The travel of people and goods between the Old and New Worlds led to an exchange of animals, plants, and diseases, a complex process known as the Columbian exchange. As we have seen, the introduction of new diseases to the Americas had devastating consequences. But other results of the exchange brought benefits not only to the Europeans but also to native peoples.

European immigrants wanted to eat foods familiar to them, so they searched the Americas for climatic zones favorable to crops grown in their homelands. Everywhere they settled, the Spanish and Portuguese brought and raised wheat with labor provided by the encomienda system. Grapes and olives brought over from Spain did well in parts of Peru and Chile. Perhaps the most significant introduction to the diet of Native Americans came via the meat and milk of the livestock that the early conquistadors brought with them, including cattle, sheep, and goats. The horse enabled both the Spanish conquerors and native populations to travel faster and farther and to transport heavy loads more easily.

In turn, Europeans returned home with many food crops that became central elements of their diet. Crops originating in the Americas included tomatoes, squash, pumpkins, peppers, and many varieties of beans, as well as tobacco. One of the most important of such crops was maize (corn). Because maize gives a high yield per unit of land, has a short growing season, and thrives in climates too dry for rice and too wet for wheat, it proved an especially important crop for the Old World. By the late seventeenth century, maize had become a staple in Spain, Portugal, southern France, and Italy, and in the eighteenth century it became one of the chief foods of southeastern Europe and southern China.

Even more valuable was the nutritious white potato, which slowly spread from west to east — to Ireland, England, and France in the seventeenth century, and to Germany, Poland, Hungary, and Russia in the eighteenth, contributing everywhere to a rise in population. Ironically, the white potato reached New England from old England in the early eighteenth century. The Portuguese quickly began exporting chili peppers from Brazil to Africa, India, and Southeast Asia along the trade routes they dominated. Chili peppers arrived in continental North America when plantation owners began to plant them as a food source for enslaved Africans, for whom they were a dietary staple.

The initial reaction to these crops was sometimes fear and hostility. Adoption of the tomato and the potato, for example, was long hampered by the belief that they were unfit for human consumption and potentially poisonous. Both plants belong to the deadly nightshade family, and both contain poison in their leaves and stems. Consequently, it took time and persuasion for these plants to win over tradition-minded European peasants, who used potatoes mostly as livestock feed. During the eighteenth-century Enlightenment, scientists and doctors played an important role in popularizing the nutritional benefits of the potato.

While the exchange of foods was a great benefit to cultures across the world, the introduction of European pathogens to the New World had a disastrous impact on the native population. The wave of catastrophic epidemic disease that swept the Western Hemisphere after 1492 can be seen as an extension of the swath of devastation wreaked by the Black Death in the 1300s, first on Asia and then on Europe. The world after Columbus was thus unified by disease as well as by trade and colonization.