A decline in biliary tract cancer risk is associated with regular consumption of diets rich in onions, garlic, and shallot.

​This study assessed the role diets play in the development and prevention of cancer of the biliary tract. A team of investigators looked at the diets and biliary tract cancer odds ratio of a large number of subjects residing in Shanghai, China. They found out that high dietary ingestion of onions, garlic, shallot, seaweed, and kelp decreased the odds of developing cancer in the gallbladder, extrahepatic bile duct, and ampulla of Vater. In contrast, increased intake of diets rich in salted meats and preserved vegetables was found to elevate biliary tract cancer development risk. The results of this study indicate that consistent consumption of diets loaded with onions, garlic, shallot, seaweed, and kelp may reduce an individual's susceptibility to biliary tract cancer