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.
The potassium helps lower high blood pressure, which can contribute to heart disease. Fiber also contributes to the heart health benefits of romaine lettuce, by removing bile salts, which requires cholesterol, thereby lowering high cholesterol as well. Another health benefit of romaine lettuce provided by potassium is improved muscle strength.