Humans can digest starch, a common carbohydrate found in many staple foods. Starch is a polymeric carbohydrate, consisting of numerous glucose units linked together. Produced by plants for energy storage, it is a primary energy source in human diets worldwide, present in foods like wheat, potatoes, rice, and corn. The human body uses specific enzymes to break down starch into simpler sugars. The body converts starch into glucose, which fuels various bodily functions.
How Starch is Digested
Starch digestion begins in the mouth, where salivary amylase, a salivary enzyme, starts breaking down starch. This initial breakdown converts starch into smaller sugars like maltose.
Starch digestion pauses in the stomach because the acidic environment denatures salivary amylase. Digestion resumes in the small intestine. The pancreas releases pancreatic amylase into the small intestine, which further breaks down carbohydrates.
Pancreatic amylase breaks starch into smaller units like maltose. The small intestine lining contains additional enzymes, like maltase, which break down maltose into individual glucose molecules. These glucose molecules are then absorbed into the bloodstream, providing the body with energy.
Understanding Different Types of Starch
Starches are broadly categorized based on their digestibility. Digestible starch, including rapidly digested starch (RDS) and slowly digested starch (SDS), is readily broken down into glucose in the small intestine. RDS is found in highly processed foods like breakfast cereals and white bread, leading to a quick glucose release. SDS, found in foods like raw cereals, digests slower, providing a more sustained glucose release.
Resistant starch is a type of starch that escapes digestion in the small intestine, passing largely intact into the large intestine. Its structure, or re-crystallization when cooked foods cool, makes it less accessible to digestive enzymes.
In the large intestine, it acts as dietary fiber, becoming a food source for beneficial gut bacteria. These microbes ferment it, producing short-chain fatty acids that can be used as energy by the body’s cells and support a healthy gut microbiome.
Factors Influencing Starch Digestion
Food preparation methods influence starch digestion. Cooking gelatinizes starch granules, disrupting their structure and making them more accessible to digestive enzymes. Highly processed foods often contain rapidly digestible starch, leading to quicker glucose release than less processed or whole-grain options.
Individual variations in enzyme production also influence starch digestion. For example, the number of salivary amylase gene copies (AMY1) varies among individuals. A higher number can lead to increased salivary amylase production, influencing initial starch breakdown.
The gut microbiome also influences starch, particularly resistant starch. Gut bacteria in the large intestine ferment it. This fermentation yields beneficial compounds, demonstrating a collaborative role between human enzymes and gut microbes.
Starch’s Impact on Health
Digestible starch is a primary energy source for the human body. Broken down into glucose, it fuels cells and organs, enabling various physiological processes.
Resistant starch provides health benefits, influencing gut health and blood sugar regulation. It bypasses digestion in the small intestine, reaching the large intestine where it acts as a prebiotic.
Fermentation by gut bacteria produces short-chain fatty acids (SCFAs), such as butyrate. These SCFAs are important for colon cell health and can have broader metabolic effects. Resistant starch also contributes to blood sugar regulation by slowing glucose release into the bloodstream, helping manage post-meal spikes.