Monday, January 25, 2010

What to Eat? Check Your Blood Sugar

by Chris Masterjohn

Dr. William Davis is a practicing cardiologist in Milwaukee, Wisconsin. He publishes interesting thoughts and practical advice on his Heart Scan Blog. Recently, he suggested measuring your blood sugar one hour after meals in order to determine what foods are best for you. Meals that result in a blood sugar under 110 mg/dL one hour after eating are best. You can read the full blog here.

This makes a lot of sense to me, because there is great variation between individuals in the glycemic index of different foods. It could also indentify foods that put your body under stress.

I went to a seminar last year given by someone who had done research contributing to the development of a glycemic index (GI) database, and she concluded that the interindividual variation was so great that the index is almost useless. 

The GI compares the rise in blood glucose after eating a food to the rise in blood glucose after consuming pure glucose. Generally, the GI is expressed as some percentage less than 100 because the body takes more time to break starches down into glucose or convert amino acids to glucose than it does to simply transport glucose from the intestines into the blood. However, in one case the researcher presented on, an individual had a much stronger rise in blood glucose after consuming white bread than after consuming glucose! Clearly, this person was not just breaking the bread down into glucose but also releasing stress hormones into his blood that would further rise his glucose levels by breaking down stored glycogen and converting his own protein into sugar. He may have been unaware of his adverse reaction to white bread, but it may have been doing damage to his body all along.

The $20 investment in a blood sugar monitor that Dr. Davis recommends may thus prove a useful investment for helping to determine your ideal diet.

Read more about the author, Chris Masterjohn, PhD, here.


  1. Is fasting insulin or fasting blood sugar more important, do you think? I know Peter at hyperlipid said his fasting sugar was 102 or something like that, which was surprising but he said there were mitigating factors involved and wasn't too concerned about it.

  2. I just started testing my post-meal blood sugar on Friday. This morning, I ate a breakfast burrito (something I--almost--never do, at least not any more). Sugar spiked to 157 and I feel odd. I won't be eating flour tortillas any more.

  3. Starch starts breaking down in the mouth and is rapidly digested in the intestine, so some starches raise blood sugar as fast as pure glucose.

  4. Chris,

    If a person has developed an intolerance to a given type of meat or a fat source like a specific kind of nut, does this mean that even a meal very low in carbohydrates can cause a much larger rise in blood sugar than might otherwise be expected by the composition of the meal if there is enough of a stress response?

    Looks like I should be investing in a glucometer and start doing some informal experimenting.

    Thanks for sharing.

  5. Zach, fasting blood sugar is an is an indication of insulin deficiency or insulin resistance and is used to diagnose diabetes. While the diabetic range is much higher, the normal range is 70-90 (some labs might use 70-100). I would not take a single reading to mean much, but consistently scoring outside the range should probably be a concern.

    Laura, wow! Well, not entirely unexpected with a carby meal of course, but that is a bit high.

    Gretchen, yes, a starch could get broken down very rapidly, but in the blog I was referring to a GI of 300+%, meaning the blood sugar rise was over triple the response to glucose. So I think that indicates that not all of the blood glucose was derived from the meal.

    Wolverine, yes if there is a stress response to the food than the blood sugar could go up more than expected from the composition of the meal, as in the case of the person who responded to white bread in that way. I don't see why it couldn't happen to meat, although meat allergies are not very common.


  6. Here is the post about higher FBG on a LC diet that Zach is thinking of -

    Peter has also written several other posts discussing physiological insulin resistance. You can find them in the list of labels on the right hand side of the page.

  7. Thanks, C. That's an interesting post. It makes some sense, but still leaves questions in my mind. If the glucose is reserved for the brain, why is it elevated in plasma? Eventually on a ketogenic diet muscles begin using more FA and less ketones and brain begins running more on ketones, making glucose less necessary. Why not store the dietary glucose as glycogen, and suppress gluconeogenesis?

    HbA1c should reflect total cumulative exposure of hemoglobin to glucose, so if his postprandial levels are normal then it makes sense that his HbA1c should be low, because we spend the greater portion of the day in the postprandial state, and high postprandial glucose levels provide a lot more glucose exposure than high fasting levels.

    Maybe he's right, maybe he's not, or maybe the truth is somewhere in the middle. One thing I do think, though, the human body should be resilient enough to eat the occasional high-carb or high-fat meal without major ill effects.


  8. How interesting you would post this at the same time I have been contemplating doing this. I've had autoimmune issues my whole life and just by chance figured out it was food related which later led to a diagnosis of Celiacs and Crohn's (much to my surprise). We had tried the gfcf for my son's autism, got no results, then tried the SCD (a grain free diet), he came out of autism three weeks later. I noticed I feel better on his food than the gluten free grain stuff. At first I thought maybe it was the Crohn's making me unable to utilize them, and my ELISA food panel did not reveal any sensitivity to gf grains. Now I'm suspecting it might be a blood sugar thing (I feel the same way if I drink a soda). I feel sleepy and have major carb cravings after eating grains and sugary items. I feel peppy and high energy after eating a higher fat/protein diet. I've been reading BloodSugar 101 to try to understand more about this and I've been tempted to try testing by bloodsugar. Thanks for this post, very good timing!!

  9. Chris,

    It is so good to see more people getting on board with doing this simple test. It can be so revealing.

    Last summer I started a yahoo group for those interested in the subject.

    I would highly recommend to everyone that they read Jenny Ruhl's site in toto to really get a good appreciation of the topic.


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  12. Wow I never thought that the different GI of foods can affect the release of stress hormones. thanks for this insight.

  13. That $20 for a blood sugar monitor is really an investment. Checking your blood glucose level frequently is important for two things. First, in planning your meals and second to know the quantity of the insulin you should consume or if necessary other medications as well.

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