What impacts blood glucose levels?
Foods that contain carbohydrates will affect blood glucose levels the most. How quickly and how much blood glucose levels rise depends on:
- Food composition
- Portion size
- Timing
Food composition
Blood glucose levels are affected differently
depending on whether you eat foods containing carbohydrates, proteins, fats, or
a combination of these three. Carbohydrates will cause blood glucose
to rise the most and the most quickly. Liquids that contain carbohydrates
(like milk and juice) will cause blood glucose to rise faster than solids that
contain carbohydrates (like bread). Because of the impact that they have
on blood glucose levels, carbohydrates are the most important macronutrient
for people with diabetes to monitor.
Portion size
The amount of food that you
eat also impacts blood glucose levels. Eating more food, or bigger portions,
will cause your blood glucose levels to rise more than eating smaller portions. Since
carbohydrates affect blood glucose levels the most, the amount of carbohydrate
that you eat each day is very important in controlling your blood glucose levels. Talk
to your health care provider or dietitian about how many grams of carbohydrates
you should eat each day.
To
find out how many grams of carbohydrates you are eating each day, it is important
to be familiar with the food groups, serving sizes, and Nutrition Facts labels. As
discussed in Food Groups and Diabetes, three food groups contain
carbohydrate:
- The Starch and Starchy Vegetables Group
- The Fruit Group
- The Milk and Yogurt Group
One serving from each of these groups contains about 15 grams of carbohydrates. Therefore, eating one serving from any of these three groups will impact your blood glucose level in about the same way. For examples of one serving from these three groups see Food Groups and Diabetes.
Another way to find out how many grams of carbohydrates
are in a particular amount of food is to read the Nutrition Facts label on
the back of a product. This is a picture of the Nutrition Facts label found
on almost all foods sold in this country. Look at the portion on the
label that tells how much “Total Carbohydrate” is in the food in
order to decide how much it might raise your blood glucose. As you can
see, this product has 13 grams of total carbohydrates per serving.
For comparison, one slice of bread (one serving
from the Starchy and Starchy Vegetables Group) has about 15 grams of carbohydrate. Since
our bodies change almost all of the carbohydrates we eat into blood glucose,
be sure to look at “Total Carbohydrate” and not just at “Sugars” to
see how much a food will raise your blood glucose. “Total
Carbohydrate” will be greater than the sum of the listed “sugars” and “fiber” because
starches are also counted in total carbohydrates. For some very high
fiber foods that have 5 or more grams of fiber per serving, net carbohydrates
may be used instead of total carbohydrates. Net carbohydrate is just
total carbohydrate in a serving of food minus the grams of fiber. Net
carbohydrates are used when considering very high fiber foods, because the
body cannot digest carbohydrates from fiber and therefore they do not raise
blood glucose levels.
Timing
Blood
glucose levels are affected by the timing of meals and snacks. Eating
three meals and possibly one or two snacks at the same time every day will
help keep your blood glucose levels more consistent. Ask your doctor
or dietitian how many meals and snacks you should eat each day. It
is also important to eat about the same amount of carbohydrate at each meal
or snack to keep your blood glucose levels within target range, or to have
your medication match your carbohydrate intake. Below is a graph of
blood glucose levels from a person without diabetes who has eaten 3 meals
and two snacks in one day. At each meal this person ate about the same
amount of carbohydrate. As you can see, this person’s blood glucose
level rose and fell in about the same way after every meal or snack. Someone
who does not have diabetes insulin secretion will automatically adjust to
match the amount of carbohydrate that they eat. However, those who
have diabetes do not react the same way. Since people with diabetes
have difficulty regulating their blood glucose levels, they should eat the
amount of carbohydrate recommended by their doctor, and space this carbohydrate
evenly throughout the day. This will help keep blood glucose levels
in their target range.
Back to: Eating for Target Blood Glucose Levels
This document is a source of information only, and is not medical advice.
