What is Resistant Starch? (and why your diet needs more)

Looking for a fool-proof (and affordable!) way to support your gut health, boost your immune system and balance your gut microbiome? Are you keen to learn what all the resistant starch fuss is really about?

Here we are going to take a look behind the scenes and discover what eating resistant starch does inside your body, which gut bacteria benefit the most and what exactly those benefits mean for your health.

And most importantly, you’ll uncover the food sources highest in resistant starch that a healthy microbiome needs you to eat – today.

Are you ready to see your food choices in a completely new light?

Let’s get started.

What is Resistant Starch?


When you think of starch, what is the first thing that comes to mind? 

For me it’s cornstarch. 

I vividly remember the kitchen-science experiment of saturating a bowl full of cornflour with water. And eagerly watching (and feeling) the different gluey consistencies with different amounts (and temperatures) of water.

This is a typical quality of starches. It is starchy – gloopy, sticky, slimy and food for gut bugs (but not always the good ones)! 

Think potatoes, bread, rice, grains and pasta. 

Not all starches are exactly the same however – due to variations in molecular structure, starch can be quickly digested, slowly digested or not digested at all. 

Those that aren’t digested in our stomachs or small intestines (by digestive enzymes and juices) reach the large intestine intact.

These starches that ‘resist’ digestion are called resistant starches (RS).

How Resistant Starch is Fermented in Your Gut

So what exactly does a resistant starch look like?

A little like this…a complex carbohydrate.

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As you can see, starches are made up of many repeating units –  in macro-nutrient terms, they are called polysaccharides.

‘Poly’ meaning many and ‘saccharide’ is the formal term for sugars – like fructose, glucose, sucrose etc.

Additionally, starches are made up of two types of polysaccharides:

  • Amylopectin: a highly branched molecule with lots of surface area. The chains branching off each other are easily accessible to digestive enzymes.

    And because of this, they are more readily broken down – so digestion of these starches happens quickly and raises blood sugar (glucose).
  • Amylose: in contrast amylose is a straight-chain polysaccharide molecule. This linear formation hinders access for digestion. And these foods are digested far slower. They resist the release of their sugars and subsequently see a slower blood sugar rise.

    Amylose molecule structures predominate in RS.

It is by virtue of this molecular makeup that RS are able to ‘resist’ digestion and travel further down into the gut – to be fermentable food for bacteria.

From here, different bacteria have the genetic advantage of producing the amylase enzymes needed to further breakdown these complex amylose structures.

Science terminology note:
Words ending in -ose are sugars (e.g., amylose) ….and…
Words ending in -ase are enzymes that degrade that sugar (e.g., amylase digests amylose)

And because of this, amylase producing bacteria like Ruminococcus bromii are keystone gut microbiome species

R.bromii initiates the breakdown of RS molecules allowing for other bacteria to use the fragments to produce beneficial short-chain fatty acids (SCFAs) like butyrate.

The Benefits of Short-Chain Fatty Acids (SCFAs)

SCFAs are synonymous with gut health. It’s hard to talk about gut health without mentioning crucial beneficial gut bacteria breakdown products – like the SCFAs butyrate, propionate and acetate.

They are an end-product of bacterial fermentation.

These important metabolites are natural chemical compounds formed from microbial digestion (fermentation) in the gut. And they play a pivotal role in the health of your gut lining, brain function, regulating your metabolism and your immune system.

In science terms, SCFAs are fatty acid molecules that have fewer than six carbon (C) atoms. For interest (and those that love a little chemistry), the common SCFAs are shown in the table below with their chemical names, formulas and structures.

SCFA NameSalt NameFormulaDiagram
Acetic acidAcetateC2H4O2rKcjQEBIajtiHaXByUM32aPT2WhNU Rj7bkDlxPdw1OF6Ac0dWQhsI2i RJD28ZH0UGiLjmhL22NefVgp1reBnv6oG9tZOiHQlCe6nNCVoPzlmmNTmbFSlEygyZbjaZhLpfLUCm
Propionic acidPropionateC3H6O2
Butyric acidButyrateC4H8O2G CiuJg3Fw3zB0UzdakS4e6vkaQHO YjxYifRaSwC0uGwfqDW 3IzTITKaUn06 c17ZEK0u7P5kgI9MGgbCZQHXvQDBo2nMQm5MZxF0AKsk4eEYz0J BlT1lfTw6422fOWsOYiq5

Don’t worry if it’s all a bit technical, your gut microbes and your amazing body take care of the biochemistry so you don’t have to!

But knowing the basics helps us to understand how we can better influence our gut health – like providing ample RS! 

