Our blood glucose still tends to peak at about 73 minutes after the first bite of our meal, if we have diabetes. But the peak comes much sooner for other people. And, of course, their peak isn't nearly as high.
In my article "New Time to Test Glucose Levels" here two and one-half years ago I suggested that on the basis of two studies the peak was generally 72 or 74 minutes after the first bite. So when I saw new reports from a research group headed by Professor Jennie Brand-Miller, I got confused. Dr. Brand-Miller is professor of human nutrition at Australia's University of Sydney and the world's leading expert on the glycemic index.
The report in her blog that peak glucose levels of all the types of foods they tested were at 30 minutes after eating (except for wholegrain breads, which went up a bit to 45 minutes) came as a big surprise to me. A correspondent who lives on isolated Norfolk Island (population 2,114) in the South Pacific is nevertheless wired into the the rest of the world via the Internet, has a good memory for what I wrote here years ago, and asked me to explain the difference.
I've worked with Dr. Brand-Miller for more than 10 years. Several years ago we wrote a book together, The New Glucose Revolution: What Makes My Blood Glucose Go Up...And Down? So I wrote her.
She then sent a me PDF of the full-text of their research report in the January issue of The American Journal of Clinical Nutrition. Only the abstract is free online.
But even after reading both the research report and the blog, I missed some key words. The title of the blog article is "Healthy Curves." The title of the journal article includes the words "healthy subjects."
This research used a database of more than 1,126 foods and 546 volunteers. It reported such a big difference from previous research on peak blood glucose times among people with diabetes that I emailed Dr. Brand-Miller, "I really would appreciate your analysis for the follow-up article that I will write."
Her reply enlightened me. "The timing of the peak would differ greatly between normal healthy subjects and diabetic individuals," she emailed me. "I would expect it to be much later in diabetes. In type 2 diabetes, first phase insulin secretion is 'blunted' so the glucose levels keep rising until enough insulin has been secreted to stem the tide."
Oh, now I get it! We are different, and the reason is because we have lost some or all of our first phase insulin release.
"This is the load of insulin that the pancreas can dump as fast as you can absorb carbs," commented RobLL here. "After this the second phase involves the steady production and release of insulin to mop up whatever excess glucose there is in the blood stream."
That's a great explanation of a concept that even many doctors don't understand. I wrote a more detailed explanation here a year and one-half ago based on my interview with Amylin's Dr. Alain Baron.
Still, the existing research on time to peak remains inconsistent. The problem is the 2005 report in the Journal of Perinatal Medicine. This study of 53 pregnant women included 13 women with gestational diabetes, four with type 1 diabetes, and 36 pregnant women who didn't have diabetes. Those women who didn't have diabetes tended to peak at 82 minutes, while those women who had either gestational or type 1 diabetes tended to peak at 74 minutes. I've written the lead author, Dr. Kai J. Bühling of Humboldt University Berlin, as well as Dr. Brand-Miller to see if either of them can clarify this discrepancy.
But both the report in the Journal of Perinatal Medicine and the oral presentation at the 2006 scientific session of the American Diabetes Association by doctors at the departments of diabetes and nutrition at the Hôtel-Dieu Hospital in Paris recommended that we test much sooner than our organizations recommend. Both the American Diabetes Association and the American Association of Clinical Endocrinologists have said that its best to check our levels two hours after the first bite of a meal. Dr. Brand-Miller indicated in her email to me that the Australian recommendation is three hours.
"We would prefer a 60-min interval," the German doctors wrote in the Journal of Perinatal Medicine. "The optimal time to assess blood glucose concentration is about 70 minutes after the start of the meal," the French doctors stated in their oral presentation at the ADA meeting.
Either 60 or 70 minutes makes more sense to me for those of us with diabetes so we can take corrective action sooner than the official recommendations would have us do. People who don't have diabetes might test earlier.