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Acarbose: The Only Real Starch Blocker


Acarbose, sold under the brand names Precose, Glucobay, and Prandase, is a most neglected and useful drug available for controlling blood sugar. Like Metformin, it has also received industrial-strength testing to see if it can prevent subjects from progressing from impaired glucose tolerance to full-fledged diabetes. Though it has long been prescribed in Europe it is rarely used in the United States and many doctors are unaware of how helpful it can be to people with both diabetes and impaired glucose tolerance.


How Acarbose Works

Acarbose, works by blocking alpha-glucosidase, the enzyme that chops up starches and complex sugars into their component glucose molecules. This results in starches and complex sugars passing largely undigested through the stomach and portions the small intestine rather than entering the bloodstream as glucose soon after eating.


However, Acarbose is not that mythical substance so beloved by health scammers the "starch blocker." That is because the starches and sugars whose digestion is temporarily blocked by Acarbose do, eventually, get broken down as they pass through the intestine where they are digested by the bacteria that live in the gut. So the glucose contained in these foods does, eventually reach the bloodstream. However, because the process is slowed down, that glucose reaches it in dribs and drabs rather than in one big blood-sugar-spiking dump.


How Much Improvement Does Acarbose Make in Blood Sugar?

The Prescribing Information provided by Bayer, the manufacturer of Precose, reports that in clinical trials Precose lowered the post-meal blood sugar numbers by 25 mg/dl to 83 mg/dl (1.4 to 4.6 mmol/L)depending on dosage. However, at the commonly prescribed dose, the change was a drop of 46 mg/dl (2.6 mmol/L). The same prescribing information insert also reports that in another study, subjects taking 100 mg of Precose over four months experienced an average drop in one-hour-post-meal numbers of 42.6 mg/dl (2.4 mmol/L).


Unfortunately, none of these studies reported the amount of carbohydrate that patients ate when they achieved these improvements. The baseline one-hour-post-meal blood sugar listed in the study cited by the manufacturer was 299.1 mg/dl, so even with the Precose, study subjects were running blood sugars that were dangerously high and it is likely that they were eating 60 to 100 grams per meal.


Adding Precose to Metformin only achieved an additional 31 mg/dl drop from a 283 mg/dl baseline post-meal blood sugar. However, unlike the case with Metformin, Precose appears to be equally effective for people who maintain healtly low blood sugar levels. Years ago when I was using it along with a low carb diet, I found that taking Precose allowed me to add an additional 15 to 20 grams of carbohydrate to my meal without seeing a dangerous spike.


Animal studies conducted throughout the 1990s suggested that even though this reduction in blood sugar was modest, Acarbose also decreased protein glycation and appeared to delay or prevent heart attacks and the other diabetic complications caused by elevated blood sugars.


Effects of the alpha-glucosidase inhibitor acarbose on the development of long-term complications in diabetic animals: pathophysioloical and therapeutic implications. Creutzfeldt W. Diabetes Metab Res rev. 1999 15(4):289-96


Does Acarbose Prevent the Development of Diabetes?

To see if Acarbose could be used to prevent the progression of impaired glucose tolerance to daibetes the multiple-research centers participating in the STOP-NIDDM Trial administered 100 mg of Acarbose three times a day to 714 subjects while giving another 715 subjects a placebo. At the end of three years the study a smaller percentage of the group taking Acarbose had developed diabetes than of the controls. This the researchers concluded meant that Acarbose could significantly decrease the progress of IGT to diabetes.


STOP-NIDDM Trial Research Group. Acarbose for prevention of type 2 diabetes mellitus: the STOP-NIDDM randomised trial. Chiasson JL, Josse RG, Gomis R, Hanefeld M, Karasik A, Laakso M; Lancet. 2002 Jun 15;359(9323):2072-7.


In addition, they appeared to have half as great a risk of cardiovascular events (heart attack, death, heart failure, stroke or peripheral vascular disease) as controls. They also had less new cass of hypertension.


STOP-NIDDM Trial Research Group. Acarbose treatment and the risk of cardiovascular disease and hypertension in patients with impaired glucose tolerance: the STOP-NIDDM trial. Chiasson JL, Josse RG, Gomis R, Hanefeld M, Karasik A, Laakso M; JAMA. 2003 Jul 23;290(4):486-94.


The Study Gets a Hostile Critique


However, the validity of this data was called into question in a published review by T. Kaiser and P. T. Sawicki of the Institute for Evidence Based Medicine in Cologne, Germany.


Acarbose for prevention of diabetes, hypertension and cardiovascular events? A critical analysis of the STOP-NIDDM data. Kaiser T, Sawicki PT. Diabetologia.2004 Mar;47(3):575-80. Epub 2004 Jan 16.


They pointed out in the critique they published in the respected journal Diabetologia that the impartiality claimed for the STOP-NIDDM study was tarnished by the fact that 5 of the 11 members of the study steering committee were employees of Bayer, the manufacturer of Acarbose and that they heavily participated in the study design, a fact not mentioned in the STOP-NIDDM publications which had specifically claimed that the main sponsor had no role in the study design.


The critiquers point out that another explanation for the study's findings might be that data supplied with the study made it clear that the people in the placebo group had worse blood sugar profiles than those in the Acarbose group at the beginning of the study--a difference that is similar to the eventual difference in the amount of diabetes that appeared in each group. That this might be the real explanation is bolstered by the fact that in their publications the researchers did not present the post-meal blood sugar levels or the HbA1c numbers of the two groups, though the study design had originally called for these to be measured. For a study of a drug that reduces post-meal blood sugars, this is a rather striking ommision.


