These substances cause excessive amounts of water to remain in the stool, leading to diarrhea. Certain foods (such as some fruits and beans) and sugar substitutes in dietetic foods, candy, and chewing gum (for example, hexitols, sorbitol, and mannitol) can cause osmotic diarrhea.
The four most common types of green lettuce -- green leaf, romaine, butterhead and iceberg -- have 13 to 17 calories in 100 grams, which is about a 1/2-cup serving of shredded lettuce. They deliver 1 gram of protein, or about 2 percent of the recommended daily intake.
In addition, romaine lettuce is a very good source of dietary fiber, manganese, potassium, biotin, vitamin B1, copper, iron and vitamin C. It is also a good source of vitamin B2, omega-3 fatty acids, vitamin B6, phosphorus, chromium, magnesium, calcium and pantothenic acid.