March 9, 2007
Here's an illuminating research study that was presented at a major European conference in September, 2006. It reports on the daily pattern of blood sugars of a group of normal subjects as revealed by continuous blood sugar monitoring. It gives a very solid answer to the question, "What is a normal blood sugar?"
What is Normal Glucose? – Continuous Glucose Monitoring Data from Healthy Subjects. Professor J.S. Christiansen, presented at the Annual Meeting of the EASD.
Above is a very revealing graph screen-captured from the dynamic display of this presentation. Click on the image to enlarge it so you can read it better.
It shows analysis of data from a study of normal people's blood sugars after a high carbohydrate breakfast eaten at 7:30 AM. The blue line is the average for the group. The brown lines are the readings for the people with the highest and lowest individual values which very possibly are those with the highest (5.4%) and lowest (4.3%) A1Cs.
The main findings here, for those of you who don't have the high speed internet connection needed to listen to this presentation, is that in normal people fasting blood glucose throughout the night stays flat in the low 80 mg/dl (4.4 mmol/L) range. After a high carb meal, blood sugar rises to about 125 mg/dl for a brief period, with the peak blood sugar being measured at 45 minutes after eating. The chart at the top of this page is taken from this presentation. Notice that in all but the people with the highest A1cs, blood sugar is under 100 mg/dl (5.5 mmol/L) at 1 hour and 15 minutes after eating and it returns to 85 mg/dl (4.7 mmol/L) by 1 hour and 45 minutes after eating.
Note also, how much lower even the highest of these normal readings are than the ADA's diagnostic cutoff for "impaired glucose tolerance" which is 140 mg/dl two hours after eating!
A few people in the study went as high as 160 mg/dl (8.9 mmol/L) after the high carb meal, which may be because they are not entirely normal. The study most likely recruited normal subjects based on their A1cs and the highest values in the group went up to 5.4% which is compatible with very early deterioration in first phase insulin secretion.
This study also documents that eating a high carb meal for breakfast results in an unacceptably high blood sugar swing much higher than any other blood sugar rise seen throughout the day, even for normal people, a point that the professor stresses in his presentation. So throw out the Corn Flakes!