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Resistant Starch

The majority of the carbohydrates in our diet are starches.  Starches are long chains of glucose that are found in grains, potatoes and various foods.  However, we don’t digest all of the starch we eat.  Sometimes a small part of it passes through the digestive tract undigested.  In other words, it is resistant to digestion.  This type of starch is called resistant starch, which functions a little bit like soluble fibre.

Resistant starch can be very beneficial to our health.  This includes improved insulin sensitivity, lower blood sugar levels, reduced appetite and other various benefits for digestion.

Resistant starch seems to have become a bit of a buzz word these days. Many people have experimented with it and seen major improvements by adding it to their diet.

The 4 Different Types of Resistant Starch

Not all resistant starches are created equal.

  • Type 1 is found in grains, seeds and legumes and resists digestion because it is bound within the fibrous cell walls.

  • Type 2 is found in some starchy foods, including raw potatoes and green (unripe) bananas.

  • Type 3 is formed when certain starchy foods, including potatoes and rice, are cooked and then cooled. The cooling turns some of the digestible starches into resistant starches via a process called retrogradation.

  • Type 4 is man-made and formed via a chemical process.


The classification is not so straightforward, though, as several different types of resistant starch can coexist in the same food.  Basically, the amount of resistant starch changes depends a lot on how foods are prepared. For example, allowing a banana to ripe (turn from green to yellow) will degrade the resistant starches and turn them into regular starches.

Let’s See How This Actually Works

The main reason why resistant starch works, is because it functions like soluble, fermentable fibre.  It goes through the stomach and small intestine undigested, ultimately reaching the colon where it feeds the gut’s friendly bacteria.  There are actually hundreds of different species of bacteria in the intestine. In fact, the number and type of bacteria can have an important impact on our health.  Resistant starch feeds the friendly bacteria in the intestine, having a positive effect on the type of bacteria as well as their quantity.  When the bacteria digest resistant starches, they form several compounds, including gases and short-chain fatty acids, in particularly a fatty acid called butyrate.  Butyrate is actually the preferred fuel of the cells that line the colon.  Kind of a superfood for digestive system bacteria.  Resistant starch both feeds the friendly bacteria and indirectly feeds the cells in the colon by increasing the amount of butyrate.

Resistant starch has several beneficial effects on the colon.

It reduces the pH level, potently reduces inflammation and leads to several beneficial changes that should lower the risk of colorectal cancer, which is a leading cause of cancer death worldwide.

The short-chain fatty acids that aren’t used by the cells in the colon get absorbed into the bloodstream, liver and the rest of the body, where they confer beneficial effects. 

Because of its therapeutic effects on the colon, resistant starch may be beneficial for various digestive disorders. This includes inflammatory bowel diseases like Ulcerative Colitis and Crohn’s Disease, constipation, diverticulitis, irritable bowel syndrome and diarrhoea.  However, this area of science is still young and requires much more research.

Resistant Starch Enhances Insulin Sensitivity, Lowers Blood Sugar Levels and Improves Metabolism

Resistant starch has various benefits for metabolic health.  Several studies show that it can improve insulin sensitivity, by increasing the body’s responsiveness to insulin.  Resistant starch is also very effective at lowering blood sugar levels after meals and it also has a “second meal effect” – meaning that if you eat resistant starch with breakfast, it will also lower the blood sugar spike at lunch.

The effect of resistant starch on glucose and insulin metabolism is very impressive. Some studies have found a 33-50% improvement in insulin sensitivity after 4 weeks of daily consumption of 15-30 grams of resistant starch.  The importance of insulin sensitivity cannot be understated.

Having low insulin sensitivity (insulin resistance) is believed to be a major cause in some serious diseases, including metabolic syndrome, type 2 diabetes, obesity, cardiovascular disease and Alzheimer’s Disease.  By improving insulin sensitivity and lowering blood sugar, resistant starch may help avoid chronic disease and prolong life and increase its quality.

However, it’s important to note not all studies agree that resistant starch has these beneficial effects. The level of the beneficial effect of resistant starch depends on the individual, the dose and the type of resistant starch used.

Resistant Starches May Help You Lose Weight by Improving Satiety

Resistant starch has half the calories of regular starch (2 vs 4 calories per gram).  Therefore, the more resistant starches found in a food, the fewer calories each serving will contain.

Resistant starch has similar effect to soluble fibre supplements in relation to its contribution to weight loss, primarily by increasing feelings of fullness and reducing hunger.  Hence, adding resistant starch to meals increases feelings of fullness and makes people consume less calories.

Personally, I doubt that adding resistant starch to your diet as a primary strategy in weight loss would lead to any major effect on your weight, but it might make it easier to lose weight combined with other strategies.

How to Add Resistant Starches to Your Diet

There are two ways to add resistant starches to your diet. Either by getting them from

the food or by taking supplements.

Foods which are high in resistant starch include raw potatoes, cooked and then cooled potatoes, green bananas, various legumes, cashews and raw oats. These are all high-carb foods, so you should avoid them if you are currently on a very low-carb diet (although you can fit some in if you’re on a low-carb diet with carbs in the 50-150-gram range – which is also considered low-carb).  Raw potato starch contains about 8 grams of resistant starch per tablespoon and almost no usable carbohydrate. It’s also very inexpensive.  If you feel it tastes bland you can add it to your diet in various ways, by sprinkling it on your food, mixing it in water, putting it in smoothies, etc.

Four tablespoons of raw potato starch should provide 32 grams of resistant starch. It is important to start slowly and work your way up, because too much, too soon can cause indigestion and discomfort.  It is not beneficial to consume much more than that, because when you reach 50-60 grams per day, the excess seems to just pass through (like fibre).  Do note that it may take time (2-4 weeks) for the production of short-chain fatty acids to increase and to notice the benefits.

Is It For Me?

If you’re currently trying to smash a weight loss plateau, have high blood sugars, digestive problems, or if you’re simply in the mood for some experimentation, then trying out resistant starch can be an interesting idea and I would love to hear about your experience with it.

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