In Japan, about 1.5 million people are infected with the hepatitis B virus and about 2 million with the hepatitis C virus; both of these infect the liver through the blood. The hepatitis B virus can also infect babies by being transferred from their mothers during childbirth, but nowadays the infection can be prevented through vaccination. Since all donated blood is now screened there is only a very minor risk of infection with the hepatitis C virus through blood transfusions.

When you consume alcoholic drinks, the alcohol contained in them is detoxified by the liver. This means that consuming large quantities of alcohol puts a big burden upon the liver. Alcohol dissolves in water, dissolves fat, and acts to denature proteins, causing direct harm to the body's cells. Furthermore, when metabolized inside the liver, it turns into acetaldehyde, which is even more toxic than the original alcohol, and can cause liver fibrosis.

Recently, the obesity rate has been increasing due to overeating and a lack of exercise; because of this fatty liver disease is now seen in about 80% of obese individuals. One type of fatty liver disease, non-alcoholic steatohepatitis (NASH) which progresses to liver cirrhosis accompanied by inflammation and fibrosis, is also known to develop in people who are obese and have diabetes. In these situations, changes in lifestyle habits are essential to help improve the function of the liver.