What Foods Are Rapidly Digestible Starch?

December 2, 2025 •

4 min read

According to The University of Sydney, rapidly digested starch (RDS) is typically found in highly processed foods and is digested within 20 to 30 minutes, causing a rapid release of glucose. Knowing what foods are rapidly digestible starch can help you make informed dietary decisions to manage your blood sugar and energy levels more effectively.

Quick Summary

This article explores the characteristics and common sources of rapidly digestible starch, explaining its impact on blood sugar and energy levels. It identifies specific processed foods, refined grains, and starchy vegetables high in RDS. The content also compares rapidly digestible starch to its slower-digesting counterparts and offers advice on healthier dietary substitutions.

Key Points

RDS Definition: Rapidly digestible starch is quickly broken down into glucose, causing a rapid rise in blood sugar and insulin levels.
Processed Grains: Refined items like white bread, many breakfast cereals, and white rice are major sources of RDS.
Starchy Vegetables: Potatoes, especially when boiled or instant, have high levels of RDS due to processing.
Blood Sugar Impact: High consumption of RDS is linked to an increased risk of insulin resistance and obesity over time.
Healthy Swaps: Choose whole-grain bread, brown rice, and legumes over their refined counterparts to manage RDS intake.
Alternative Starches: Slowly digestible and resistant starches, found in foods like lentils and cooked-then-cooled potatoes, provide more stable energy.
Cooking Matters: The preparation of starchy foods, such as cooking and cooling, can influence their digestibility and alter RDS content.

Understanding Rapidly Digestible Starch

Starch is a complex carbohydrate found in many plant-based foods, including grains, vegetables, and fruits. When we consume starch, our digestive system breaks it down into glucose, which is then absorbed into the bloodstream to be used for energy. Starches can be classified into three main categories based on how quickly they are digested: rapidly digestible starch (RDS), slowly digestible starch (SDS), and resistant starch (RS). RDS, as its name suggests, is quickly and easily broken down in the small intestine, leading to a rapid and pronounced spike in blood glucose levels and a subsequent insulin response. This rapid release of glucose can be a double-edged sword; while it provides a quick burst of energy, frequent spikes can increase the risk of health issues like diabetes and obesity over time.

The structure of starch, specifically the ratio of amylose to amylopectin, influences its digestibility. Rapidly digestible starches are typically rich in amylopectin, a highly branched starch molecule that is easily accessed and broken down by digestive enzymes.

A Comprehensive List of Rapidly Digestible Starch Foods

Many common foods, especially those that are highly processed or refined, are significant sources of rapidly digestible starch. Cooking methods also play a critical role, as heat and processing can alter the starch structure and increase its digestibility. Here is a detailed look at common sources:

Processed Grains and Refined Carbohydrates

White Bread and White Flour Products: The refining process strips away the fibrous outer layers of grains, leaving behind a high concentration of RDS. White bagels, rolls, and crackers are all examples.
Many Breakfast Cereals: Highly processed breakfast cereals, such as corn flakes and rice krispies, are designed to be rapidly digestible and cause quick blood sugar spikes.
White Rice: Unlike its brown counterpart, white rice has been milled to remove the bran and germ, resulting in a higher RDS content.
Instant Potato Products: Instant mashed potatoes are a classic example of a food engineered for rapid digestion. The processing involved makes the starch highly available for enzymatic breakdown.
Potato Crisps and Corn Chips: The manufacturing process for many snack foods involves heat and pressure, which gelatinizes the starch and makes it extremely easy to digest.

Starchy Vegetables and Tubers

Potatoes: Potatoes, especially when boiled or baked and eaten hot, are a well-known source of RDS. The cooking process breaks down the starch granules, making them readily available for digestion. Frying potatoes, as in french fries, also contributes to a high glycemic load.
Cassava and Yam: These starchy root vegetables provide digestible starch, especially when cooked.

Other Sources

Ripe Bananas: As a banana ripens, its resistant starch is converted into simple sugars and rapidly digestible starch. A very ripe, soft banana will have a much higher RDS content than a firm, green one.
Many Cookies and Biscuits: Baked goods made with refined flours and sugars are concentrated sources of RDS.

