Green leafy vegetables have little or no nutritive value, and are eaten as "eye food". In fact some, like celery and lettuce have less caloric value than it takes to process them through your system, like sand. Some, like spinach, contain a toxic blood poison, oxalic acid. This dangerous chemical is so high in rhubarb that the green leaves are capable of causing death. Why eat this rubbish?
I agree that there is only maybe 20 percent of the weight of "leafy greens" which is carbs, but why eat something so toxic and rough? Would you intentionally put a pinch of sand in the crankcase of your car? Older people suffer from malnutrition in spite of "excellent diets" due to the scar tissue in their intestines from a lifetime of exposure to roughage in their food. In the short term it causes the intestines to coat themselves with mucus, which also interferes with absorption of nutrients.
All plants have toxins, chemical defenses against herbivores are much older than the mechanical ones like the spines of cacti. People have struggled for hundreds of years to breed out most of these defenses, which is why you cannot grow them without pesticides.
If you doubt me, eat a cupful of wild lettuce (a very common weed), and see how long you can remain awake. It contains a glucoside, letucin, called "lettuce opium", which was bred out of the cultivated plant.
http://zerocarbpath.blogspot.com/
