Oatmeal is a great brain food to keep us sharp,” Angela Martindale, a celebrity nutritionist, says. The complex carbs cause the brain to produce serotonin. Beta-glucan, a type of soluble fiber found in oatmeal, has reflected higher satiety scores than other whole grains in food research, she adds, which means it’s better for the brain in keeping people sharp and energy high than other types of soluble fiber.