Originally Posted by trigger

I don't know about the science of it all, but I can tell you what I've experienced.

I'm female, and have been a vegetarian for about 9 years. When I first starting to ride and really clean up / focus on my diet, I didn't worry too much about my protein intake, and did just fine. Normal amounts of tofu, tempeh, yogurt etc.

However, now in my third year of cycling and really starting to "train" instead of just riding lots, I noticed that my leg muscles were not able to keep pace with my aerobic system, that I felt run-down for days after hard efforts, and that it was just generally hard to get to the next level.

Enter a whey protein supplement and most of those symptoms have disappeared. I recover much faster and more fully from hard efforts, feel less run down, and I can slowly feel my legs getting stronger - largely, I believe, as they are now getting enough fuel to properly repair and build muscle.

So yes, for an average person, even one who is above average in terms of activity, there is likely no need to supplement as long as you eat well, but for one who is actively training, I think supplementation to a vegan or vegetarian diet is helpful.

TO THE OP - if this is your first year of cycling seriously, I wouldn't worry about it. Track what you eat, keep an eye on eating well and adjust things if you feel you need to. Likely you'll be just fine until you start to really "train" (hard, painful, puke inducing training). Otherwise just eat clean and well. On the bike snacks that I enjoy include Lara Bars, Clif Bars, Homemade Oatmeal cookies, figs, dates etc.