There was a time when lunch was a sandwich. You remember, people would take a sandwich to school or work, perhaps with an apple or a bit of dessert. Now, few people will settle for such a simple lunch. People are eating a more elaborate cooked meal for lunch similar to their evening meal. Most often it's a full meal with salad, main course with meat and dessert.
Sandwiches can be a healthy choice or they can be deadly.
Some really healthy choices require imagination and creativity. Here are my suggestions all made on whole wheat bread. For these I use spicy mustard for a dressing. I love to have a raw onion on a toasted onion and poppy seed bagel. It was in Italy that I first discovered vegetable sandwiches such as asparagus.