Wednesday, May 18, 2011

EAT TO GROW : Carb Blocking A hill of beans? Not so fast; new studies suggest they may work—for certain carbs by Jerry Brainum

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, rice—even 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, it’s 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 didn’t 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 aren’t 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.

Starch-based carbs were formerly thought to be just like other complex carbs, which were considered the healthiest carb form because their structure required longer digestion time and provoked far less insulin release. While that’s true for most forms of complex carbs, the advent of the glycemic index—a measure of how rapidly foods reach the blood—showed that not all of them act the same way in the body. The faster the carb gets into the blood, the greater the release of insulin.

The glycemic index exposed some complex carbs as nothing more than disguised forms of simple sugars, entering the blood as rapidly as simple carbs. Among those that turned out to be high-glycemic, or rapidly absorbed, were pasta, baked potatoes, bread and white rice. Taking a carb-blocking supplement prior to eating such foods should blunt the high insulin response that would normally follow. The net effect should be greater fat loss.

That’s precisely what a few initial studies confirmed. The problem was that most did not get published in reputable medical journals, and they were sponsored by marketers of carb-blocking supplements. That didn’t mean that the studies were tainted, just that they didn’t meet scientific standards.

Adding to the problem were inflated claims for the new carb blockers. Some ads didn’t mention that the supplements blocked only starch-based carbs, leading unwary consumers to believe that they blocked all carbs. Since that wasn’t true, those who stuffed themselves with simple-sugar foods after using carb blockers would conclude that the supplement was just another ripoff.

The hyperbole eventually attracted the attention of the FDA. On October 22, 2004, the FDA sent warning letters to several companies that market carb blockers, cautioning against the inflated claims for the products and indicating that no proof of effectiveness backed up such claims. The wording of the letters suggests that the FDA is basing its warning on the original starch blockers of the 1970s—which didn’t work as advertised.

The solution is simple. The companies that make and distribute the new bean-based carb blockers need to sponsor a double-blind, placebo-controlled study and publish in a reputable medical journal. If the study shows that the carb blockers work as advertised, that should get the FDA off their backs. It may also behoove the companies to revert to the former name, “starch blockers,” which more accurately reflects the function of the supplements.

In order to work properly, carb blockers must be taken 10 to 15 minutes prior to a meal containing starch or during the meal itself. The supplements are specific for the alpha-amylase enzyme and won’t adversely affect the uptake of other nutrients. By the way, undigested starch is a favorite delicacy of intestinal bacteria. You’ll recognize that by the increased level of intestinal gas. Eating additional sources of fiber, however, should keep things moving along nicely.

©,2011 Jerry Brainum.Any reprinting in any type of media, including electronic and foreign is expressly prohibited.     

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The Applied Ergogenics blog is a collection of articles written and published by Jerry Brainum over the past 20 years. These articles have appeared in Muscle and Fitness, Ironman, and other magazines. Many of the posts on the blog are original articles, having appeared here for the first time. For Jerry’s most recent articles, which are far more in depth than anything that appears on this blog site, please subscribe to his Applied Metabolics Newsletter, at This newsletter, which is more correctly referred to as a monthly e-book, since its average length is 35 to 40 pages, contains the latest findings about nutrition, exercise science, fat-loss, anti-aging, ergogenic aids, food supplements, and other topics. For 33 cents a day you get the benefit of Jerry’s 53 years of writing and intense study of all matters pertaining to fitness,health, bodybuilding, and disease prevention.


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