May 27, 2008

Resistant Starch: Don’t Resist Its Effects!

Amy Campbell

Just when you thought you had mastered food exchanges, carbohydrate counting, and the glycemic index, along comes something else that you may want to include in your meal-planning arsenal: resistant starch.

When you're first learning about carbohydrate counting, you're typically taught that all carbohydrates (with the exception of fiber) are broken down into glucose in the small intestine. For the most part, this is true. However, about 10% of carbohydrate isn't digested. This carb, called resistant starch because it "resists" digestion, leaves the small intestine pretty much intact and enters the large intestine. Once it's in the large intestine, this resistant starch is fermented by bacteria, and short-chain fatty acids are formed. It's thought that short-chain fatty acids play a role in our health, including:

• Promoting colon health
• Preventing colon cancer
• Lowering blood glucose levels
• Lowering blood cholesterol levels
• Boosting the immune system
• Reducing appetite
• Increasing the amount of fat used for fuel
• Helping with weight loss

In fact, one study has shown that when subjects replaced some of the carbohydrate they were eating with resistant starch, they had between 20% and 30% higher fat oxidation (fat "burning") after a meal. One of the short-chain fatty acids in particular, called butyrate, appears to block the body's ability to use carbohydrate as a fuel; therefore, the body responds by burning more fat instead.

Resistant starch may help people with diabetes better manage their blood glucose levels, too. Blood glucose levels tend to rise less quickly and not as high after meals high in resistant starch compared to "regular" carbohydrate foods. And because resistant starch tends to improve insulin sensitivity, it may also help those who are at risk for diabetes or who have prediabetes. Resistant starch is found in some snack bars aimed at preventing hypoglycemia, too, such as the ExtendBar.

Sounds pretty good, doesn't it? But where the heck do you find resistant starch? You probably need to look no further than your kitchen cupboard or refrigerator. Here are some top sources:

• Legumes (beans, lentils, dried peas)
• Whole grains, such as oats, wheat, rye, brown rice, barley, and corn
• Slightly green bananas
• Potatoes
• Yams

Legumes contain the highest amount of resistant starch. You can also find some breads and cereals made with added resistant starch called Hi-maize.

You might find it interesting to know that cooking and then chilling certain starchy foods, such as potatoes and pasta, also increases their resistant starch content. When starch is heated, the starch granules in the food will swell during a process called gelatinization. When that same food is then cooled (think pasta salad and potato salad), some of that gelatinized starch gets converted to a less digestible, or resistant, type of starch.

There's no RDA for resistant starch, at least at this point. Some estimates put our typical resistant starch intake, at least in the U.S., at about 4 grams. We should probably aim to double that. And it's not that hard to do. Including 1/2 to 1 cup of foods high in resistant starch can definitely help. One half cup of navy beans contains 3.8 grams of resistant starch, 1 cup of cold pasta contains 1.4 grams, and one cold potato contains 1.1 grams.

So don't write off all carbs as being bad. Start getting some resistant starch into your eating plan and reap the benefits!

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