1. The Physical Form of Food and Digestion
A food’s glycemic response is affected not only by its chemical composition (ingredients) but also by its ‘physical form.’ This is because our body’s digestive enzymes begin to work on the surface of the food.
2. The Principle of Surface Area
– The Principle: For the same weight of food, the smaller the particles and the more pieces there are, the larger the total ‘surface area.’ The larger the surface area, the more places digestive enzymes can attach to and the faster they can break down the food.
– Example: A whole potato vs. mashed potatoes. Mashed potatoes have an extremely large surface area, are digested and absorbed much faster, and spike blood sugar more sharply than a whole potato.
3. Bread Thickness and Blood Sugar
This principle can also be applied to sliced bread.
– Thickly Sliced Bread: Has a relatively small surface area for its volume. It also requires more effort to chew.
– Thinly Sliced Bread: For the same weight, several thin slices have a larger total surface area than a single thick slice.
– A Minor Difference: For this reason, theoretically, a thick slice of bread may be digested and absorbed slightly more slowly than a thin slice, resulting in a very slightly more gradual glycemic response.
4. What is More Important
Of course, this effect is very minimal compared to factors like the type of bread (white vs. whole wheat), the foods eaten with it, and the total amount consumed. It is far more important for blood sugar management to choose 100% whole wheat bread, control portion sizes, and eat it with protein/fat, rather than worrying about the thickness of the slice. However, understanding the principle that the physical form of food affects digestion speed is helpful for understanding healthy eating habits.
Summary: For the same bread, a thick piece has a smaller surface area than thin slices, so it takes slightly longer to digest, which can result in a very minimally more gradual blood sugar response.
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