Student guest post: Cholesterol, a bacterium, and gallbladder cancer

It's time for this year's second installment of student guest posts for my class on infectious causes of chronic disease. Fourth one this round is by Kristen Coleman. 

If you are anything like me, you have been told countless reasons over the years why we must watch what we eat, keep our cholesterol intake down, and try to work out. It shouldn’t really come as a surprise then that I, since I am a public health student after all, aim to convince you of yet another reason why a healthy diet and exercise are valuable. What is this huge reason to avoid Big Macs and think about taking the stairs instead of the elevator you ask? Well, it may help you to prevent gall bladder cancer, is all.

All of this begins with gallstone formation. Gallstones are hard deposits, usually of cholesterol, that become lodged in your gallbladder over time. Your gallbladder is an organ that helps to aid in digestion through the storage and release of bile which helps to break down fats in your small intestine. The gallbladder is located on the right side of the body attached to the liver. The process of gallstone formation is called cholelithiasis. In this process, cholesterol, which is not very soluble, becomes clustered together in droplets in the bile called micelles. This cholesterol droplet then hardens into the crystals that make up a gallstone. Obesity causes bile to transit the gallbladder less rapidly and increased cholesterol in the diet means there is more cholesterol available to form stones. It does not require and active imagination then, to understand how obesity and high cholesterol intake contribute to stone formation, but how does this all tie into cancer you ask? http://www.umm.edu/patiented/articles/what_gallstones_gallbladder_disease_000010_1.htm

It all comes down to infection with a bacterium known as Salmonella typhi. Yes, this is the same bacterium that causes Typhoid fever and was the malady that afflicted the famous Typhoid Mary. While many people may become infected with S. typhi over the course of their lives, those individuals with gallstones are 6-15 times more likely to become carriers of S. typhi in the gallbladder. This is important because those people with a chronic infection of S. typhi have been shown to have 3-200 times higher risk of developing gallbladder cancer then non-carriers. Furthermore, chronic carriers have a 1-6% lifetime risk of developing gallbladder cancer. In fact, gallbladder cancer is so linked to S. typhi infection that gallbladder removal, called cholecystectomy, is recommended for those people with gallstone disease who live in high risk areas. Where is a high risk area? Most developing countries of the world are high risk areas for S. typhi, especially countries in Asia, Africa, and Latin America. This means that travelers from the USA and other developed countries to these regions are at risk for developing the infection. However, even at home in the USA, low risk doesn’t mean no risk, and we should be vigilant against emergence of this bacterium.  

In conclusion for all my gallbladder-containing friends out there (I make this distinction because I, myself, am no longer at risk for gallbladder cancer since I had mine removed in 2006 after a bout with gallstone disease) stay aware of your cholesterol levels and pay attention to making sure you have a healthy diet because, like every health care professional will tell you, it might just save your life….perhaps in a way you don’t expect!

References:

1. University of Maryland Medical Center. Gallstones and gallbladder disease. Online http://www.umm.edu/patiented/articles/what_gallstones_gallbladder_disease_000010_1.htm
2. Ferreccio, Catterina. Salmonella typhi and Gallbladder Cancer. http://link.springer.com/chapter/10.1007/978-94-007-2585-0_5#page-1

Center for Disease Control online source. http://www.cdc.gov/nczved/divisions/dfbmd/diseases/typhoid_fever/