Select the type of study where 500 people were randomly assigned to three different groups; one was put on an average American control diet, a second was put on a diet rich in fruits and vegetables, and the third was put on a combination diet rich in fruits, vegetables, and low-fat dairy products with reduced saturated and total fat intake. The groups remained on the diets for eight weeks. Blood sugar levels were measured before starting the diets and after eight weeks.

Epidemiological studies

Interventional clinical trial studies

Randomized clinical interventional trial studies

Laboratory studies conducted on animals or cells