making the case for milk: it's Cloudy

​Why do we start feeding babies cow’s milk when they turn one? Where did this practice come from and why, if at all, is it so important? 

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Milk is a controversial beverage. Food is extremely personal, of course, but milk seems especially highly charged these days. It often stands in as a touchstone for deep-seated beliefs about diet and nutrition, and milk can even be an indication for people’s views about the environment, animals, government regulation, or business. Americans tend to take milk’s place at the table for granted, but it was not always a staple of human consumption. Scholars on both sides of the so-called “milk wars” debate milk’s role in the human diet, and it’s very easy to find a nutritionist or physician guru to back up almost any individual inclinations about milk. Regardless of personal opinion, it is undeniable that a spate of research in the past five or ten years has raised questions about whether milk is a helpful or harmful substance, and whether daily milk-intake recommendations actually align with available evidence – for children and for adults. As tends to be the case with nutrition, to say that the answers to various questions about milk are elusive is a gross understatement. Yet amid the muck, there does seem to be a consensus that milk is not, contrary to existing advice, an “essential” food. In fact, anthropologists, geneticists, and archeologists are befuddled as to the reasons why humans developed the evolutionary capacity to consume milk at all.[1] “Humans have no nutritional requirement for animal milk,” write physicians David Ludwig and Walter Willet.[2]

But what about babies? Do they have nutritional needs that only milk can meet? Why do we herald the transition to cow’s milk at the age of one? Where did this practice come from and why, if at all, is it so important?
 
When Did Babies Start Drinking Cow’s Milk, Anyways?
To begin to understand the place of cow’s milk in babies’ diets, it is helpful to step back and take a look at when and why babies began drinking cow’s milk in the first place. In the US, most mothers breastfed their babies until the turn of the twentieth century, when mothers started feeding their babies alternative food from bottles. For the most part, that alternative food was cow’s milk. There are a host of fascinating reasons why women became less inclined to breastfeed, but it is abundantly clear that mothers stopped breastfeeding en masse around the turn of the twentieth century. (For anyone interested in more details about how and why breastfeeding declined around 1900, check out these books: Don’t Kill Your Baby, by Jacqueline Wolf, and Mothers and Medicine: A Social History of Infant Feeding, by Rima Apple.)
           By the mid-1900s, breastfeeding had become quite uncommon and bottle-feeding was the undisputed default norm in infant feeding. This exchange – bottle for breast – occurred rapidly, and it ushered in a concurrent, and equally sweeping, shift in Americans’ milk-consumption habits. Cow’s milk appeared the sensible replacement for breastmilk for babies, and it was certainly the most widely-used replacement. “The use of less human milk meant, simply, that more babies consumed cow’s milk.”[3]
            But here’s the thing: in its initial heyday as the foodstuff for babies, fresh milk was actually a very dangerous substance – nutrition aside.[4] Prior to pasteurization, refrigeration technology, antibiotics, and government regulation, milk could be lethal for babies. Indeed, milk consumption was the underlying cause for a vast number of infant deaths. The milk supply was frequently riddled with bacteria, diluted with water, damaged by dubious additives such as chalk to make it appear palatable, or spoiled.[5] At the time, physicians responded to the crisis in part by promoting breastfeeding, but also by helping instigate major public health reforms to sanitize the nation’s milk supply. The result was that cow’s milk became much safer for human consumption.[6]

