Naturally Immune For Life

For most of human history feeding an infant when the mother could not breastfeed depended on another woman’s milk. Long before commercial formula or modern bottles existed, wet nursing was the primary alternative to maternal breastfeeding. Historical evidence places the practice as far back as 2000 BC, and it remained an established profession for centuries. The development of artificial feeding eventually transformed this system, but the transition was gradual and shaped by changes in medicine, technology, social attitudes, economics, and eventually commercial interests.

Wet nursing was not just an informal arrangement, in many societies it became a regulated profession, particularly among wealthy families who employed women to nurse their children. During the Roman Empire, contracts specified the length of nursing, compensation, clothing, and other responsibilities. Medical writers also discussed the qualities of an appropriate wet nurse, including her health, recent childbirth, temperament, and the perceived quality of her milk. Attitudes toward the practice changed over time and during the Middle Ages and Renaissance, concerns emerged that a wet nurse might transmit physical or behavioral characteristics to the infant. At the same time, breastfeeding by the biological mother increasingly became associated with maternal responsibility and virtue.

Social class also influenced how infants were fed as aristocratic women in parts of Europe sometimes avoided breastfeeding because it was considered unfashionable, interfered with clothing and social activities, or was believed to affect their figures. The wives of merchants, lawyers, and doctors also did not breastfeed because it was less expensive to employ a wet nurse than it was to hire a woman to run their husband’s business or take care of the household in their place. Among working families, economic pressures eventually became an even more important factor as the Industrial Revolution moved populations into cities, increased the need for women to earn wages, and made caring for an infant while working increasingly difficult. Wet nursing consequently shifted from an occupation serving wealthy households to one increasingly associated with poorer women and by the beginning of the twentieth century, the once widespread profession had largely disappeared.

The feeding bottle provided another important turning point. Although vessels for feeding infants had existed for thousands of years, early devices were difficult to clean and could harbor dangerous bacteria. Archaeological evidence shows that ancient vessels contained residues of animal milk, demonstrating that artificial feeding is not a modern invention. Medieval and early modern feeding devices included animal horns, ceramic containers, wooden vessels, metal pots, cloth, and sponges and their practical limitations made artificial feeding hazardous. During the early nineteenth century, contamination of feeding equipment, combined with inadequate milk storage and sterilization, contributed to extremely high mortality among artificially fed infants.

Even when bottles could be cleaned safely, the milk itself posed serious risks. During this time, milk transported into growing cities was often heavily contaminated. A series of exposés in Frank Leslie’s Illustrated Newspaper in 1858 revealed the dangers of New York’s “swill milk” trade, where cows were kept in filthy conditions and fed waste products from liquor distilleries. The resulting outcry led to milk becoming a major public health concern. The dangers of artificial feeding were reflected in the staggering infant mortality of the period and the combination of dirty feeding devices, poor milk storage, and inadequate sterilization was associated with the death of one third of artificially fed infants during their first year of life.

The Industrial Revolution also brought improvements in both bottle design and food preservation. Glass bottles became increasingly practical, while improved nipples and better household refrigeration gradually reduced some of the dangers associated with artificial feeding. 

The initial steps toward modern infant bottle-feeding took shape in 1841 when Dr. Charles M. Windship patented the first glass nursing bottle in the United States, an invention that laid the groundwork for flexible feeding methods. This mid-19th-century design relied on a long rubber tube connected to an early iteration of a rubber nipple, allowing infants to feed without constant adult assistance. Though this development provided a softer alternative to rigid materials like pewter, bone, or wood, early crude rubber possessed a pungent odor, warped easily in boiling water, and trapped deadly bacteria inside the uncleansable tubing, a fatal design flaw that was not fully resolved until Elijah Pratt patented a standalone vulcanized India-rubber nipple in 1845. 

At the same time, animal milk particularly cow’s milk became a major substitute for human milk. By the eighteenth century, scientists were comparing the chemical composition of human and animal milk and recognizing that they were not nutritionally identical. This led researchers to search for ways of modifying nonhuman milk so that it would more closely resemble human milk.

