As far as vegan & endurance sports, I haven't tried the iron distance on a vegan diet yet, but I ran the 50 with no GI problems which is unusual for a full day of solid exercise. Also, I did a 6 mile swim last season with no GI issues. No energy loss, ether. On the 50 I ate dates and bananas with Hammer Endurolytes supplements as needed. Did the trick.
Last night I had braised eggplant with tofu over brown rice and later had a giant smoothie with banana, strawberry, orange, spinach, flax, and hemp protein. mmmm.... that's a celebration right there.