Bile acids, which are made in the liver from cholesterol and secreted into the bile along with cholesterol, have a number of important functions. The bile acids help keep the cholesterol in the bile in liquid form and thus reduce the formation of cholesterol gall stones, by far the most common type of gall stones.

Within the intestine, bile acids play a critical role in the absorption of dietary fats. A major fraction of the bile acids that enter the intestine are reabsorbed and then returned to the liver, where they are once again secreted into the bile. Loss of the remaining bile acids in the stools is a major way that cholesterol is removed from the body.

A number of studies have recently made the surprising finding that disruption of the reabsorption of bile acids lowers blood glucose levels in people with diabetes.

Drugs referred to as bile acid sequestrants were among the earliest drugs that could effectively lower total and LDL cholesterol levels. By binding with bile acids in the intestine, these drugs prevent the bile acids from being reabsorbed while in the intestine, thus increasing the amount of bile acids that are evaculated with the stools. The use of bile acid sequestrants has largely been replaced with the statin drugs, which are more convenient to take, have fewer side effects, and can lower cholesterol by considerably more than the average 25 percent reduction accomplished with bile acid sequestrants.

Recent articles in the journal Archives of Internal Medicine reported that in randomized clinical trials the bile acid sequestrant pill colesevelam (Welcol^®) lowered HbA1c levels by an average of 0.5 percent when added to diabetes treatment with insulin, sulfonylureas, or metformin. The fall in HbA1c was greatest in those whose starting values were higher than 8 percent. The modest improvement in glycemic control was accompanied by a 13 percent reduction in LDL cholesterol at the end of one 12-week study.

Because they are not absorbed from the intestine, bile acid sequestrants cause no significant adverse effects. Their use is often accompanied, however, by some excess gas and constipation. These drugs can raise blood levels of triglycerides, the most common lipid abnormality in diabetes, and so must be used with caution, if at all, in those with elevated triglyceride levels.