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Tame Blood Glucose Swings
caused by High vs. Low Glycemic Index Foods (and Fat)
Have you noticed your T1D child’s blood glucose soar after pizza night? Are you fighting lows right after she eats pasta? Glycemic index may be playing a role, which may be compounded by the fat content of those foods. If the rate at which food is digesting doesn’t match the insulin action, then blood glucose can swing wildly. But the good news is that you can adapt your strategy, and reduce the swings. Here are some practical solutions to tame those blood glucose swings…
Glycemic Index and Type 1 Diabetes
From all this talk about low GI foods (see “When to Choose HiLo GI” for critical background information), it’s easy to assume that the goal is to eat only low GI foods. But that is NOT what we want you to take away from this reading. There are times when you may choose to steer your child toward low glycemic foods, and there are times when you may want to steer them towards high glycemic foods (more on that below).
There are also times when you want them to eat whatever your family would be eating if the diabetes dragon hadn’t complicated things so much! You may want your child to have the freedom to eat, without having to restrict her options based on the fact that she has diabetes. In those times, if you know how to respond effectively, the inescapable fact that your child has diabetes doesn’t mess things up so much (with unexpected post-meal lows, or extreme or persistent post-meal highs).
(A short but relevant tangent… individuals with type 2 diabetes are more reliant on a low-fat, low-GI, lower-carb diet than those with type 1. Type 1’s are able to eat the same things as appropriate for their peers who do not have diabetes – eating good food is good for all of us; kids with type 1 diabetes are no more restricted in eating fat, carbs, and high GI foods than anyone else is.)
The point that we are making is that an awareness of differing GI levels may help explain some seemingly inexplicable post-meal blood glucose swings. In addition, you MAY choose to use this awareness to modify your family’s eating habits and/or how you deliver insulin when eating foods with either a high or low GI value.
How Do We Reduce Blood Sugar Swings?
If you want to adjust circumstances based on the glycemic level of the foods your child eats, here are a few different approaches you could try:
1. Make Your Meals Medium GI
Moderate-GI meals corresponds most closely to the insulin action curve of today’s fast-acting insulin, thereby reducing the swings that result from meals that are primarily either high glycemic or low glycemic.
A medium glycemic meal can be constructed either by serving mostly foods which are medium GI by nature, OR by combining low GI with high GI foods. For example, including watermelon (high GI) or sugar cookies (high GI) for dessert with a (low GI) pasta-based meal will result in a meal that is more moderate GI overall. The same is true for serving mashed potatoes (high GI) with roast beef, rich gravy (low GI) and corn (low GI).
We have not heard of any formulas nor rules of thumb that dictate what proportion of high to low glycemic foods you need to arrive at a moderate GI meal overall, but in our own experience it seems to make sense that roughly (VERY roughly) equal proportions of high and low glycemic foods, based on the carb content they contribute to the total meal, result in a more or less medium GI meal. For example, eating 1 (high glycemic) sugar cookie containing 5g of carbohydrate might not make as much of an impact when combined with (low glycemic) pasta containing 40g of carbs, compared to eating 30g of carbs in fluffy French bread (high GI), along with the same 40g of carbs from pasta; the latter is more likely to result in a moderate GI meal.
The only way to see what will work well for your child is to try a combination of foods and record the resulting blood glucose pattern. If you are still seeing a significant drop in blood glucose followed by a significant rise, you may need to increase the amount of high glycemic foods, or decrease the amount of low glycemic foods. Keep experimenting until you arrive at a balance you find acceptable.
If constructing moderate GI meals doesn’t resolve the issue, instead (or in addition) you could…
2. Adjust the Timing of Insulin Delivery Based on Glycemic Index
A standard recommendation for many individuals with type 1 diabetes is to deliver the insulin dose 15 minutes before the start of the meal. However, this timing may be adjusted to account for the glycemic index value of the foods you are about to eat.
High GI Foods
Low GI Foods
Adjustments in timing of insulin may also be made based on the pre-meal blood glucose reading:
If blood sugar is elevated before the meal…
If blood sugar is below target before the meal…
What do we mean by “soon”, “later”, “less time” and “more time”? There are no universal rules that work in every case, however, to arrive at an appropriate timing balance, bear in mind that rapid-acting insulin (used as bolus insulin in most cases) starts to work about 15 minutes after delivery, and peaks about 1 hour after delivery**. Your goal is to match this insulin action curve to the digestion of the food.
**Note: As mentioned above, this insulin action curve most closely matches the rate of digestion of a moderate GI meal – if eating a meal of this type, you may not need a large pre-bolus, and certainly won’t need to delay bolus delivery.)
