What is resistant starch?
Resistant starch has created some buzz in the world of nutrition and inflammatory bowel disease (IBD) recently with claims suggesting it may be a beneficial dietary component or supplement. In today’s blog we take a deeper look at the research on resistant starch and leave you with some recommendations.
What is resistant starch?
Resistant starch is a type of non-digestible carbohydrate that acts as a prebiotic, or food, for our gut microbes. Instead of being digested and absorbed in our small intestine, resistant starch travels down to our large intestine where it is fermented by our gut microbes (1). Prebiotics, such as resistant starch, have long been thought to promote health benefits in humans because of the production of short chain fatty acids (SCFA). SCFA are by-products of the fermentation process that have been linked to supporting gut barrier permeability and reducing intestinal inflammation (2). Resistant starch in particular has been studied for its effects on prevention of heart disease, insulin resistance, and weight management (3).
What is the research saying about resistant starch and IBD?
A 2020 meta-analysis summarized and compared animal and human studies that were looking at resistant starch intake and its impact on inflammatory bowel disease (4). This is what it found:
Eleven animal studies were reviewed showing that on average, the mice taking a resistant starch supplement had significantly less intestinal damage compared to animals that did not take the supplement. This finding was consistent after pooling all of the results together. Additional findings suggest that animals consuming resistant starch had:
- Significantly lower levels of myeloperoxidase (MPO) an enzyme associated with inflammation
- Significant increase in SCFA concentration
- Potential beneficial changes in the gut microbiota
Of the seven human studies that were reviewed, six looked at patients with ulcerative colitis and one studied patients with Crohn’s disease and ulcerative colitis. All of the studies were a bit different in design, type of resistant starch, and outcomes assessed; making it challenging to summarize and draw conclusions. However, the majority of studies did report multiple benefits for those taking resistant starch supplements compared to those who did not.
- Two studies in those with UC showed resistant starch consumption significantly reduced disease activity
- Three studies showed those with UC remained in remission after consuming a resistant starch supplement
- Three out of four studies measuring SCFA production showed an improvement with resistant starch intakes
Although not all studies reported on the potential side effects of resistant starch, those that did found that there were no negative effects suggesting resistant starch was likely safe. The results of these studies look promising however, the meta-analysis reported that the studies are at a high risk of bias meaning, we need to be careful when interpreting these results.
How much resistant starch do I need and where can I find it in my diet?
The dose of resistant starch in the meta-analysis studies ranged from 0.6g per day to 34.8g per day, making it hard to narrow down a recommended dose. While we don’t know exactly how much resistant starch people with IBD need, we do know that those with IBD generally tend to consume inadequate amounts of dietary fibre and prebiotics, including resistant starch (4). You can increase your resistant starch intake by including certain foods in your diet regularly. The most common sources of resistant starch are (5):
- Cooked and cooled potatoes and rice
- Plantains and green bananas
- Beans, peas and lentils
- Whole grains including oats and barley
It’s important to know that cooking can impact the amount of resistant starch in certain foods.
- Resistant starch is found in potatoes, rice, pasta, and beans once they have been cooked then cooled. Reheating these items will not impact the resistant starch content (5). Try using cooked then cooled ingredients in pasta or potato salad or eat them as leftovers to increase the resistant starch content!
- Green bananas, plantains and oats lose their resistant starch content when cooked. Try making overnight oats using uncooked oats soaked in your choice of milk or yogurt and leave it in the fridge overnight. You can also add green banana flour or potato flour to foods, however resistant starch will be lost if baking or cooking with this (5).
- Resistant starch is a prebiotic fibre that acts as food for our gut microbes
- Animal and human studies show that resistance starch may play a role in reducing intestinal damage, reducing IBD activity and supporting intestinal health.
- The majority of these studies are in people with UC and more research is needed to understand how those with Crohn’s disease may benefit from resistant starch.
- More research is needed to understand exactly how much resistant starch is needed to improve IBD.
- There are many sources of resistant starch that can be added to your diet. Make sure you prepare them properly to maximize the amount of resistant starch.
Written by: Kaity McLaughlin, MPH RD
Makki K, Deehan EC, Walter J, Bäckhed F. The impact of dietary fiber on gut microbiota in host health and disease. Cell Host Microbe. 2018;23(6):705–715. .
Blaak EE, Canfora EE, Theis S, Frost G, Groen AK, Mithieux G, Nauta A, Scott K, Stahl B, van Harsselaar J, van Tol R. Short chain fatty acids in human gut and metabolic health. Beneficial microbes. 2020.
Higgins JA. Resistant starch: metabolic effects and potential health benefits. J AOAC Int. 2004 May-Jun;87(3):761-8. PMID: 15287677.
Montroy J, Berjawi R, Lalu MM, Podolsky E, Peixoto C, Sahin L, Stintzi A, Mack D, Fergusson DA. The effects of resistant starches on inflammatory bowel disease in preclinical and clinical settings: a systematic review and meta-analysis. BMC gastroenterology. 2020 Dec;20(1):1-4.
McKinney, C. What is resistant starch? [Internet]. The John Hopkins Patient Guide to Diabetes. Available from: https://hopkinsdiabetesinfo.org/what-is-resistant-starch/