Hi jc,
Great post and great question, as always.
For those reading, Dr. Fuhrman recommends 1 cup of beans daily, minimum, unlimited.
Dr. McDougall recommends 1 cup of beans max. So did Pritikin. The concern was too much protein.
So, who's right?
Pritikin did not recognize the difference between animal and plant protein. Animal protein causes an acid metabolism (due to sulfur content). Plant protein does not. Animal protein is correlated with heart disease and cancer incidence. Plant protein is not.
Note that Jellen, towards the bottom of the first page, said "I'm one with beginning stages kidney concerns and I personally wrote dr. M. and asked about legume amounts per day. For me, I'm not to exceed 1/2 cup beans per day."
Jellen continued "When I was at ETL, dr. Fuhrman said not to exceed a cup of beans per day--but to split the amount over several meals to not tax the kidneys."
So, for anyone with kidney problems, 1 cup (perhaps 1/2 cup) is a limit. Both agree that beans are healthy up to 1/2 to 1 cup, even for some with kidney issues.
Personally, I eat 1 to 2 cups a day.
If someone is lean, down to the recommendation of Dr. Fuhrman (pinch 3/4 inch by the navel for men, and 1 inch for women **) and has fewer meals (2 or 3 meals a day), that slows the metabolism, and reduces the burden of metabolic waste products and free radicals, to be disposed by the liver and kidneys. This makes the body more tolerant of a variety of carb/fat/protein ratios. This is also remarked in the Longevity Diet, Lisa Walford. This is the beginning of the calorie restriction regime, where lifespan is increased. In this regime, the life extension aspect is observed, over a wide range of carb/fat/protein ratios.
The important thing is that 90% of McDougall and Fuhrman, is the same.
I agree with you, that my answer is not definitive. ^_^
Best regards, EngineerGuy
** Note the change, increase from 1/2 inch to 3/4 inch, for men. This is one change, in the new edition of Eat To Live.