Because SCFAs are the main source of energy for colonocytes (the cells lining your large intestine), regulate our metabolism, appetite, body composition and immune function – each SCFA type has different abundance and roles within the gut.

Acetate (also called acetic acid – similar to the vinegar in your cupboard) is produced in the greatest abundance followed by propionate and finally the mighty butyrate. The ratio of different SCFAs is important too. For example:

Acetate & Propionate – the ratio of acetate to propionate is important in regulating liver fat metabolism. Acetate & Butyrate – the ratio of acetate to butyrate is thought to control the gut IgA immune response to the gut microbiome itself.

To understand a little deeper let’s have a brief look at each of these primary SCFAs.

  • Acetate: Is the most abundant because many bacteria can produce it. It acts as an essential energy source for many other bacteria – many of which actually use acetate to produce butyrate.
  • Propionate: Involved in the release of glucose from the liver which is important in maintaining blood glucose levels. It also helps to trigger the release of anti-inflammatory molecules and also those that control appetite.
  • Butyrate: One of the most important SCFAs for gut health. Provides fuel for intestinal cells and assists in maintaining integrity of the gut lining. It can also trigger the release of anti-inflammatory molecules and control appetite like propionate.

It is via the many beneficial actions of SCFAs that resistant starch gains it’s impressive reputation. And much of this is due to the amazing microbes that ferment it.

Are You Getting Enough Resistant Starch?

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One surefire way to know if you are consuming enough RS is to test for the bacteria in your gut that produce SCFAs.

Because the amount of SCFAs we have in our colon depends on:

  1. The amount (and type) of carbohydrates we eat
  2. The abundance (or lack) of SCFA producing gut bacteria we have and feed

If we eat adequate RS, we feed the beneficial bacteria (and probiotic bacteria) that make plenty of SCFAs.

Which gut bacteria assist in this crucial gut health foodweb…?

> Akkermansia muciniphila

> Bacteroides thetaiotamicron

> Bifidobacterium
> Eubacterium rectale

> Faecalibacterium prausnitzii

> Lactobacillus
> Ruminococcus bromii
> Roseburia 

Each of these species are reported in the advanced gut microbiome testing we use. In order to accurately determine the exact state of your health – gut testing is an integral part of the gut health programs we offer.

If you are interested in learning more about your unique gut microbiome signature (and if you are eating enough RS) you can learn more about our programs here.

Ultimately, RS functions just like soluble fermentable fibre, nourishing the SCFA producing gut bacteria that reside in your large intestine.

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The Difference between Resistant Starch and Fibre

Hang on, so if resistant starch acts like fibre – what is the difference between resistant starch and good ol’ fibre?

This is a great question and something that many people are confused about – even some gut health gurus. 

One source of confusion comes from the fact that in nature nothing occurs in isolation – many parts make up the whole.

Resistant starch and various types of fibre co-exist in most fruits and vegetables. 

Basically fibre is another type of polysaccharide – just made up of different molecules.

  • Resistant starch: predominantly amylose
  • Fibre: cellulose, hemicellulose, pectin, inulin, lignin, beta-glucans

Fibre is categorised by its ability to dissolve in water (solubility). As we mentioned earlier, RS acts like a soluble fibre – inulin, pectin and vegetable gums. These are also great examples of prebiotic fibres.

Prebiotics are crucial for well balanced gut health as, similar to RS, they promote SCFA production. To gain a comprehensive understanding of prebiotics, read The Ultimate Prebiotics A-Z Guide (plus 31 of the most common prebiotics).

Fundamentally, you want to expand the diversity of your gut microbiome and enhance the production of beneficial metabolites like SCFAs. The best way to reap the many benefits, is by eating a wide variety of all different types of RS and fibres/prebiotics.

This also encourages bacterial abundance, cross-feeding of different species from each other’s metabolites and evenness in your gut population (no one species dominates – well balanced). 

All positive traits of a healthy gut microbiome and resulting wellbeing.

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What Science Says About Resistant Starch Benefits

Now that we have a good understanding of what resistant starch is, how it’s fermented and by whom – let’s have a closer look at some of the amazing benefits of consuming resistant starch…

