Traditionally, bread (like other baked goods) is considered unhealthy high-carbohydrate food with a high glycemic index. However, whole-grain bread can be included in the diabetic diet – which proves the ambiguity of this food product.
In a study, scientists set out to determine the GI of white bread. Based on the measurement of 63 people, the average glycemic index was 62 ± 15 units – that is, it varied in values from 47 to 77. Moreover, even in the same person, the difference reached 25%.
The glycemic index of bread – how to calculate?
First of all, let’s briefly recall the mechanics of calculating the glycemic index of a product. It is important that the figure is always determined for the amount containing 50 g of carbohydrates – in the case of white bread, this is about 100 g. For comparison, a typical loaf weighs about 400 g.
The subjects consume the product (for example, 100 g of white bread) on an empty stomach – after which they measure insulin production and blood glucose levels for 5 hours. The glycemic index itself is represented as the area of the figure located under the graph for increasing glucose.
At the same time, the glycemic index is far from a universal figure. Ultimately, it depends on the individual’s ability to process carbohydrates – and the mentioned study proves that even in the same person this ability changes throughout the day.
GI Research for white bread
According to a study, the average glycemic index of the same white bread (in an amount of 100 g) can vary from 47 to 77 units – in fact, this allows the product to be classified into all three categories (low GI, medium, and high).
The explanatory note notes that the figure varied in the value of ±20% for different people and ±25% for some of them. The insulin index of white bread varied within ±15%. The researchers note that such high variability in values casts doubt on the entire theory of GI.
Research results:
- Low GI (35 – 55) – 22 people
- Average GI (57 – 67) – 23 people
- High GI (70 – 103) – 18 people
The carbohydrate content in bread
Let’s return from practice to theory. In addition to the glycemic index of the product, the total carbohydrate content in it must also be taken into account. For example, carrots have a high GI but a low glycemic load. Although it quickly raises blood sugar levels, the low carbohydrate content is not harmful.
Bread, on the other hand, contains a moderate amount of carbohydrates. One small piece of white bread (weighing 25-30 g) contains about 12-15 g of carbohydrates. Again, this figure is acceptable not only for a low-carb diet for weight loss – but also for diabetics.
Sweet baked goods contain more sugar (and, in some cases, calorie-adding butter or vegetable oil), while whole grain and rye bread are lower in carbs and higher in fiber:
Types of bread, their composition of carbs and fibers (per 100g):
- Sweet bread and pastries – 46g carbs (of which 3g fiber and 11g sugar)
- White bread – 49g carbs (of which 3g fiber and 5g sugar)
- Rye bread – 48g carbs (of which 6g fiber and 4g sugar)
- Whole grain bread – 43g carbs (of which 7g fiber and 6g sugar)
Glycemic load
Glycemic load (GL) is a measure of the increase in blood glucose after a meal. Unlike the glycemic index, the glycemic load takes into account the number of carbohydrates in a serving – this affects how much glucose enters the bloodstream:
GL = GI * (number of carbohydrates per serving) / serving size
On average, the glycemic load of white bread is about 10 units per 30 g serving (one piece) – which is comparable to a bowl of buckwheat, pearl barley, or bulgur.
How to lower the glycemic index of bread?
One of the myths about bread is that it’s healthier to eat frozen – some even believe it can reduce calories. In reality, freezing is definitely not able to change the calorie content – but it can affect the glycemic index.
The composition of bread includes resistant starch – when cooled, it changes its structure, and, like fiber, becomes indigestible for humans. Plus, toasting bread (both in the form of crackers and toast) also reduces the percentage of absorption.
Here are the results of a study that measured the rise in blood glucose two hours after consuming the product:
How processing bread affects glucose levels:
- Fresh homemade bread – IAUC 259 mmol min/l
- Bread after toasting – IAUC 193 mmol min/l
- Bread after freezing and thawing – IAUC 179 mmol min/l
- Bread after freezing and toasting – IAUC 157 mmol min/l
Although the glycemic index of bread is an extremely variable figure, the glycemic load of one medium-sized piece is comparable to a bowl of buckwheat or pearl barley. In addition, freezing and toasting bread can actually lower its GI.