Although carbs tend to get a bad rap these days, abundant research suggests that starch has been a staple in our diets for millions of years.
From the days of our ancestors, the hunter-gatherer diet included a variety of starches in the form of tubers, fruits, roots, and nuts. Almost 250,000 years ago, Neanderthals in France created tools to dig starchy roots up from the ground for sustenance.
It's no secret that our diets have shifted dramatically since the time of our Paleolithic ancestors. Over the past century, our starch consumption has increased significantly due to modern food processing and industrialization.
Beginning in the 1940s, the advent of processed foods embodied a shift towards making foods more easily digestible. We began to strip away the seed, the shell, or the hull that protects the starch from digestion (which our microbiome has grown evolutionarily accustomed to).
As a result, we removed the vast majority of resistant starch, one of the three types of complex carbs, from our diets and replaced it with high-glycemic, digestible starch to the detriment of our health. To put it into perspective, our ancestors consumed around 30-50 grams of resistant starch each day, while the resistant starch intake of a typical modern Western diet includes a meager 3-8 grams per day.
In today's edition, we'll dive into resistant starches, examining how the fermentable fiber produces beneficial byproducts in your gut and why you might want to consider making sushi with your rice leftovers.
What is Resistant Starch and Why Should I Care?
It's a type of carb resistant to digestion.
Unlike regular starch, which is broken down into sugar when digested, resistant starch (RS) is one of three types of complex carbohydrates that resists digestion in the small intestine. Once it reaches the large intestine, it's fermented and used as fuel by specific bacteria, producing beneficial compounds like short-chain fatty acids and other metabolites. (Source)
It has prebiotic effects.
Resistant starch is a highly fermentable type of insoluble fiber. As the fibers ferment in the large intestine, they act as a prebiotic and feed the good bacteria in the gut. By lowering the pH level and producing short-chain fatty acids in the large intestines, resistant starches create an environment where beneficial bacteria can thrive. Studies have shown that this prebiotic environment can help keep colon cancer at bay, reduce the severity of inflammatory bowel disease (IBD), and help maintain a healthy weight or promote weight loss. (Source, Source)
There are four different types.
Type 1 (RS1): starchy foods coated with seeds or germ (e.g., unprocessed whole grains, legumes including soybean seeds, beans, lentils, and dried peas)
Type 2 (RS2): naturally resistant starchy foods (e.g., uncooked potatoes, green banana flour, and high-amylose corn flour). This is also the most common supplemental form of RS.
Type 3 (RS3): retrograded starch — starchy food that has been cooked and then cooled, which increases its resistant starch content (e.g., potatoes or pasta cooked-and-cooled, sushi rice, etc.)
Type 4 (RS4): synthetic starchy foods chemically modified by manufacturers to be digestion-proof (e.g., food additives derived from corn, potatoes, or rice) (Source)
Studies have demonstrated the numerous potential health benefits of resistant starch.
Some of the beneficial effects of RS backed by research include improved insulin sensitivity, reduced blood glucose after meals, and increased satiety. Resistant starch also supports the gut by boosting the production of short-chain fatty acids, increasing uptake of minerals from the gut, and supporting colonic health. (Source, Source)
What Does the Research Show About Resistant Starch Foods?
Responses to resistant starch supplementation vary based on the individual and type of starch
Researchers have found that responses to RS are highly individualized based on the baseline gut microbiota composition (this adds to the complexity of studying its effects on the body). For example, one study reported a 50% increase in butyrate levels after treatment with potato starch, but a further examination of the results reveals that individual responses were quite varied. Evidence currently suggests that we may need to transition from the message of “eat more resistant starch” to “eat the resistant starch that is right for your microbiome.” (Source, Source)
It improves the integrity and function of the gut
Resistant starch improves the integrity of the cell lining in the colon, reducing cell damage and immune reactivity. It also prevents bacterial toxins from circulating in the body and reduces leaky gut, which could have positive effects on inflammatory conditions, such as allergies and autoimmune diseases. (Source)