Some years after going gluten-free I noticed I was sensitive to other things as well.  I try to limit sugar and caffeine now.  In regards to refined sugar, it doesn't take long for it to hit my system and cause problems like migraines and general fatigue.  Here is a no-sugar-added smoothie I like to make.

PB & Banana Smoothie

Ingredients:

1 frozen ripe banana, pre-chopped
1/3 c. plain yogurt
1 c. unsweetened almond milk
2 Tb. natural peanut butter
2 tsp. flax seeds
one or two dashes of cinnamon

Directions:  Combine all in blender and mix until smooth.  Add more almond milk for desired consistency.  Healthy and yummy!