To Alice - I would expect that bottle feeding and straw feeding, which rely on suction, would both exert higher pressures - and pressures more directly affecting the site of extraction - than the pressure from breastfeeding, which relies on the upward push and wave-like motion of the tongue. 

To Barbara - As a former pre-school teacher, who used to make butter with the children by shaking whipping cream in a glass jar, I always assumed the caution about shaking was that the fat (being together in one layer) would form little butter balls that would not pass through the nipple hole. Not as deeply scientific as the articles but perhaps as plausible an explanation? 

Cindy Garrison BS IBCLC 
practicing in Pittsburgh, PA 

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