I make fruit smoothies often, and started off adding sugar. I'm looking for a more "natural" sweetener though. I know I can use honey, but it adds a distinct taste that I'd like to avoid. I've tried using dates as well, and it's a workable alternative, but also changes the taste slightly (and makes the smoothie "stickier"). What are other natural sweeteners to try, preferably that don't make a big difference to taste?
You could try agave nectar -- but I'm not sure if it will be that much of an improvement over honey. A tiny pinch of salt might also help make the smoothie taste sweeter.
Usually though, if I want my smoothies to be sweeter I just add more juice or fruit (e.g. ripe berries, peaches etc).
The very act of sweetening it will change the taste. That's really the point.
However, if you like the taste of the smoothie sweetened with cane sugar, but are looking to ditch the cane sugar, there are three things you can try:
Dextrose is basically glucose, rather than the fructose-glucose molecule of cane sugar. It isn't as sweet as cane sugar, but it won't alter the taste of your smoothie in any other way.
Stevia is quite different. Gram-for-gram, stevia is much sweeter than cane sugar. It also has a very slight aftertaste for some people, but nowhere near as pronounced as with something like aspartame. There is also suggestions your body doesn't even process it as sugar.
One other trick that I'm sure you won't have thought of is to add a little dairy cream. However, this only really works if you've cut right back on your fructose intake already (cane sugar and HFCS). The reason it works is because your taste has, by then, been resensitised to genuinely natural sweetness.
When you have a bunch of bananas go overripe, peel them, cut them into pieces, put them in a freezer bag and freeze them -- then use them in your smoothies. When bananas go black, they get very sweet and are ideal for things like smoothies (or banana bread), where texture doesn't matter, but the sweetness is desired.