Jean-Louis Tu writes:

>We note that green vegetables contain MORE proteins than meat.

By percentage of calories, yes. By percentage of weight/mass, however, not
by a long shot.

>Of course, for a human it is impossible to eat a significant amount of
>proteins from green vegs (to get 2000 calories, you would have to
>ingest 7.4 kg = 16.3 lbs of bamboo shoots, or 7.1 kg = 15.7 lbs of
>broccoli, or 14.3 kg = 31.5 lbs of lettuce), but a gorilla probably
>can. Perhaps this explains why vegan animals can be so strong
>(assuming of course that the gorilla's staples also have a 40% protein
>content, approximately).

To state this more clearly, in this kind of situation it's the percentage
of protein BY MASS OR WEIGHT (not percentage by calories) that's most
relevant in determining how much one can actually eat and get out of a
food, since our digestive systems have to deal with food-as-a-MASS (i.e.,
as bulk). Stating the amount of protein present measured in calories as a
percentage of all calories is misleading when there is such a large
disparity in concentration of protein by weight, as there is in this
comparison.

According to the figures provided in the table, BY WEIGHT, meat (average of
pork chops and beef steak) is 6.8 times as concentrated in protein calories
as greens (average of bamboo shoots, broccoli, romaine). So while greens
have more kcals than meat as a percentage of total calories, by itself that
tells us little that's relevant to the human digestive system's comparative
ability to extract a given amount of protein efficiently from one or the
other of the food sources. As stated in the original post, we'd have to eat
like gorillas to process the requisite bulk on a daily basis to get
sufficient calories from greens alone.

Also, this is completely aside from potential bioavailability issues (how
well-absorbed the protein may be, depending on the food source). Perhaps
someone else can fill us in on that question.

Ward Nicholson
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