The study aimed to find out which foods are the main sources of whole grains in people's diets and to create a database of the whole grain content of foods. Researchers collected dietary information from over 1500 adults in the Baltimore Longitudinal Study of Aging and used this data to calculate how much whole grains people were eating. They found that the top sources of whole grains were ready-to-eat breakfast cereals, hot breakfast cereals, multi-grain bread, and whole wheat bread. This research helps us understand the importance of whole grains in our diets and the need for tools like databases to accurately measure how much we are consuming.