The dairy industry has long marketed dairy as beneficial to health, ingraining slogans like “Got Milk?” and “Milk – It Does a Body Good” into the minds of consumers. For decades, the United States Department of Agriculture (USDA) has recommended that both children and adults consume dairy products daily. Many see milk as one of the easiest ways to meet their needs for some minerals, vitamins, and protein. A cup of milk contains around 28% of the RDI for calcium and is often fortified with vitamin D and A. Milk is also a complete protein source, which means it contains all of the essential amino acids in adequate amounts. However, the nutrients contained in milk can vary greatly depending on its source and fat content, and fattier products like cheese and butter also have a much different nutrient composition than milk. Despite dairy’s nutrient content, opinions surrounding dairy intake are mixed, with more and more evidence questioning its health benefits and pointing towards health risks. In this post, we’re going to explore 7 common questions about dairy.
1. Is it natural for humans to consume dairy products?
Humans are the only species to consume any type of milk into adulthood, as well as the only to drink the milk of other animals. From a biological standpoint, cow’s milk is produced as food for a growing calf. Therefore, the nutrient composition of cow's milk is naturally designed for a growing calf, not humans. Because of this, one of the most common arguments against dairy products is that it is unnatural to consume them. Throughout history, humans only drank mothers milk as infants and then ceased to consume dairy as adults. However, for the past few thousand years, some cultures have incorporated regular dairy into their diets, and studies have shown that some people’s genes have adapted to eating dairy. But because dairy isn’t the sole source of the nutrients it provides, dairy is not necessary for optimal health.
2. Does dairy build strong bones?
Dairy contains important nutrients for bone health, including phosphorus, magnesium, vitamin D, protein, and perhaps most importantly, calcium. Both vitamin D and calcium are needed in adequate amounts to prevent bone loss and osteoporosis. While dairy is a source of calcium, evidence linking dairy and bone health is conflicting. A systematic review and meta-analysis showed that the risk of osteoporosis and hip fracture decreased with dairy intake in some studies, but not in others. But, it is interesting to note that osteoporosis and bone fractures are the most common in countries where people consume the most dairy products: the United States, the United Kingdom, Sweden, and Finland. So, while the results are mixed, the evidence against dairy for bone health may leave you feeling uneasy about including it in your diet. The good news is that you can easily get your calcium, phosphorus, magnesium, and protein from plant-based sources! Many scientists and doctors agree that it’s best for us to get key nutrients from sources other than dairy, like from vegetables, fruits, beans, whole grains, nuts, seeds, and seaweed. Of note, calcium absorption from dairy is about 30 percent. The calcium absorption from soy is similar, about 30 percent. However, the amount of calcium absorbed from greens such as kale, broccoli, and bok choy can be as high as 60 percent! Vitamin D can be challenging to obtain for vegans and non-vegans alike. A daily dose of sunshine is your best source of vitamin D. Consider supplementation after getting vitamin D levels checked by your healthcare provider if you don't get some daily sunshine.
3. Does dairy cause digestive issues?
Lactose, a milk sugar composed of the simple sugars glucose and galactose, is the main carbohydrate in dairy. It is also present in human breast milk. To break down lactose, our bodies need to produce the digestive enzyme lactase. While an infant’s body produces lactase, lactase production slows down post-infancy in almost 75% of the world’s population. The resulting inability to break down lactose, called lactose intolerance, leads to digestive symptoms like bloating, nausea, vomiting, and diarrhea when dairy products are consumed. Lactose intolerance is common in Africa, Asia and South America and less prevalent in North America, Europe and Australia. These days, if you have difficulty digesting lactose, you’re in luck! Plant-based dairy products made with soy, nuts, and other creative ingredients are all over the supermarkets and great alternatives for those with lactose intolerance.
4. Does dairy increase the risk of cancer?
Dairy consumption may increase your risk for certain cancers, possibly due to sex hormones like estrogen and other growth factors that are naturally present in milk. A study of over 20,000 men found that those having 2.5 servings of dairy products each day had a 34% increased risk of prostate cancer compared to those consuming little or no dairy products. Another study of almost 50,000 showed similar results, with men having 2 or more milk servings per day having a 60% increased risk of prostate cancer. However, a meta-analysis showed that overall, the association between dairy and prostate cancer is inconsistent.
While studies are limited looking at dairy's direct effect on breast cancer, numerous studies show that a high-fat, Western diet is associated with higher incidences of breast cancer. These studies show a link between unhealthy dietary patterns containing foods higher in fats (processed foods, meat, dairy, and animal fat and protein) and breast cancer.
When considering other types of cancer, many associations between dairy intake and cancer risk have only been examined in small cohort studies with data being inconsistent. However, Dr. Colin Campbell, author of The China Study, found in his research (one of the most comprehensive studies of nutrition and health ever conducted) that casein, the protein in dairy, is responsible for cancer initiation and tumor growth. You can learn more about his research here.
