Not long ago, it was assumed that if a restaurant sold smoothies, the most popular flavor would be strawberry–banana, two popular fruits that go well together and give consumers a sense of wellbeing.

That was true at Tropical Smoothie Café, whose strawberry–banana Jetty Punch smoothie long reigned as the top menu item at the chain, which currently has around 380 units.

But now its top seller is the Island Green smoothie, which combines spinach and kale with mango, pineapple and banana, and outsells the Jetty Punch by a wide margin.

“I mean, like almost three times the sales of strawberry and banana,” chief executive Mike Rotondo said, adding that it now accounts for 6.8 percent of the chain’s total sales.

Although this summer has seen a boom in new hamburgers, a new line of Tater Tot omelets at Huddle House, new giant deli sandwiches from Arby’s, and a bunch of new meaty and cheesy breakfast items, not to mention several knockoffs of New York pastry chef Dominique Ansel’s Cronut, it also has been a season of more healthful items, including a wider range of salads, lighter beverages, leaner proteins and smaller portions.

Tropical Smoothie Café introduced a limited-time Totally Green smoothie, made with green apple, celery, spinach, kale, cucumber and kiwi, which is currently its fourth-best-selling drink. It is also rolling out a red “antioxidant powerhouse” smoothie with beets, strawberry and cranberry pureed with blueberries.

Boloco, a 22-unit fast-casual burrito chain based in Boston, also introduced a smoothie combining fruit and vegetables. The Tropi-Kale combines kale, mango, cucumber, celery and apple juice, and is sweetened with honey and mixed with crushed ice. 

Planet Smoothie took a more traditional flavor approach for its line of 10 “Planet Lite” smoothies it introduced as permanent additions this summer, combining fruit with nonfat milk or yogurt. It also uses LeanLeaf, a proprietary sweetener made from agave and stevia, to come up with blends that each have fewer than 300 calories for a 22-ounce serving.

The options are:

• 2 Piece Bikini: Strawberries, bananas, vanilla, nonfat milk and fat burner blast supplement

• Crazy Bee: Mangos, strawberries, honey and a multivitamin supplement

• Leapin’ Lizard: Peaches, strawberries and fat burner blast supplement

• Luna Lemonade: Strawberry or raspberry, lemonade, bananas and a fat burner supplement

• Mediterranean Monster: Strawberries, bananas, splash of orange juice and fat burner supplement

• Piña Colada: Banana or strawberry, coconut, pineapple, nonfat milk, vanilla, fat burner supplement

• Strawberry Aphrodite: Strawberries, banana and Greek yogurt

• Screamsicle: Pineapples, peaches, orange juice, frozen yogurt, orange sherbet and multivitamin or immunity supplement.