The preset smoothie mode actually does that, so no joy there. But....tried today with frozen fruit, and it calmed the foam down a lot. Plus the blades actually warm things up with the Vitamix, so it didn't leave me a freezing mix to chug before work.
Threw some fresh Kale in there (part of the idea was to use up this kind of stuff which is pouring out of the garden right now) and it vaporized it, like I hoped.