How Many Calories are in Your Blood?

Any idea? Here is a helpful comment by SixtiesLibber on the SLD forums:

When you get your fasting blood sugar tested, it’s supposed to be below 100. And it should almost never go above 200. Well, I finally checked and found what what those numbers mean, that’s 100 milligrams per deciliter. That’s kind of a weird measurement but it’s actually the same as 1000 milligrams per liter or 1 gram per liter. In other words, normally your blood has only 1 gram of glucose (sugar) per liter. (A liter is almost the same as a quart.) Adults have something like 5 quarts of blood in their bodies. So at any one time you only have about 5 grams of glucose circulating in your blood. That’s the equivalent of about 1 teaspoon of sugar or one-third of a piece of “squishy white bread.”

Answer: Not many.

10 Replies to “How Many Calories are in Your Blood?”

  1. So a 24-ounce Starbucks Caramel Frappuccino Blended Coffee with whipped cream (530 calories, 17 grams of fat, 71 grams of sugar) shouldn’t really affect that too dramatically, right?


  2. Though there’s also some fat in the blood, being shuttled to and from adipose tissue, right? (I seem to remember once when I gave platelets, they showed me the fat that had been skimmed out of my blood along with the platelets.)

    And, of course, there’s lots of protein in the red blood cells themselves–but I assume we aren’t counting that, because we’re just considering how much fuel is being carried by the bloodstream, not the energy locked up in the blood itself (which isn’t really available, unless you’re starving).

  3. At a triglyceride level of 150 mg/dl, that comes to 1.5 g/l, times 5 l, equals 7.5 g. At 9 Kcal/g, a grand total of 67.5 Kcal of fat in your blood. Cholesterol at 200 mg/dl would more than double that.

  4. Gee, only five grams of sugar, compared to 71 grams of sugar in a standard extra large drink. No wonder low carb diets, as long as they are ultra low carb, don’t seem to have effects.

    I’m trying one now. I realized that when I couldn’t tolerate Atkins I was cutting carbs to a gram or so a day and cutting calories to those in 60 grams of protein.

    On a more Taubes like limitation, it isn’t so bad at all.

    It is kind of fun to experiment. SLD makes that possible.

    BTW, kind of interesting:

  5. That’s the amount of sugar (glucose) in the serum not the whole blood. If you counted the intracellular glucose, we’d be talking totally different numbers (but not exponentially more). I promise your W/RBCs have to have glucose IN the cell to do all the work they need to do, but w/o looking it up I don’t know how what that quantity would be.

    More food, er, sugar, for thought. 😉

  6. That’s most likley how many calories it takes for your body to replace that pint, i.e. manufacturing new blood cells, producing plasma, etc.

    Probably not the healthiest way to burn calories though…

  7. Seth – I’ve written up a show-the-math answer for eHow that has been accepted but not yet posted. Once it is up a search on “calories human blood” will find it. You contributors are on the right track by adding up components. Calculating for a unit of donated blood (500 ml), it would contain between 400 and 500 calories (men average higher than women). It’s mostly protein in the red blood cells and plasma, smaller amounts for contributions from white blood cells and platelets.

  8. I definitely have to give you a lot of credit for this post. I am writing an article on what to eat before a workout and trying to figure out how long it takes to deplete your blood sugar. I was surprised to learn that blood lipid levels are also important to consider in this equation. I know with cardiovascular training the primary source burned is fat and for muscular endurance it is carbohydrates. I suppose if you are going to do a boot camp style of workout with cardio and resistance training it is best to eat something with complex carbs and perhaps a small amount of fat. I have talked to triathletes who actually concern themselves with eating enough fat the day of the event. Beyond that I have never heard of anyone concern themselves with eating enough fat.

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