Rapidly Digestible Starch vs. Other Starch Types

It's important to understand how RDS compares to other forms of starch to make balanced dietary choices. This table highlights the key differences.


Feature	Rapidly Digestible Starch (RDS)	Slowly Digestible Starch (SDS)	Resistant Starch (RS)
Digestion Rate	Very fast; within 20-30 minutes.	Slow; digested over 20-120 minutes.	Passes undigested through the small intestine.
Blood Sugar Impact	Causes a rapid and high spike in blood glucose.	Results in a gradual and sustained release of glucose.	Does not raise blood glucose levels significantly.
Associated Foods	White bread, instant potatoes, refined cereals, boiled white rice.	Whole-grain cereals, pasta, nuts, seeds, legumes.	Legumes (beans, lentils), raw potatoes, unripe bananas, cooked and cooled potatoes/rice.
Health Implications	Associated with higher glycemic index and risk of insulin resistance.	Helps with stable blood sugar and sustained energy.	Acts like dietary fiber, promoting gut health and satiety.
Food Processing	Highly processed foods often contain more RDS.	Less processed foods and specific cooking methods can increase SDS.	Cooking and cooling certain starchy foods can increase resistant starch.

Managing Your Intake of Rapidly Digestible Starch

While avoiding RDS entirely is not necessary, especially for athletes needing quick energy, managing your intake is wise for overall health and blood sugar stability. A key strategy is to substitute high-RDS foods with options richer in slowly digestible and resistant starches. For example, swapping white bread for whole-grain or pumpernickel bread can dramatically reduce your RDS intake. Opting for brown or wild rice instead of white rice provides more fiber and nutrients while moderating the blood glucose response. When eating potatoes, consider healthier cooking methods like roasting skin-on redskin potatoes rather than frying or mashing them without the skin, as the skin contains fiber.

Combining high-RDS foods with protein, fiber, or healthy fats can also mitigate the rapid blood sugar spike. For instance, pairing white rice with lentils or beans will slow digestion. Portion control is another effective method, as the total amount of carbohydrates consumed directly impacts blood glucose levels. Reading food labels and prioritizing whole foods over highly processed products will naturally reduce your exposure to RDS.

Conclusion

Understanding which foods contain rapidly digestible starch is essential for managing blood sugar levels and achieving balanced energy throughout the day. Foods like white bread, instant cereals, and boiled potatoes are key examples, characterized by their high processing and fast conversion to glucose. By opting for whole-grain alternatives, prioritizing resistant and slowly digestible starches, and incorporating fiber and protein, individuals can control their glycemic response and support better long-term metabolic health. Making conscious dietary choices is the first step towards leveraging the power of starch for sustained well-being.

Outbound link to an authoritative source on nutrition or dietetics: British Nutrition Foundation: Starchy Foods and Carbohydrates

Frequently Asked Questions

Rapidly digestible starch (RDS) is broken down very quickly into glucose in the small intestine, causing a rapid spike in blood sugar. Resistant starch (RS), however, is not digested in the small intestine and instead ferments in the large intestine, behaving similarly to dietary fiber and producing less impact on blood glucose levels.

Yes, cooking methods significantly influence a food's digestibility. Processes involving heat, such as boiling or baking, can alter the starch structure and increase the rapidly digestible starch content. For example, instant potatoes have a higher RDS content than a regular baked potato.

While hot potatoes are high in rapidly digestible starch, cooling them after cooking can increase their resistant starch content. This process, known as retrogradation, makes the starch less digestible.

You can reduce your RDS intake by choosing less processed versions of starchy foods, such as whole grains over refined ones. Pairing starchy foods with sources of fiber, protein, or healthy fats also helps to slow down digestion.

As a banana ripens, its starch naturally converts into simpler sugars and more rapidly digestible starch. A green, unripe banana contains more resistant starch, which digests much more slowly.

Good low-RDS breakfast options include steel-cut oats, which are less processed than instant oatmeal, or eggs with vegetables. These choices promote a more gradual release of energy.

Rapidly digestible starch is not inherently bad. For people with balanced blood sugar, it's a quick source of energy. However, for those managing blood sugar conditions like diabetes or seeking sustained energy, minimizing RDS intake is often recommended.