After-Meal BGs

Just How Important Are They

| Apr 1, 2002

You keep your A1Cs in line by testing your fasting and before-meal blood-glucose levels, but could you have a time bomb ticking in your body by failing to keep after-meal glucose levels down?

While studies have proven that after-meal glucose measurements are important in pregnancy, there is controversy over whether everyone else should hold these after-meal readings down as well.

"Yes," says the American Association of Clinical Endocrinologists, along with others, citing a lowered risk of cardiovascular complications.

But the American Diabetes Association (ADA) shrugs off the notion, saying it has not been proven that after-meal readings are important.

Endocrine Association Supports Importance of After-Meal Levels

The American Association of Clinical Endocrinologists (AACE) published its guidelines for blood-glucose control in the December 2001 issue of Endocrine Practice and these guidelines advocate the importance of measuring after-meal glucose levels.

"[After-meal] hyperglycemia is a key element of the total glycemic burden in patients with diabetes and is an important component of the A1C level," the AACE says. "The A1C can, therefore, be seen as the sum of both [pre-meal and after-meal] glycemia. In order to maximally reduce A1C levels, assessments of both [pre-meal and after-meal] glucose levels are necessary."

The risk of diabetic complications comes when tissues are exposed to abnormally high blood-glucose levels both before and after meals, says Dr. Rhoda Cobin, AACE president.

"Addressing the after-meal levels is significant not only because it will reduce tissue damage for patients but also because it alerts them to a problem previously unaddressed in blood-glucose monitoring."

The AACE recommends that the A1C target should be less than 6.5%. In addition, it recommends a targeted two-hour after-meal glucose level of less than 140 mg/dl for nonpregnant adults with diabetes.

ADA Not Bending

The ADA, on the other hand, still holds that fasting (waking), pre-meal and bedtime blood-glucose levels are the most important ones to test.

The ADA's position, published in the April 2001 issue of Diabetes Care, is that the relationship between after-meal blood-glucose levels and complications requires research before the organization will support after-meal testing (except during pregnancy). In fact, the ADA does not even urge treatment that specifically targets after-meal high blood glucose, despite the availability of several agents that can lower blood glucose after eating.

Many insulin users take rapid-acting insulin lispro (Humalog) or insulin aspart (NovoLog), which starts to work in five to 15 minutes and peaks in about one hour, matching after-meal blood-glucose excursions. In addition, for people with type 2 diabetes, newer oral agents such as repaglinide (Prandin) and nateglinide (Starlix) are designed to control after-meal blood-glucose rises.

"It is unclear to what extent A1C is lowered by these drugs because of their effects on [after-meal] glucose as compared with their effects on fasting blood glucose," the ADA writes in its consensus statement. "It has been suggested that agents that specifically lower [after-meal] glucose may decrease the risk of hypoglycemia and weight gain. These claims have not been consistently supported by randomized, controlled studies."

The ADA stated that it will not take a position in favor of after-meal glucose testing and treatments until additional studies are performed to prove their importance. (The organization defines an after-meal glucose level as that measured two hours after the start of a meal, except during pregnancy, when one-hour after-meal measurement is the standard.)

The ADA adds that gestational diabetes (during pregnancy) is the only setting in which after-meal monitoring has been proven to help outcomes.

"There are insufficient data either to support or to refute the need for extensive or routine [after-meal] glucose monitoring in diabetes, except in the setting of pregnancy," the ADA said in its position paper. "Since self monitoring of blood glucose represents a significant financial and personal burden for patients, decisions regarding [after-meal] glucose monitoring should be based on the needs and responses of individual patients."

Lack of Clinical Trials Cited as Reasoning

To predict the risk of complications, just watch your A1Cs, say researchers writing in the July 2001 issue of Clinical Diabetes.

"In recent years, [the A1C] has been demonstrated to be an accurate predictor of risk of complications in long-term, randomized, prospective controlled clinical trials," according to William Herman, MD, MPH, and Michael Engelgau, MD, MS. "Unfortunately, [A1C testing] does not measure the magnitude or frequency of short-term fluctuations of blood glucose, and no clinical trials have prospectively assessed whether [after-meal] glucose plays a unique role in the pathogenesis of diabetes-specific complications."

Fasting BGs Not the Only Determinant of Complications

"Most peoples' bodies, especially as we age, can't tolerate those spikes and troughs," says Ruth Ferrarotti, APRN and CDE at Hartford Hospital's Diabetes Life Care Center in Connecticut. "What we have to remember about the A1C test is that it is an average of the blood glucose for the last three months. If you have someone who tests in the 60 mg/dl range and also in the 300 mg/dl range, his or her average is going to be somewhere around 140 to 150 mg/dl. This is an A1C of 7%—the goal the American Diabetes Association recommends."

The A1C range of people without diabetes is usually between 4% and 6%.

What people with diabetes might not know, says Ferrarotti, is that you can achieve normal A1C control and still suffer the impact of high blood glucose if after-meal levels are not controlled.

"In my opinion, it's not just the fasting blood glucose that has an impact on complications," Ferrarotti said. "It really is that after-meal glucose spike and how long the blood glucose stays up after meals."