Commercial infant foods emerged from this scientific and technological environment. In 1865, Justus von Liebig developed and marketed an infant food made from cow’s milk, wheat and malt flour, and potassium bicarbonate. Other commercial products soon followed. Henri Nestlé, a German-born pharmacist, founded his company in 1866 and revolutionized infant nutrition in 1867 by introducing Farine Lactée (“Milk Flour”) in Vevey, Switzerland. Developed to combat high infant mortality rates, this breakthrough product gained rapid international popularity and forming the foundation of the modern Nestle brand and by the 1870s the formula is sold across five continents. By 1883, the historical review reports that 27 patented infant-food brands existed, many consisting largely of carbohydrates intended to be added to milk. Products associated with companies such as Nestlé, Horlick’s, Mellin, and others became increasingly recognizable to consumers.

Another important scientific advancement of the 19th century was food preservation. In 1810,Nicholas Appert developed a technique to sterilize food in sealed containers. His development was followed by the invention of evaporated milk, which was patented in 1835 by William Newton. In 1853, Texan Gale Borden added sugar to the evaporated milk, canned the substance, and sold it as Eagle Brand Condensed Milk, which became a popular infant food. In 1885, John B. Myerling developed an unsweetened condensed milk, labeling it as ‘‘evaporated milk.’’ Myerling’s product was also a popular choice for infant feeding and was highly recommended by pediatricians from the 1930s to the 1940s.

The rise of commercial feeding was not driven by formulation alone. Advertising became a powerful force in shaping public perception. As manufacturers refined their products, they increasingly promoted them as convenient, reliable alternatives to breastfeeding. Formula companies also cultivated relationships with physicians. In the United States, the American Medical Association established a Committee on Foods in 1929 to evaluate the safety and quality of infant-food composition. Advertising restrictions introduced in the early 1930s limited direct solicitation of nonmedical audiences, while simultaneously creating a close relationship between manufacturers and medical professionals. By the 1940s and 1950s, formula had become widely accepted by both physicians and consumers as a safe and modern substitute for breastmilk. Breastfeeding subsequently declined for decades.

The history also demonstrates why the nutritional comparison between human milk and manufactured substitutes is more complicated than simply matching calories, protein, fat, carbohydrates, vitamins, and minerals. Human milk is a dynamic biological system, whereas traditional formula was designed as a relatively fixed nutritional product. The paper notes that formula does not change composition as an infant develops, while breastmilk changes over time. Researchers therefore became increasingly interested not merely in supplying nutrients, but in understanding how infant feeding influences digestion, immunity, allergy, metabolism, and later health.

The twentieth century eventually brought a growing recognition that feeding choices could have consequences beyond immediate nutrition. The historical review discusses research associating breastfeeding with lower rates of several childhood conditions, including atopy, diabetes, and obesity. It also describes evidence suggesting that longer breastfeeding was associated with reduced risk of certain allergic outcomes and childhood overweight. These findings helped shift the discussion from whether formula could provide adequate nourishment to a broader question: what biological functions might be missing when human milk is replaced?

This question became particularly important as researchers learned more about the complexity of human milk. What earlier generations viewed primarily as nourishment is now understood to contain a diverse collection of biologically active components that interact with the developing gastrointestinal tract, immune system, and microbial environment. The historical progression from wet nursing to animal milk, bottles, preserved foods, and increasingly sophisticated formulas represents more than a technological story and is the history of an evolving understanding of what an infant actually needs.

By the end of the twentieth century, regulation had become another major part of that story. The Infant Formula Act of 1980 established federal oversight of formula quality in the United States, while international controversy surrounding formula marketing contributed to the development of the World Health Organization’s International Code of Marketing of Breast-milk Substitutes. The historical record shows that infant feeding has never been determined by biology alone. Cultural expectations, economic circumstances, scientific discoveries, technology, advertising, medical practice, and public policy have all influenced how societies feed their youngest members.

The enduring lesson is that replacing human milk is fundamentally different from simply replacing a food. The history of infant feeding shows a progression from finding an alternative source of milk to attempting to reproduce the nutritional and biological functions of human milk. Modern research into human milk oligosaccharides, immune factors, microbiota, and other components continues that centuries old effort but with a much deeper understanding of what makes human milk biologically distinctive.