Deeper Dive: How do structural aspects of dietary carbohydrates determine glycemic response and appetite?

The human body often experiences changes in blood glucose and insulin in response to food consumption, which is called the glycemic response. The glycemic response to individual foods is an important aspect of managing metabolic diseases, such as type 2 diabetes^[1]. Carbohydrates are the primary food constituent that elicit a glycemic response, and starch constitutes the majority of carbohydrate intake in most diets. The precise effect that a given starchy food has on the glycemic response depends on the extent and rate (i.e. fast or slow) of starch digestion. Insulin levels in the blood tend to correlate with this effect, such that carbohydrate-laden foods that cause fast, large increases in blood glucose also tend to cause fast, large increases in circulating insulin.

The structure of a starchy food is known to regulate the extent to which a starch is digested, as well as the rate at which it is digested. Much of the structural differences in starch sources can be observed at the microstructural level (less than 100 μm), which is mostly determined by different molecular structures of starch. There are two primary forms of starch: amylopectin and amylose. As shown in Figure 1, amylopectin has a highly branched structure, similar to glycogen, whereas amylose has a more linear structure, similar to cellulose. The branched structure of amylose allows it to be digested more rapidly and more completely due to the fact that there are more bonds accessible to enzymes for digestion. There are also other microstructural aspects that can affect digestibility, such as gelatinization, retrogradation, interactions with lipids and proteins, and whether a carbohydrate source has intact cell walls or not.