Final answer:
Fortified margarine is the type of food that may include plant stanol esters, as they are added to lower cholesterol levels.
Step-by-step explanation:
The foods that may include plant stanol esters are typically fortified products, such as some types of margarine. Plant stanol esters are added to foods to help lower cholesterol levels and are not naturally present in high amounts in whole grains, nuts and seeds, or fruits and vegetables. While these foods contain a variety of essential nutrients and are part of a healthy diet, it is specially fortified margarine that often has plant stanol esters included to aid in reducing cholesterol.