Yes eating a banana a day is good for you and your health.
Bananas are full of vitamins, minerals, nutrients, potassium etc.
Eating one banana per day is very good and will provide you with energy, may help prevent some diseases, boosts your bodies immune system etc.
Bananas are also a great source of fiber as one medium sized banana contains 3 grams of fiber so eating bananas can also help treat constipation as well as possibly prevent constipation.
Bananas are one of the healthiest fruits you can eat and even even more than a couple of bananas will improve your health.
I have at least one banana everyday and also eat some apples, oranges, pears and other fruits that make great healthy snacks.