The World's Healthiest Foods

Why is cow's milk one of your 10 Most Controversial WHFoods?

What makes cow's milk controversial is not any particular aspect of this food - for example, whether it is grass-fed or non grass-fed, organic or non-organic, or whole, reduced fat, or nonfat. It's the nature of the food itself.

Four of the most controversial aspects of cow's milk are (1) a disproportional number of adverse reactions to cow's milk in comparison to other commonly eaten foods; (2) lack of regulatory standards needed to assure a natural lifestyle for dairy cows; (3) potential contribution of large-scale cow's milk production to excess greenhouse gas emissions and global warming; and (4) relatively high total fat, saturated fat, and calorie content of cow's milk in comparison with many other foods. Here is more information about each of those controversies.

Adverse Reactions to Cow's Milk

From a research perspective, there is no question about the greater number of adverse reactions to cow's milk—whether grass-fed or conventionally fed—than most other commonly consumed foods. Adverse reactions to cow's milk include two distinctly different types of reaction. The first type is cow's milk allergy (CMA), and the second type is cow's milk intolerance.

CMA typically involves an immune system response to certain casein proteins contained in cow's milk. Cow's milk contains some casein proteins—for example, alpha-s1-casein, alpha-s2-casein, and gamma-casein—that are simply not present in human milk as consumed by breastfeeding infants or in other foods commonly consumed by adults. In the U.S., cow's milk is included in a list of eight foods that account for over 90% of all reported allergic food reactions. These eight foods include (1) wheat, (2) cow's milk, (3) hen's eggs, (4) fish, (5) crustacean shellfish (including shrimp, prawns, lobster and crab); (6) tree nuts (including cashews, almonds, walnuts, pecans, pistachios, Brazil nuts, hazelnuts and chestnuts); (7) peanuts (which are not true nuts but rather legumes); and (8) soy foods.

The symptoms of CMA can be quite different in different individuals. These symptoms can include skin-related problems like rashes, hives and eczema; respiratory-related problems like wheezing and coughing; or digestive tract problems like diarrhea, gas, cramping, and bloating. (These digestive tract symptoms, however, are less commonly experienced in cow's milk allergy than in cow's milk intolerance, which we will describe next.) For some adults, the symptoms of CMA are experienced in a much more generalized way—for example, as overall fatigue or as "brain fog."

An adverse reaction to cow's milk can also stem from intolerance. Intolerance does not involve an immune system reaction to casein proteins in cow's milk but rather to other cow's milk components.

By far the most common of these components is the sugar called lactose. Lactose is a sugar that is present primarily in the milk of mammals, including cows. (For this reason, lactose is often referred to as "milk sugar.") Lactose is also classified as a disaccharide sugar because it's a combination of two simple sugars called glucose and galactose. An enzyme called lactase (which is present in the digestive tract of some individuals more than others) can break lactose apart into these two simple sugar components (glucose and galactose). If the lactase enzyme effectively breaks down lactose into glucose and galactose, cow's milk tolerance is often not experienced. However, this "if" is a big one, since many people do not have enough lactase enzyme in their digestive tract to break down substantial amounts of lactose (that would be contained, for example, in a glass of cow's milk consumed as a beverage).

There are three ways for you to lower your risk of cow's milk intolerance. In all three ways, the goal is to get all of the lactose in cow's milk broken down into glucose and galactose.

The first way is to purchase lactose-free milk. Lactose-free milk has been pre-treated with the enzyme lactase to break the lactose apart into glucose and galactose. (We should note here that we have yet to see lactose-free versions of grass-fed cow's milk in stores, but we expect them to eventually become available. In the meantime, you can purchase regular grass-fed cow's milk and use the second method described below.)

A second method is to purchase lactase enzyme supplements in liquid form and add drops to the milk. (About 10-15 drops per quart of milk is often recommended.) Let the milk sit overnight in the refrigerator if you use this method to allow time for the enzymes to take effect.

A third method is to purchase lactase enzyme supplements in chewable, caplet, or tablet form and then swallow the supplement along with cow's milk whenever it is consumed. Some individuals with lactose intolerance find these steps very effective in overcoming a cow's milk intolerance. However, the first two methods in which the milk is treated directly tend to produce better results than use of the oral enzyme supplements. It's not that the oral supplements don't work—it's that our stomach is a more complicated place containing other foods, other enzymes, and more complex chemistry. Still, oral supplements can be helpful at restaurants and when consuming foods like casseroles and baked goods where milk may have been included as an ingredient. Given all of the issues described above, some individuals with milk intolerance prefer to simply avoid milk and milk-containing foods.

Fermented milk products—like most cheeses and most yogurts—tend to trigger fewer adverse reactions than fresh liquid milk. This reduction in adverse reactions is due to the use of microorganisms in fermentation. Microorganisms change the composition of the milk, including the structure of proteins, fats, and carbohydrates. Both casein proteins and lactose may be changed during fermentation in such a way as to lower the risk of an adverse reaction. Individuals who enjoy dairy products but experience adverse reactions to fresh liquid milk may discover less problems with fermented dairy products, especially live-culture yogurts based on 100% grass-fed cow's milk or 100% grass-fed cheeses. But once again, avoidance of all milk-related foods is more effective in eliminating adverse reactions.

