Resistant starch is a type of carbohydrate that “resists” digestion in the small intestine and instead ferments in the large intestine, acting more like dietary fiber than a typical starch. Unlike rapidly digested starches that quickly convert to glucose and raise blood sugar, resistant starch passes through the upper digestive tract intact. Once in the colon, it becomes food for beneficial gut bacteria, producing short-chain fatty acids like butyrate that support colon health, reduce inflammation, and may lower the risk of certain chronic diseases.
Because it slows digestion and absorption, resistant starch can help improve satiety, stabilize blood sugar, and enhance insulin sensitivity. It is naturally present in foods such as cooked and cooled potatoes, green bananas, legumes, and certain whole grains. Some food preparation methods, like cooking and then cooling pasta or rice, can increase resistant starch content. With its dual role as both a prebiotic and a blood sugar–friendly carbohydrate, resistant starch is gaining attention for its potential benefits in digestive wellness, weight management, and type 2 diabetes care.
🍞 Regular Starch
- White bread, mashed potatoes, white rice (freshly cooked):
The starch granules in these foods are gelatinized by cooking, so digestive enzymes easily break them into glucose. Blood sugar rises quickly after eating. - Cornflakes & crackers:
Highly processed, almost all starch is rapidly available, so they act much like sugar in the body.
🌱 Resistant Starch
- Cooked and cooled potatoes or rice:
When you cook, then chill them (like in potato salad or sushi rice), some of the starch recrystallizes into a form your small intestine can’t break down. That fraction is resistant starch. - Green bananas:
Before ripening, much of their starch is in a resistant form. As they ripen, the starch converts to sugar, losing that resistant quality. - Beans and lentils:
Naturally high in resistant starch even after cooking, which is part of why they have a lower glycemic impact than pasta or bread.
🍝 Pasta (retrogradation effect)
- When pasta is boiled, the starch granules gelatinize and become easy for enzymes to digest → regular starch.
- If you cool the pasta after cooking, some of those starch chains “recrystallize” into a structure that enzymes can’t easily break apart. This process is called retrogradation, and it increases resistant starch.
- Even if you reheat cooled pasta, much of that resistant starch stays intact — so you still get some of the lower glycemic benefit.
🥣 Steel-Cut Oats
- Raw oats already contain some natural resistant starch.
- Cooking breaks much of that down into digestible starch.
- But, if you cook the oats, let them cool, and then eat them chilled (or re-warmed), you increase resistant starch through the same retrogradation process. Overnight oats (soaked and then chilled) can also deliver RS.
👉 Key contrast:
- Regular starch → digested fast → glucose surge.
- Resistant starch → bypasses digestion → ferments in the colon → feeds gut bacteria, moderates blood sugar.
Bill Gibson, II 