Carbohydrates are manifest primarily in sugars, starches and fiber. These are found in a wide range of foods, including breads, pastries, fruits, vegetables, grains and legumes.Your digestive system breaks down carbohydrates into sugars that subsequently enter your bloodstream as glucose, or blood sugar. Because all carbohydrates are not identical, nor are the bodies that receive them, you may experience sleepiness after eating them .
As a rule, glucose levels rise when carbohydrates are eaten. There are variables, however, that affect the tempo of blood sugar elevation and the body’s response to such an increase. A healthy body will release insulin hormone from the pancreas in order to open cells for the reception of glucose. The cells, in turn, convert the glucose to immediately usable energy or store it for future use. Excepted are your brain cells, which only use glucose upon receipt and possess no storage capacity. Certain carbohydrates consumed in large amounts will quickly enter the bloodstream, causing a spike in blood sugar and – consequently -- a flood of insulin. You cells then consume the glucose for storage, leaving little glucose on which brain cells can operate. Over time, this deficiency will result in brain fog and lethargy.
Eating sugary desserts or drinking sweetened beverages produces rises in glucose almost as quickly as injecting it directly into the veins. Because the form in which they enter the digestive tract is so close to glucose in composition, the digestive system takes little time to release sugars into the bloodstream. Eating candy or drinking soda in significant quantity all but assures the massive insulin response that leads to sleepiness and diminished concentration. Under these circumstances, carbohydrates are the culprit.
Starches are less uniform in their ability to trigger a rapid insulin reaction. Potatoes, for instance, are reputed to have an accelerated carbohydrate-to-glucose conversion, as does white bread. Pasta takes a little longer to be broken down, particularly if it is of the whole-grain variety. Of course many starchy foods also contain fiber, which slows the entry of carbohydrates into the bloodstream. The glycemic index ranks foods by their glucose conversion velocity. It ranks some starchy vegetables and legumes – peas, beans, and carrots – lower on the scale than potatoes and corn. Higher glycemic numbers make fatigue a greater possibility.
Fiber is a complex carbohydrate which is invincible to digestion, thus passes through the digestive tract without being absorbed. It is abundant in plant foods like vegetables, fruits and whole grains. In addition to being beneficial to your digestive system, fiber slows the release of carbohydrates into the bloodstream. It takes time for digestive enzymes to separate sugars and starches from the fiber, thereby keeping the rise in glucose gradual. Accordingly, the pancreas will not release a deluge of insulin, so symptoms of sleepiness and lack of focus will be minimized. Where orange juice might cause subsequent fatigue, a whole orange is less likely to do so, due to its high fiber content.