The lack of animals to domesticate meant fewer zoonotic diseases in Native American populations, so they were ill equipped when those diseases appeared.
IIRC, there was a massive plague in North America a decade or so before Columbus arrived.
It's probably whatever "1 cup" means to the patient. The researchers would want them to stick to their status quo for the best results.
For example, 1 cup of coffee for my wife involves a blend of coffee and espresso beans with no adders, but 1 cup to her dad means lighter roast bean with milk. Both options have different caffeine contents and nutritional values.
IIRC, there was a massive plague in North America a decade or so before Columbus arrived.