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John

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Blogging blood sugar [Mar. 10th, 2012|09:16 pm]
John


So, the first thing I learned about blood sugar is that it's... well, it's flippin' *amazing*.

In the US, people tend to measure blood sugar by milligrams per deciliter. 100 is "a" normal value - really, normal can range from 70-120 (plus a bit), depending on what's going on. Just slammed down a Coke? You're probably pressing 120. Just woke up, starving? Probably closer to 70.

Anyway: 100 milligrams, per deciliter. That means 1 gram per liter - a deciliter is a tenth of a liter, every deciliter has 100mg, voila, 1 gram.

The human body might contain 5 liters of blood. 5 grams. Now, here's something to think about. An athlete who is running at a good clip might be burning 20 calories a minute. That's 5 grams of carbohydrate right there. Every minute, the body would have to cycle a full supply of blood sugar, and would have to keep it nearly constant - it can't let it drop to 40, and then boost it up to 100 again. It can boost it to 120 (and it might!), but it won't intentionally go higher that that, in most circumstances.

And if you've just slammed down that Coke, that's about 35 grams of carbohydrate going into your blood stream that has to be put somewhere, so the body can use it - even if you're that athlete, because it's got to be farmed out over 7 minutes.

Me, when I first learned I had to watch my blood sugar, I thought "Okay, I'll just run a sugar deficit. If I eat 100 grams of carbohydrate, I'll make sure I burn at least 400 calories from exercise each day. Then, my body will use sugar through the day for the basic stuff, so I'll be in deficit. That will lower my blood sugar!"

That certainly helps. But if my blood sugar, when fasting, was 120, it doesn't fix that underlying problem: that my body *wants* my blood sugar to be relatively close to the danger zone, just starting out. It's not the sugar itself - I only have around 6 grams, rather than around 5 grams, if my mg/dl is 120. It's not just burning off the sugar - that would only take 24 calories of exercise. No, it's that whole complicated system of trying to put my blood sugar in a place where my body feels comfortable, plus how to deal with the incoming sugars.

Then, there's the other side of it. If a person has a fasting blood sugar of 120, then the odds are very high that eating a meal with significant carbohydrate in it - say, a burger and small order of fries - their blood sugar might shoot up into the danger zone, and stay there for a long time.

(I say "danger zone", but a blood sugar higher than 140 isn't acutely dangerous. There *is* an acutely dangerous level - I don't know what it is. But it is chronically dangerous - if your blood sugar keeps going that high, and staying that high, things get bad.)

So, it's not just that a fasting blood sugar of 120 is "too close" to 140. It's also that, if a person has that fasting blood sugar, they probably also have a problem with that delicate, complicated regulatory system that keeps the blood sugar at a stable, and lower, value.

Here's one of the complicated things. Doctors know how this *can* happen. For example, if the liver sees low insulin, it can decide it needs to dump more glucose into the blood. It doesn't sense your sugar directly - it senses stuff related to your sugar. So, if your beta cells (the cells in your pancreas that create insulin) are just exhausted (or damaged), your liver can respond by dumping glucose, which exacerbates the problem.

So, they know how it can happen, but they may not know why it does happen... lots of possibilities, but no definitive answers.

There is one happy note in this confusion: for most folks, in most circumstances, whose blood sugar is rising, exercise will help reduce it. Exercise opens channels for the muscles to use to burn glucose. These channels do not require insulin, so even if the body is producing a weak insulin response, the exercise can drop a blood sugar spike. And, of course, exercise in excess of the amount of sugar coming in from recent food will burn up some glycogen, and then, afterward, muscles will be a bit hungrier for some sugar to replenish this glycogen. But this requires insulin - and if the insulin response is weak, or the muscles are insulin resistant, this can be slower and less efficient, leaving blood sugar higher for longer.

There is one risk to exercise which doesn't affect people like me: if a person's blood sugar is really high, it might mean their body has essentially run out of insulin, and the body has gone into ketosis - fat burning for energy. Exercise won't reduce blood sugar (the muscles don't want sugar, they want fat), and can make the problem a lot worse. This is when you'll see references to diabetic ketoacidosis. (It's also why low carb diets have a bit of a bad rap from some - they try to encourage ketosis, which isn't dangerous for most people, most of the time. But I reckon the time most doctors hear about ketosis is when hearing about how to deal with ketoacidosis.)

Anyway: this means that one way to control blood sugar is to take a walk after eating. It might help to wait a bit after finishing eating; it takes some time for blood sugar to rise, and it peaks at different times for different people. But if your sugar peaks at 1 hour after eating, and you take a half-hour walk starting 45 minutes after eating, you'll probably burn some of your sugar off, and keep it from rising as high.
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