Lack of regulatory standards to assure a natural lifestyle for dairy cows

In the U.S. and in many other countries, the role of dairy cows in our cultures has changed dramatically over the centuries. Instead of a small number of cows being cared for by humans living on small family farms, or a small number of cows being herded by nomadic cultures who traveled to find pasture land and water for their herds, dairy production in the United States now involves nine million dairy cows who produce about 20,000 pounds of milk each year or 180 trillion pounds total. This level of production is not possible without certain constraints on the lifestyle of the cattle. Maximal milk production is difficult if cows are left to graze in pasture year-round. Maximal milk production is also difficult if cows are only milked during the first trimester of pregnancy, rather than continuously throughout the second and third trimesters. Artificial insemination is often necessary to allow for near year-round milk production. Maximal production also tends to require milking at least twice per day. All of these practices impact the life of dairy cows.

One of the most controversial practices impacting the life of dairy cows is use of rbGH. rbGH stands for "recombinant bovine growth hormone," and it is estimated to be used in the raising of approximately 15-20% of U.S. dairy cows. You'll also see this hormone called rbST (recombinant bovine somatotropin). Originally developed by Monsanto and now produced by Elanco (a company that acquired rights to the synthetic hormone from Monsanto in 2008), rbGH is sold under the brand name Posilac (TM) and it is one of the largest dairy animal pharmaceutical products sold in the U.S. Use of rbGH in dairy cows in the U.S. began in the mid-1990's as a way of increasing milk production. From a physiological perspective, rbGH is part of a complicated network of hormones and hormone-like substances that are required for growth and proper differentiation of cells.

An especially important part of this network is a polypeptide (small protein-like molecule) called insulin-like growth factor 1, or IGF-1. In humans, elevated blood levels of IGF-1 are associated with increased risk of certain cancers, especially breast cancer in women and prostate cancer in men. Cows injected with rbGH would, of course, be expected to have elevated amounts of rbGH in their bodies. In addition, however, cows injected with rbGH would be expected to have higher levels of IGF-1 as well. A question raised by many scientists is whether humans regularly consuming milk from rbGH-injected dairy cows are at increased risk for IGF-1 exposure and IGF-1 associated cancers. We have not seen any large-scale human study that has determined regular consumption of milk from rbGH-injected cows to be a risk factor for cancer. In fact, we've found indexed-journal reviews in this area that report no evidence for this association. Still, the connection between excessive exposure to growth hormone, IGF-1, and increased cancer risk makes logical sense to us, and it is an issue that seems worthy of concern.

In the U.S., the only regulatory standards prohibiting use of rbGH in dairy products involve certified organic dairy products. rbGH is strictly prohibited in certified organic foods. In other countries—including countries like Canada, Australia, New Zealand, Japan, and all countries belonging to the European Union (27 countries, including the United Kingdom, France, Spain, Italy, Germany, Greece, Hungary, Poland, Norway, Sweden and Denmark)—regulations have banned rbGH in all dairy products.

One of the reasons we recommend purchase of 100% grass-fed cow's milk involves the better lifestyle that 100% grass feeding affords dairy cows. The vast majority of dairy cows in the U.S. are raised in Intensive Production Systems (IPSs) that provide little access to fresh pasture. IPSs generally involve confinement facilities consisting of barns, feedlots, stalls, pens, feeding alleys, and sorting alleys. In place of a fresh pasture diet, IPSs typically rely on total mixed rations (TMRs) and concentrates made from grains, fermented grains, hays, fermented hays, soymeal, soybean hulls, citrus pulp, linseed meal, cottonseed meal, and other ingredients. TMRs and concentrates can result in digestive problems for the cows including bloat and other problems.

U.S. governmental regulatory agencies do not currently provide strict dietary or pasture standards for dairy cows. For example, certified organic cow's milk does not provide strict regulations for pasture feeding. Certified organic cow's milk may be obtained from cows who only had access to pasture on 120 days of the year, and who only obtained 30% of their food from pasture on those days. Similarly, USDA certification for grass-fed beef requires continuous access to pasture during the growing season but not during other parts of the year. While it is true that USDA grass-fed animals are required to consume grasses and forages as their food source year-round, they can still be denied access to pasture and fresh grasses during the non-growing season, provided that they continue to consume grasses and forage in some form (for example, in dried or fermented form). USDA grass-fed standards also allow pasture forage to include cereal grain plants like corn, but only if those plants are in the early stages of development before forming seeds.

Requirements for pasture access and grass-based diets are stricter with third-party certification by the Food Alliance (FA) and the American Grassfed Association (AGA). These stricter requirements, which help improve the lifestyle of the cow, are one of the reasons that we recommend purchase of grass-fed cow's milk that has been certified by one or both of these organizations.

