The vast majority of the evidence supports the latest US Dietary Guidelines, which state that a “healthy” 1,800-to-2,000-calorie diet could include six slices of bread a day—including up to three slices of “refined-grain” white bread.
For the most part, healthier breads tend to be more dense, and weigh closer to 50 grams per slice. Therefore they will usually display 1 slice as the serving size.