A nutrient in the vitamin B complex that the body needs in small amounts to function and stay healthy. Choline helps cells make membranes, make a neurotransmitter (a chemical that helps nerve cells communicate with other cells), and remove fat from the liver. It is found in whole milk, beef liver, eggs, soy foods, and peanuts. Choline is water-soluble (can dissolve in water) and must be taken in every day. Not enough choline can cause diseases of the heart and blood vessels and damage to the liver. A form of choline is being studied in the treatment of some types of cancer and to reduce pain and fever. Choline is also being studied together with vitamin B12 in the prevention and treatment of cancer.