The Long Dawn Phenomenon

Our bodies are more sensitive to carbohydrates in the morning. That’s why Dr. Richard K. Bernstein recommends that we eat half as many grams of carbs for breakfast compared with lunch or dinner.

“I usually advise patients to restrict their carbohydrate intake to no more than 6 grams of slow-acting carbohydrate at breakfast, 12 grams at lunch, and 12 grams at supper,” he writes in his book Dr. Bernstein’s Diabetes Solution. He knows from experience that carbs at breakfast will raise our blood glucose level more than at meals later in the day, but his book doesn’t tell us why that is a fact.

This difference has puzzled me for years. But now I understand.

I am in San Diego for the 71st Scientific Sessions of the American Diabetes Association. Yesterday a late-breaking poster here explained it for me.

The poster, “Morning Hyperglycemia: Breakfast or Dawn Phenomenon,” tells us more about the dawn phenomenon than we ever knew before. In the past we understood that it began about 4 a.m. and ended about 8 a.m., the typical start of breakfast. The new study by Dr. Allen King, an endocrinologist practicing at the Diabetes Care Center in Salinas, California, and two of his associates there, had 37 subjects skip their breakfast to see what happens.

The subjects used a basal insulin, Lantus, and a continuous glucose monitor. The CGM showed that in fact the dawn phenomenon doesn’t stop at 8 a.m. The dawn phenomenon does rise at 4 a.m., but it peaks at 10 a.m. and doesn’t return to baseline until 1 p.m.

“The dawn phenomenon contributes a major share to the ‘breakfast’ meal hyperglycemia,” they write.

One of my most popular posts here, “Taming the Dawn Phenomenon,” has 99 comments as of today. That post has many suggestions by me and others about how to keep our blood glucose levels in check.

Now, we know that minimizing carbs at breakfast is another arrow in our quiver.

This article is based on an earlier version of my article published by HealthCentral.