Literatus: The third type

WHAT most of us know about dietary fiber is that there are two types: the soluble and the insoluble. Soluble fibers dissolve in water to form a gel-like material, which help lower blood cholesterol and glucose levels.

Insoluble fibers, conversely, do not dissolve in water, making these effective in promoting healthy bowel movement by increasing stool bulking. Being so, these help resolve problems with constipation and irregular bowel movement.

But there’s a third type of dietary fiber that most of us do not know about. These are called resistant starch—a product of degradation of starch that escapes digestion in the small intestines of healthy individuals. Like other carbohydrates, starch usually gets digested in the intestines, but resistant starch does not. It instead passes through the large intestine where it acts like insoluble dietary fiber.

Resistant starch can “deliver some of the benefits of insoluble fiber and some of soluble fibers,” reported CL Bodinham, GS Frost and MD Robertson in the British Journal of Nutrition, published in March 2010.

Another team under GH Anderson classified resistant starch into four types, and reported it in the American Journal of Clinical Nutrition (April 2010).

The first type (RS1) is physically inaccessible. It can be found in seeds, legumes and unprocessed whole grains. Thus, they are not supposed to be eaten.

RS2 occurs in its natural granular form, as in uncooked potato, green banana, flour and high amylase corn. This starch is raw material for cooking. A medium-sized raw banana contains 4.7 grams. A tablespoon contains 9.5 grams.

RS3 is formed when starch-containing foods are cooked and cooled (as with legumes, bread and cornflakes), or cooked and chilled (as with potatoes, pasta salad or sushi).

Of course, these are food-grade starch. Half-a cup of cooked navy beans contains 9.8
grams. Cold pasta has 1.9 grams per cup. Cold potato, a half-inch in diameter, contains 3.2 grams. A cup of cooked oatmeal has 700 mg. And two slices of wholegrain bread contains 500 mg.

RS4, however, is not your kind of starch. It is chemically modified to resist digestion; thus it is not found in nature. It is produced through chemical wizardry.

One good thing about this synthetic type of starch is its lack of satiety impact. You eat it, and you will not feel full despite the volume you take.

Resistant starch has specific health benefits, which we cannot cover it right here, right now. But this must be for our future article. Meanwhile have some fun guessing which type of resistant starch you will expect in the food in your hand before eating it. Try to find out how often you get your guesses right.