The more exercise, the fewer the gallstones
Physical activity appears to play an important role in the prevention of gallstones, which occur in up to 20 percent of American women and 10 percent of American men by age 60. Harvard researchers made the finding when they studied almost 46,000 men ages 40 to 75 for eight years. Those who exercised the most had the least risk for gallstones.
Gallstones are generally not life-threatening but can be very painful, resulting in an estimated 800,000 hospital admissions each year. They form in the gallbladder--a pouch located next to the liver.
The gallbladder stores bile--greenish-yellow, cholesterol-containing fluid secreted by the liver into the small intestine that helps emulsify fatty components of food during digestion. But sometimes cholesterol precipitates out of the bile and ends up accumulating, clumping together, and forming solid crystals, or gallstones.
Gallstones can range in size from tiny sand-like particles to larger, pealike masses. Most people's gallstones are "silent," meaning they are not symptomatic and do not require treatment. But those with symptomatic stones experience episodic attacks of severe abdominal pain (severe enough to wake them from sleep) and sometimes nausea, vomiting, and intolerance to fatty foods.
Treatment involves taking medication to dissolve the stones, but the success rate is variable. In some cases, surgical removal of the gallbladder is necessary. (The gallbladder, like the appendix, is not essential. Once it is removed, bile is secreted directly from the liver to the intestine.)
Several risk factors for developing gallstones have already been identified, including obesity, advancing age, being female, having had multiple pregnancies, and consuming a high-fat, low-fiber diet.
Because obesity is a common risk factor, it's possible that physical activity can reduce gallstone risk just by reducing body weight. But, say the Harvard researchers, the effects they observed in their study go beyond that, pointing to a possible independent effect of exercise on gallstone prevention. However, exactly what that effect is remains to be determined.
Regardless of the mechanism, "the good news is that all the types of exercise studied were associated with reduced risk for gallstone disease," says lead researcher Michael Leitzmann, MD, MPH. That included jogging, racquet sports, rowing, cycling, swimming, stair climbing, and walking.
The greatest reductions in risk were observed in men who spent the most time exercising--and who engaged in the most vigorous activity. For example, running four or more hours a week was associated with a 43 percent risk reduction compared to not exercising, while running for two and a half hours a week was associated with a 30 percent risk reduction. And men who walked three miles per hour or faster had a 31 percent risk reduction, compared with only a 16 percent risk reduction for those who walked more slowly.