If you feel tired after eating bread, chances are you're responding to changes in blood sugar or brain chemistry caused by higher levels of insulin. Gluten intolerance is another possible culprit in bread-induced lethargy. However, many different factors have an influence, so consult a health care provider if tiredness continues to interrupt your day.
Wheat, rye and barley contain a type of protein called gluten. Some people are sensitive to gluten, so they experience symptoms after eating gluten-containing bread. Bloating and diarrhea are frequent side effects, but lethargy and brain fatigue, or brain fog, are also symptoms commonly associated with gluten intolerance, reports UCLA Health. The extent of your sensitivity determines whether you should avoid all gluten or can eat a small amount. If you think gluten is a problem, talk to your health care provider to get an accurate diagnosis.
Boost Levels of Tryptophan
After the carbohydrates in bread are digested, sugar floods into your bloodstream. This triggers the release of insulin, which transports extra sugar out of your blood. However, insulin affects not only blood sugar but also amino acids circulating in your blood, resulting in more tryptophan gaining access to your brain, according to the Encyclopedia of Neuroscience. As brain levels of tryptophan increase, more serotonin is produced, and serotonin makes you feel calm and sleepy. You’re more likely to feel tired if you eat high-tryptophan foods along with your bread, such as cheese, eggs, turkey, chicken, peanut butter and fish.
Swings in Blood Sugar
When your blood sugar goes up, it swings down to a low level before it finally stabilizes. Low blood sugar can make you feel tired and interfere with your ability to concentrate as the brain is deprived of glucose for energy. The extent of your sluggishness after eating bread may vary, depending on the amount you eat -- big portions with more sugar cause higher swings -- and whether your meal includes fats or protein that slow down the rate at which sugar enters your bloodstream. Changes in blood sugar are also more significant if your bread is made from processed white flour instead of whole grains.
Go With Whole Grains
You can prevent tiredness related to swings in blood sugar by choosing high-fiber bread. Fiber slows down digestion, which helps keep blood sugar balanced. Look for products that are 100 percent whole grain or have a whole grain, like whole-wheat flour, listed as the first ingredient. Processed bread doesn't retain the grain's natural fiber, but some brands of refined breads are fortified with bran, inulin or other types of fiber. Compare the fiber content in the bread you buy to whole-wheat bread, which has nearly 2 grams of fiber in one slice, according to the U.S. Department of Agriculture. By comparison, a slice of processed white bread has only half that amount.