Timing of blood sugars

Because different foods generate different blood sugar (glucose) responses, the timing of your blood sugar is an important factor to consider.

This question has come up a number of times. Commenters have asked whether the one-hour postprandial glucose is timed with the start of the meal or the conclusion of the meal.

In my view, if we simply ignored all aspects of meal composition, then blood glucose should be obtained one hour after the conclusion of a meal. This is because most mixed meals (i.e., mixed in composition among proteins, fats, and carbohydrates) yield peak blood glucose levels at 60-90 minutes after consumption. Timing blood glucose to 60 minutes after the conclusion of a meal puts the sample right about at the peak.

But this is an oversimplification. For instance, here is the blood glucose behavior after so-called "complex" carbohydrates wheat bread, rye bread, rye made with beta glucan, and whole wheat pasta (50 grams carbohydrates each) in slender, healthy volunteers, mean age 29 years:

From Juntunen et al 2002

Note that blood glucose peaks at 35 minutes postprandial. (To convert glucose in mmol/L to mg/dl, multiple by 18. Thus, whole wheat bread increased blood glucose from 94 mg/dl to 122 mg/dl. Also note the lower peak glucose for pasta, but sustained higher glucose levels hours later.)

In another study, older (mean age 64 years), overweight (BMI 27.9) females with diabetes were given 50 grams carbohydrate, 50 grams carbohydrate with olive oil, or 50 grams carbohydrate with butter:

From Thomsen et al 2003. Control meal of soup plus 50 g carbohydrates ({blacktriangledown}), the control meal plus 80 g olive oil ({circ}), and the control meal plus 100 g butter (•).

In this experience, note that postprandial glucose peaks 60-120 minutes after the meals (consumed within 10 minutes), delayed more when either oil is included. Blood glucose started at 144 mg/dl and peaked as high as 230 mg/dl with carbohydrates only; peaks were reduced (along with AUC) when oil was included. (Note the differential effect, olive oil vs. butter.)

These two sets of observations give you a range of blood glucose behavior. One side lesson: Carbohydrates should never consumed by themselves, else you will pay with a high blood sugar (not to mention the hypoglycemic response later for many).

Comments (5) -

  • steve

    3/3/2010 5:14:02 PM |

    does this include eating celery or cucumbers as a snack, or other veggies?

  • Hollie

    3/3/2010 6:12:24 PM |

    I began checking my blood sugar after reading about it here a few weeks ago, and was surprised to find that my blood sugar peaked a full two hours after a meal. At first I'd been doing the 1-hour, which this site suggests, but then I read fully the directions that came with my reader, and it said to check 2 hours after a meal.

    Of course, these directions are aimed at diabetics, and I'm assuming this site is aimed at folks who are either normal or perhaps pre-diabetic. I was a little disturbed to find that my insulin response appears to react in a diabetic way, although my actual blood sugars are still in the pre-diabetic range. Either way, I'm watching this a lot more carefully now, and this whole experience is the first thing in years that has really inspired me to work at getting off my lifelong sugar addiction. Thanks Doc!

  • Anonymous

    3/3/2010 9:46:00 PM |

    Dr. Davis,

    In cases where lean meat is included with vegetables and some fat, would this lead to an even more gradual rise in blood glucose?

    For several years now I have been in the habit of never consuming carbohydrates alone and always make sure to include either 20-30g protein + vegetables or 20-30g protein + vegetables + fat with any carbohydrates ingested.

    Bill Virdon

  • Adolfo David

    3/4/2010 2:40:46 AM |

    In your last LEF Magazine article about Frailty was a little strange to me not find Q10 when you talk about energy boosters. I usually recommend Q10 Ubiquinol for this purpose to old people. Anyway, thanks for your work, I hope one day I can read next parts of "Understanding Risk Factors for Heart Disease" you started in August 2009 in this great magazine.

  • Anonymous

    3/28/2010 6:33:35 PM |

    You'll have to determine when your own peaks occur after meals, but ours are consistently within the range of 30 to 60 minutes, depending on the meal. Of course, if the meal includes a dessert, etc., then you'll get multiple peaks. And if the meal is prolonged, such as a holiday meal, then all bets are off. But for those consuming lots of small meals during the day (to keep peaks low), 60 minutes is almost certainly too long to wait.