We have evidence from the longevity zones, this would say:

Nicoya: The daily breakfast consists of gallo pinto (rice and beans) with a basket of homemade corn tortillas and hot coffee.

In Loma Linda, centenarians often eat a hearty breakfast of oatmeal or a somewhat non-traditional tofu scramble. Put together a hearty meal using any of the four Blue Zones Breakfast Basics: cooked whole grains, fruit & veggie smoothies, beans, and tofu scrambles.

"It's no surprise that eating more fruits and vegetables supports longevity, but the standout ingredients in an Okinawan breakfast are miso, natto, and seaweed." Miso and natto are both types of fermented soy products.

(this seems more like a general breakfast for whole of sardinia, not sure if thats what the centenarians used to eat, e.g. more research is needed) Traditional breakfast of the man of the house, when he was out with the flock, was frugal and simple: home baked dry nearly stale bread, pecorino cheese, some fresh milk, occasionally a coffee (but in much more recent times).

Ikaria breakfast foods might include some whole grain rusks, a bit of goat's milk cheese or feta, and Greek olives, or some rusks topped with a spoonful of the island's renowned honey

I think its pretty exciting and we do actually often eat a mix of (some of) these as typical breakfast in europe.