Lecithin is used for treating memory disorders such as dementia and Alzheimer's disease. It is also used for treating gallbladder disease, liver disease, certain types of depression, high cholesterol, anxiety, and a skin disease called eczema.
It's generally used as an emulsifier, or lubricant, when added to food, but also has uses as an antioxidant and flavor protector. Like many food additives, soy lecithin isn't without controversy.
There is no recommended dosage for lecithin. As a general rule, dosage should not exceed 5,000 mg daily.