Hi! I think a slice of bread can be part of a healthy breakfast (even better if whole grain and sourdough). However it needs to be accompanied by healthy proteins and fats, for example a slice of bread with almond butter or one egg, some cucumber and a slice of bread.
Just bread? It would be better to combine it with something with protein and/or healthy fats. So maybe bread with cheese or peanut butter, or a sandwich 😃
Bread can definitely be counted as a healthy breakfast. The grains in it provide for much sustainable energy. Some breads are obviously better for you, like multi-grain over white bread. However, while bread simply by itself is quite healthy, it won’t be enough to get you through the day until your next meal. Other healthy toppings, such as avocado, should be added for that extra bit of energy.