How to Read Food Labels

People with type 1 diabetes (T1D) have to learn how to count carbs in order to calculate their insulin doses at mealtimes. However, even with years of practice, carb counting remains a challenge for a lot of them.

According to a study conducted in Quebec, people generally underestimate their carb count by about 15 g per meal. This underestimation could be due to a calculation error, or be voluntary, for instance to reduce the risk of hypoglycemia.

However, the study shows that an accurate carb count helps to decrease blood sugar variability and promotes improved glycated hemoglobin (HbA1c) levels.

The information on nutrition labels is a valuable tool for determining the carbohydrate content of a food, and thus help you better manage your blood sugar. But you still need to know what to look for when calculating carbohydrates. Here are some useful nutritional concepts.

Carbs, sugars and fibres

Looking at the nutrition facts label will give you a glimpse of the amount of carbs found in a food. The information on carbs is presented in two sections:

Sugars are the simple sugars that are naturally found in or added to foods. They can cause a rapid rise in blood sugar levels because they are digested and absorbed quickly. Since they are included in the carb count, you don’t need to add them to the total carb count.
Fibre is a type of carbs that is undigested by the body. It does not pass from the digestive tract to the bloodstream, and so, it doesn’t increase blood sugar levels. This means you have to subtract the fibre content from the total carb count. Fiber requirements are estimated at 25 grams per day for women and 38 grams per day for men. Although these recommendations are rarely met by the Canadian population, a high fiber intake can help reduce blood sugar levels after meals, lower blood cholesterol and constipation, and prolong the feeling of satiety between meals.

So, to calculate the number of carbohydrates to consider for a food, we subtract fiber from the carbohydrates shown on the label, and ignore simple sugars.

For instance, if you eat 2 slices of bread containing 31 g of carbohydrates, which include 3 g of fiber (as shown on the label below), you’ll need to factor in 28 g (31 g minus 3 g) of carbohydrates to determine your insulin dose.

Sugar substitutes

The use of certain sugar substitutes is authorized by Health Canada. These are products that impart a sweet taste to foods without causing a significant rise in blood sugar levels. Sugar substitutes on the market include aspartame, stevia and sucralose. These do not appear on the nutrition label and should therefore not be considered when calculating carbohydrates.

However, polyalcohols or sugar alcohols (e.g., maltitol, sorbitol and xylitol) are indicated on the nutrition label and counted as part of the total carbohydrate count. Some recommendations suggest subtracting the entire amount from the carbohydrate count on the label, while others recommend subtracting half. In fact, this type of sugar substitute is partially absorbed by the body and can contribute to a rise in blood sugar levels. It’s up to you to see what effect polyalcohols have on your blood sugar levels, and to adjust your calculation accordingly. Remember that an excessive consumption of polyalcohols can lead to gastrointestinal discomfort and laxative effects.

In the label below, a 42 g cookie contains 15 g of carbohydrates. You need to subtract the 2 g of fiber, as well as some or all of the polyalcohols. If you decide to subtract half the polyalcohols (8 g / 2 = 4 g), your total carbohydrate amount for the cookie will be 9 g (15 g – 2 g fiber – 4 g polyalcohols). If the polyalcohols have no effect on your blood sugar, you can also subtract them altogether. The total carbohydrate count for this cookie would then be 5 g (15 g – 2 g fiber – 8 g polyalcohols).

Other packaging information

Watch out for certain marketing tricks. Some companies use “no sugar added” on their packaging, but this does not mean that the food is carb-free. It simply means that no sugar was added to those naturally found in the food.

Other claims can also be found on food packaging. Here are a few examples:

Gluten-free: This information can be very useful for people who have celiac disease. However, there is no indication or recommendation that says you should limit your gluten intake if you have not been diagnosed with that disease. Moreover, gluten-free products generally contain less fiber, so their carbohydrates are absorbed more quickly than their gluten-free equivalents.
Organic: The word “organic” means that the food item was produced without using pesticides, antibiotics or hormones. However, this does not change its nutritional value. An organic cookie could very well have the same amount of carbs than a non-organic cookie.
Natural: The term “natural” is very vague and not formally regulated by Health Canada. It means that, at some point in the food’s manufacturing process, one or several natural ingredients were used. Almost any food could be considered natural, and this is definitely not a guarantee of good nutritional value.
Low in sodium and/or fat: This information is very useful if your healthcare team has recommended that you reduce your salt or fat intake. However, this does not affect the amount of carbohydrates contained in either product. So be sure to check the nutrition label.

If you feel overwhelmed by all this information and are having a hard time adapting your diet to T1D, please don’t hesitate to talk to a nutritionist or dietician.

Some apps can also be useful for finding the nutritional value of certain foods. We’ve put together a list of these apps, with their positive and negative points, to help you make your choice. Find the list here.