What’s a resistant starch and what is it resisting?
What Are Resistant Starches?
Don’t feel bad if you’ve never heard of resistant starches. Although they’ve always been around, they haven’t gotten a lot of attention until recently. Lately, we’ve been learning more about the potential health benefits of resistant starches. In particular, they may be helpful for diabetics, those who are watching their weight, and those who suffer from constipation.
But the people with the most to gain from resistant starches may be food processors and manufacturers. They have latched onto resistant starches in a big way because it gives them something new to sell to diabetics, those who are watching their weight, and those who suffer from constipation.
Of course, you can also get resistant starches in regular foods—if you know where to find them.
What Are Starches?
Before I 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. I’ve talked quite a bit about sugar and fiber before but I’ve never talked too much 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.
A Starch Experiment
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!
Resistant starches don't break down into sugar and so they pass largely undigested into the large intestine instead of being absorbed in the bloodsteam.
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.
Because they don’t break down into sugar, resistant starches aren’t absorbed into the bloodstream. Instead, they pass largely undigested into the large intestine.
What Are the Benefits of Resistant Starches?
Now that you understand what a resistant starch is, let’s talk about what they can do for you.
Improve bowel function. Resistant starches act a lot like fiber, which I talked about in episode #2. As with fiber, adding resistant starch to your diet can improve regularity and bowel function. Some people find that when they up their fiber intake, especially if they do it suddenly, they have bloating, gas pains, and other effects usually lumped together under the heading of “GI distress.” One nice thing about resistant starch is that it doesn’t have this unwelcome side effect.
Appetite Control. Another fiber-like benefit of resistant starch is that it appears to help with appetite control, helping you feel fuller, longer, even when you are eating fewer calories
Regulate blood sugar. When you include resistant starches in a meal, it slows down the absorption of sugars from other foods. That means that you get a more gradual rise and fall in blood sugar levels after eating. That’s particularly helpful for diabetics, who need to keep their blood sugar levels steady. But the blood sugar roller coaster isn’t a ride you want to be on, even if you’re not diabetic. I discussed why in episode #32,
Reduce calories. Foods containing a lot of resistant starches are somewhat lower in calories than other carbohydrates because at least some of the food energy stays locked up in the resistant starch and doesn’t get digested and absorbed.