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(Examining the Effectiveness of Phase ‘oLean and Other Starch Blockers

On the Digestion of Carbohydrates)

By: Elizabeth Tenny




Table of Contents



2.     CLAIMS











1.  Introduction


Starch Blockers are all the rage in the weight loss industry.  Archangel Health Store proudly announces Dr. Marshall’s Phase 'oLean it's Product of the Month ( One patron claims that she lost 14 pounds in her first week of using starch blockers.  Another declares, "Honey, from now on, you'll be seeing less of me." (  If these claims are accurate, then why is America's Food and Drug Administration (FDA) working to eliminate starch blockers from the market?  Why are medical test results showing that starch blockers are not only ineffective against weight loss, but are harmful to the people who ingest them?



2.  Claims


      Manufacturers of Phase ‘oLean claim that taking their starch blockers will block most of those “empty calories” from that dinner of spaghetti and bread. This happens when the alpha-amylase inhibitor in the product stops the digestion of carbohydrates, causing the starch to pass through the digestive tract without being absorbed.  Advertising emphasizes that people can heap on the potatoes and pasta and still lose weight.  All the consumer has to do is take one pill 15-20 minutes before each meal.  An additional pill may be taken if the meal consists of heavy starches.  Weight loss can be expected to occur almost immediately after beginning use of Phase 'oLean.  Consumers may take the starch blockers until they reach their desired weight, and then use them again if they need help maintaining that weight.  (



3.  How It Supposedly Works


The Phase 'oLean formula is a kidney bean protein extract that is supposed to inhibit the action of alpha-amylase, which is the enzyme that they say digests starches in the bowel.  Manufacturers claim that any carbohydrate that is ingested in the presence of this extract will simply pass through the system undigested and be lost as feces.  Phase 'oLean supposedly absorbs only starch calories and leaves the nutrients from food to be digested normally.  (  Marketers claim that carbohydrates are not essential to the human diet because after they are eaten, they break up into starches and sugars, which are then used either as a quick source of energy or are stored as fat.  Calories from carbohydrates should make up 40%- 60% of the average person's daily food intake. (   Manufacturers of Phase 'oLean take advantage of this fact by pointing out that one dose of their product can block the digestion of up to 400 carbohydrate calories.  This means that someone can cut 25% of his or her caloric intake without even changing diet habits.  Sounds simple enough, right?



4.  Well, Maybe…. (How It Could Work)


First of all, it must be pointed out that digestion of starches does not simply take place in the bowel, but that it begins in the mouth and is not completed until it absorbed by the body from the small intestine.  The function of the bowel in digestion is to reabsorb water from the intestine into the body, and to prepare feces for excretion.  When carbohydrates are ingested, saliva-amylase is immediately released into the mouth and esophagus and begins the break down of the food into starches and sugars.   After swallowed, the carbohydrates are digested further by acid in the stomach.  The final stage of digestion occurs in the small intestine, where an alpha-amylase enzyme further reduces the complex sugars, which are then absorbed as calories from the intestinal wall into the bloodstream.  (http:/ 

Doctors agree that the logic in the idea is reasonable.  It is suggested that the product could inhibit the action of alpha- amylase by binding with the enzyme to stop the combining of starch with the enzyme.  Hence, the carbohydrates should pass through the digestive tract without being broken down into simple sugars.  The body cannot absorb large complex sugars, so the calories should simply pass through the tract and be excreted as feces. (  Most researchers who have tested this claim, however, have found that the theory does not carry well in reality.



5.  Critical Reviews


Dr. Marshall reports that he has proven his product's effectiveness in both animal and human clinical studies.  However, these studies are not available for review by the public.  Advertisements of consumer success stories are extensive and suggest unwavering success.

 Dr. Mirkin, a published doctor with a Medical Degree from Harvard, challenges that he can tell off-hand that the starch blockers are ineffective.  Sizeable amounts of undigested foods in the digestive tract will result in large bowel movements, especially diarrhea. Since most customers do not complain of such side effects, the starches must be digested, allowing normal bowel movements to occur. (   Various tests were conducted on both humans and rats that compared the fecal calories of subjects taking starch blockers to subjects taking a placebo after each had eaten a meal that contained starch.  Results generally show that the fecal calorie excretion was the same, and researchers concluded that the starch blockers were ineffective.  One study even states, "while use of 'starch blockers' did not promote weight loss in the mature female rats, utilization of copper and zinc were negatively affected."  Copper and zinc deficiencies can lead to various illnesses, including anemia.  Thus, not only was the drug deemed ineffective, it was considered harmful to some consumers.  ( 

Plus, carbohydrates make up the base of the Food Pyramid and people are expected to get 40 to 60 per cent of their daily calories from carbohydrates.  Sugars obtained from the digestion of sugars are necessary in the diet to maintain mental and physical energy.  Starch blockers would cause one’s energy level to drop and result in fatigue. 



6.  How Do the Tests Work?


    The New England Journal of Medicine presents a very thorough description of a common procedure used to test the effectiveness of starch blockers.  Five participants between the ages of 25 to 34 were selected for this experiment.  Firstly, the intestinal tract is flushed by ingestion of an electrolyte-containing solution.  The subject then eats a planned meal that contains CrCl3, which is a marker that cannot be absorbed in the digestive tract.  The amount of CrCl3 in stool collections is evaluated for recovery and accuracy of the experiment.  A stool collection is taken after the first meal, which is completely uninfluenced by starch blockers to refer to as a control.  Once again, the intestine is cleansed and then the subject is fed a calorie-free lunch via IV.  Researchers assure that all calorie consumption was controlled and uniform.  The next morning, the participants are each given the same amount of water, spaghetti, tomato sauce, and buttered bread to eat, a meal that contains 97 grams of starch.  After 14 hours of fasting, the intestinal tract was once again cleansed.  Stool samples from each of the subjects in the time between the test meal and the last intestinal flush are collected and analyzed by means of using a bomb calorimeter1.

