Resistant starch

Resistant starch is a type of carbohydrate that is partially digested, functioning as fiber in the large intestine, supporting gut health.

Related reading: The Complete Guide to Proper Nutrition — an essential guide from the expert team at Sport Zona.

What it is

Resistant starch (RS) is a category of carbohydrates that, unlike other types of starch, do not undergo standardized enzymatic digestion and absorption in the small intestine. Instead, they functionally behave similarly to soluble dietary fibers, reaching the large intestine unchanged. This distinguishes RS from rapidly digestible carbohydrates, which break down into simple sugars and quickly raise blood sugar.

There are four main types of resistant starch based on their origin and structure: RS1 (physically resistant starch in whole grains, seeds, and legumes), RS2 (naturally resistant starch in raw potato, green bananas, and high-amylose corn starch), RS3 (retrograded starch formed by cooling cooked starchy foods like potatoes, rice, and pasta), and RS4 (chemically modified starch created through food processing technologies). Each type has unique physicochemical properties that influence its fermentation and physiological effects.

How it works

Resistant starch exerts its physiological effects through a series of complex mechanisms that begin after it reaches the large intestine. Since it has not been broken down by digestive enzymes like amylase in the upper gastrointestinal tract, it becomes available for fermentation by the resident microflora. This fermentation process is key to its benefits.

Bacteria in the large intestine metabolize resistant starch, producing short-chain fatty acids (SCFAs) such as acetate, propionate, and butyrate. Butyrate is particularly important as it serves as a primary energy source for the cells of the large intestine (colonocytes), supporting their integrity and function. Furthermore, SCFAs have proven anti-inflammatory properties and can influence glucose and fat metabolism throughout the body. In summary, resistant starch works by:

• Bypassing digestion in the small intestine.
• Being fermented by gut microflora in the large intestine.
• Producing short-chain fatty acids like butyrate.
• Maintaining gut barrier function and modulating systemic metabolism.

Why it's important for athletes

For athletes, resistant starch offers several key advantages that extend beyond general digestive health. One of the most significant aspects is its impact on glycemic control. Consuming foods rich in resistant starch can help stabilize blood sugar and insulin levels after meals, which is important for avoiding energy crashes and maintaining consistent energy during workouts. Studies suggest that replacing rapidly digestible carbohydrates with RS can reduce the glycemic index of meals and improve insulin sensitivity.

In addition to glycemic control, resistant starch can contribute to enhanced satiety (feeling of fullness), which is beneficial for athletes aiming for weight management or adhering to specific dietary plans. As it ferments slowly in the large intestine, it can provide a prolonged feeling of fullness, reducing unwanted calorie intake. The recommended daily intake of fiber, which includes resistant starch, is between 25-38 grams for adults, and incorporating at least 6-10 grams of resistant starch into the daily diet can significantly contribute to these goals. While there are no official recommendations specifically for sports nutrition, the ISSN (International Society of Sports Nutrition) highlights the importance of adequate fiber intake for optimizing digestive function and overall health in athletes.

Related concepts

• Glycemic Index (GI) — Resistant starch lowers the overall glycemic index of foods, contributing to more stable blood sugar levels.
• Glycemic Load (GL) — By slowing down carbohydrate absorption, resistant starch effectively reduces the glycemic load of a meal.
• Isomaltulose — Isomaltulose, similar to resistant starch, is a carbohydrate with a low glycemic response, providing sustained energy.
• Fructose — Unlike fructose, which is primarily metabolized in the liver, resistant starch is fermented in the large intestine.