 In terms of preventing acid reflux, heartburn, I've talked about how high-fat meals cause dramatically more acid exposure in the esophagus in the hours after a meal. But why does high fiber intake decrease the risk? One typically thinks of fiber helping out much lower in the digestive tract. A systematic review and meta-analysis found a highly significant protective association between esophageal adenocarcinoma and dietary fiber intake, suggesting that individuals with the highest fiber intakes have approximately 30% lower risk of cancer. This could be because of the phytates in high fiber foods, slowing cancer growth, could be the anti-inflammatory effects, fiber could be removing carcinogens, but those are all generic anti-cancer effects of whole plant foods, specific to this type of acid-irritation-induced esophageal cancer. Fiber may decrease the risk of reflux in the first place. But how? Hyatus hernia occurs when part of the stomach is pushed up through the diaphragm into the chest cavity, which makes it easy for acid to reflux up into the esophagus and throat. It affects more than one in five American adults. In contrast, in rural African communities that were eating their traditional plant-based diets, it wasn't one in five who was closer to one in a thousand, almost unheard of. It's almost peculiar to those who consume Western-type diets. Why are plant-based populations protected? Perhaps because they pass such large, soft stools. Three or four times the volume is Westerners. What does the size and consistency of one's bowel movement have to do with thytal hernia? A simple model may help illustrate the mechanism producing upward herniation of the stomach through the hole in the diaphragm that separates the abdomen from the chest, called the esophageal hiatus. That's the opening. If a ball with a hole in it is filled with water and squeezed, the water is pushed out through the hole. The abdominal cavity may be likened to a ball. The hole in the ball corresponded to that esophageal hiatus in the diaphragm. So, abdominal straining during efforts to evacuate firm feces corresponds to squeezing the ball and may result in gradual expulsion of the upper end of the stomach from the abdominal cavity up into the chest. It's like when you squeeze one of those stress balls. Straining at stool raises pressures inside our abdominal cavity more than almost any other factor. When we bear down and strain at stool, it's like squeezing our abdomen and may herniate part of our stomach up. Consistent with this concept is the observation that in Africans, the lower esophageal sphincter is entirely sub-diaphomatic, because it usually straddles the diaphragm in Westerners and is above the diaphragm in the presence of hiatus hernia. And the same abdominal pressure from straining that may cause hiatal hernias may cause a number of other problems. The straining can cause herniation to the wall of the colon itself known as diverticulosis. And the same pressure can also back up blood flow into the veins around the anus causing hemorrhoids to push blood flow back into the legs, resulting in varicose veins as well.