Our gut flora is determined by what we eat, for good or for ill. When we eat meat, dairy, eggs, and seafood, our gut flora can take certain components in them (carnitine and choline) and produce something that ends up as a toxic compound called TMAO, which may set us up for a heart attack, stroke, and death.
So, give people two eggs, and you get a spike of TMAO in their bloodstream within hours of consumption. Because gut bacteria play a critical role in this process, though, if you then give them a week of antibiotics to wipe out their gut flora, and re-feed them two more eggs, nothing happens. No TMAO in their bloodstream because they have no egg-eating bacteria to make it. But give it a month for their gut bacteria to start to grow back, and the eggs start to cause TMAO production once again….