With all of these potential benefits, I bet you’re ready to find out how to include more resistant starch in your diet.
Let's get up-to-date on resistant starches, a category of nutrients that appear to offer a variety of benefits across the body.
Nutrition Diva is hosted by Monica Reinagel. A transcript is available at Simplecast.
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Hello and welcome to the Nutrition Diva podcast—a show where we put the latest nutrition trends and headlines into perspective so you can make the best choices for your own health and wellbeing. I’m your host, Monica Reinagel and today, I want to bring you up to date on resistant starches, a category of nutrients that people started paying more attention to back in the aughts.
I first talked about this on the podcast back in 2009 and since then, there’s been a lot more research on them, so we have a better understanding of how they work in the body. And they appear to offer a variety of benefits, including improved digestion and gut health, blood sugar regulation, weight management, reduced risk of chronic diseases, and even improved nutrient absorption.
Before we go any further, let’s back up and talk for a second about regular, old non-resistant starch. There are three main types of carbohydrates: sugars, starches, and fiber. We tend to talk a lot more about sugar and fiber than we do about starch.
Starches are nothing more than long chains of glucose (or, sugar) molecules glued together with a special type of chemical bond called a covalent bond. When you eat a starchy food, such as a potato or a bowl of oatmeal, enzymes called amylases break these covalent bonds. When that happens, large starch molecules turn into lots of tiny sugar molecules, which are then absorbed into the bloodstream. That’s how starches are digested.
One day, when I was in fifth grade, our science teacher handed out some unsalted saltines and told us to chew them up but not to swallow them—just to keep chewing. Maybe you remember doing this too. After you chew them for a while, the saltines start tasting sweet. That’s because your saliva contains amylase. When you chew a saltine for long enough, the conversion of starch molecules into sugar molecules happens right there in your mouth!
A resistant starch is a starch that resists this enzymatic action and doesn’t break down into sugar molecules. For example, raw cornstarch contains a fair amount of resistant starch. If you were to put some in your mouth and chew on it, it wouldn’t start to taste sweet no matter how long you chewed it.
Instead, these long carbohydrate molecules pass through to the large intestine, where they act as prebiotics, nourishing beneficial gut bacteria and promoting a healthy balance of microorganisms in the digestive system. This can enhance digestion, reduce inflammation, and support overall gut health. This promotes a diverse and balanced microbiome, which is crucial for optimal digestion, immune function, and overall well-being. Resistant starches can add also promote bowel regularity, preventing or alleviating constipation.
Foods that contain a lot of resistant starch also help stabilize blood sugar levels, making them particularly beneficial for individuals with diabetes or those aiming to manage their blood sugar.
Like other forms of fiber, resistant starches can help with weight management by increasing satiety and reducing calorie intake. They’ve also been shown to improve cholesterol profiles, lowering LDL and increasing HDL. All of this helps to explain why diets that are higher in resistant starches are associated with a lower risk of chronic diseases, including type 2 diabetes, cardiovascular disease, and colorectal cancer.
Fiber-rich foods, such as whole grains and legumes, often get a bad rap because they contain compounds such as phytates and oxalates, which can reduce mineral absorption. As I’ve explored in many previous episodes, I think concerns about the mineral-binding tendencies of phytates and oxalate are wildly overblown.
But it’s interesting to note that resistant starches can actually increase the absorption of calcium, magnesium, and other minerals through a few different mechanisms, including the production of short-chain fatty acids, which increase the expression of transporters responsible for calcium and magnesium uptake, thereby improving their absorption.
With all of these potential benefits, I bet you’re ready to find out how to include more resistant starch in your diet. And you’re going to be happy to learn that the best sources include foods that we often feel we should be avoiding: potatoes, rice, and pasta.
The key to maximizing resistant starch content in starchy foods like pasta and potatoes lies in the cooking and cooling process. When these foods are cooked, the starches undergo changes in their molecular structure, forming resistant starch. But here's the trick: allowing these cooked foods to cool before consuming them can further increase their resistant starch content.
For example, if you cook a batch of pasta, rice, or potatoes, and then cool them in the refrigerator for several hours, you'll end up with a higher proportion of resistant starch compared to when they were freshly cooked. This is because the cooling process allows some of the digestible starches to convert into resistant starch.
But what happens if you were to heat these foods up again? Would the resistant starch be converted back into regular starch?
