Question:
What exactly is dumping?

I read about people 'dumping' and it does not sound good. What exactly is dumping, what causes it and what can you do to avoid it?    — Susan M. (posted on August 2, 2001)

August 2, 2001
Dumping syndrome is usually divided into "early" and "late" phases - the two phases have separate physiologic causes and will be described separately. In practical fact, a patient usually experiences a combination of these events and there is no clear-cut division between them. Early dumping is caused by the high osmolarity of simple carbohydrates in the bowel. The various types of sugar all have small molecules, so that a gram of (for example) sucrose has MANY more molecules than a gram of protein, creating a higher concentration (number of molecules per cc) from simple sugars than from other foods. This matters because, inside the body, fluid shifts will generally go toward the higher concentration of molecules. So, if a patient consumes a bite of milk chocolate (lots of sugar), when it gets to the Roux limb it will quickly "suck" a significant amount of fluid into the bowel. This rapid filling of the small bowel causes it to be stretched (which causes cramping pain). This also causes the activation of hormonal and nerve responses that cause the heart to race (palpitations) and cause the individual to become clammy and sweaty. Vomiting or diarrhea may follow as the intestine tries to quickly rid itself of this "irritant." Late dumping has to do with the blood sugar level. The small bowel is very effective in absorbing sugar, so that the rapid absorption of a relatively small amount of sugar can cause the glucose level in the blood to "spike" upward. The pancreas responds to this glucose challenge by "cranking up" its output of insulin. Unfortunately, the sugar that started the whole cycle was such a small amount that it does not sustain the increase in blood glucose, which tends to fall back down at about the time the insulin surge really gets going. These factors combine to produce hypoglycemia (low blood sugar) which causes the individual to feel weak, sleepy, and profoundly fatigued. Late dumping is the mechanism by which sugar intake can create low blood sugar, and it is also a way for gastric bypass patients to get into a vicious cycle of eating. If the patient takes in sugar or a food that is closely related to sugar (simple carbohydrates like rice, pasta, potatoes) they will experience some degree of hypoglycemia in the hour or two after eating. The hypoglycemia stimulates appetite, and it's easy to see where that is going.... The reason that sugar does not cause dumping in non-operated people is that the stomach, pancreas, and liver work together to prepare nutrients (or sugar) before they reach the small intestine for absorption. The stomach serves as a reservoir that releases food downstream only at a controlled rate, avoiding sudden large influxes of sugar that can occur after a Roux-en-Y. The released food is also mixed with stomach acid, bile, and pancreatic juice to control the chemical makeup of the stuff that goes downstream and avoid all the effects outlined above. Obviously, surgeons consider dumping syndrome to be a beneficial effect of gastric bypass - it seems to be important to provide quick and reliable negative feedback for intake of the "wrong" foods. In practice, most patients do NOT experience full-blown dumping more than once or twice. Most simply say that they have "lost their taste" for sweets.
   — Julia M.