Test Procedures

Test Procedures & Standards
The rationale behind our tests and rankings

This web site compares food products based on how much they raise blood glucose. I use a simple means to determine whether a food product causes my blood glucose to spike: I measure my blood glucose with a glucometer just before I eat and an hour after I eat. There are some issues with this approach:

  • My blood glucose test results show a lot of variation. This is because of changes over the day in how insulin resistant by body is and in the amount of insulin I produce, lingering effects of previous meals, glucometer inaccuracies, and other factors. To mitigate the effects of these variations, I take two measurements for each test – one just before eating and the second an hour after eating – and calculate the increase in blood glucose for each test. I start each test at least two hours after my previous test. I do a lot of tests of each product and compute the average and standard deviation of the results.
  • Different foods affect blood glucose at a different rate than others. Some food products may cause a blood glucose peak earlier or later than others. This is not reflected in my tests. At some point, I may get a continuous blood glucose meter to measure my total glucose response, but this is definitely a limitation of my current tests.

YODA GTT April 21, 2008

The reason I selected an hour after eating for postprandial measurements is that I had a Glucose Tolerance Test in 2008 and my blood glucose peaked 70 minutes after eating. It usually takes me about five minutes to eat, though I drank 75g of dextrose, the stimulus for my GTT, in under a minute. I have done other tests that show a peak about an hour after finishing eating. However, I have found some food takes longer to peak in my body.

All measurements were made with a pair of Accucheck Aviva glucometers and a Bayer Contour USB glucometer. Both measurements for each test (one before and one after eating) were made with the same meter.

Blood Glucose Target

What should one’s blood glucose target be?

The American Association of Clinical Endocrinologists recommends that blood sugar not be allowed to rise above 140 mg/dl two hours after eating. The American Diabetes Association suggests keeping postprandial plasma glucose under 180 mg/dl. I am very skeptical of these targets, which do not appear to fully consider the consequences of blood glucose levels this high or how lower targets can be reached with a very low carb diet.

What does the science say? Jenny Ruhl has guidance on this at her excellent web site Blood Sugar 101. Jenny points out that researchers have discovered beta cell dysfunction when blood sugar rises just above 100 mg/dl.

My personal take on blood glucose targets and the selection of food to eat: my #1 goal is to never have to be on insulin. I am strongly motivated to avoid the need to inject myself with a drug that has to be carefully calibrated for the food I eat and the time I eat it.  I thus am very protective of my beta cells, which are the ones that produce insulin. Also, some of these food products are rarely eaten with no other, the way I tested them; sandwich bread might be eaten with peanut butter and sugar-free pickles, rather than carb-free cheese,  and a salad.

As a practical matter, I look at the results of the food tests in this web site and will, in the future, eat only those that have a minimal effect on my blood glucose.

I use a color scale to help interpret my blood test results. The table below shows colors associated with various average blood glucose increases measured an hour after eating.

Minimal
  
Low
 10 to 19 mg/dl      
Moderate
 20 to 29 mg/dl                
High
 30 mg/dl and above                       

How Low to Go

There are, unfortunately, no formal guidelines for low carb diets. I hope this changes in the future.

The infamous Institute of Medicine Dietary Reference Intakes Report makes a convincing case that no carbs are required at all, citing examples of societies that live on minimal carbs – and goes on to commit the colossal blunder of “setting” its Recommended Daily Allowance for carbohydrate at 130g/day. Ignore this dangerous IoM RDA, especially if you are diabetic.

The New Atkins for a New You recommends that those trying to lose weight limit net carbs (total carbs minus fiber) to 20g during induction, then gradually add carbs in 5g increments as long as weight loss is not halted or other problems do not arise.

Carb limits for diabetics – Dr. Richard Bernstein recommends that diabetics eat no more than 6 grams at breakfast, 12g at lunch and 12g at dinner for a total of no more than 30g per day. He recommends subtracting half of the fiber from the total carb count to estimate effective carbs.

Dr. Eric Westman has had clinical success with diabetes patients at Duke University with a diet of just 20g net carbs per day.

My target – When I’m done with the food tests for this site, I want to keep my postprandial blood glucose under 110 mg/dl. I plan to achieve this by eating food products that lie in the green range of average blood glucose increases on this site – those that raise blood glucose by no more than 10 mg/dl. Whenever possible, I will choose products at the lower end of the green range.

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    I’m a very busy guy with the site, but if you have a special request for an item that should be tested, let me know. I’ll see if I can squeeze it in on a future date.