Resistant starch: The Key to Gut Health?

Resistant Starch: Understand it or Have a Broken Gut

In the world of nutrition nothing ever seems to be simple. The topic of resistant starch is no exception.

Whether considering high or low carb, Vegan or Paleo, there are many upsides and drawbacks to any approach.  As well as seemingly endless questions for which the answer is: it depends.

We are definitely not living life as a controlled trial.  When is comes to gut health this could not be more true.  There are several compounding factors that make taking control of your gut health difficult to attack. First because everyone is so different, what works for one person, may not work for the next. Second the gut micro-biome is so diverse and ever changing that it is a very difficult thing to study and create protocols for.  Environment can factor in and undermine ones efforts.  Also what you eat and when you eat it greatly influences the gut.  How the food was prepared, what the meal make up was, the stress level a person had while consuming the meal all factor in.  The list goes on and on.

If you want to improve gut health, then you’ll need to understand Resistant Starch (RS).  Many people have no clue what it is. This article will attempt to make sense of resistance starch and potential approaches to taking it. Also, which people may benefit from adding some form of resistant starch to their diet.  There are many sources of RS.  This article will focus on banana flour, a form of RS known as RS2.

First and foremost, you may be wondering: what is resistant starch?  Resistant starch is a form of carbohydrate that can not be digested by humans.  Why would you want to eat something you can’t digest?  Well, that is where the gut micro-biome comes into play.  We are host to a massive population of various species of bacteria.  They break down the things we can’t, into usable substrates for us, as well as micronutrients for other bacteria.  The entire micro biome helps to support the host’s (you) system.  Including neurotransmitter production, vitamin synthesis and absorption, repairing the gut lining, metabolism and immunity.

When things can’t be broken down in the small intestine, they are sent along to the colon to be digested by our bacteria.  A major problem people are running into lately is their gut population is not diverse enough and something called dysbiosis occurs.  This can lead to intestinal permeability, food intolerances and irritable bowl syndrome.   The gut can also influence the expression of various enzymes responsible for fat burning signaling, insulin response and even mood via influence on neurotransmitter production and the brain gut axis.  Needless to say, what is going on the in gut is vital to our general health and performance.

Resistant starch can be broken down into four categories: RS1, RS2,RS3 and RS4.

RS1 are the undigestible parts of seeds, legumes or unprocessed whole grains.

RS2 is found in things like potato, green bananas, high amylose corn and roots. This part of the plants are convertible to digestible carbohydrate when heated and hard to eat when raw.

That is why people typically cook potatoes and wait for bananas to get ripe before they eat them.  Not to mention they taste much better that way.  Nonetheless, you can eat these food in their raw or unripe form and they will not be digested in the SI.  This will give your bacteria something to munch on.  Some would argue that is critical.  Scientist are in the beginning stages of trying to ascertain the particular ways in which eating RS2 could be beneficial.

RS3 is created when otherwise RS2 formats are cooked and cooled.  If you eat a cold potato, a small percentage of that will be RS3.  More than when it is still hot and less than when it is raw.  Another name for Rs3 is retrograde starch.  Check out this interesting article in Time magazine on white rice preparation and how to reduce the net caloric load of rice.

RS4 is commercial grade starch that have been chemically modified to resist digestion.

Ok so what does all this mean?

At this point, it’s hard to draw conclusions from the current literature, as the science of the gut micro-biome is in it’s relative infancy.  Most of the studies have been conducted on rats.  And as far as directly correlating resistant starch to performance in an endurance bout for example, nothing has really been done yet.  Most of the studies have been centered around insulin sensitivity and fat oxidation pathways.  What is known for RS2, including Potato Starch and HAM-Starch (High amylase maize) is that certain serving sizes will blunt the glucose response to a meal. It also may improve insulin sensitivity in Type 2 diabetics.  In other words, when you take a dose of RS2 with a meal your blood glucose levels will rise less than sans RS2.

A study conducted Janine A Higgins and colleagues at the University of Colorado looked to see if banana flour could impact fat oxidation rates in 12 healthy subjects.  They measured respiratory quotient (RQ) at various times after a meal. Post prandial of a macronutrient balanced mixed meal and up to 24 hours post ingestion.  RQ measures the percentages of the substates being metabolized and exhaled.  1 is all carbs and .7 is all fat.  They showed no impact on glucose, insulin, FFA or triglyceride excursions in the blood. The blunting effect of the glycemic response to a mixed meal is typical compared to a test meal of just carbs, which RS has shown efficacy for.

They did however find that in one of the trial groups, fat oxidation was significantly increased.  They tested RS as 0%, 2.7%, 5.4% and 10.7% of total daily carbohydrate ingestion.  The 5.4% group showed  a 23% increase in fat oxidation compared to the 10.7% group and 0% group.  The 5.4% RS group had the lowest RQ for 24 hours.  Here are the data:

This next image looked at total fat oxidation from the specific test meal.  This data was assessed via indirect

calorimetry:

 

What these two data sets show is that not only are you going to burn a greater percentage of total energy as fat during the day, but you will also oxidize more of the fat in a specific meal with a concurrent banana flour ingestion.

This can be applied for two populations.  There are many dietary approaches to increase fat burning. Including ketosis, keeping carbs low glycemic index and various ergogenic aids.  For those in ketosis or eating very low carb this may actually be less significant because they are already burning fat at a great clip, but they could use this to either lessen the impact of carbohydrates consumed on a workout day or this could be incorporated as a technique to get back into ketosis if you had slipped out.

Another potential use for people on a ketotic diet would be to simply add “gut food” to your diet without increasing “carb” intake.  Many whole foods containing RS or fiber contain carbohydrates as well.  These are great foods like beans, lentils, whole grains, underripe bananas and cold rice or potatoes.  While these foods are fine for someone on a low carb diet, they might not be appropriate for a person in full on ketosis.  Also, gut dysbiosis seems to be one of the main drawbacks of maintaining a very low carb diet.  It takes special attention and know how to keep digestion in line when doing carb restriction, especially if you wish to maintain high blood ketones.

Keep in mind that this study was not conducted on people in ketosis, or in the context of a high fat test meal, but RS alone has shown to not impact blood sugar levels or insulin, as it is not absorbed in the small intestine.  Which means these carbs will not impact ketosis because they are not absorbed in the small intestine thus raising the blood sugar and effecting liver glycogen levels.  The bacteria actually metabolize them into the fatty acid Butyrate.

Including a serving of banana starch at 5.4% of your total carbohydrate intake is a hack you can use to not only potentially increase overall fat oxidation, but also keep a healthy gut flora.  Consider adding a probiotic as well.  This will insure that there are some bacteria there to eat the resistant starch,  Also, don’t go crazy with the resistant starch either, especially one specific type.  You can cause dysbiosis in the other direction as well.

If getting fermented foods and Fiber is hard for you on a low carb diet, you might want to give Resistant Starch a try.  Start out with a small amount like 1 tsp and move up to 1 tbsp.  The main indication that the dose is too high is bloating or disruption in either direction (backed up or the runs) of regularity.

And if you are maintaining a “normal” carbohydrate profile, adding banana starch equal to 5.4% of your daily carb intake may help you to burn more fat as fuel, without giving up all of your favorite carb laden foods.  Thanks for reading!