For many people, breakfast includes sugary carbohydrates, said Dr. Carlos Gonzalez-Cabezas, a dentist, professor and associate dean for academic affairs at the University of Michigan School of Dentistry. Cereals, breads, muffins and pancakes — these all contain fermentable carbohydrates that bacteria love to feed on.
And when you wake up in the morning, Dr. de Aguiar Ribeiro added, bacterial levels in your mouth are at their peak — “that’s why we have bad breath when we wake up.”
So a mouth rife with bacteria and a breakfast full of sugary carbs means that conditions are perfect for the bacteria to flourish and multiply. When this happens, they release acids that can wear down the protective enamel on your teeth, making them more prone to cavities, Dr. de Aguiar Ribeiro said. Brushing before breakfast clears that bacteria away, denying them the opportunity to feed on your food.