But “safe milk” was only the surface of the issue – on a deeper level, there remained questions about cow’s milk’s adequacy for human infants. As Jacqueline Wolf explains, “even a pristine and perpetually refrigerated milk supply would have continued to pose a problem for some infants.” The actual makeup of milk varies from one mammal to another, and “at best,” Wolf describes, “the milk of one species is not easy for the newborn of another to digest.” Doctors teamed up with allies to play with the structure of cow’s milk and make it more similar to human milk. Their product was infant formula.[7]
            The campaigns to purify milk had dramatic benefits – infant mortality plummeted as mothers gained access to safe, clean milk and milk-based formulas. But in the process, the significance of cow’s milk as a nutritional beverage was exaggerated.[8] In the first two decades of the twentieth century, milk was “elevated . . . to an almost untouchable status as the perfect food for both infants and children.”[9] By 1920, the “nutritional perfection” of milk was written into government policy and scientific gospel, and the stuff was omnipresent in American homes.[10]
            Milk’s importance only deepened over the coming decades. By the mid-1900s, more mothers were feeding their babies milk earlier and earlier. Although the data is limited, what is available suggests that more than half of American mothers from the 1940s to 1960s were offering their infants whole milk by the time they were just four months old. By 1970, about 70% of infants had consumed whole milk by six months of age.[11]
            Then, over the course of the next ten or fifteen years, this practice nearly reversed – beginning in 1971, mothers moved away from feeding their babies milk by a “steady and impressive” trend. By 1985, just 10% of babies had tasted whole milk at six months.[12] As of that year, pediatricians were advising that parents could start feeding their babies whole milk only after the six-month mark, and only if their solid food diets were otherwise sufficient.[13] Why the about-face? What happened?
 
Pass the Milk
There appear to be two major reasons for the abrupt shift in milk-drinking habits among babies in the late-1900s. First, in the 1970s, after decades of dropping rates, breastfeeding skyrocketed – and not just in the United States. Women across the globe breastfed in greater numbers, and longer. Along with higher rates of breastfeeding came higher rates of formula feeding, and women were consequently less likely to feed their babies plain old milk.[14]
            Secondly, a series of articles in the 1960s detailed some potential problems for babies drinking cow’s milk. Physicians found that infants who drank whole milk had higher rates of iron-deficiency anemia, both because milk itself did not offer them much iron and because what iron it did offer was not very “bioavailable,” meaning that babies were less able to actually process and utilize it.[15] (Breastmilk also does not contain much iron, but it is highly bioavailable – babies can use about 40% of iron in breastmilk, compared to just about 10% of iron in whole milk.[16]) Physicians also learned that cow’s milk could potentially lead to gastrointestinal bleeding in babies with iron-deficiency anemia.[17] Other concerns were budding, too, including milk’s possible ties to obesity and diabetes, as well as allergy and intolerance.
            These reports emerged at the same time that the field of Pediatrics was stepping into nutrition. In 1954, the American Academy of Pediatrics (AAP) formed the Committee on Nutrition (CON); the group issued its first report in 1958, emphasizing developmental maturity, instead of age, as the best gauge for timing the introduction of solid foods. This inaugural report described that historically, perceptions regarding the ideal timing for introducing solid foods had swung back and forth, and noted that “present knowledge of nutrition is admittedly incomplete.”[18] In the 1960s, the FDA tapped the CON to help establish standards in infant feeding and childhood nutrition. Especially after this, explained Samuel J. Fomon, a pioneer in the field of pediatric nutrition, the CON “exerted an enormous influence on childhood nutrition, most notably on aspects of infant feeding.”[19]
 
In looking at the history of the AAP’s Committee on Nutrition reports regarding milk consumption, a prominent theme is the concept of uncertainty. The Committee repeatedly asserted that it was operating with a major handicap: broad gaps in knowledge about the ideal nutritional profile for babies and children.
            It 1974 the CON released a report in response to “public concerns about milk”: “Should Milk Drinking by Children Be Discouraged?” The piece was indecisive – the CON answered its own question with a tentative “probably not.” In regards to a number of issues, the article conveyed that evidence was insufficient as to be conclusive. Reviewing milk’s potential associations with obesity, for example, committee members explained that “there is no evidence that milk consumption per se makes any specific contribution to the development of obesity,” and determined that “a general recommendation to restrict milk fat is difficult to justify scientifically and may promote unnecessary anxiety in the general population.”
            In reference to milk as a calcium-delivery mechanism, the committee members reflected that “the concept that children and teen-agers should drink plenty of milk as a source of calcium (and phosphorous) to ensure ‘healthy bones and teeth’ is a tenet of North American health culture that is rarely questioned and one to which many physicians, dentists, and nutritionists subscribe.” But they pointed out that pediatric calcium intake requirements were undetermined, citing a World Health Organization report from 1961 that was “unable to define minimum or optimum calcium requirements for infants and children based on any data then available.” The CON estimated that existing daily milk recommendations probably exceeded babies’ and children’s calcium needs.
Ultimately, the committee took a noncommittal, pragmatic stance: milk “supplies a large proportion of essential nutrients and calories,” it said, “but it is not an essential component of the diet for anyone whose diet is otherwise adequate.” “The amount of milk that should be consumed by healthy older infants and children,” it continued, “cannot be stated with convincing accuracy . . . [and] the Committee believes that the sum of pertinent, current knowledge does not permit a more dogmatic position.”[20]
 
