Monday, June 20, 2011

Testing Blood Glucose Levels on a Low Carb Diet – Facts and Myths

Last month Jimmy Moore started testing his blood sugar after eating popular low carb products. Here’s the facts and myths about blood glucose levels when eating low carb.

Saturday was the first time I heard about Jimmy Moore testing his blood glucose levels after eating some of his favorite low carb foods. While Twitter is a great place to keep in touch with your favorite bloggers, it’s easy to miss important tweets – unless you think to pull up their most recent posts. While most low carbers stop by Jimmy's blog every day or two, I quit doing that about a year ago when videos became the norm there. At that time, I didn't have a high-speed internet connection, so wasn't getting anything out of that blog.

Saturday, I just happened to be reading the tweets of the people I follow on Twitter when Jimmy announced his blood sugar testing results from eating Julian Bakery’s CarbSmart breads was in. Since I now have high-speed access, I clicked on the link he provided, and began to read the post.

Dreamsfield Pasta Digests the Same as Regular Pasta

It quickly became apparent that in my absence, I’d missed Jimmy’s first test using Dreamsfield Pasta; so I followed the link back to that first experiment. When I saw what he actually did – how he compared the coated pasta to regular pasta – I gained a new respect for him. I never thought I’d ever see him confront low carb products in the way he’s currently doing. However, there are a few myths about blood glucose levels and low carb diets that need addressing.

A lot of diabetics can tell you from their own experiments that Dreamsfield Pasta digests the same as regular pasta, and that’s what Jimmy’s self test clearly showed as well: there is no such thing as protected carbs. However, he stopped testing his blood sugar after 180 minutes. Pasta takes 5 to 7 hours to digest completely; and most diabetics and pre-diabetics see a sharp rise in glucose somewhere between 5 and 7 hours. For those who don’t, they generally see much higher fasting glucose the following morning.

Also keep in mind that while both the Dreamsfield and regular pasta curves on Jimmy’s chart are within safe margins for glucose toxicity, you can clearly see that Dreamsfield’s pasta digests slower – but that means potentially higher insulin levels over a much longer time period, since blood sugar levels kept bouncing. Plus, we don’t know what happened between the significant 5 to 7 hour period.

Julian Bakery’s CarbSmart Breads

When eaten the way Jimmy would normally use bread, Jimmy’s curves fit well within safe margins for glucose toxicity – even when eating regular wheat bread. What we learn is that his blood glucose levels tend to spike much faster than the average person. If testing at 1 and 2 hours, as recommended, you could easily be deceived.

At 1 hour the low carb breads left Jimmy’s sugar level at just above or just below 100 mg/dl; and at 2 hours, the raisin-free bread was back to his typical fasting level. Even the raisin bread stayed about the same as where it was at 1 hour. The chart is extremely enlightening, because the 9-grain bread (not low carb) actually gave Jimmy the best blood sugar control.

Low Carb Myths

Now, you may be tempted to interpret these results as Dreamsfield Pasta and Julian Bakery deceiving low carbers; that low carb bread and pastas must have more carbohydrates than what the label claims. But that isn’t necessarily true. Why? Because blood glucose control doesn’t fall in line with how many carbs you eat. That’s a low carb myth.

The glycemic index is another myth that spawned the South Beach Diet and other low glycemic plans, but the folks who participated were healthy non-diabetics. That makes the chart (even the glycemic load chart) useless for those with insulin resistance, pre-diabetes, or diabetes. Eating low and lower glycemic foods like berries or even vegetables doesn’t guarantee good blood sugar control.

So What About Low Carb Dieting Itself?  

When you eat only low carb foods, the body down-regulates basal insulin levels, the amount of insulin you store, and the enzymes needed to digest carbohydrate foods. If you haven’t been eating carbs and you suddenly eat something like bread or pasta, your blood glucose levels will rise higher than they otherwise would – if you ate that amount of carbohydrates on a daily basis.

Results won’t be accurate – unless (like Jimmy) you just want to test these foods within a low carbohydrate context. If you want to know your true level of glucose control, you must eat carbohydrates for at least 3 or 4 days prior to testing. You can’t just go from 20 or 30 grams per day to 60, 80, or 100 grams without raising your blood sugar levels for a couple of days while your body re-learns how much insulin to store, and up-regulates necessary enzymes.

