As a quick refresher, resistant starch is a type of carbohydrate and is high in amylose (3). It takes longer for us to break down and absorb amylose so it doesn’t spike our blood sugar the same way that some other types of carbohydrates do. RS also feeds our gut bacteria at the same time.
Let’s look at some of the recent research in the area of RS and healthy metabolism:
The bacteria in our gut use resistant starch and produces short-chain fatty acids (SCFAs). In a study of participants with metabolic syndrome placed on either a Western-style diet or a diet containing both resistant starch and arabinoxylan (another type of dietary fiber), the diet with the resistant starch resulted in greater levels of SCFAs1.
It also resulted in the promotion of beneficial bacteria, like Bifidobacterium1. The SCFAs produced by beneficial bacteria play a role in protecting against pathogens in the gut1. On the other hand, the Western-style diet led to increases in bacterial species associated with inflammatory bowel disease1.
Aid your digestion, aid your life, bolster your fiber today…
Bottom Line: Is it all about the bacteria? Animal studies suggest that RS actually has beneficial effects on insulin sensitivity beyond its effects on the gut bacteria2. Now it’s time to dive into some of the human studies on the topic.
Earlier this year, the study design and baseline results were published for a new study on resistant starch, aptly named the STARCH trial3. This is a trial that enrolled people ages 35-75 years old with confirmed prediabetes and an elevated BMI.
This was a randomized trial, where one set of participants did not receive RS and one set of participants did receive it. Those that did were given 45 grams per day of RS for 12 weeks. The researchers studied the result of this supplementation in insulin secretion, insulin sensitivity, and many other markers.
Key Insight: The results were surprising, given the promising outcomes of other studies previously. They found that RS supplementation did not improve parameters of metabolic health like they expected it to4.
Why might this be? Well, one factor to consider is that the participants in this study were under no particular dietary constraints and diet was not controlled for. Another consideration is the particular age range they were studying and the fact that these participants already had type 2 diabetes.
Could it be that RS would be more helpful alongside dietary interventions, or for factors this study did not measure or perhaps in a different age group?
As the authors of another study5 pointed out, changes in body composition take time and these studies may not reflect the full potential effect of RS supplementation over a longer period of time. They also suggest that there are likely subgroups of participants that respond better to RS than others.
Their own study looked at supplementation with RS in the context of the gut microbiome. The results of this study found that RS supplementation was related to positive changes in the gut microbiome, including increasing bacteria found in people with a healthy BMI5.
RS also had an effect on lowering percentage body fat, along with improving lipid profiles5. There was a trend towards smaller waist circumference, lower HbA1c and fasting blood glucose in those taking the RS supplement5.
Bottom Line: The key takeaway here is that RS may have a greater impact on parameters of health for some people than others and that the changes we are looking to see with RS supplementation take months or years. Keep in mind that there are also different types of RS (4), which may have slightly different effects.
There are other studies that show the promise of RS for healthy metabolism. This very interesting study compared bagels with 25 grams of RS to regular bagels consumed every day for 56 days.
The results of this study were a significantly lower fasting and postprandial insulin response in the RS group than in the controlled group6. In other words, RS resulted in better insulin sensitivity, even when it was wrapped up in bagels!6
Beneficial effects were also seen in a study using 25g of RS supplementation in women with type 2 diabetes. These women had:
Unfortunately, although the authors of the study named the recipe developer, they did not provide the full recipe for their RS bagels. On the bright side, I’m sure you’ll be able to find some foods you like amongst these 30 foods with high RS content (5)!
Promising results have also been seen in a healthy elderly population specifically. In this group, resistant starch supplementation for 12 weeks was well tolerated and was associated with a significant 7% reduction in blood glucose levels and a 41% drop in insulin levels8. This study used a lower amount of RS per day than some of the other studies.
Overall, studies on resistant starch supplementation are encouraging in terms of improving metabolic health and body composition. It’s easier than you think to start incorporating more resistant starch into your everyday meals (6).
Key Insight: One simple and delicious recipe you can try are these Yukon gold potatoes (7). There’s even a study that can provide insight into how having that resistant starch tonight might impact you in the short-term – as early as tomorrow morning.
This study examined healthy participants and their reactions to resistant starch within a 14-hour window of time9. When participants consumed resistant starch in their evening meal, they had a decreased glucose and insulin response after their breakfast the next morning9.
They also had increased p-PYY the next morning, both while fasting and after their breakfast9. P-PYY is a peptide hormone responsible for helping you to feel satiated.
There is a significant amount of resistant starch in the Daily Reset Shake. If you already have some of this shake on hand, check out the Banana Oatmeal Cinnamon Shake recipe (8). It will only take you two minutes to make dinner tonight! Get ready to improve your insulin sensitivity and feel more satiated after your morning meal.
1. Hald, S. et al. Effects of Arabinoxylan and Resistant Starch on Intestinal Microbiota and Short-Chain Fatty Acids in Subjects with Metabolic Syndrome: A Randomised Crossover Study. PLoS One 11, e0159223 (2016).
2. Bindels, L. B. et al. Resistant starch can improve insulin sensitivity independently of the gut microbiota. Microbiome 5, 12 (2017).
3. Marlatt, K. L. et al. Role of resistant starch on diabetes risk factors in people with prediabetes: Design, conduct, and baseline results of the STARCH trial. Contemp. Clin. Trials 65, 99–108 (2018).
4. Peterson, C. M. et al. Effect of 12 wk of resistant starch supplementation on cardiometabolic risk factors in adults with prediabetes: a randomized controlled trial. Am. J. Clin. Nutr. (2018). doi:10.1093/ajcn/nqy121
5. Upadhyaya, B. et al. Impact of dietary resistant starch type 4 on human gut microbiota and immunometabolic functions. Sci. Rep. 6, 28797 (2016).
6. Dainty, S. A. et al. Resistant Starch Bagels Reduce Fasting and Postprandial Insulin in Adults at Risk of Type 2 Diabetes. J. Nutr. 146, 2252–2259 (2016).
7. Karimi, P. et al. The Therapeutic Potential of Resistant Starch in Modulation of Insulin Resistance, Endotoxemia, Oxidative Stress and Antioxidant Biomarkers in Women with Type 2 Diabetes: A Randomized Controlled Clinical Trial. Ann. Nutr. Metab. 68, 85–93 (2016).
8. Alfa, M. J. et al. A Randomized Placebo Controlled Clinical Trial to Determine the Impact of Digestion Resistant Starch MSPrebiotic® on Glucose, Insulin, and Insulin Resistance in Elderly and Mid-Age Adults. Front. Med. 4, 260 (2018).
9. Sandberg, J. C., Björck, I. M. E. & Nilsson, A. C. Effects of whole grain rye, with and without resistant starch type 2 supplementation, on glucose tolerance, gut hormones, inflammation and appetite regulation in an 11-14.5 hour perspective; a randomized controlled study in healthy subjects. doi:10.1186/s12937-017-0246-5