“Few Facts and Many Opinions”
A few years later, in 1979, leading experts reiterated that they did not have enough information: “definitive studies to guide us in our recommendations regarding many aspects of nutritional management are not yet available. Therefore, our reasoning in some areas is speculative and the recommendations must be considered tentative.” Furthermore, they stated, “our current recommendations for infant feeding are based on relatively few facts and many opinions.” The milk recommendations were tentative; once a baby was six months old and eating solid food, he could consume homogenized, vitamin-D fortified milk.[21]
            In 1984, Frank Oski – an outspoken critic of milk-drinking in general – delivered a provocative address that was subsequently published in the AAP’s journal, Pediatrics. His lecture detailed the health hazards of milk for babies and children. Contradicting the current pediatric teaching that babies could drink milk at six months, Oski pleaded that babies not be fed whole milk at all. He advised that even after children turned one, parents should avoid feeding them cow’s milk. He cited iron-deficiency, anemia, gastrointestinal bleeding, allergies, and longitudinal health problems such as obesity, atherosclerosis, and coronary artery disease as compelling reasons for Americans to quit milk. He was resolute about the issue for children: “If pediatricians sincerely believe that adult dietary patterns may be established in early childhood, then efforts should be made for dietary guidance that is consistent with the recommendations of the AHA [American Heart Association], NRC [National Research Council], and the US Select Senate Committee on Nutrition . . . The elimination of whole bovine milk from the diet would be a desirable first step in childhood,” he said. Oski thought the existence of so many unanswered questions about cow’s milk consumption was a big problem. “The Committee [on Nutrition] provides up with no cogent reasons, actually no reasons at all, why bovine milk should be introduced before the first birthday yet recommends that if ‘infants are consuming one third of their calories as supplemental foods . . . whole cow’s milk may be introduced.” But “why give it at all – then or ever?” he asked.[22]
            Oski was an east coast, ivy-league educated physician; in 1985 he became the Chair of Pediatrics at the prestigious Johns Hopkins University Hospital. But his questions were largely treated as the crazed rantings of an outsider. Writers expressed that his recommendations were radical, ungrounded, and overstated.[23] Oski held his ground, even publishing a titillating book – Don’t Drink Your Milk! – explicating his viewpoints and exposing American biases about the “naturalness” of milk. “Being against cow milk is equated with being un-American,” he said. Oski was resolute that breastfeeding was the best option for babies, but that formula should be used (even past one year) instead of whole cow’s milk, and he urged Americans of all ages to relinquish milk.[24] (This is especially interesting given that European scientists are beginning to play around with the development of “young-child formula” for toddlers.[25])
            Even if Oski’s perspective was unorthodox, in the 1980s, the question of when it was
safe and sensible to begin feeding cow’s milk to babies was prominent in pediatric literature.
New concerns and ambiguities emerged, and the “milk question” blossomed into an intriguing medical debate. A particularly vexing finding was that milk appeared to have a possible correlation with type 1 diabetes. One review article surveying twenty studies concluded that “there was a modest, but statistically significant association between the early introduction of cow’s milk and the development of IDDM [insulin-dependent diabetes mellitus] in childhood.”[26] Researchers also found that babies who consumed milk earlier tended to eat more “adult” foods, therefore consuming a “diet not well suited to the needs of the developing infant.”[27]
            The CON revisited the milk question in 1983, and again assessed that it was unsure about the place of cow’s milk in the ideal infant diet: “the appropriate age at which unheated, whole cow’s milk (WCM) can be safely introduced into the infant diet is unknown and remains an area of controversy.”[28] The percolating debate about using whole-fat, reduced-fat, or skim milk in infants’ diets could make for a separate piece in itself. Pediatricians discouraged parents from feeding their babies reduced-fat milk because of its potential to interfere with babies’ ability to consume enough calories and grow sufficiently. Reduced-fat milk threw off babies’ gauges for self-regulating food intake, and babies fed skim milk gained weight at slow rates. Plus, in several studies, infants who drank reduced-fat milk exhibited a “rapid decrease in skinfold thickness,” indicating that they were burning through their bodies’ fat stores just to meet their daily energy needs.[29]
 
