A highly confusing thing is the difference between whole wheat and whole grain; particularly when we talk about bread. However, if you empower yourself with some knowledge, you can choose the best bread option for yourself.
The U.S. FDA explains that whole-grain food is something, which is made from grain, which is whole or flaked. And, at the same time, contains endosperm, germ and bran. So, if we go by this definition, whole wheat bread can be considered as whole-grain food. Whole wheat bread made from whole wheat flour, which is further made from whole grains qualifies for this definition.
To know how carbohydrates affect the body, you need to understand how the body digests them. The carbs that you eat get broken down into smallest possible molecules by the body. Majority of this gets converted to glucose, so carbohydrates directly affect the level of blood glucose.
Also, the processing and what you eat with it can also affect the blood glucose levels. Whole-grain and whole-wheat breads are not processed or less processed as compared to white bread, so whole grain bread is your best bet. This is when we need to understand about glycemic index.
Glycemic Index and Diabetes
Glycemic index measures the effect of a food or carbohydrate in the food on the glucose in the blood. This takes into account the processing of the food. For example, food that is less processed will have more fiber and will be more complex.
When the food is less processed, the digestion and absorption process slow down. It would take more time by the body to break down the food, so there will be a slow and sustained spike in the blood glucose levels.
The index is used for rating the foods from 0-100 and accordingly, the foods are classified as moderate, low and high. If the index scores are greater, it implies greater increase in blood glucose.
Whole-wheat bread and whole-grain bread rank differently on the glycemic index. Whole-grain bread measures 51 on the index, while whole-wheat bread scores 71 on the index. So, whole-wheat bread has a greater glycemic index, making it a high glycemic food. A person with diabetes should opt for whole grain bread instead of whole-wheat bread.
While you are selecting a bread for yourself, have a look at the labels. Choose the one, which has whole grain written in the ingredients. Also, look at the nutrition label. High content of fiber implies low digestion. It should have at least 2 gm of fiber per serving.