Why does bread cause blood sugar to rise?Grains like wheat are mostly starch, and starch is made up of long strings of glucose. These starch molecules begin to break down into sugars in the mouth, because of enzymes in saliva. By the time they get through the stomach, most starches have been converted to sugar. But there are exceptions, and these are things to pay attention to when buying bread.
What to Look For when Buying Bread
1. Less "Usable" Carbohydrate - that is, subtract the fiber from the total carbohydrate (more on this here). This is far and away the most important thing when figuring out a food's effect on blood glucose (how glycemic it is). All the other factors really pale in comparison. If you are counting carbs, you must read the label and see how much carbohydrate you are eating. But even if you don't care to do carb counting, do take a look at a few loaves of bread to get familiar with how much carbohydrate they contain.
2. Thin Bread - Obviously, smaller or thinner bread usually has less carbohydrate, because it has less of everything! However watch out for very dense thin bread (often imported) as this can be similar to regular bread in the amount of starch.
3. Lots of Fiber - Some breads substitute fiber for some of the starch in the bread, reducing calories as well as carbohydrate. However, more fiber doesn't necessarily mean a smaller impact on blood sugar, if that fiber is simply added to the other ingredients, rather than being a substitute for the starch. Again, subtract the fiber from the total carbohydrate to figure this out.
4. Rough, Grainy Texture - The more finely ground a kernel of wheat or other grain is, the more quickly the starch will break down into sugar. There has been an effort by some bread manufacturers to make 100% whole grain bread that is softer, with a texture that is more like white bread. The problem is that this bread is generally every bit as glycemic as white bread. On the other hand, bread with is more roughly-textured will, generally, be less glycemic. The best bread for this purpose has visible pieces of grains - some cracked wheat bread is like this.
5. Sprouted Grain Bread - There has not been much research on this, but some preliminary evidence shows that sprouted grain bread does not cause as high or fast of a blood sugar rise as regular bread. However, sprouted grains are not entirely fiber, as some bread labels claim, so read labels carefully if they are claiming large amounts of fiber and very low "net carbs" on sprouted grain breads. I have heard reports from people who's blood sugar goes up from these breads.
6. High Protein Breads - Some breads use a lot of wheat gluten instead of the whole grain. Since gluten is the protein part of the wheat, these breads can be good bets.
7. Sourdough Bread - Sourdough bread has been shown to produce a less glycemic response than regular bread. One study comparing white sourdough bread with regular whole wheat bread showed that the sourdough bread was less glycemic.
Note on "Light" Breads: "Light" bread may not make you lighter! Light breads have fewer calories than their regular counterparts, but this can be achieved by simply adding more air and making the slices smaller. On the other hand, some "light breads" are lower in carbs than regular. For example, one slice of Oroweat 100% whole wheat bread weighs 38 grams and contains 17 grams of carbohydrate, 3 of which is fiber, and 100 calories, a slice of their Light 100% whole wheat bread weighs 23 grams and contains 9 grams of total carbohydrate, 3.5 of which is fiber, and 40 calories. In this case, most of the calorie savings is simply from making the slices smaller, but there has apparently been some substitution of starch for fiber.
Great Choice!Perhaps the best commercial bread substitute is a low-carb tortilla. They are reasonably priced, and many grocery stores now carry them. Make a wrap, use it as a hot dog bun, or as the basis for a pizza - low-carb tortillas are one of the best choices. If your local store doesn't carry them, they can be found online ( )
Bread to Avoid
1. Bagels and Rolls - Bagels and rolls are often deceptive, in that they can contain 2, 3, or even 4 normal servings of bread. They also are far less likely to be 100% whole grain. However, there are also "thin bagels" in some markets now, and you could look for them.
2. Soft Bread - As mentioned above, soft bread is usually made from white and/or very finely ground flour which turns to sugar more quickly.
3. Sweet Breads - Obviously, any bread with added sugar is to be avoided, but most bread on the market is made with at least some sugar. A good rule is to avoid breads where one of the first five ingredients is sugar, honey, molasses, fructose, etc.
4. Alternative Grain Breads - Since wheat actually has more protein than most other grains, alternative grain breads such as gluten-free breads are usually even higher in carbohydrate than breads made with wheat.
Leroux, MarcusFoster-Powell, Kaye, Holt, Susanna and Brand-Miller, Janette. "International table of glycemic index and glycemic load values: 2002." American Journal of Clinical Nutrition. Vol. 76, No. 1, 5-56, (2002).
Najjar, AM, Parsons, PM, et al. "The acute impact of ingestion of breads of varying composition on blood glucose, insulin and incretins following first and second meals." Human and Clinical Nutrition. Vol. 101, No. 3 391-398 (2009).
Najjar, AM. "The Impact of Breads of Varying Composition on Biomarkers of Glucose Metabolism in Overweight and Obese Adults." University of Guelph, December 2009