Medicine and Milk: It’s Cloudy
 In 1992, the CON recommended that babies be fed either breastmilk or formula for at least one year, and that milk should be introduced after the first birthday.[30] In 1998 it made a change allowing for decreased-fat milk after a child turned two: “low-fat cow milk is appropriate during the second year if growth and weight are appropriate,” it said.[31]

But the reasons why parents should feed their babies whole milk are still difficult to pin down. The history of pediatric recommendations for feeding babies cow’s milk does not offer decisive answers about the place of milk in the human infant’s diet. It does, however, convey three key items of import:

1. The overwhelming trend in pediatric advice in the second half of the twentieth century has been to delay the introduction of cow’s milk to babies – pediatricians have continually pushed back the "ideal" age for introducing cow’s milk to babies.
2. Historically, the issue of cow’s milk consumption for babies has been characterized by uncertainty and questions. Although the prevailing societal ideology is that babies absolutely must drink milk, there is an apparent disconnect between the dominant medical literature and the cultural credo to offer babies cow’s milk.
3. As a practice, feeding babies and children cow’s milk was not something that initiated within medicine – quite the opposite. Women began feeding their babies cow’s milk in the early 1900s to replace breastmilk, and since then the pediatric community has juggled questions and tried to sort out the best practice when it comes to milk. But consuming milk was a complex, socially-instigated custom – not a medical revolution.

 
So where does this leave parents in the twenty-first century? Probably, wherever they are
inclined. This historical overview corroborates journalist Tia Ghose’s observation that “it turns out the case for milk is fairly weak.”[32] So is the case against it. Melinda Moyer, a wonderful science writer I’ve referenced elsewhere, wrote in 2015 that the “milk controversy” is all in parents’ heads – it’s “pointless, for several reasons,” she says. Her piece navigates the current science, assessing that “cow’s milk isn’t perfect, and some of its claims may be overtouted, [but] many of the scary claims made about it are overblown.” Confused parents stressed about milk should definitely read her article. After reviewing the nuanced benefits and detriments associated with feeding young children milk from various sources, Moyer advises parents not to “waste your precious parenting capital” worrying about milk. “And really,” she writes, “there’s no need to stress about milk anyway: The idea that toddlers and older kids need milk and are going to suffer without the right kind is silly. Milk provides important nutrients, but if your kid eats a balanced diet and stays hydrated, she doesn’t need it at all.”[33]
 