5. Does dairy increase the risk of heart disease?
To many public health officials, the biggest concern with dairy products is its high saturated fat content. According to the National Health and Nutrition Examination Survey (NHANES), cheese is the biggest source of saturated fat in America. The American Heart Association (AHA) says that eating foods with saturated fats raises the level of cholesterol in your blood, which can increase your risk of heart disease and stroke. But, recent evidence suggests that the role of saturated fat in heart disease may be exaggerated. Some research shows that a high intake of refined carbohydrate-rich foods including sugars may be the root of increased rates of heart disease. Because of the inconsistent evidence, Harvard researchers followed more than 43,000 men from the Health Professionals Follow-Up Study, 87,000 women in the Nurses Health Study and 90,000 women in the Nurses’ Healthy Study II to look at the relationship between dairy fat and heart disease risk. While various high-fat dairy foods were not found to increase heart disease risk*, when dairy fat was replaced with the same number of calories from vegetable fat, the risk of cardiovascular disease dropped by 10% - 24%. Furthermore, replacing the same number of calories from dairy fat with healthful carbohydrates from whole grains was associated with a 28% lower risk of cardiovascular disease. Public health guidelines advise limiting saturated fat intake, which includes high-fat dairy products.
*Important note: dairy was compared to a diet that typically contains high amounts of refined carbohydrates and sugars.
6. Is dairy production humane?
Recent dairy-promoting campaigns display photos of “happy” cows and other idealized pictures of the modern dairy industry. But in reality, only a small percentage of modern farms produce milk from cows who are allowed to graze outside. The vast majority of cows live inside steel sheds, frequently connected to a milking machine, with little to no access to the outdoors—otherwise known as factory farms. Cows are artificially impregnated annually, allowing them to produce more than 20,000 pounds of milk per year (anything but natural). They also may be fed antibiotics and feed that is contaminated with herbicide or pesticide residues and injected with growth hormones. Male calves born to these cows are removed right away, often shot when born, placed in crates to be raised as veal, or raised until they are 2 years old for beef. Dairy cows have a hierarchical social structure and communicate by touch, smell, vocalizations, and body language. It is thought that cows can identify 50-70 different cows. The cow has a strong maternal instinct and is normally distressed by the removal of her calf. Both the calf and mother will make loud calls trying to locate each other after they are separated. The bottom line—cows, just like humans, can feel emotional and physical pain, especially when mama's baby is taken away at birth.
7. Does dairy production hurt the environment?
Meat and dairy companies contribute significantly to greenhouse gas emissions. In 2018, a study was released finding that the world’s top five meat and dairy producers combined emit more greenhouse gases than Exxon-Mobil, Shell, or BP. The combined emissions of the top 20 meat and dairy companies surpass the emissions for entire nations, like Germany, Canada, the United Kingdom, or Australia. Most of these companies are not taking adequate steps to reduce emissions, and are instead pushing for even more production. If this growth continues, meat and dairy companies could be responsible for 81% of global emissions targets as set by the 2015 Paris climate agreement. Not to mention, animal agriculture is responsible for massive deforestation causing destruction of natural plants' habitat (that feed us oxygen), indigenous people's homes, and indigenous animals' habitats, causing the extinction of many species. Up to 50,000 acres of forests are cleared by farmers and loggers per day worldwide, and the equivalent of over 10,000 football fields is destroyed each day in the Amazon alone.
Overall, while some of the existing research on the health impact of dairy is mixed, there are well-designed research studies linking dairy to lifestyle diseases. The ethical and environmental implications of dairy production? They're quite compelling. When choosing whether or not to include dairy in your diet, consider this: a well-balanced, plant-based diet can provide you with all the nutrients your body needs in amounts even higher than from dairy. Instead of dairy, try these plant-based sources to meet your nutrient needs:
Thiébaut AC, Kipnis V, Chang SC, et al. Dietary fat and postmenopausal invasive breast cancer in the National Institutes of Health-AARP Diet and Health Study cohort. J Natl Cancer Inst. 2007 Mar 21;99(6):451-62.
Xing MY, Xu SZ, Shen P. Effect of low-fat diet on breast cancer survival: a meta-analysis. Asian Pac J Cancer Prev. 2014;15(3):1141-4.
Hi! My name is Katie Philippi and I am a student in Georgia State University's Coordinated Program for Dietetics. I have loved getting the opportunity to learn more and more about food and nutrition, and have taken a special interest in sports nutrition, intuitive eating, and disordered eating. Outside of nutrition, I enjoy traveling and spending time outdoors with friends, cooking, and trying new restaurants whenever I get the chance!