Carb Blocking

Jerry Brainum

A hill of beans? Not so fast; new studies suggest they may work—for certain carbs

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Although still a matter of fierce contention among scientists, low-carbohydrate diets appear to be the most effective eating plan for the majority of people seeking to lose excess bodyfat. The consensus, based on most recent studies, is that on a calorie-by-calorie basis, people lose more fat when they eat fewer carbs than they do on either lowfat or reduced-calorie diet plans. On the other hand, recent long-term studies, lasting more than six months, show that the weight loss on various diets is similar.

Frequent dieters say that low-carb diets are easier to follow, since they feature more fat and protein, which are potent appetite suppressors. From a bodybuilding standpoint, getting more protein helps prevent lean-tissue loss.

Even low-carb diets require willpower, however. What would make low-carb dieting easier is some kind of substance that enabled you to eat more food with relative impunity.

Some research shows that supplements known as carb blockers may fill the bill. Back in the 1940s scientists discovered that white kidney beans contained a protein that blocked the activity of alpha-amylase, a digestive enzyme that breaks down starchy carbohydrate foods, such as bread, pasta, potatoes, riceóeven beans.

Alpha-amylase begins to work in the mouth, where parotid glands secrete salivary alpha-amylase in response to starchy carbs. It converts the longer-chained starch into the simple sugar maltose. But since food remains in the mouth only briefly, that initial process accounts for only about 5 percent of total starch digestion.

The major digestive activity occurs in the upper intestine, where pancreatic cells squirt far larger amounts of alpha-amylase. By the time starch reaches the lower portions of the small intestine, itís been converted into glucose, the most elemental sugar and the only type that circulates in the blood. The idea behind carb blockers, originally known as starch blockers (a more accurate term, since they only work on starch), was to nullify the effect of alpha-amylase, thereby inhibiting the absorption and uptake of starch-based carbs.

Starch-blocking supplements first appeared on the commercial market in the early 1970s but soon fell out of favor. They did work as advertised outside the body, in a test-tube environment, but they were too weak to show any kind of effectiveness in the human body. Researchers at the Mayo Clinic synthesized a far more potent version. It was stable in the hostile environment of the gastric and intestinal areas, which enabled it to reach the site where alpha-amylase degrades starch in the upper intestines.

The Food and Drug Administration ordered the removal of starch blockers from commercial sales in 1983, based on research indicating that the products didnít work as advertised. Recently, though, the Mayo Clinic work of nearly 30 years ago resurfaced, a result of the renewed popularity of low-carb diets, and the more potent bean extracts again appeared on the market.

An initial study of the new carb blockers showed that 1,000 milligrams of the extract could block 2,250 starch calories, an amount equal to a pound of pasta or an entire loaf of bread. The new extract survived passage through the formidable barriers of the gastrointestinal tract, retaining 70 to 80 percent of full potency. It acted only on alpha-amylase, not affecting any other digestive enzymes.

Subsequent studies, nearly all of which were sponsored by the primary company distributing the improved bean extract, had impressive results. In one experiment human subjects on the carb blocker showed 57 percent less starch absorption than those taking a placebo or inactive substance. Other studies indicated a lower glucose response, pointing to decreased carb uptake from starch-based meals.

It appeared that the carb blockers had finally been perfected, but the supplements still provoked serious criticism. Some pointed out that starch-based carbs arenít the primary cause of obesity; the true culprit is simple sugars, which provoke a huge insulin release, particularly when not packaged with some form of fiber. Excess insulin not only promotes bodyfat synthesis but also inhibits fat oxidation while promoting hunger, leading to a vicious cycle of more calorie intake.