Five years ago, I wrote an article for Diabetes Self-Management about the management of after-meal blood glucose spikes. It was called “Strike the Spike” and no article I’ve ever written has led to greater reader response. To this day, I still receive calls, letters, and e-mails thanking me for offering practical answers to this perplexing challenge. I’ve even been asked to speak on the topic at some major conferences. So when presented with the opportunity to readdress the issue, I jumped at the chance.
A lot has changed in the past five years: we know more than ever about the harmful effects of after-meal blood glucose spikes, but we also have a number of potent new tools and techniques for preventing them. Now that I know how important this topic is to so many people, I’ll do my absolute best to bring you up to date.
What’s a spike?
After-meal, or “postprandial,” spikes are temporary high blood glucose levels that occur soon after eating. It is normal for the level of glucose in the blood to rise a small amount after eating, even in people who do not have diabetes. However, if the rise is too high, it can affect your quality of life today and contribute to serious health problems down the road.
The reason blood glucose tends to spike after eating in many people with diabetes is a simple matter of timing. In a person who doesn’t have diabetes, eating foods containing carbohydrate causes two important reactions in the pancreas: the immediate release of insulin into the bloodstream, and the release of a hormone called amylin. The insulin starts working almost immediately (to move glucose out of the bloodstream and into cells) and finishes its job in a matter of minutes. The amylin keeps food from reaching the small intestine too quickly (where the nutrients are absorbed into the bloodstream). As a result, the moment blood glucose starts to rise, insulin is there to sweep the incoming glucose into the body’s cells. In most cases, the after-meal blood glucose rise is barely noticeable.
However, in people with diabetes, the situation is like that of a batter with very slow reflexes facing a pitcher who throws 98-mph fastballs: The timing is all fouled up. Rapid-acting insulin that is injected (or infused by a pump) at mealtimes takes approximately 15 minutes to start working, 60–90 minutes to “peak,” or reach maximum effectiveness, and 4 hours or more to finish working. Meanwhile, amylin is either produced in insufficient amounts or not at all, so the movement of food from the stomach to the intestines is not slowed the way it should be. As a result, food digests even faster than usual. This combination of slower insulin and faster food can cause the blood glucose level to rise quite high soon after eating. Once the mealtime insulin finally kicks in, the high is followed by a sharp drop.
Why are spikes a problem?
Even though after-meal blood glucose spikes are temporary, several spikes a day, day after day, can raise your glycosylated hemoglobin, or A1C level, and a high A1C level has been shown to raise the risk of long-term diabetes complications.
Your A1C test result reflects your average blood glucose level for all times of day (before and after meals) over the past two to three months, with the more recent weeks influencing the result more than earlier weeks. So if your pre-meal blood glucose average is 130 mg/dl for a given three-month period, and your post-meal average is 240 mg/dl, your A1C will probably reflect an overall average somewhere in the middle of these two numbers.