Not to Be Ignored

A group of Italian researchers, who published their findings in the December 2001 issue of Diabetes Care, report that most of their patients had frequent after-meal high blood glucose, even though their A1Cs were acceptable.

Dr. Enzo Bonora and colleagues in the Division of Endocrinology and Metabolic Disease at the University of Verona revealed that about 70 percent of the patients they studied had high blood glucose after breakfast and lunch. They also found that the A1Cs of the same people were less than 7%.

"You can't ignore fasting levels," says Dr. Mark Feinglos, a professor who heads the Division of Endocrinology and Metabolism at Duke University. "But you can't ignore after-meal blood glucose either."

For a long time, however, professionals in the diabetes community have done just that.

"It's an extremely important area," Feinglos argues. "You can't really achieve tight control of diabetes without paying attention to after-meal blood-glucose levels."

Feinglos led a study, published in the October 1997 issue of Diabetes Care, demonstrating for the first time that after-meal glucose levels affect the entire day. The study concludes that modifying after-meal blood glucose can have a significant impact on diabetes control.

Are We Just Being Too Lazy?

"The ADA has made it so that we can be lazy," says Lois Jovanovic, MD, a board-certified endocrinologist and director of research at the Sansum Clinic in Santa Barbara, California. "We don't have to measure after-meal glucose until we go up that high after meals repeatedly? To me, that is unconscionable."

Jovanovic took some time to respond to the ADA's position.

"My position is that since it is entirely likely that the after-meal glucose will relate to complications, we should start to look at that question," she asserts. "Doctors don't want to look because it's a lot of work, and the ADA supports a lazy point of view. It's just easy for them to say that you don't have to do it until there's proof."

It's pretty simple, adds Jovanovic. "If your after-meal glucose relates to your A1C, and your A1C relates to cardiovascular disease risk, why wouldn't anyone believe that your after-meal glucose is related to your cardiovascular risk and risk of death?"

Jovanovic was the first to publish data, back in 1991, describing the relationship between after-meal blood glucose and macrosomia, or "big, sick babies."

"All of it seems laughable to me, since we published this 10 years ago. Obviously, if it's good to watch after-meal glucose for a pregnant woman, why would it not be important for a nonpregnant person? We found that you can minimize problems in the baby if the mother's blood glucoses are kept normal. However, outside pregnancy there's a huge controversy over the importance of after-meal glucose."

Jovanovic says the early studies showed that mortality and cardiovascular disease both increased when after-meal glucose was high. But most doctors are just now starting to ask patients to monitor after eating. So the data on the importance of after-meal glucose monitoring is only now starting to accumulate.

"It will take a lifetime to prove whether after-meal glucose monitoring and treatment improve risk for cardiovascular disease and complications, as the ADA wants to see," says Jovanovic. "Retinopathy and nephro-pathy don't happen overnight."

After-Meal BGs Should Not Be Downplayed

Richard K. Bernstein, MD, FACE, FACN, CWS, author of "Dr. Bernstein's Diabetes Solution," has had type 1 diabetes for 55 years. He also responded to the ADA position of not supporting after-meal testing and treatment.

"They do what is easy and what leaves the least work for physicians," says Bernstein. "This is a very important thing that has been played down by the ADA because they had no means of coping with it."

Bernstein observes that the evidence supporting the importance of after-meal blood glucose is becoming more and more overwhelming.

"Even in studies looking at nondiabetics and mortality—especially cardiac mortality—that include both A1C and after-meal glucose, we're finding that after-meal glucose is important."

After-meal glucose spikes are guaranteed to cause damage over the long term, Bernstein adds.

"But the effects are going to be negligible over the short term."

Studies on the Horizon?

With today's new insulins and the tools to measure blood-glucose levels, studies addressing the effect of after-meal blood glucose on diabetes complications should be forthcoming.

Drs. Herman and Engelgau, in their commentary "Postprandial Hyperglycemia: Actor or Understudy?" note that clinical trials "to assess the contribution of [after-meal] glucose to the long-term complications of diabetes were not possible before the advent of. continuous glucose monitoring and the development of. rapid-acting insulin analogs."

However, now that these more effective ways to measure and treat after-meal blood-glucose levels are available, "the necessary trials may be undertaken."

Better Control Overall

Jovanovic also believes that the ADA has allowed A1C targets to remain too high. She asks her patients who are pregnant to aim for an A1C lower than 6%. She also asks them to test one hour after eating, in order to see their "worst" numbers before they start going down.

"The two-hour time point is a transition number," says Jovanovic. "It's not the worst number. They're already starting to go down at that point."

She notes that if an A1C in the 7% to 8% range is considered "OK," testing after meals might not seem so important. But if you have an A1C target goal of less than 6%, you can't achieve that just by pre-meal testing.

The ADA won't change its policy unless there's scientific proof, Jovanovic says. "My idea is: Let's go with the best possible methods for control we can, until there's scientific data that we don't have to work so hard."

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Categories: A1c Test, Blood Glucose, Diabetes, Diabetes, Insulin, Low Blood Sugar, Meters, Type 1 Issues, Type 2 Issues


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