    The stool collections took place over three days.  First, the control feces sample is collected.  The next day, the participants are each given two starch blockers that contain 500 mg of the enzyme inhibitor to take at meal- time.  On the last day, the subjects are given two placebos to take in a similar manner.  Stool samples were analyzed, and it was reported that the mean recovery of the CrCl3 was 96.4+ 0.5 per cent, so the tests were relatively accurate.  If the product had blocked all of the starch absorption, the fecal calorie output would have increased by 680 kcal.  After the meal was taken with placebos, the fecal caloric output was 677+4 kcal.  The fecal caloric output after the meal eaten with starch blockers was 676+ 4 kcal.  It was concluded that the fecal calorie output was not greater when starch blockers instead of placebos were administered1.  Several sources cite similar procedures and outcomes, though without sharing statistical results.  Detailed research on the effectiveness of starch blockers on starch is rather scarce, though opinions abound on web sites and in magazines, mainly to support commercialism.   (  Other researchers have used a similar procedure and placebo comparison, but measured tidal breath hydrogen, plasma glucose, and insulin responses to a constant test meal instead of fecal calorie output.    They also reported that there were no significant differences in breath hydrogen, or plasma glucose and insulin responses and concluded that starch blockers are ineffective weight loss supplements.  (

One study reported that people who took the starch blocker before eating a high starch meal had lower blood sugar levels after the meal than those who took a placebo before the meal.  This means that the starch blockers did not allow the digestion of carbohydrates to sugar, and ultimately that the pill was effective. (  Also, the FDA has received complaints of nausea, vomiting, intestinal cramps, and diarrhea from Phase 'oLean customers.  (  According to Dr. Mirkin's theory, these are signs that the drug is working. 



7.  So What Went Wrong?


Professor John Garrow admits that the idea of a starch blocker is a good one.  He attributes its ineffectiveness to protein-digesting enzymes in the human system that break down the protein extract before it can inhibit digestive actions of alpha-amylase enzymes.  (  The New England Journal of Medicine suggests that much more alpha-amylase is secreted than is needed to actually digest the starch.  If this is so, then even after the all of the starch blocker had bound to the alpha-amylase enzyme, there was still alpha-amylase to break down the starch into digestible forms1.

    Even the manufacturers of Phase ‘oLean admit that the success of their product depends on timing the administration of the pill and the ingestion of carbohydrates.  They recommend that the product be taken about 15 or 20 minutes before eating starch so that the tablet has time to become active and block the alpha- amylase enzyme.  If food is not eaten soon enough after the product is taken, then it will simply pass through the digestive tract and will not be present to inhibit the alpha-amylase when the starch is actually digested.  (



8.  Not Quite Approved…


The FDA is opposed to the marketing of starch blockers as "natural foods" because it considers starch blockers as drugs that impede normal, healthy digestion.   Also, the FDA points out the pill's danger to diabetics whose health depend on strict regulation of blood sugar levels, which are effected by the digestion of starches.   (  The New England Journal of Medicine calls for the need for more educated consumers who do not turn their head at every diet fad that they hear about.  The FDA has been ineffective in keeping starch blockers off of the market because they have no proof that the product affects physiological actions because “there are no clinical studies that establish the effectiveness or indeed the safety” of starch blockers.  (The New England Journal of Medicine.  Massachusetts Medical Society.  December 2, 1982. pp1444) 



9.  Conclusion


Well, Dr. Marshall is all about the commercial success of his product.  Several published researchers are convinced that starch blockers are ineffective against weight loss.  The FDA is trying desperately to take starch blockers off the market for fear that they affect the physiologic functions of the body and should therefore be considered a drug. 

As a general weight loss program is concerned, I believe that the habits learned from using starch blockers may cause weight gain after the supply of pills is depleted.  Most consumers realize that if they increase the amount of starches they ingest while taking the starch blockers, they will increase the amount of calories that are eaten but not digested.  Hence, they will lose more weight by eating more starches. (  If people stop taking the starch blockers but continue to eat a lot of carbohydrates, the calories add up, and the consumers gain weight.  Also, carbohydrates are broken down into sugars, which supply people with energy.  If starches are not digested, the body's supply of sugar decreases, and low blood sugar and energy levels result.  After reviewing the trends of research studies, I am lead to believe that starch blockers are ineffective against weight loss.  Once again, I must emphasize the importance of a balanced diet and regular exercise because it seems to be the only weight loss method that is proven to be effective in weight loss.

Dr. Marshall presents his idea with a scientific approach that seems credible to the average consumer.  Even critics who believe that the starch blocker is ineffective can understand Dr. Marshall's logic.  The product is directed toward a very general audience, which includes people of all ages and all weights, but with one similar goal: to lose weight.  Whether Phase 'oLean is a sure solution to your weight loss problems, however, remains a question.







1.            Bo-Linn, George W., Santa Ana, Carol A., Morawski, Stephen G., Fordtran, John S.  The New England   Journal of Medicine.  Massachusetts Medical Society.  December 2, 1982.  1414- 1416, 1444, 1445.



4.            http:/







11.        Taber’s Cyclopedic Medical Dictionary.  F.A. Davis Company.  1993.  542-545


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