Another explanation for the apparent benefit of Acarbose, according to Kaiser and Sawicki, was the fact that the placebo group were followed for three months longer than the Acarbose group giving them a longer time to develop diabetes. When the number of people who developed diabetes during the three month "washout" phase during which the drug was discontinued was included in the study results, a further 15.4% of the Acarbose subjects developed diabetes. Since the original finding was that 32% of patients randomized to Acarbose and 42% of patients randomized to placebo developed diabetes as measured by OGTT the addition of that extra 15.4% of the Acarbose group that developed diabetes when the drug was discontinued wipes out any real advantage the drug might have conferred.


When discussing the supposed improvement in cardiovascular risk, the critiquers make the point that the criteria for assessing whether or not a cardiovascular event occurred were changed during the course of the study, suggesting that the researchers redefined "cardiovascular event" in a way that made the drug group's results look better.


The original authors responded to this critique by claiming that reanalyzing their data showed it was not true but the critiquers countered that the response did not address most of the issues they had raised.

The Critiquers Miss the Point!


Once again, the point that seems to have been missed by everyone reviewing this study is that there is no information about the post-meal blood sugar levels that the participants maintained. Since they appear to have been on a high carbohydrate diet, it is almost certain that those blood sugar levels, even with Acarbose, were high enough to damage organs and beta cells. It is possible that if Acarbose is used along with carbohydrate restriction to keep blood sugars under 140 mg/dl at all times, it may help halt the progression of impaired glucose tolerance and of type 2 diabetes.


Acarbose and a Low Carb Diet

Unfortunately, as usual, there are no studies that look at what happens when people who control their carbohydrate intake use Acarbose to achieve healthy blood sugar targets.


The Anecdotal Evidence

When used to allow an occasional indulgence while following a low carb diet, Acarbose worked very well for me. I used it along with a low carb diet for for several years and my blood sugar response did not deteriorate at all during that time. I find that when I am eating a mostly low carb diet, taking 50 to 100 mg of Acarbose with a meal will allow me to add an additional fifteen or twenty grams of carbohydrate without seeing a spike that lifted my blood sugar into the dangerous range.


My endocrinologist reports that several of her other patients have experienced similar results with Acarbose and have told her that it is the best drug they have tried.


On the other hand, I have also spoken with people who felt that Acarbose only pushed their blood sugar spike further into the future. The people who report this appear to be those who are no longer producing much insulin.


From this I conclude that Acarbose works best for people who have lost their first phase insulin response but still have a functional second phase response. That is because by slowing down the release of glucose from food, Acarbose delays the release of most glucose until the second phase insulin response kicks


Acarbose Does Not Block Simple Sugars like Fructose and Glucose

If you are using Acarbose it is important to understand that Acarbose does notslow the digestion of simple sugars such as fructose or glucose because they do not require digestion but are absorbed from the stomach as soon as they are eaten.


The carbohydrates from foods like corn syrup, maple syrup, or candies containing dextrose will go straight into your blood stream, whether you have taken Acarbose or not.Acarbose works well with sucrose (table sugar) and starches like wheat flour, rice, and beans.


Dosing and Time to Take Effect

You should start out taking the lowest dose of Acarbose available and then work up. This will help you avoid gastric side effects. You take Acarbose with your first bite of food and it begins to work immediately.


Unlike other drugs, Precose does not get into your body in any significant amounts. It exerts its effect within the digestive tract and is not absorbed.


Side Effects

Gas - The Killer Side Effect of Acarbose


Fully 24% of the people assigned to the Acarbose group in the STOP-NIDDM study dropped out of the study long before it completed. There's a reason for that, and the reason is this: remember how we said that when undigested carbohydrate gets further down in your digestive tract the so-called friendly bacteria can digest it? Well, that digestion also goes by the name of "fermentation" and one of its byproducts is gas.


This means that the more carbohydrates you eat with Acarbose, the greater the amount of gas will be produced in your gut. The resulting gas production can be such that it limits your social life or gets you cutting down on your carbohydrate intake very steeply because you quickly learn to associate carbohydrate dinners with hours of post-meal flatulence.


That, by the way, is why the drug manufacturer stopped marketing Precose in the US. Most Patients eating a typical high carbohydrate American diet were unable to tolerate it.


However, if you use Acarbose while eating at a more modest level of carbohydrate intake Acarbose can be useful. I found that it worked best if I only used it at one meal a day and if I limited my carbohydrate intake at that one meal 30 grams or less. I also found that foods containing wheat caused more gastric symptoms than did other starchy or sugary foods.


Used with moderation Precose makes it possible to occasionally eat foods that would otherwise be completely forbidden on a low carb diet without destroying blood sugar control.


Combining Acarbose and Metformin

I found that adding Acarbose to Metformin achieved even better blood sugar control but made the gastric symptoms common with both medications much worse.


Fake Over The Counter Starch Blockers

There are quite a few products sold as "starch blockers" which are available without a prescription. Unlike acarbose, they don't work. You can easily tell if a starch blocker works with a simple test. If you take a starch blocker with 20 or 30 grams of carbohydrate and do not get an intense attack of gas afterwards, the "blocker" is a fake. That's because all undigested starches and sugars go to the gut where tough little bacteria ferment them. That's where the gas comes from. If starches and sugars aren't being fermented, they are being digested in your stomach and small intestine.


Also, remember, no drug can block digestion of glucose because glucose doesn't get digested. Glucose is absorbed into the blood stream directly from the stomach without any need for processing.

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