The Role of Food Sensitivities

In my own experience, food sensitivities play a major role in blood glucose control. If you have undiagnosed celiac disease, gluten intolerance, or a wheat allergy or sensitivity, low carb products can raise your blood sugar higher than safe, even though it might not raise someone else’s. That’s because the inflammation produced by allergies, sensitivities, and autoimmune issues keeps your body in a state of alert.

The body uses extra glucose to both heal inflammation and fight off invaders. Plus higher cortisone levels also keep blood sugar and insulin levels elevated, as well. But there is also the strange phenomenon of food individuality.

Since I began testing my glucose levels, I’ve learned that the number of carbohydrates I eat doesn’t accurately predict the amount of glucose produced from food, nor whether or not my body is able to store and dump enough insulin to handle what I eat. It doesn’t predict whether my insulin receptors are working properly. Glucose control depends on what type of defects I have in my metabolic system, and whether or not my immune system is working properly.

That translates into some pretty freaky results. For example, my daughter-in-law (a diabetic) can eat white rice with her meat and veggies, and her blood sugar stays within acceptable limits. But if she tries to eat the same amount of brown rice, her glucose levels go through the roof. That’s backwards to what the glycemic index says should happen.

If I eat 40 carbs of homemade gluten-free oatmeal bread (2 slices like Jimmy ate in his experiment), my blood glucose levels go above 140 mg/dl at 1 hour – putting me in glucose toxicity. In fact, the homemade gluten-free hamburger bun I tried last week sent my sugar level soaring to 175 mg/dl at 1 hour, and stayed high for 2 hours before dipping back down below 120 mg/dl (the safe zone). But – if I eat a 40-carb baked potato, my blood sugar level only goes up to about 105 and then returns to normal, around 84, by the 2nd hour. That makes white potatoes a perfectly acceptable maintenance food for me.

Everyone is Not Insulin Resistant

The biggest myth floating around low carb circles today is that if you’re overweight or obese, you’re insulin resistant – period. Carbohydrates will raise your blood sugar, low carb diets will automatically correct that, and lowering insulin levels is a good thing. However, some of us don’t make enough insulin. We’re insulin ‘sensitive’ – not insulin resistant. Lowering our current insulin levels can result in glucose toxicity. That’s not a good thing.

But that’s why testing your own blood sugars and finding what foods work for you is so important.


  1. Dear Vickie,
    Many thanks for your post.
    But how do I start?
    I've found that eating exactly the same foods on different days produces different results. (maybe stress plays a part?)
    I feel worse after breakfast, but less affects after lunch or dinner?
    Also you imply that previous days eating affects your blood sugar levels?
    I await your response.

  2. Eh-san,
    You said, "But how do I start?" I'm not sure what it is you want to start. Do you want to know how to start a low carb diet?

    Stress plays a very large role in glucose control. Cortisol is a hormone released when we are under stress. Its job is to get fuel as quickly as possible so we have the energy we need to handle the emergency (real or imagined). Its also released about 3 in the morning to start waking us up.

    Depending on our physical condition, cortisol can signal the liver to mobilize stored body fat to fuel glyconeogenesis or it can signal the pancreas to release insulin so the liver will use its glycogen stores.

    Morning is when most people have the least glucose control. Dr. Bernstein recommends eating no more than 6 carbs at breakfast. Mostly, that's due to the cortisol that's released to help us wake up and get moving.

    Feeling worse in the morning could also mean your fasting blood sugar is too high.

  3. I am on the Paleo diet, and to my shock my fasting blood glucose went from 90 before Paleo to 115 after Paleo. That's enough of a warning that something isn't quite as expected that I have a glucometer on order and will start using that. Is there any way to interact with you by email? Do you have a Contact form on some site?

  4. Hi P1,

    Somehow, I accidentally deleted by email from the sidebar. Thanks for asking. I put it back. It's toward the top on the right now.

    Sorry to hear you're having blood glucose issues with Paleo.

  5. There are no “special” foods for diabetes; rather, some food choices are better than others. A healthy diabetes diet is a diet that would benefit anyone, says Alison Massey, RD, LDN, CDE, a registered dietitian and diabetes educator at the Diabetes Center of Mercy Medical in Baltimore. The American Diabetes Association recommends a diet that is low in fat with meals centered around whole-grain foods, vegetables, and fruits.
    Facts And Myths About Diabetes