  1. Improved insulin sensitivity
    RS slowly digests and doesn’t spike blood sugar – meaning that the body doesn’t need to release insulin in response.
  2. Lower blood cholesterol and fats
    Early studies suggest that RS improves blood fat profiles and has the potential to reduce risk factors involved with atherosclerosis and type 2 diabetes development in overweight individuals.
  3. Nourish and repair gut lining
    One of the cornerstones of gut health is nurturing a healthy gut lining. Long term intake of RS has been shown to improve the integrity of mucus lining the gut, reduces gut cell death and inflammation.
  4. Boost beneficial gut bacteria
    Increases in the abundance and diversity of beneficial gut microbes has been recorded with RS supplementation. Not only does this boost SCFA production it also strengthens the immune system and resistance against non-beneficial microbes.
  5. Lower bowel pH and inflammation
    Promising studies have identified RS as being a promising dietary addition for the prevention and/or treatment of inflammatory bowel conditions. It has been shown to reduce the pH and prompt lactobacilli and bifidobacteria levels.
  6. Aids in weight loss
    Reduction in food consumption is associated with RS intake. As is the ability of RS to increase fat oxidation and reduce fat storage cells. 
  1. Enhanced immunity

Due to the supportive benefits of SCFAs, RS has been associated with supporting important immune regulation roles. Via this microbe mediated role a number of harmful metabolites are also reduced, including ammonia and phenol. 

Are you ready to fill your plate with supportive RS-rich foods yet?

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The Top 10 Resistant Starch Foods

Similar to increasing your prebiotic fibre quota, resistant starch is found most abundantly in plants.

Here are the most plentiful sources of RS in no particular order. Enjoy liberally!

  1. Beans: Navy, white,kidney, black-eyed are all great sources of RS. Soak them overnight (6 to 12 hours) before cooking and enjoy in salads, as homemade baked beans and more…
  2. Legumes: Chickpeas and lentils are another great choice to enhance your weekly RS quota. Similar to beans, soak legumes overnight before cooking and cooling. Hummus is a delicious and easy way to include more chickpeas in your diet.
  3. White potato: Both types of potato (white and sweet) contain RS. The highest levels from white potatoes are available once they are cooled and then reheated. Potato starch is another way to use white potato in cooking – use it in place of cornstarch or arrowroot.
  4. Sweet potato or yams: The ever-versatile sweet potato whether purple, white or orange is another delicious source of RS. Again cooked and cooled work best.
  5. Whole grains: Oats, buckwheat, quinoa, millet, amaranth, barley, millet, brown rice, wheat etc. all have a percentage of RS. To increase the levels, cook in advance and cool before eating. Oats which are uncooked have the highest quota (like in overnight oats for bircher muesli). Grain-based products like bread and pasta have some RS present also.
  6. Rice: White rice that has been cooked and then cooled (similar to traditional fried rice cooking methods) yields higher resistant starch levels than freshly cooked rice.
  7. Green bananas or plantains: Green bananas are unripe regular bananas and are one of the richest RS sources. Substituting a portion of green banana flour in baking is an easy way to increase your RS. Plantains are different to green bananas (although can look like a green banana) – both yellow and green are high in RS. Or you could try our Cassava and Green Banana Pancakes for a RS boosting breakfast!
  8. Cassava (tapioca): Is a tuberous vegetable prevalent in tropical climates and cuisine. This RS powerhouse can be added as a flour or if you’re lucky as a fresh tuber. We love cassava and enjoy numerous delicious cassava recipes:

    > Cassava Flour Tortillas
    > Beetroot & Cassava Flour Crepes
    > Cassava & Almond Meal Carrot Cake
    > Cassava Flour Pizza Crust
    > Cassava & Flaxseed Bread
  9. Seeds: Pumpkin, flax, sunflower, pistachio and sesame also contain some RS. Enjoying these along with other sources adds variety and offers their many other healthful benefits too.
  10. Green peas: Peas, cooked or raw are a very good source of RS. However if you know you’re sensitive to FODMAPs and the prebiotic GOS another source may be less problematic as GOS is often not tolerated in IBS and severe leaky gut.
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What it Means for Your Gut Health 

Increasing or introducing resistant starch into your diet can be a powerful tool on your gut health journey. Anything that balances your microbiome, helps heal your gut and comes from wholefood sources is nearly always a good idea…

…But…

In some cases increasing these foods can actually lead to further discomfort and increased symptoms. They can make you feel worse before you feel better.

If you struggle with FODMAP foods or have severe leaky gut or gut dysbiosis – I can’t stress the importance of working with a qualified health professional enough.

In addition to a personalized food plan and individual gut microbiome testing, it is helpful to know exactly which probiotics you have in abundance (and which you lack) to correct these imbalances and reap the benefits of all those nutritious RS foods you are eating.

Our programs offer all this and much more, if you are interested in a truly supportive and tailored approach towards improving your gut health we’d love to hear from you.

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  • Sophia says:

    Hi. Great article, thanks for the information.
    I was curious – what was the reason behind eating refrigerating the resistant starches before consumption? Does this help the to develop in some way?

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