Resistant Starch includes the portion of starch from plant foods that can resist digestion by human pancreatic amylase in the small intestine and as a result, it reaches the colon where it is fermented by bacteria. There are a number of well-established health benefits associated with resistant starch including improvements in glycemic control and decreased risk of developing cardiovascular and bowel disease.
Resistant Starch has become a bit of an adjunct buzz term linked with the non-abating digestive health trend that is a big craze at the moment with food manufacturers, scientists and of course consumers. Resistant starch is often touted by media and health experts as one of the key dietary fibres to achieving optimal digestive health. Whilst there is a growing body of evidence to support these claims, there is still a lot that we don’t know about this unique starch and exactly how it imparts these health benefits.
To help nutrition professionals and food scientists understand more about resistant starch, we have delved a bit deeper into some of the unique characteristics of this not very well understood, yet very important prebiotic fibre.
- Five different types
Up to five different types of resistant starch have been identified. Different foods contain different types of resistant starch and some contain a number of varieties1,2:
- RS1 includes physically inaccessible starch within cell walls. It is heat stable and is therefore a preferred ingredient in many foods
- RS2 comprises starch granules with a structure that limits the accessibility of digestive enzymes. after cooking, most of the starch becomes highly digestible as a result of starch gelatinization.
- RS3 is the starch formed after cooking and is found in cooled pasta and potatoes and bread crusts. RS3 is of particular interest to food manufacturers because of its thermal stability. Whereas RS1 and RS2 can be destroyed during cooking, RS3 can be formed.
- RS4 includes modified starches used by food manufacturers to alter the functional characteristics of the starch
- RS5 refers to amylose-lipid complex that resists amylase digestion. RS5 has been found to promote the formation of short chain fatty acids like butyrate, which can help prevent colon cancer.
- Foods with surprisingly high amounts of resistant starch 1
Many people know that resistant starch is found in whole grains, cooked and cooled pasta and rice, as well as green bananas. But there are actually a number of other food types that you may not necessarily associated with resistant starch yet are relatively high sources. Some of these less common foods are listed in the table below.
|Food Type||Resistant Starch (per 100g)|
- Resistant starch improves the population of the gut microbiota
Whilst resistant starch has a great repertoire when it comes to health benefits, not many people understand just how these health benefits are realised. The content of resistant starch has a high ratio of amylose and a low ratio of amylopectin. It is this physical structure that allows resistant starch to improve the population of gut microbiota by triggering cell signalling pathways that are associated with reducing diabetes, obesity and diabetes. The exact mechanism as to how this happens is still unknown and is an exciting area for emerging nutrition science.
- The “second-meal effect”
Resistant Starch has been associated with improved insulin sensitivity of up to 50% by consuming 15-30g of resistant starch per day 3,4 . Resistant starch is also very effective at lowering blood glucose levels after a meal. This is known as the “second-meal effect”. If you eat resistant starch at breakfast, it is likely to produce a lower blood sugar spike at the lunch meal a few hours later. 5 By improving insulin sensitivity and lowering blood glucose levels, resistant starch can decrease the risks of developing metabolic disease.
- Resistant starch has fewer calories than regular starch.
Resistant starch functions like soluble fibre when it comes to weight loss, by increasing feelings of fullness and reducing appetite. SCFAs can trigger the release of hormones that reduce the drive to eat (leptin, peptide YY, glucagon like peptide). This is an exciting area of research to potentially help fight the global obesity epidemic.
- Resistant starch imparts health benefits via SCFAs
We hear a lot of information about the fermentation of resistant starch in the colon and the associated production of short chain fatty acids (SCFAs). But what exactly is it about SCFAs that makes them so useful?
These SCFAs include acetate, butyrate and propionate which can be absorbed into the body or used by bacteria for energy. There are a number of benefits of SCFAs which include:
- stimulate blood flow to the colon
- increase nutrient circulation
- inhibit the growth of pathogenic bacteria
- help us absorb minerals
- help prevent us from absorbing toxic/carcinogenic compounds
The amount of SCFAs we have in our colon is related to the amount and type of carbohydrate we consume. And if we eat plenty of RS, we have plenty of SCFAs.
This video explains the role of SCFAs in feeding our hungry gut microbiome.
CSIRO has recommended that intakes of resistant starch should be more than 20 grams per day, which is almost four times greater than a typical western diet currently provides. 6 An estimate of resistant starch intake for Australian adults derived from the most recent National Nutrition Survey, suggested the range of intake to be from 3-9 grams per day with adult men consuming more resistant starch than women. 7
As the suggested intakes for resistant starch are significantly higher than current consumption, there is considerable scope for food manufacturers to increase resistant starch consumption on a population basis. Innovative food product development should look to include ingredients that are naturally good sources of resistant starch, to help consumers all over the world achieve optimal digestive wellness.
Have a question about Resistant Starch? Feel free to leave a comment below!
Teri Lichtenstein (APD)
The Healthy Grain Nutrition Ambassador
Fuentes Zaragoza et al (2001) Resistant starch as prebiotic: A review . Starch/Sta ̈ rke 2011, 63, 406–415
Baghurst PA et al (1996) Dietary fibre, non- starch polysaccharides and resistant starch – a review. Food Aust 48(Suppl):S3–S35.
Roberts J et al (2004) Resistant starch in the Australian Diet. Nutr Diet 61:98-104.