Resistant starch is advertised as a game-changer for those who want to manage blood sugar, improve gut health, or lose weight. But is it as revolutionary as it seems?
If you have heard people talking about “resistant” starch, it certainly sounds like the best thing since sliced bread — or rather, carb-free sliced bread — with a similar undertone of wait, does what I’m eating even count?
And while a part of me enjoys squashing a new nutrition trend, with a big eye roll to boot, I promised myself (and Ann!) I’d take a hard look at the facts about resistant starch, sans judgment of course.
In this case, I was surprised to discover there’s more nuance to resistant starch than I had originally assumed, and I’m looking forward to sharing more here. It’s an eyebrow-raiser for sure (as I’ve discovered during casual conversations with people recently) and it could change the way we think about starchy foods.
First, what is starch?
A polysaccharide (or a unit of multiple glucoses bonded together) produced by plants for energy storage. Starch can be found in wheat, potatoes, corn, rice, cassava, beans, oats, legumes, and much more.
Starch is digested in the stomach and small intestines, where the glucose molecules are broken apart and absorbed as single molecules into the lining of the small intestines. The single glucose molecules are then absorbed into the bloodstream.
How does “resistant” differ?
Resistant starch in food bypasses the digestion of the small intestine, and won’t contribute to increase in blood sugar. Instead, it ferments in the large intestine and contribute to prebiotics, or food for probiotics.
This doesn’t mean that an entire food is calorie or sugar free.
Remember, whole foods contain a wide variety of nutrients. Meaning, resistant starch is simply a component of the whole food, which may also contain other kinds of fibers, proteins, fats, and micronutrients.
How does it differ from insoluble fiber?
The concept is pretty similar but casts a bit of a wider net, including foods that are soluble and can turn into non-digestible nutrients (more on that below).
Depending on the food source, resistant starch acts in a variety of ways, sometimes like a mixture of soluble and insoluble fiber, in turn aiding in bowel regularity, as well as gut microbiota.
How is this different from what I’ve heard about fiber before?
The message is generally the same as we’ve always heard. Eat a wide variety of fruits, vegetables and whole grains, to get as many different nutrients and fibers from your foods.
The big difference (the interesting eyebrow-raising part) regarding the concept of resistant starch, is the idea that some of the simple carbs found in foods such as white rice and pastas can actually be turned into resistant starch.
YES.
Wait, how do we turn regular starch into resistant starch?
Studies have shown that by cooking and then refrigerating foods such as rice, pasta, or potatoes for at least 24 hours, the product develops resistant starch. The longer the starch is cooled, the more resistant starch it will build.
What do human studies on resistant starch tell us?
Most studies conducted compare subjects who eat a plain bowl of rice (rice seems to be the most utilized, likely for ease) versus those who eat rice that has been refrigerated over 24 hours. Outcomes focus on glucose or insulin response, weight management, and gut health.
There are some conflicting results, and also results that are difficult to extrapolate to real life scenarios. I had questions about this, and many of you may too. And while there are no definitive answers, it helps to think through them.
- How can resistant starch help with weight management?
Some studies (not all) showed an increase in satiety when people ate more resistant starch. The idea is that diets higher in resistant starch contribute more to feelings of satiety, therefore, a decrease in appetite.This is not new news, and can be achieved eating a varied diet high in fruits, vegetables, whole grains, and/or legumes.But resistant starch doesn’t live in a silo, meaning you eat it along with everything else that food provides.
For instance, some of the highest levels of resistant starch are found in French fries which are often fried, the cooled, and fried again to order. And we know fried foods don’t have the best reputation! - Does resistant starch impact glucose?
In some studies, a lower glycemic response was seen compared with those who ate regular once-cooked starch.For those with diabetes or pre-diabetes and monitoring blood sugar, I can see why it would be tempting to experiment with refrigerated leftover rice, pasta compared with once-cooked starches. Especially in this population, where starchy foods are often seen as taboo.Just be aware that it’s impossible to quantify how much resistant starch versus simple sugars we consume after the chilling process. Otherwise, incorporating a wide variety of fibers in our diets probably has a similar impact, and provides a wider variety of beneficial nutrients to boot. - Can study results be extrapolated to the whole population?
While limiting variables is vital to determine the impact of resistant starch, studies of this nature can’t replicate what it would be like to eat a mixed meal as we normally do outside a lab.For example, how can we tell what kind of impact extra resistant starch could have after a mixed meal of rice and vegetables and protein? - Is it practical to eat starch in this new way?
Cold potatoes, pasta, or rice in picnic-style salads is appealing, but otherwise we tend to eat these starchy foods warm.It’s a bit of a reach to expect us to cook and cool these foods for at least 24 hours (and then re-heat) for a chance they may develop some resistant starch.Especially since there’s no tool to determine how much extra resistant starch we are actually consuming. - Are processed “rs” foods the way to go?
We already reviewed a few types of starch, including the types that come from legumes, seeds & whole grains, heated and cooled simple starch, as well as unripe bananas.The last type is chemically modified or processed resistant starch (“rs”) such as resistant starch bagels.Studies have been conducted similarly to the one noted above. Glucose response is compared in subjects who eat a plain “rs” bagel to those who ate a regular plain bagel.Some studies showed a decrease in insulin response after eating the bagel, and some studies did not. Some studies showed a decrease in fasting glucose after a month of eating a daily “rs” bagel, and some did not. Participants did not seem to eat less overall when consuming a daily “rs” bagel.
Consider this: how would a plain “rs” bagel compare to a veggie scramble with toast or a regular bagel with cream cheese, sliced cucumbers, sliced tomato and onion? Would either option similarly temper glucose response and perhaps be more appealing anyway?
Infection Control
This past year, there’s been a lot of attention focused on the dangers of leftover pasta and rice, bringing awareness to the fact that grains can develop bacteria if left out. This made people feel uneasy about using leftover rice at all.
In reality, re-heated leftover rice that’s been properly stored is safe to eat. But I think it’s interesting to point out the pendulum in the media here, where one day the message is to avoid leftover rice and the next day we are told it’s the best thing for our gut health.
My Takeaway
For those who need to monitor blood sugar, there may be value in experimenting with cooking and cooling foods like rice, pasta, and potatoes, too see if there’s any impact on blood sugar after eating.
Otherwise, by simply eating a wide variety of foods including fruits, vegetables, and whole grains, we get the nutrients we need, including resistant starch.
Will it’s interesting to take note of how different foods have the potential to impact our health, food doesn’t always have to be a functional choice. Embrace foods that are culturally important to you and your family; foods you enjoy; foods you like to make. This has a positive impact on our health too!
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