Resistant Starch: A Simple Cooking Trick to Lower Blood Glucose Levels

What is resistant starch?

Resistant starch is a type of carbohydrate that resists digestion in the small intestine. Instead of being broken down quickly into glucose, it passes through to the large intestine where it is fermented by gut bacteria.

Because it is digested more slowly (or not at all), resistant starch:

• Causes a smaller rise in blood glucose levels after eating
• Helps you feel fuller for longer
• Feeds beneficial gut bacteria by producing short-chain fatty acids
• Can improve blood glucose responses at the next meal too, a phenomenon known as the ‘second meal effect’.

So how do you create more resistant starch?

The Cook–Cool Method

Some foods naturally contain resistant starch such as legumes, green bananas, barley and brown rice. However, you can create more resistant starch through the way you cook and store certain carbohydrates.

The cook–cool method involves:

1. Cooking a starchy food in water (boiling, steaming, or baking)
2. Allowing it to cool completely, ideally in the fridge for at least 12 hours

During cooling, part of the starch changes in structure. This new structure is harder for the body to break down and resists digestion.

The good news? Resistant starch remains even if you reheat the food gently. This means if you eat leftover food the next day, it will contain more resistant starch, even if you reheat it.

Which Carbohydrates Work Best?

Not all carbohydrates form resistant starch equally. The cook–cool method works best with starchy, minimally processed foods such as:

• Potatoes (white or sweet)
• Rice, especially medium or long-grain rice
• Pasta
• Pearl barley
• Oats (especially cooked rolled oats)
• Corn
• Barley
• Quinoa

The Cook-Cool Method Changes the Carbohydrate Quality, Not Quantity

It’s important to understand that the cook–cool method does not reduce the total amount of carbohydrate in the food. A cup of rice, pasta, or potatoes still contains the same grams of carbohydrate whether it is eaten hot or cooked and cooled.

What changes is how your body digests that carbohydrate. This is why portion size still matters, even when using the cook–cool method.

Practical Tips to Increase Resistant Starch

Here are some easy ways to use the cook–cool method in everyday meals:

• Cook rice or pasta ahead of time, cool it overnight, and use it the next day
• Turn cooled rice into a salad, stir-fry, or gently reheated side dish
• Use cooled potatoes in potato salad, tray bakes, or reheated wedges
• Make a large batch of lentil or bean-based meals and eat leftovers over several days
• Prepare overnight oats using cooked oats that have been cooled

How to Check If It Works for You

Everyone responds differently to carbohydrates, so checking your blood glucose levels is the best way to see if the cook–cool method helps you.

Try this simple self-experiment:

1. Before the meal
   • Check your blood glucose just before eating e.g. 6.2mmol/L
2. Eat your meal
   • Include a cooked-and-cooled starch (for example, cooled rice or potatoes)
   • Keep other parts of the meal the same as usual
3. After the meal
   • Check your blood glucose 2 hours after starting the meal e.g. 8.1mmol/L
   • Write down how much your blood glucose levels increased by e.g. 8.1 - 6.2 = 1.9mmol/L. My blood glucose levels increased by 1.9mmol/L using cook-cool method
4. Compare
   • On another day, eat the same meal made with freshly cooked starch (e.g. warm rice or potatoes)
   • Follow the same process of checking your blood glucose readings before and 2- hours after starting the meal
   • Write down how much your blood glucose levels increased by
   • Compare the results

Many people notice a smaller rise when using cooled starches, but results vary depending on portion size, medications, activity levels, and the overall meal.

Summary

Creating more resistant starch in your meal will improve the way your carbohydrates are digested, without removing them entirely. By using the cook–cool method with everyday foods like rice, pasta, potatoes, and legumes you may be able to lower your blood glucose levels after eating while still enjoying familiar meals.

Monitoring blood glucose before and after meals can help you decide whether this approach works for you.