 This is House Call for Health. A recent study suggests Americans need to do their homework on diet. The Food is Medicine Institute at Tufts University says Americans have improved from an F to only a D on diet in just over 20 years. The study finds bad diets decreased from about 49% to 37% from 1999 to 2020, and that we eat too much refined grains, ultra-processed foods, and processed meats.