I looked up the protein percentage at Calorie Counthttp://caloriecount.about.com/calories-spinach-i11457
Their percentage of protein is more like 13.5%. I've always been confused by these numbers. When the chart says spinach has 49%, how is that determined? In my mind that would say, essentially, half of a spinach leaf contains protein but I don't believe that to be the case, unless you are Popeye.
How much spinach would I need to eat to get the same protein contained in a single egg? That would help answer this question.
It isn't that it is X% protein, it is that X% of the total calories are from protein. These foods are mainly going to be water, which has no calories. What's left will provide calories, which will be from carbs, fat and protein. The total calories are very low, per weight. But of those calories, there is very low amount from fat, high from protein and very high from carbs. To say 'calories from' means that if you have 100 calories of a food, and say 20% come from protein, the that is 20 calories from protein. Since each gram of protein has 4 calories, that would mean it has 5g of protein per 100 calories. I don't understand the disagreement of protein quantities in food either, it is confusing. I generally see around 30% for spinach.