Do You Need Fiber on a Ketogenic Diet? The Benefits of Resistant Starch

Do You Need Fiber on a Ketogenic Diet? The Benefits of Resistant Starch

Keto fiber

Whilst I do not follow a ketogenic diet most of the time, I do like to go keto every once in awhile.  This helps to reset my insulin sensitivity and I get the brain benefits from the beta hydroxybutyrate. I stock up on the usual keto diet supplements such as MCT oil, then I begin my keto reset.

Information such as this paper however, leaves me asking how does ketosis affect gut health? Fiber is said to be a key player in keeping your microbiome healthy, but when we think fiber, we think carbs. Keen to learn more about the information out there on this topic, I dug into the research. Here is what I found.

Firstly, what is fiber?


We should take a brief look at what fiber actually is and what role it plays in our health. When we speak of fiber in relation to diet, we are talking about plant fiber that we get from food. There are two types of fiber, soluble fiber and insoluble fiber. Soluble fiber dissolves into water and is fermented by our good bacteria in the colon. Insoluble fiber does not dissolve into water and acts as a bulking agent in our poop and helps keep us regular.

You may even be taking psyllium husk as one of your keto diet supplements now. Many who experience keto diarrhea may take the hit of the carbs that come with psyllium for gut benefits it infers. Psyllium husk contains mostly soluble fiber.

Plant based foods contain both soluble and insoluble fibre in varying amounts. Here are some common keto diet foods and estimated insoluble (%I), and soluble (%S) fibre content as an example-

Almonds- 90%I, 10%S

Asparagus- 40%I, 60%S

Avocado- 80%I, 20%S

Soluble fiber

When digested soluble fibre is mixed with the liquid in the digestive tract which gives it a gel like consistency. This helps with feelings of satiety after a meal by slowing down digestion, which in turn helps to maintain a healthy weight. Soluble fiber also helps to reduce cholesterol in the body by binding to cholesterol particles. Lowering cholesterol helps to reduce the risk of heart disease in those who have high cholesterol.

Insoluble fiber

Insoluble fiber bulks out our poop to produce soft, regular stools. Both can be fermented by our gut bacteria, insoluble fiber to a lesser extent.

Food for our gut bacteria

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Gut bacteria proliferate with prebiotics. We’ve all heard of probiotics, like the kind we get from fermented foods in my primal probiotics course, but not so many have heard of prebiotics. A prebiotic is typically either soluble or insoluble fiber that passes through the upper part of the gastrointestinal tract and stimulates the growth and activity of beneficial bacteria in the colon. Prebiotics are considered an essential nutrient by the codex alimentarius. In other words, they are pretty important to incorporate into a healthy eating regime.


These prebiotic foods, are flora foods. They feed our gut flora and it is important to get both soluble and insoluble fiber to feed your gut bacteria and keep you regular. A diet high in fibre has been shown to have a host of health benefits.

There are many kinds of fiber, we are going to focus on an important one that can be hard to get on a ketogenic diet, resistant starch. Resistant starch gets its name because it resists digestion. Instead it passes through the digestive tract into the colon where beneficial bacteria use it as a substrate.  Foods containing a high amount of resistant starch are cooked then cooled potatoes, cooked then cooled rice and green bananas. So you see how it can be hard to get it on a keto diet!

How can we get the resistant starch from our keto diet foods? Potatoes and rice are off limits. Unripe green bananas shouldn’t push you out, but do you like the taste of them? Is there something else we can add to our arsenal of keto diet supplements to make up for the unintentional omission of resistant starch?

Here is a list of foods high in resistant starch and their general carb count –

1 medium banana, net carbs – 23.9 g (green bananas will have fewer digestible carbs)

1 cup of oats, net carbs – 46.7 g

1 cup of beans, net carbs – 26 g (average for common varieties)

1 large boiled potato, net carbs – 53.8 g

1 cup of white rice, net carbs – 44 g

Unless you are following a cyclical keto diet, you won’t be eating these. If you are very strict with your keto diet, you may be missing out on the health benefits of resistant starch



Benefits of resistant starch

After digging into the research, I found some pretty cool info on resistant starch.This paper goes into more detail if you would like to read it. Here are some of those benefits-

Stimulation of colonic blood flow

Stimulation of fluid and electrolyte uptake

Production of short chain fatty acids

Resistant starch is broken down by gut bacteria into short chain fatty acids. These fatty acids comprise mainly of acetate, propionate and butyrate. Butyrate is the key player here, here are some of butyrates roles in the body-

*Energy source for epithelial cells (gut lining cells)

*Anti inflammatory

*May influence gut permeability (leaky gut)

*May play a role in fighting conditions such as ulcerative colitis, antibiotic related diarrhea, and pouchitis amongst others.

*There are many other proposed benefits, but these listed above seem to be the most important in my estimation seem to the most important.

Those benefits sound pretty impressive to me, definitely something I want to incorporate into my keto diet meals if I can. But if it is difficult to get resistant starch from food on a keto diet, what keto diet supplements can we use to get our fibre on keto diet? Not really classed as one of the the keto diet supplements, but something that could be used to this end which would give us a source of resistant starch is unmodified potato starch.

What is unmodified potato starch?


Unmodified potato starch means the starch is released from the potatoes without the use of chemicals or enzymes. Instead, potatoes are crushed and the starch is released from the crushed cells and the starch is collected. It is then then dried out into a white powder. It is a really good thickening agent. For purposes of encouraging your gut flora however, it should be taken with some cold water. Heat will change the starch into digestible starch and we will miss out on the resistant starch benefits.

Most importantly for those following a ketogenic diet, unmodified potato starch will not cause an insulin spike because it is not broken down into sugars. As mentioned earlier, resistant starch passes through the stomach and is broken down into short chain fatty acids in the colon instead, in other words, its keto friendly.

Start with a low amount such as half a teaspoon. Fermentation in the gut equals gas. A bit of gas is not a bad thing but it shouldn’t be excessive. Increase the quantity if you have no issues. I have about a tablespoon when i eat my first meal, and a tablespoon when i eat my last and have no issues. I use Bob’s red mill unmodified potato starch. They have excellent products and are an employee owned business.

Interested in making your own probiotic fermented foods? Sign up at my website for free content. Good luck with your ongoing journey to optimal health, next blog coming soon!

Full disclosure, I am not a nutritionist or doctor. I am however a personal trainer and a health and fitness nerd. I research for my blogs in depth by looking at studies and getting information from reliable sources. I encourage you to do your own research, and look through the studies in the links I provide. You should consult any dietary change with a professional, especially if you have a health condition. I am an amazon affiliate, if you buy any products through the links provided, I will receive a small amount of money. This will not affect the cost of the product to you.