Monday, January 9, 2012

Resistant Starch: The New Carb on the Block

Resistant starch is the next hot topic that you’ll be hearing about in the news, and I’m not talking about the laundry. This is nutrition science discovering new things about how foods impact our health. In the early 1980’s it was discovered that a component of starch could not be absorbed by the small intestine and passed into the large intestine where it was digested by bacteria, releasing beneficial compounds for the cells of the colon. It was identified as resistant starch (RS). RS is different from dietary fiber because it is bound along with other starchy carbohydrates, not the bran or the germ.

RS can be found naturally in legumes, seeds, whole grains, under-ripe bananas, raw potatoes, and (to a lesser extent) processed starchy foods that have been cooked and cooled, such as breads, cereals, potatoes, rice and pasta. A brand of corn has been engineered to contain a large amount of RS for use in food manufacturing; it is called high-amylose corn (Hi-Maize). This isn’t the corn that you eat at your dinner table. High-amylose corn is processed into flour and added to baked goods to decrease the overall absorbable carbohydrate and increase the RS of a product.

There has been a surge of recent research looking at the health properties of RS. Much of the research uses processed products such as Hi-Maize. Some benefits are improved glycemic control, decreased insulin secretion, decreased cholesterol levels, increased fat burning and improved colonic health. Negative effects have been discovered too, especially with highly purified RS diets that do not include the other components of dietary fiber. There is a concern for increased risk of colon cancer in this situation.

The consumption of RS in the US is currently estimated to be about 3-6 grams per day. In developing countries where unprocessed starch consumption is high the intake ranges from 30-40 grams per day. RS intake in China is about 18 grams per day. Research has identified the beneficial intake of resistant starch to be between 10-20 grams per day. With RS, more is not necessarily better, and a healthful intake can be as little as 5% of total carbohydrates.

Over-processing of foods diminishes RS content along with many other nutrients. This is one plague of industrialized food production. Our goal for healthy eating should be to include whole grains, legumes, and seeds while decreasing processed baked goods. Processed and engineered foods are no match for the panoply of nutrients that whole foods provide.

Engineered RS has been developed to be a functional food, a food or dietary component that may provide a health benefit beyond basic nutrition. I wonder if eating high-amylose corn muffins, pasta, or bread will benefit the consumer as much as the manufacturer. Only time, and more research will tell.

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