Potential contribution of cow's milk production to excess greenhouse gas emissions and global warming

According to the Intergovernmental Panel on Climate Change (, the average surface temperature of the earth has increased by 1.3 degrees Fahrenheit over the past 100 years. This increase in temperature is commonly referred to as "global warming," and it's due to excessive accumulation of certain gases in the atmosphere surrounding the earth. These gases are called "greenhouse gases" because they help turn the earth into a greenhouse that is warm enough for living things to survive. Greenhouse gases are a good thing. Without them, the earth would still be frozen and unable to support life. However, too many greenhouse gases create a blanket around the earth that is too thick and traps too much of the sun's heat. If too much heat is trapped, the earth's ecosystem balances get disrupted, including the flow of rivers, patterns of wind, and animal habitats.

On a global basis, about 10-15% of unwanted increases in greenhouse gases (GHGs) come from agriculture. Even though there is unwanted release of carbon dioxide (a key greenhouse gas) into the atmosphere due to the use of industrial farm equipment that requires the use of gasoline, oil, or natural gas, carbon dioxide is not the primary greenhouse gas of concern in agriculture. That distinction goes to two other greenhouse gases: methane, which is released into the atmosphere from manure (and primarily cow manure), and nitrous oxide, which is released into the atmosphere following use of nitrogen-containing fertilizers used in the cultivation of feed crops for animals (and primarily cows). So there are some direct links between the phenomenon of global warming and the raising of dairy cows in Intensive Production Systems that involve increased reliance on nitrogen-containing fertilizers and feed concentrates that increase nutrient intake, growth, and as a by-product of increased growth and consumption, manure. A more natural lifestyle for dairy cows involving 100% grass feeding can lessen both of these problems. Less focus on intensive production can mean less use of nitrogen-containing fertilizer, as well as less concentrated dietary intake resulting in less manure. These favorable environmental consequences of 100% grass feeding are another reason that we recommend selection of 100% grass-fed cow's milk.

It's also worth noting that 100% grass feeding typically means more emphasis on the existence of pasture land within dairy farms. This increased focused on pasture land brings with it more cultivation of food crops and cover crops. Increased crop cultivation, in turn, means increased capture of carbon dioxide by the crops and less lease of carbon dioxide into the atmosphere. (Plants take in carbon dioxide and release oxygen into the air.) Some scientists have estimated that widespread use of cover crops and planted pasture land in global agriculture could turn global agriculture into an industry that actually helps reduce the amount of carbon dioxide in the atmosphere rather than increasing it.

Relatively high total fat, saturated fat, and calorie content of cow's milk

Whole cow's milk (3.25% fat) gets 48% of its calories from fat, and 27% of its calories from saturated fat. Since the American Heart Association recommends that we get 25-35% of our calories from fat and 7% of our calories from saturated fat, you can see how these percentages raise concern for many individuals. From a calorie perspective, a person consuming 1,800 calories of food per day would get about 8% of a day's calories from one 8-ounce glass of whole cow's milk. Three glasses of cow's milk per day would provide about one-quarter of the day's total calories. Once again, you can see how that percentage would be of concern to many individuals.

While we share this general concern about total fat, saturated fat, and calorie content of whole cow's milk, we believe that this concern can be answered through two steps: (1) consumption of cow's milk in smaller serving sizes of 4 ounces or less, and (2) consumption of 100% grass-fed milk.

The impact of smaller serving sizes should be fairly obvious. One 4-ounce serving of whole milk provides only 4 grams of total fat and 2.75 grams of saturated fat. Within a 1,800-calorie meal plan, those amounts constitute 2% of calories from fat and 1.4% of calories from saturated fat. So there is plenty of room left in the day for some higher-fat foods in the diet to still have the total fat percentage at or below 35%. There is also plenty of room left for some foods higher in saturated fat that still leaves the total saturated fat percentage at or below 7%. In terms of calories, 4 ounces of whole milk only provide 75 calories or 4% of the day's calories. So we believe that smaller serving sizes are part of the solution to these nutritional concerns.

A second part of the solution involves selection of 100% grass-fed milk. Grass feeding is unlikely to mean less total fat or less saturated fat in the milk, but it is likely to mean higher total fat quality, including higher quality saturated fat. Whole milk that is 100% grass-fed gets about 25% of its fat from oleic acid, the monounsaturated fatty acid that is the primary fat in olive oil. It also contains about half as much short-chain and medium-chain saturated fat as long-chain saturated fat, and these short-chain and medium-chain fats are typically considered to be beneficial to our health rather than detrimental. Finally, 100% grass-fed cow's milk contains substantial amounts of CLA (conjugated linoleic acid), which has been shown to provide benefits to our cardiovascular and immune systems. These fat quality-related benefits of 100% grass-fed milk are another reason we recommend its selection over other milk types.


While we believe that whole cow's milk from 100%-grass fed cows can help lessen some of the concerns about this food, we understand how controversial it remains and we respect the decision of many individuals to avoid it in their meal plan. We do not consider intake of cow's milk to be mandatory for anyone. At the same time, however, we recognize that some people do well when including it in their diet, and we want to provide as accurate information as we can about this controversial food.