We have found the chart on “Adjustments to bolus timing based on GI and pre-meal blood sugar” in Gary Scheiner’s book Think Like a Pancreas to have very helpful guidelines for timing.
From there, we recommend recording: the foods eaten; the timing and amount of insulin delivered; and the resulting blood glucose pattern at different times after eating, and then making adjustments for future meals based on those results. If you are still seeing a significant drop in blood glucose followed by a significant rise, this may mean the insulin is peaking before the food, so you may need to decrease the pre-bolus period. Keep experimenting until you arrive at a balance you find acceptable.
It is very important to CLOSELY MONITOR BLOOD GLUCOSE during this process, first and foremost for your child’s safety, and also for the information you glean, which will guide future decisions.
In addition to modifying the GI level of the whole meal (#1, above), and/or timing insulin delivery (#2, above), to smooth out post-meal blood glucose readings you may want to split or extend the food bolus (for insulin pumps, and injections, respectively):
3. Extend the Insulin Bolus for Low GI Meals
Extending the meal bolus involves spreading out the delivery of onsulin so that, instead of being given at the same moment in time, in a single dose, the total amount of insulin is split up into more than one dose, and delivery is spread out over time. The actual process of extending the bolus looks different for injected insulin vs. insulin pumps.
a. Extending the bolus – Insulin Pumps
To deal with the low GI issue, if your child uses an insulin pump, some version of an extended bolus (Combo Bolus on Animas pumps, Dual Wave Bolus on Medtronic pumps, etc) may be helpful. An extended bolus allows you to specify what portion of the total bolus you want delivered immediately (up front); then the remaining amount of the total bolus will be spread out over the time period specified. Consult your child’s diabetes health care team and/or pump company for guidance on using extended bolus functions, but here’s what worked in our experience…
As always, to find the right balance for your child you will need to experiment with each target food and note the results for each food, adjusting future actions based on those results. It is very important to CLOSELY MONITOR BLOOD GLUCOSE during this process, first and foremost for your child’s safety, and also for the information you glean, which will guide future decisions.
Remember, the lower the first number in the extended bolus ratio (the “40” in a 40:60 split, for example), the less insulin your child is receiving up front, and therefore the more insulin she is receiving later, during the extended portion of the bolus. This is key to understanding how to tweak the numbers based on the results of your experimentation:
b. Extending the bolus – Injections
If your child is on injections for insulin delivery, you may want to experiment with splitting the meal insulin dose into two or more separate doses, or delaying the meal insulin dose for a period of time after the food has been eaten. Consult your child’s diabetes health care team for guidance on splitting the meal bolus to deal with low glycemic meals, but here’s what worked in our experience…
When Fat Content Complicates the Issue…
When your child eats food which is both low glycemic AND high in saturated fat… a double-whammy approach may be most effective.
The first “wham” deals with the low GI nature of the food as described above, by splitting or delaying the bolus if on injections or by using an extended bolus if on a pump.
The second “wham” involves giving more insulin to deal with the effects of saturated fat. Saturated fat causes insulin resistance about 6-8 hours after eating (the more saturated fat consumed, the more pronounced the insulin resistance becomes). This means that more insulin may be needed later to deal with the high fat aspect (in the form of an injected correction dose, or a Temporary Basal function on an insulin pump).
More on Dealing with Tricky Foods:The Pizza Solution under Advanced Carb Counting
More Details on Dealing with High Fat Foods:How Fat and Protein Affect Blood Glucose
Reduce Post-Meal Spikes Caused by Fat and Protein
Which foods are high in saturated fat?
Some common high-fat foods, which may require a double approach to minimize post-meal spikes, include:
- Pizza (the more cheesy the pizza, plus the greater the number of high-fat meat toppings, the more saturated fat it contains. For eating out, this varies greatly from restaurant to restaurant. In our experience, Boston Pizza tends to use much less cheese compared to Panago, and thus is lower in saturated fat, resulting in relatively less insulin resistant post-meal.)
- Fatty processed meats (such as sausages)
- Creamy sauce (those made with heavy cream or lots of butter)
- Rich cheesecake (the full-on, high-fat variety)
- Desserts made with real whipping cream
- Ice cream made with heavy cream
- Foods/desserts made with lots of butter
- Foods fried in shortening, lard or bacon grease (which could include French Fries, Hashbrowns, Deep-Fried Fish, etc)
The above information was reviewed for content accuracy by clinical staff of the Alberta Children’s Hospital Diabetes Clinic.
This material has been developed from sources that we believe are accurate, however, as the field of medicine (in particular as it applies to diabetes) is rapidly evolving, the information should not be relied upon, as it is designed for informational purposes only. It should not be used in place of medical advice, instruction and/or treatment. If you have specific questions, please consult your doctor or appropriate health care professional.
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