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Alpha Amylase Inhibitors
The use of starch blockers has recently gained in popularity with the success and growth of carbohydrate restricted diets. There are many enzymes in the human digestive system which help digest the variety of foods we consume. The alpha amylase enzyme is responsible for breaking down starchy foods, such as breads, potatoes, rice, and pasta into sugars that can be absorbed through the intestinal wall. Alpha amylase inhibitors are molecules which interfere with the action of the alpha amylase enzyme. Commercial starch blockers contain protein extracted from wheat or white kidney beans, both of which naturally contain alpha amylase inhibitors (AAI).
During the 1980ís Mayo clinic researchers evaluated bean derived AAI and found that it delayed starch digestion and reduced amylase activity in the human intestinal tract. Their focus was on the potential for AAI to reduce post meal blood sugar peaks in diabetics. Similar results were published by a group from SUNY Stony Brook in 19871.
In 1995 the Mayo group published a paper2 on wheat derived AAI, describing it as having a significantly higher activity against human pancreatic amylase than bean derived AAI. They also found that the wheat derived AAI was effective against human salivary amylase while the bean derived AAI was not. This is important because salivary amylase digests a portion of ingested starch in the stomach, before it enters the intestine and is exposed to pancreatic amylase. The paper discusses the importance of an adequate dose of AAI so that sufficient amylase inhibition activity is present to delay/prevent digestion. Doses below a threshold delayed digestion but did not prevent starch digestion. Delayed digestion, however, has the beneficial effect of prolonging the feeling of fullness and, therefore, delaying the urge to consume more food.
In 1996 the group published3 a study on wheat derived AAI, having abandoned the bean derived AAI because of it relatively low strength. Standard food laboratory tests are available which measure the amylase inhibition activity4. They show results consistent with the Mayo groupís findings.
The Mayo group went on to publish two more papers in 19985 and 19996, both studying the effects of wheat derived AAI. They did not see any AAI associated complications in their human subjects. A reduction of amylase activity was observed which had the effect of reducing post meal blood sugar peaks and of slowing gastric emptying. Further, they speculated that the passage of undigested carbohydrate into the colon may have a probiotic effect on colonic flora.
AAI products may be an effective aid in weight control as a part of an overall regime of diet modification and exercise. They effect the rate of digestion and, with sufficient activity, may actually prevent digestion of carbohydrates. Today, both wheat and bean derived AAI products are available. Consumers should choose the product that provides the greatest amylase inhibition activity per dose and per dollar. They should also make sure a product has little or no trypsin inhibition activity if they plan to use the product for an extended period of time.
1. Brugge, et. al., The Am. J of Gastroenterology 1987;Vol. 82, No. 8 pp.
2. Koike, et. al., Gastroenterology 1995;108:1221-9
3. Choudhury, et. al., Gastroenterology 1996;111:1313-20
4. Murao, et. al., Agric. Biol. Chem., 45(11), 2599~2604, 1981
5. Lankisch, et. al., Pancreas 1998;Vol. 17, No. 2, pp.176-81
6. Kataoka, et. al., Nutrition 1999; Vol. 15, No. 2, pp. 123-9