The first thing we have to define when we speak of normal blood sugar is how we're going to define normal. We could speak of the mean among all people, regardless of what condition they are in, for instance we're taking people with so called normal blood sugar and including people who have impaired blood sugar, and also throwing in diabetics in there as well, because all these people are part of the set of human beings if we're looking to figure out what the average is.
This is basically how labs determine normal results by the way, they take all the data they have and then do a statistical analysis on it, and the extremes get tagged. So if you are extremely high or extremely low than you fall outside the normal range.
So it's not hard to imagine that this approach has its issues, and in fact normal itself, perfectly normal, might not be healthy. There are nutrients that the majority of people are deficient in for instance and just because you aren't super deficient, falling outside the range, which by the way generally is the top 5% or the bottom 5%, the two standard deviations statistical model, in other words you are in the 90% of people who don't fall outside this range, then you are OK.
This model basically requires that 90% of people are healthy as far as the variable you are measuring, and health doesn't quite work that way, it just doesn't conform to all of this, and there are cases where most of the people in the 90% normal range may be suffering from a condition but they are all told that they are fine.
So when we say normal, what we really are looking for is normal blood sugar in healthy individuals, and that's not necessarily the same thing. Normal blood sugar is actually rising each year, but this doesn't mean that what's healthy goes up.
With all this said though, the standards for normal blood sugar that we use isn't like that, at least not too much anyway, at least from a diagnostic perspective. So we have three ranges here, normal, impaired, which is used to diagnose prediabetes, and diabetes itself.
That's not what we're after here though, we instead want to know what blood sugar is in healthy subjects, which is different than saying, well there's a healthy range and then as it starts to get more and more unhealthy until you get to the point where you've crossed this line and we're going to call it something else now, like impaired glucose tolerance.
I do want to point out though that while we may measure normal blood sugar in healthy individuals, that doesn't mean that blood sugar that falls outside this range is unhealthy, that's going to depend, and when we say unhealthy this is going to have to be by a meaningful degree, and this is actually something that a lot of diabetics get confused about.
However it is educational at least to know what the normal reference ranges are here among healthy subjects, those who don't have any glucose tolerance or any other manifestations of metabolic disorders, including elevated insulin levels as well, something we tend to neglect a lot.
So this particular study sought to do just that, and you can click here if you want to watch the video presentation on it, although I will warn you that it's on the dry side, but interesting nonetheless.
So what they did is take a group of subjects who were screened for various things such as BMI, A1C, insulin levels, and so on, and were determined to be fit in all these categories. The BMI average was 22 by the way, so we're talking people that are pretty lean, and that's what we want. Average A1C was 5, a very healthy number, prediabetes is 5.7 to 6.4 to give you an idea, and diabetes is 6.5 and up.
So these subjects aren't anywhere near prediabetic, which is what we want, we want the standard for people who don't have any issues. Insulin levels were not just normal but on the low end of normal, the optimal end.
So they used continuous glucose monitoring for several days under controlled conditions, and fed them at regular times with snacking not allowed, and measured the results. Post prandial spikes were almost all under 125, and what was noteworthy here is the brief time that the subjects stayed at this level, a matter of a few minutes, and then their blood sugar was on the way down, although the drop was slow and steady, bringing them down to a fasting baseline of around 80.
Throughout the night, their blood sugar remained remarkably stable at the same baseline of 80, only showing very slight variations during the hours that they slept.
Breakfast was the meal that produced the biggest spike, but this is understandable, and this was significantly higher than the other two meals of the day, however they are under the influence of morning elevated cortisol and this does show us that even these people get a little liver dumping, as the meal itself would not have produced this higher reading.
We also see insulin levels spiking within a half hour of meals, and glucose levels spiking a little before the one hour mark, which is very distinct from diabetics, with both taking a lot longer to peak and much longer to come down to normal.
After two hours, both glucose and insulin levels are almost all the way down to normal, where with diabetics they often are still rising.
They also did a study where they took diabetics and measured their average glucose with and without feeding them breakfast, with total caloric intake the same, and they found that average blood sugar was 7.06 mmol/l without, and 7.42 with, so that's super interesting. This might cause us to think twice about having breakfast, they say it does keep your energy up, but it does that by keeping your blood sugar up it seems, something we may not want as diabetics.
This might also make a case for eating less often as diabetics, as you are subjecting yourself to additional periods of postprandial (after meal) peaks, and eating less often also leads to less overall insulin secretion, a desirable trait as well.
So this is all good information to have, including how our glucose metabolism is supposed to work when not under stress or dysfunction, this doesn't mean by the way that this is something we need to demand of ourselves as diabetics or even strive for, as that may involve paying a price where the costs and risks exceed the benefits, but it's still good to know what this is all supposed to look like.