This is not wrong—by our Rating System, bananas are a good source of potassium. But there are 32 foods on our Rating Chart with more potassium per calorie than the banana. Speaking more generally, the most potassium-rich food sources of potassium are fruits and vegetables.Some legumes, fish, and dairy products can also make important contributions to our daily potassium intake; yet, because these foods have more calories, they are not as highly rated by our Nutrient Richness System.his is not wrong—by our Rating System, bananas are a good source of potassium. But there are 32 foods on our Rating Chart with more potassium per calorie than the banana. Speaking more generally, the most potassium-rich food sources of potassium are fruits and vegetables.