Choline is considered an essential nutrient, because even healthy individuals cannot synthesize enough to maintain health.
From the Linus Pauling Institute :
The main criterion for establishing the Adequate Intake level for choline was the prevention of liver damage (see Deficiency).
Very little information is available on the choline content of foods (4). Most choline in foods is found in the form of phosphatidylcholine. Milk, eggs, liver, and peanuts are especially rich in choline.
Strict vegetarians who consume no milk or eggs may be at risk of inadequate choline intake.