Have a look at "A Movable Feast: Ten Millennia of Food Globalization" by Kenneth Kiple. The argument is made that the introduction of foodstuffs from the American continent sustained the population rise in Qing Dynasty-era China (p. 146):

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But even without the beans, the American plants are once again credited with bringing about a mushrooming population, said by some to have reached an incredible 150 million Chinese by the beginning of the Qing (or Ch’ing, or Manchu) dynasty in the middle of the seventeenth century. We cannot know how accurate that figure is; indeed we cannot be certain that the American foods were the initial cause of a population explosion that began in China in the seventeenth century, accelerated in the eighteenth and nineteenth centuries, and produced an astronomical number of people in the twentieth century.

On the other hand, we can be certain that such population growth could not have been sustained without them. As in Europe and Africa, the new American foods vastly improved the caloric intake of the masses.

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The apt sequence is introduction of American foodstuffs->Europe/Asia in enabling a rise of caloric intake elsewhere and hence sustainable population size. The comparative component is how bringing American foodstuffs affected population growth in Europe vis-a-vis Asia (particularly China).

http://ebooks.cambridge.org/ebook.jsf?bid=CBO9780511512148

Many thanks, Emmanuel, this will help to put our source material in perspectice.