Yes, the nutrient
database is very extensive. It's true, for some reason, the food
database does not appear to be so.
I did a search on foods with Arginine (which aids in blood flow during exercise) for the following and found the following gram values for Arginine, per 100 grams (so it winds up in %) for the following foods:
Peanuts 2.832 grams
Almonds 2.446 grams
Walnuts, English 2.278 g
Pistachio, raw 2.012 g
Brown Rice, long grained, cooked 0.196 g
Coconut meat, raw 0.546
Cereals, oats, instant, fortified, plain, dry 0.839 grams
Raisins, seedless .413 g
Sunflower seeds 1.816 g.
Pumpkin Seeds 5.284 g
Bread, Multi-Grain (includes whole-grain) 0.485 grams
From this information, I was able to conclude that my current practice of eating peanuts and pumpkin seeds is spot on, since they have the most amounts of Arginine than the other nuts and seeds that I searched.
I can't explain why their foods are limited, but their nutrient database is extensive.
Yes, they don't have "egg whites" or edamame as foods, but they do have "eggs" (whole) and "soy nuts" (edamame).
[EDIT] By the way, I never thought about checking out soy nuts ("Soybeans, mature seeds, dry roasted") until you mentioned it. I just found that they contain 3.071 grams of Arginine, which tops even peanuts!