One of our most stubborn challenges is to control the dawn phenomenon. That's when our fasting blood glucose readings in the morning are higher than when we went to bed.

The dawn phenomenon is a normal physiological process where certain hormones in our body work to raise blood glucose levels before we wake up, as we wrote in The New Glucose Revolution: What Makes My Blood Glucose Go Up...And Down? Professor Jennie Brand-Miller of the University of Sydney, Kaye Foster-Powell, and I co-authored that book (Marlowe & Co., first edition 2003, second American edition 2006).

These so-called counter-regulatory hormones, including glucagon, epinephrine, growth hormone, and cortisol, work against the action of insulin. They stimulate glucose release from the liver and inhibit glucose utilization throughout the body. The result is an increase in blood glucose levels, ensuring a supply of fuel in anticipation of the wakening body’s needs.

If you take insulin injections, it could be that the effect of insulin you took is waning. Your blood glucose will rise if you didn’t take enough to keep your insulin level up through the night.

The dawn phenomenon varies from person to person and can even vary from time to time in each of us. That much was clear when our book came out.

But how to control it was a different story. A couple of years ago here I wrote about several efforts for “Taming the Dawn Phenomenon.” People have tried everything from eating a green apple at bedtime to high-maize grain to uncooked cornstarch.

None of these remedies that I have been able to try ever worked for me. I always thought that the most promising remedy was one that a correspondent named Renee suggested – vinegar capsules.

"I am still using vinegar tablets (usually 8) each night and have used vinegar when tabs are not handy," Renee just tells me. "I have never added food to that, however. I still do have success in reducing the morning reading as proven by the times when I do not use the vinegar tabs and the reading in the a.m. is usually 20 points higher. I am doing well overall with an A1C of 5.6 for some time now. I have been on Byetta for a year now and have lost 35 pounds."

This makes sense, because several studies in the professional literature clearly show that vinegar can reduce our blood glucose levels.

One of these studies, by Dr. Carol Johnston and two associates in the department of nutrition at Arizona State University in Mesa, Arizona, is particularly intriguing. They reported that “Vinegar Improves Insulin Sensitivity to a High-Carbohydrate Meal in Subjects With Insulin Resistance or Type 2 Diabetes” in a 2004 issue of the professional journal Diabetes Care.

Now, Dr. Johnston and an associate have zeroed in on using vinegar to control the dawn phenomenon. Their study, “Vinegar Ingestion at Bedtime Moderates Waking Glucose Concentrations in Adults With Well-Controlled Type 2 Diabetes, appears in the November 2007 issue of Diabetes Care.