Dairy Milk or Soy Milk:

A Sustainability and Nutrition Perspective

By Emily Powell

There seems to be a new milk substitute on the shelves each time I go to the grocery store. The most common (and least taboo, I suppose) is soymilk, but the list goes on from there—it seems that you can get a milky, watery substance out of almost anything from almonds to rice to cashews to coconuts to hemp to oats. I tend to wonder what it takes to produce these substitutes, and whether or not these substitutes could be considered friendlier alternatives to dairy milk. How much water/energy/arable land is needed? And are they as nutritionally balanced and fortified as naturally-occurring milk? From a sustainability/nutrition perspective, does a soymilk alternative compare to dairy milk like apples to apples?

It comes as no surprise that cows, dairy or beef, are energy-intensive, both in the amount of feed they require and the amount of water they consume – soy production is less impactful, but the production of milk from soybeans can’t be definitively identified. In terms of energy requirements, dairy production requires 14 calories of energy (traditionally fossil fuel-based) to produce one calorie of milk protein (for some perspective: one calorie of beef protein requires 40 calories energy, while one calorie of chicken requires 4 calories energy). The ratio for soy production is astoundingly more impressive: in conventional farming, 14 calories of energy would produce 44.8 calories of soy protein. The UN’s Food and Agriculture organization says the dairy industry accounts for nearly 4% of human-caused greenhouse gas emissions – milk, cheese, yogurt, etc. This feed often comes from corn, soy or grain; crops with which we could probably create a milk substitute. In addition, cows’ digestive systems produce a massively potent compound called methane, which, when released into the atmosphere, is twenty times more effective at trapping heat than the familiar climate change culprit carbon dioxide. However, in terms of greenhouse gas release, the production of soy releases less greenhouse gases than the extensive process needed to turn whole soybeans into soymilk (roasting, grinding, emulsifying, flavoring, fortifying). In this case, the grand total of greenhouse gas release might be more difficult to identify. Other sustainability aspects that could take years to discuss are the social implications of dairy cow agriculture and soybean farming, the environmental impacts of soybean monoculture, soil erosion, GMO engineering, and humane animal welfare. But for the sake of my sanity, let’s move on.
From a nutritional perspective, soybeans are a hearty plant-based alternative to animal proteins (see one of my previous articles for details), however, the nutritional content of soymilk commonly includes added sugars, added vitamins (to compete with the calcium and Vitamin D in milk), and a less-balanced fat/carb/protein ratio than dairy milk. A balanced macronutrient ratio provides different forms of energy for long-term sustenance – carbohydrates enable short-term metabolism for short-term energy, while fat/protein take longer to digest and therefore create a longer-term energy supply, keeping you satisfied for longer. In addition, all sugars in milk are naturally occurring and unrefined, unlike the sugars commonly added to milk substitutes for extra flavor. For the same number of calories, you get more protein from milk and a less-processed/refined beverage.
For more detail on the nutritional value of different milk alternatives, don’t take my word for it. Gander upon the nutritional fact charts on the side of the cartons. Look for fat content, protein content, and carbohydrates to see if it’s an adequately balanced ratio of about 40% carbs/30% protein/30% fat, along with the length of the ingredient list and the pronounceability of the ingredients (this can be a good indication of the naturalness of the ingredients and the amount of processing that was needed). Not all milk substitutes are created equal. Also remember that determining the sustainability of a product is not a cut-and-dry process – and though it might take less energy to produce soybeans, those soybeans might have had to travel thousands of miles to reach your glass, while the milk at your local, independent grocer came from a local farm down the road. The moving pieces never stop, and it’s only becoming more complex. Luckily, we have a wholesome snack of milk (or milk product) to fuel our continued investigations.
 
Emily’s exuberant passion for sustainability and sustainable nutrition stems from her everlasting love for the outdoors, people, dirt, and broccoli. As an undergraduate in the School of Sustainability at Arizona State University, Emily is working towards becoming a spokesperson for everyday sustainable food and lifestyle choices, including decisions on what foods you buy, where you buy them, and how you make the most of foods’ energy. Leveraging communication through writing, Emily has been recognized in competitions such as the DuPont Challenge and the Apprentice Ecologist Initiative for her essays on sustainability issues and initiatives, including Honeybee Colony Collapse Disorder and community gardens in elementary schools. Emily aspires to utilize relationships with other academic disciplines to plant the seeds of sustainability and nutrition principles in the young adults of her generation. She plans to earn her Registered Dietician credential and work either on the community or personalized sustainable nutrition level.