It is unlikely that parents’ questions about cow’s milk will be definitively answered anytime soon. What’s more, the legacy of milk-drinking for babies cuts to the core of fundamental aspects of pediatrics, nutrition, and parenting. At the base of uncertainties about milk are not just doubts about the beverage itself (“is milk healthy?”), but about children’s nutritional needs more broadly (“should children eat what is healthy for adults, or something else?”), and answering these questions isn’t any easier. As for me, I'm incorporating milk as a component of my son's whole-foods diet, but I hold no delusions about its wonders. It's just milk, ​right?
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[1] Laura Blue, “A Brief History of Drinking Milk: What Our Genes Can Tell Us,” Time, August 27, 2009, http://healthland.time.com/2009/08/27/the-history-of-milk-drinking/; Benjamin Phelan, “The Most Spectacular Mutation in Recent Human History: How Did Milk Help Found Western Civilization?,” Slate, October 23, 2012, http://www.slate.com/articles/health_and_science/human_evolution/2012/10/evolution_of_lactose_tolerance_why_do_humans_keep_drinking_milk.html; Andrew Curry, “Archaeology: The Milk Revolution,” July 31, 2013, http://www.nature.com/news/archaeology-the-milk-revolution-1.13471.
[2] Aaron E. Carroll, “Got Milk? Might Not Be Doing You Much Good,” New York Times, November 17, 2004, http://www.nytimes.com/2014/11/18/upshot/got-milk-might-not-be-doing-you-much-good.html?_r=1; David S. Ludwig and Walter C. Willett, “Three Daily Servings of Reduced-Fat Milk: An Evidence-Based Recommendation?,” JAMA Pediatrics 167, no. 9 (September 2013): 788–89.
[3] Janet Golden, “Review: ‘Mothers and Medicine: A Social History of Infant Feeding, 1890-1950,’ by Rima Apple,” Isis 80, no. 1 (March 1989): 110; Rima Apple, “The Medicalization of Infant Feeding in the United States and New Zealand: Two Countries, One Experience,” Journal of Human Lactation 10, no. 1 (1994): 31–37; Amy Bentley, “Booming Baby Food: Infant Food and Feeding in Post-World War II America,” Michigan Historical Review 32, no. 2 (Fall 2006): 65, quote from 68; Jacqueline Wolf, “Saving Babies and Mothers: Pioneering Efforts to Decrease Infant and Maternal Mortality,” in Silent Victories: The History and Practice of Public Health in Twentieth-Century America, ed. John W. Ward and Christian Warren (Oxford: Oxford University Press, 2007), 227; Jacqueline Wolf, Don’t Kill Your Baby: Public Health and the Decline of Breastfeeding in the Nineteenth and Twentieth Centuries (Columbus, Ohio: The Ohio State University Press, 2001), 42.
[4] Veronique Greenwood, “How Did Milk Become a Staple?,” BBC News, July 6, 2015, http://www.bbc.com/future/story/20150706-how-did-milk-become-a-staple-food.
[5] Wolf, “Saving Babies and Mothers: Pioneering Efforts to Decrease Infant and Maternal Mortality,” 224, 220, 227.
[6] Wolf, Don’t Kill Your Baby: Public Health and the Decline of Breastfeeding in the Nineteenth and Twentieth Centuries; Richard Meckel, Save the Babies: American Public Health Reform and the Prevention of Infant Mortality (Baltimore: The Johns Hopkins University Press, 1990); Wolf, “Saving Babies and Mothers: Pioneering Efforts to Decrease Infant and Maternal Mortality,” 137–39.
[7] Wolf, “Saving Babies and Mothers: Pioneering Efforts to Decrease Infant and Maternal Mortality,” 227–28, 230.
[8] Ibid., 146.
[9] Golden, “Review: ‘Mothers and Medicine: A Social History of Infant Feeding, 1890-1950,’ by Rima Apple,” 110; Apple, “The Medicalization of Infant Feeding in the United States and New Zealand: Two Countries, One Experience”; Bentley, “Booming Baby Food: Infant Food and Feeding in Post-World War II America,” 65, quote from 68; Wolf, “Saving Babies and Mothers: Pioneering Efforts to Decrease Infant and Maternal Mortality,” 227; Wolf, Don’t Kill Your Baby: Public Health and the Decline of Breastfeeding in the Nineteenth and Twentieth Centuries, 42.
