up of three elements: carbon, hydrogen, and oxygen. Carbohydrates in foods exist in multiple forms, from the most simple to the more complex. How a food gets categorized depends on how many glucose, or individual sugar units, are contained within this carbohydrate. 

The simple carbohydrates are termed “simple sugars.” They’re categorized as “mono,” meaning one, “di,” meaning two, and “saccharides,” meaning sugar. 

The most important monosaccharides in human nutrition are glucose, galactose, and fructose. Many of these words you might not be familiar with because most monosaccharides don’t exist in simple form in food.

The disaccharides—two sugar units that are stuck together—are sucrose, which is table sugar, maltose, which is malt sugar, and lactose, or milk sugar. Both disaccharides and monosaccharides are listed on a food label as sugar. 

If you look at a carton of milk, it will tell you that each serving of milk has 12 grams of sugar. That is not sugar added by the manufacturer. This is lactose, a disaccharide, which naturally exists in the milk.

Lactose is glucose and galactose. Sucrose is made up of glucose and fructose. Maltose is two glucose units stuck together. 

Keep in mind that for every disaccharide, an enzyme will split it into monosaccharide form. For sucrose, there’s sucrase. Maltose has maltase, and lactose has lactase. 

High-Fructose Corn Syrup

Table sugar, high-fructose corn syrup, and the sugar in milk are all examples of disaccharides. High-fructose corn syrup is a relative newcomer in the American food supply, as it was a creation of science in the 1960s. 

Enzymatic changes in corn syrup increased the fructose content from 15% in the original, natural version to 42% during its first modification. Further advances through chemistry increased the fructose concentration to 55%, and this is the form that is found in high-fructose corn syrup in most soft drinks. 

Ironically, products labeled as light—a reduced calorie version—usually contain high-fructose corn syrup. When food chemists reduce the fat content, they often add high-fructose corn syrup so that the food still tastes good. 

Complex Carbohydrates

Complex carbohydrates are groups of carbohydrates known as polysaccharides. “Poly” means many, but in this case it means 20 or more sugar units stuck together in different forms. It can be in a chain or branched in different forms. 

Given the length of the compound, it takes longer physiologically to break these molecules down into their component part than for a simple carbohydrate. Most of the absorption of carbohydrate to get it from your gut into the blood has to be predominantly in a monosaccharide form. 

The goal of your gut is to break down these molecules into at least a disaccharide—but preferably a monosaccharide—in order to be absorbed. Thus, the digestion of long complex carbohydrates takes a longer time.

Starches or complex carbohydrates are categorized by the organization of these sugar units in space. For example, the phenyla configuration means those glucose or carbohydrate units are arranged in a long chain. In this chain molecule, the enzymes can only attack from the ends of that molecule. 

Amylopectin, however, is a branched chain configuration of a complex carbohydrate, and this means that it looks like the branches of a tree, so there are more spots on that molecule for the digestive enzymes to attack. Additionally, in this configuration water can be held between those branch chains, and oftentimes that food has a slightly different property.

Whole Grains Versus Refined

Breads, cereals, and fruits are mostly complex carbohydrates, but nature usually combines mono, disaccharides, and complex carbohydrates in these foods as well. The true benefit of these whole foods is that—particularly in grains—they are 100 percent whole grains versus white bread, which is refined. 

The carbohydrate content of a slice of white bread and a slice of whole-grain bread are actually the same, but they behave differently physiologically. Also, in the process of refining carbohydrates, which involves removing the outer bran layer, not all the nutrients that are lost are replaced in the enrichment process that follows. 

Most notable are fiber and magnesium. This loss of fiber and magnesium can negatively impact our health.

Large public health surveys suggest that the more magnesium you include in your diet, the less likely you are to have type 2 diabetes. If you’re not eating whole grains, you’ve lost a major source of magnesium. Low fiber can lead to digestive issues as well as long-term health issues such as colon cancer and high cholesterol levels.

This article was edited by Kate Findley, Writer for Wondrium Daily, and proofread by Angela Shoemaker, Proofreader and Copy Editor for Wondrium Daily.

Professor Roberta H. Anding is a registered dietitian and Director of Sports Nutrition and a clinical dietitian at Baylor College of Medicine and Texas Children’s Hospital. She also teaches and lectures in the Baylor College of Medicine’s Department of Pediatrics, Section of Adolescent Medicine and Sports Medicine, and in the Department of Kinesiology at Rice University.