Although I don't disagree that you will most likely get enough protein if you eat enough (non-junkfood) calories, 2-5% of your daily food intake seems to be quite low. Having a protein intake of around 10-15% of your daily calories would be much more reasonable. Getting this isn't hard, given that wheat flour is about 15% protein by calories and many vegetables are over 20% protein. As long as you aren't eating a ton of junk food and fruit, you are probably going to be fine as a cyclist.