Diabetes in Control reported today on a study presented at EASD by Dr Esther van 't Riet which found that in normal people the A1c is predictive of non-fatal heart attack, but, both fasting bg and the 2 hour OGTT [Oral Glucose Tolerance Test] results are not.
http://www.diabetesincontrol.com/results.php?storyarticle=5146
Before you conclude that this study "proves" that post-meal spikes are not what cause heart attacks, it is worth considering how the OGTT works and why it does NOT mimic the way your body responds to high carb meals.
The OGTT involves sucking down 70-75 grams of pure glucose and then testing blood sugar at various intervals to see what happens. It is a convention of medical research to use the OGTT value to diagnose "Impaired glucose tolerance" when the 2 hour result is over 140 mg/dl (7.7 mmol/L) and to diagnose diabetes when the 2 hour result is over 200 mg/dl (11.1 mmol/L).
However, glucose is the one form of sugar that does not require any digestion. It goes directly into the bloodstream within 15 minutes, unlike starch or sucrose which must be broken down in the stomach and may take up to an hour to reach the blood.
So the 75 grams of glucose you swill during an OGTT hit the blood in 15 minutes. In most people with the kinds of blood sugar control likely to result in a 5.5% A1c (the level Dr. Riet's study showed to correlate with heart attack)this initial very high blood sugar spike provokes reactive hypoglyecmia.
So what typically happens is that the person with marginal blood sugar control--the 5.5% A1c that marks a higher risk of heart attack--will get a very high blood sugar reading at 1 hour only to have the blood sugar plummet in the second hour. it is quite possible to have a normal or even a low blood sugar two hours after taking an OGTT where the one hour value was over 200 mg/dl (11.1 mmol/L). But this study only looked at that second hour response in diagnosing "impaired glucose tolerance."
However, look what happens when these same people with the 5.5% A1cs and "normal" two hour OGTT values eat the same number of grams of carbohydrate that are used in the OGTT in the form of real food.
That hamburger bun and order of fries with the 75 grams of carbohydrate digest more slowly, thanks to the carbohydrate they contain being combined with fat and protein. So if you have an A1c of 5.5% and test your blood sugar after eating 75 grams of carb in real food you are more likely to see something like 180 mg/dl (10 mmol/L) at one hour after eating and 160 (8.9 mmol/L) at two hours. By 3 hours your blood sugar may have dropped to 120 mg/dl, but until it does you have spend a couple hours with blood sugar levels that are known to be high enough to damage the organs!
It is a shame that almost no medical authorities test people for meal tolerance rather than using pure glucose syrup for the OGTT. The meal tolerance test, where a meal containing real food with a known carb count is served and blood sugar measured at one and two hours, would give doctors a much better idea of what is happening in the patient's body day in and day out. It would also be very likely to show a very tight correlation between exposure to elevated blood sugars after meals and increased incidence of heart attack.
Instead, the researchers here, who clearly have NEVER MEASURED THEIR OWN BLOOD SUGARS and do not understand that a "normal" two hour results on an OGTT may not indicate normal blood sugar response to meals day in and day out, look at that 2 hour OGTT results and conclude that, since the OGTT results don't correlate with heart attack incidence, blood sugar is not causing heart attack. Instead they hypothesize that the A1c is only "a marker" and elevated blood sugars is NOT the cause of heart disease.
This is tragic. Because lowering blood sugar after meals is probably the single most powerful tool available to us to avoid heart disease!
But sadly, the researchers in this case conclude that doctors should not attempt to lower A1c but should just keep treating cardiac risk factors with expensive drugs.
I am sure you will hear doctors citing this study as a reason to avoid testing after meals or reducing blood sugar spikes since "clearly" the study shows that spikes don't correlate with heart disease.
But those of us who do control our blood sugar and avoid post-meal blood sugar spikes know that controlling spikes so that they don't go over 140 mg/dl (7.7 mmol/L) lowers blood pressure, lowers triglycerides and LDL and raises HDL without the need for expensive drugs. Which suggests that elevated post-meal blood sugars are what raise the risk factors and that normalizing blood sugar could prevent heart disease.
Sadly, bad science in the form of over-reliance on the OGTT will keep most people from ever learning this.
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