[10] Greenwood, “How Did Milk Become a Staple?”
[11] Samuel J. Fomon, “Infant Feeding in the 20th Century: Formula and Beikost,” Journal of Nutrition 131 (2001): 413S–414S; Samuel J. Fomon, “Reflections on Infant Feeding in the 1970s and 1980s,” American Journal of Clinical Nutrition 46 (1987): 171.
[12] Fomon, “Infant Feeding in the 20th Century: Formula and Beikost,” 417S; Fomon, “Reflections on Infant Feeding in the 1970s and 1980s,” 171.
[13] Michael B. Montalto, John D. Benson, and Gilbert A. Martinez, “Nutrient Intakes of Formula-Fed Infants and Infants Fed Cow’s Milk,” Pediatrics 75, no. 2 (February 1985): 343.
[14] Fomon, “Infant Feeding in the 20th Century: Formula and Beikost,” 415S; Fomon, “Reflections on Infant Feeding in the 1970s and 1980s,” 171–72; Gilbert A. Martinez and Douglas A. Stahle, “The Recent Trend in Milk Feeding Among WIC Infants,” American Journal of Public Health 72, no. 1 (1982): 69, 71.
[15] AAP Committee on Nutrition, “The Use of Whole Cow’s Milk in Infancy,” Pediatrics 72, no. 2 (August 1983): 253.
[16] Alexander K.C. Leung and Reginald S Sauve, “Whole Cow’s Milk in Infancy,” Pediatric Child Health 8, no. 7 (September 2003): 420.
[17] Fomon, “Infant Feeding in the 20th Century: Formula and Beikost,” 417S.
[18] AAP Committee on Nutrition, “On the Feeding of Solid Foods to Infants,” Pediatrics 21, no. 4 (April 1958): 686, quote from 691.
[19] Fomon, “Infant Feeding in the 20th Century: Formula and Beikost,” 415S.
[20] AAP Committee on Nutrition, “Should Milk Drinking by Children Be Discouraged?,” Pediatrics 53, no. 4 (April 1974): 576, 578, 579, 580.
[21] Samuel J. Fomon et al., “Recommendations for Feeding Normal Infants,” Pediatrics 63, no. 1 (January 1979): 52, 56, 57.
[22] Frank A. Oski, “Is Bovine Milk a Health Hazard?,” Pediatrics 75, no. Supplement (1985): 182–86.
[23] Swiss Pediatric Association Committee on Nutrition, “Letter to the Editor: Health Hazards of Cow’s Milk,” Pediatrics 76, no. 6 (1985): 1021–22.
[24] Frank A. Oski, Don’t Drink Your Milk!: The Frightening New Medical Facts About the World’s Most Overrated Nutrient (Wyden Books, 1977).
[25] Simone R.B.M. Eussen et al., “Theoretical Impact of Replacing Whole Cow’s Milk by Young-Child Formula on Nutrient Intakes of UK Children: Results of a Simulation Study,” Annals of Nutrition & Metabolism 67, no. 4 (November 2015): 247–56.
[26] Work Group on Cow’s Milk Protein and Diabetes Mellitus, “Infant Feeding Practices and Their Possible Relationship to the Etiology of Diabetes Mellitus,” Pediatrics 94, no. 5 (November 1994): 752.
[27] Montalto, Benson, and Martinez, “Nutrient Intakes of Formula-Fed Infants and Infants Fed Cow’s Milk,” 351.
[28] AAP Committee on Nutrition, “The Use of Whole Cow’s Milk in Infancy,” 253.
[29] Ibid., 254; Fomon, “Infant Feeding in the 20th Century: Formula and Beikost,” 417S.
[30] Fomon, “Infant Feeding in the 20th Century: Formula and Beikost,” 417S.
[31] Ronald E. Kleinman and Frances A. Coletta, “Historical Overview of Transitional Feeding Recommendations and Vegetable Feeding Practices for Infants and Young Children,” Nutrition Today 51, no. 1 (2016): 10.
[32] Tia Ghose, “Do Kids Really Need to Drink Milk?,” LiveScience, January 25, 2015, http://www.livescience.com/49551-should-kids-drink-milk.html.
[33] Melinda Wenner Moyer, “Cows vs. Almonds,” Slate, July 28, 2015, http://www.slate.com/articles/life/the_kids/2015/07/is_cow_s_milk_healthy_for_kids_or_should_kids_drink_almond_milk_instead.html; see also Alice Callahan, “Can a Child Drink Too Much Milk?,” New York Times, October 21, 2016.