The Nutrition Debate #66: Fasting Glucose Best Predictor of Diabetes Risk (NOT!)

Okay, this is going to be a rant. Sorry, but I am angry at the current state of the medical community and how it seems to me to perpetuate the status quo at the most elemental and, frankly, idiotic level. A recent example is this headline, “Fasting Glucose Best Predictor of Diabetes Risk,” which appeared in an email from diabetesincontrol.com, a website for medical professionals (free subscription).

The report covers Ajay Gupta MD’s (Imperial College London) presentation at the European Society of Cardiology/World Congress of Cardiology last year. The study was milking another one of those large epidemiological studies (a 19,343 patient “trial”) to find “associations” for the occurrence of “new-onset (T2) diabetes.” It also compared outcomes of pharmacological therapies for hypertension, which explains the “study’s” funding.

This report ticked me off in particular because it is targeted to clinicians with a misleading and patently wrong headline.  It reminds me of the report recently that eggs were nearly as bad for you as cigarettes. I have read so many authoritative dismissals of this report that I am embarrassed for the Canadian researchers who produced it. Shame on them for such bad science! And of course, the journalists and editors who also misrepresent findings are to blame too.

But, on a positive note, and the reason for writing this column: YOUR FASTING BLOOD GLUCOSE IS NOT THE BEST PREDICTOR OF DIABETES RISK. Anyone who is informed in this field knows that. I do not see the necessity of citing references for authority as I usually do since this is widely known and accepted in the informed community. Fasting blood glucose as a diagnostic tool is an artifact of the last century. But, just for the record, the diagnosis of Type 2 used to be two consecutive fasting blood glucose tests at or above 126 (+/- ten years earlier ≥ 140). More recently the standard of practice came to include a hemoglobin (Hg) A1c test ≥ 6.5 (formerly 7.0). This test is inexpensive and measures the average serum glucose (from markers on red blood cells over their two to three month life cycle).

The best predictors of diabetes risk today are the indications of Metabolic Syndrome (see The Nutrition Debate #9). And the best diagnostic tool for Type 2 diabetes itself is the GTT, the Glucose Tolerance Test. It tells you if you are glucose (carbohydrate) intolerant as a result of developing insulin resistance. This is a relatively expensive and time consuming test, however, because it takes from 2 to 4 hours to administer. In my case, it was done in a hospital out-patient setting.

There is a much easier way, however, to find out if you are glucose intolerant: measure your one-hour and two-hour postprandial (after meal) blood sugar using a glucometer. See how the Low Carb Dietitian, an RD/CDE, discovered herself to be Pre-Diabetic here in my last column (#65). And learn what she is doing to avert developing full-blown T2.

You may have had an A1c test in addition to a fasting blood glucose at your last checkup. You should keep a record of these to see the trend over time; if the A1c has been rising over the years, now is the time to act. Most practitioners, like the Low Carb Dietitian’s, will not be “concerned” if your A1c is rising but not yet approaching 6.5, BUT YOU SHOULD BE as heart attack risk rises steadily above an A1c of 5.5. Some specialists, such as Dr Richard K. Bernstein, consider an A1c of 5.8 to indicate full-blown Type 2 diabetes.

If your A1c test is higher than the normal range of 4.0 to 4.9 (and if your doctor tested it, he probably suspects it is), you will want to test your blood sugar at home and learn to “eat to the meter.” If your blood sugar rises above 140ml/dl after 1 hour or does not drop back to “normal” (in the low 80s) after 2 hours, you are developing insulin resistance and have become glucose intolerant. YOU ARE PRE-DIABETIC and YOU NEED TO CHANGE YOUR DIET to minimize your intake of carbohydrates to control your blood sugar.

As I said, this is not my usual researched and referenced column. I am rushing it out there because there are so many readers who need to be informed that incipient (“new-onset”) diabetes 1) needs to be recognized and diagnosed early and 2) needs to be seen NOT as a problem with fasting blood glucose but as a problem with postprandial glucose. The way our bodies react to what we eat tells us we have a problem. And the best and least expensive way to find that out for yourself is to test your own blood sugar right before eating and again one and two hours after you have eaten a meal. To do this you will need a glucometer and some test strips. You can get both at Walmart, your local drugstore or buying club (Costco and similar places). The “pearl” here is to know that it is NOT your fasting blood glucose that is the best indicator of diabetes risk; it is your postprandial blood glucose (at 1 and 2 hours after a meal).

As the Diabetes in Control headline that is the title of this column indicates, most of the medical community is hopelessly out of date and behind the times. The solution: TAKE CHARGE of your own health, for your own well being.

© Dan Brown 9/16/12