Dr. Denise Robertson of the University of Surrey in England compared the effects of freshly cooked pasta, cooked and cooled pasta, and cooked, cooled, and reheated pasta on eaters' blood sugar levels.
As expected, the cold pasta caused less of a rise in blood sugar than the freshly cooked pasta due to the increase in resistant starch. But the difference was fairly modest. The real shocker was the reheated pasta: the rise in blood sugar after eating reheated pasta was 30-50% lower than the rise after eating freshly cooked pasta. In effect, the reheated white pasta acted in the body as if it were whole wheat pasta. But, of course, it still had the taste and texture of regular pasta.
Similar results have been found by cooking and chilling rice—and one Sri Lankan research group found that adding a small amount of oil to the cooking water further boosts the resistant starch content of rice.
One word of caution about cooling rice, however. Uncooked rice can harbor spores of Bacillus cereus. These critters are heat resistant and are not killed by normal cooking. This is not a problem if you eat the cooked rice immediately. But if cooked rice is left to sit at room temperature for a few hours, these spores can grow into bacteria and multiply. These bacteria and the toxins they create can cause nausea and diarrhea.
I have to confess that I've been improperly handling rice for my entire life—letting it slowly cool to room temperature in the pot before refrigerating leftovers—and have somehow lived to tell the tale. Indeed, food poisoning caused by Bacillus cereus is not very common; it's responsible for only 2-5% of all cases of food poisoning. And, although unpleasant, it's rarely severe enough to be life-threatening.
Nonetheless, the best way to cool hot rice is to spread it in a shallow pan, such as a casserole or baking sheet, where it will cool more quickly. As soon as it is lukewarm (which shouldn't take more than 5-10 minutes), pack it into an air-tight container and keep it in the fridge or freezer until you're ready to eat it.
Cooking, cooling, and reheating your pasta, rice, and potatoes does have a modest impact on the caloric content of these starchy foods. But it’s not the 30 to 50% reduction that enthusiasts sometimes claim. At best, you might get a 10-15% reduction in calories.
The bigger and more important effect is on the glycemic impact. Enhancing the resistant starch content means that these foods will be digested and absorbed more slowly. This translates into steadier blood sugar as well as greater satiety, or appetite control. Ultimately, that is likely to have a bigger impact on your weight than the relatively small difference in the calories.
So far, we’ve been talking about taking advantage of the resistant starches to be found in whole and minimally-processed foods. However, food processors and manufacturers have also been using resistant starches as an ingredient in processed foods, especially those pitched to people who are watching their weight, managing their blood sugar, or just generally suspicious of carbs.
One such ingredient that you might find in ingredient lists for “carb-smart” tortillas, pasta, and bread is high-amylose starch. It can be derived from corn, rice, or potato and it has a much higher proportion of resistant starch compared to regular starch. They may also use isolated fibers or resistant starches derived from wheat.
There’s even a flour replacement product called Hi-Maize, which is made from modified cornstarch. The idea is that you can replace some of the flour in your recipes with this product and end up with baked goods that are lower in digestible carbohydrates and calories—and have some extra fiber-like benefits as well.
All of these ingredients can help food manufacturers bump up the amount of fiber on the nutrition facts label and decrease the “net carbs.”
To calculate net carbs, you subtract the grams of dietary fiber and sugar alcohols from the total carbohydrate content. Food manufacturers will often list net carbs on products designed to appeal to people following low-carb or ketogenic diets or those who are monitoring their carbohydrate intake for blood sugar management. Keep in mind that “net carbs” is not a standardized or regulated term. There are varying guidelines or definitions for calculating and labeling net carbs.
But the bigger point I want to make is this: using these ingredients to bump up fiber or lower net carbs in processed foods doesn’t necessarily result in a healthier product overall. Other factors like added sugars, artificial sweeteners, overall nutrient composition, and ingredient quality should all be considered when evaluating the nutritional quality of processed foods. A slice of low-carb bread made with resistant starch may have the same number of carbs or calories as an orange or a helping of broccoli. But there’s obviously no comparison in terms of nutrient density.
If you’re attracted to the many potential benefits of resistant starches, my advice is to take advantage of these cooking and cooling techniques to increase the resistant starch content of pasta, potatoes, rice, and breads—but continue to exercise some portion control with these foods, and make sure your diet also includes plenty of fruits, vegetables, legumes, nuts, and healthy sources of protein.
If you have a question you'd like me to answer, you can email me at nutrition@quickanddirtytips.com You can also leave me a message at 443-961-6206
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