Does a Low Carb Diet Cause Gallstones?

That Nice Boy I Married got a question from a friend of his today. She'd heard that a low carb diet increased the risk of gallstones, and wanted to know if that was true. It's an excellent question, and the answer is a little complicated.

First, it helps to know what your gallbladder does. Your gallbladder resides under your liver, and collects a fluid called bile, which the liver secretes. Bile is a digestive fluid that breaks down fat. The bile hangs out in your gallbladder until you eat fat. When your body senses fat in your intestine, the gallbladder contracts, squirting a concentrated dose of bile into the fatty food so you can digest and absorb it.

There are a number of causes of gall stones -- hard stone-like objects that develop inside the pouch-like gallbladder. According to Medline, they include anything that keeps the gallbladder from emptying completely. Since a very low fat diet does not stimulate the gallbladder to contract strongly, it is implicated. Medline also states that rapid weight loss from a very low calorie diet is also a cause of gallstones. (Long-time intravenous feeding can also cause gallstones, apparently also because it does not stimulate the gallbladder to contract.) These are not the only causes of gallstones, which appear not to be completely understood, but they are among them.

Low carbohydrate diets, however, derive a majority of their calories from fat (at least if you're doing it right,) and therefore stimulate strong gallbladder contractions. If you have no stones in your gallbladder, this is great, may well be preventive. But if you already have gallstones -- and remember, most of us have spent years trying to lose weight through fat restriction before we go low carb -- eating a high fat meal can cause the gallbladder to squeeze down on them, causing pain. If you have a stone clogging the bile duct (the tube the bile comes through), you're going to be in great pain indeed.

Did the low carb diet cause the gallstones? No, it did not. Did it stimulate a gall bladder attack? Yes, it did. But the chances are excellent the stones were there to begin with.