Eating the exact same breakfast every morning is convenient, but research on dietary variety suggests convenience has a cost for your gut bacteria. People with lower dietary variety scores show lower microbial richness than people who eat a wider range of foods.[1]
The American Gut Project, one of the largest microbiome studies conducted, found that people eating 30 or more different plant types per week had more diverse gut bacteria. That was true compared with people eating fewer than 10 types.[1] Eating 30 different plant types isn't the same as eating 30 different meals. A single serving of mixed greens, plus a handful of nuts, plus a few different vegetables across a week, adds up toward that number quickly.
What to do with this
A repetitive breakfast isn't itself the problem; a repetitive diet across the whole day and week is what the research ties to lower gut bacteria diversity. Counting different plant types loosely, not perfectly, across a week and aiming for something near 20 to 30 is a reasonable, research-backed target without becoming a tracking chore. If your breakfast rarely changes, use lunch and dinner as the place to rotate in different vegetables, grains, legumes, nuts, and fruits.
