The mini sweet potatoes I buy literally ooze with caramelized sugary sweet goodness after roasting in the oven. Top them with coconut oil or butter, and enjoy a little taste of heaven. GI value be damned.
I've experimented with boiling vs. microwaving. Boiling definitely produces lower BG. When you microwave, you basically suck out all the moisture from the sweet potato and make it more dense. It's about 30% less volume. So it's no brainer. When you boil, you're increasing the volume with water, which stays in the sweet potato, thus diluting the net carbs of the pre-boiled sweet potato.
The effect is the same with potatoes, yuca and yams.
anyone interested in some more quantitative (and objective) data on the potato vs. sweet potato, baking vs. boiling and other related issues may want to take a look at my "Potato Manifesto" > Part 1 and Part 2 at the SuppVersity
I vaguely remember an episode of Cook's Illustrated that involved braising sweet potatoes in cream rather than boiling them in water. Their rationale was something along the lines of sweet potatoes boiled in water absorb (or hold onto) water, resulting in a poor texture when mashed. Perhaps this explains the lower GI as well?
Re the "safe starches" argument, I think Paul Jaminet makes a very good case for the various other factors affecting GI, so I'll stick to roasting sweet potatoes and just making sure that the rest of my meal compensates!
This makes sense to me...the sugars concentrate the most when roasting, that's why they taste all carmelized and yummy. I don't eat very many sweet potatoes, so I'll stick with roasting in plenty of delectable fat.