“Light starch” is a descriptive term referring to starches that are quickly and easily broken down by the body. While not a formal scientific classification, it highlights starches that undergo rapid digestion. These starches are characterized by how quickly their glucose molecules become available for absorption.
Characteristics of Easily Digestible Starches
Easily digestible starches, often termed rapidly digestible starch (RDS), possess specific molecular structures that allow for their quick breakdown. They have a high content of amylopectin, a branched polysaccharide that makes up 70-80% of starch by weight. Amylopectin’s highly branched structure, with branching points approximately every 24-30 glucose units, provides numerous sites for digestive enzymes to act upon simultaneously. This open configuration enhances solubility and allows for rapid enzymatic hydrolysis.
The presence of less complex branching and a lack of associated fiber or a dense matrix contribute to their rapid digestion. Starch digestion begins in the mouth with salivary amylase and continues in the small intestine with pancreatic amylase. The application of heat and absorption of water during cooking further disrupts the starch structure, making it more accessible to these enzymes and increasing its digestibility.
Common Food Sources
Many common food items are rich in easily digestible, or “light,” starches. These include highly processed foods such as white bread, many breakfast cereals, and biscuits. Potatoes, especially freshly cooked ones, are also a significant source of rapidly digestible starch.
White rice is another staple food known for its high rapidly digestible starch content. Instant oatmeal, refined grains, and certain fruits like bananas and pineapple also fall into this category.
Impact on the Body
Consuming easily digestible starches leads to a rapid elevation in blood glucose levels. This occurs because the starch is broken down into glucose and absorbed in the upper small intestine within 20 to 30 minutes. The swift rise in blood sugar triggers a rapid release of insulin from the pancreas to lower glucose levels.
This quick energy release can be followed by a subsequent drop in blood sugar, potentially leading to feelings of fatigue or a “crash.” Foods high in rapidly digestible starches are less filling. This is because they do not provide the sustained energy or fullness associated with slower-digesting starches.