Some nutritionists recommend variety, moderation, and balance in choosing foods.
This has not been popular in over 30 years, primarily because we have been promised miracles of health and weight loss from diets that combined foods in certain ways, excluded specific foods, or included others. This is exactly the reason to ignore diet fads. When a food is found to contain something healthy, chances are you will have been eating it, at least occasionally. You are most likely to get a wider range of nutrients this way. There are some medical conditions, such as allergies or celiac disease, that require elimination of certain foods from the diet.