I’m going to start this post with a defense of the burger. While they get a bit of a bad rep, hamburgers can actually be pretty healthy. A 3-oz. burger (at least half the size of the burgers most restaurants serve) has a pretty low amount of calories (184), and it's an excellent source of iron, zinc, protein and niacin.

But things can start to go downhill in the nutrient department when you top the burger with bacon, cheese, mayo — all extras that drive up the calories and saturated fat content. Keep your burger virtuous with these healthy toppings:

Avocado: Take your burger in a California direction with avocado slices. You’ll get an extra dose of heart-healthy monounsaturated fatty acids and potassium with this topping that’s so creamy you won’t miss mayo. (pictured: South-of-the-Border Burgers)

Sauteed mushrooms and onions: You get a lot of flavor for not a whole lot of calories with this combination. Just slowly saute mushrooms and onions in a bit of olive oil until the onions are soft and golden brown.

Lettuce and tomatoes: These traditional toppings make your burger into a salad (OK, not quite, but at least you’re getting some veggies in!). Tomatoes have vitamin C, which helps you absorb the iron from your burger, and lettuce has vitamin A, which is important for building bones.

Pickled beets: Go Aussie-style with your burger by topping it with homemade pickled beets, like these from Alton Brown. Dark red beets are high in anthocyanins — a phytochemical tied to brain and heart health.

Sharp cheese: I know you’re going to put cheese on your burger, so you might as well go with a really good one. And to be fair, cheese does offer calcium and protein. You can get a whole lot of flavor with just a small amount of sharp cheddar, blue or Gouda.

Greek yogurt: Hear me out. If you’re having, say, a lamb burger, then a bit of tzatziki (plain Greek yogurt mixed with minced garlic, diced cucumber and fresh herbs) is just the thing to top it.

Watercress or arugula: Get extra flavor from sharp greens like watercress or arugula. Again, you’ll squeeze in extra veggies.

Kerri-Ann is a registered dietitian and nutrition coach who writes on food and health trends. Find more of her work at kerriannjennings.com or follow her on Twitter @kerriannrd or Facebook.