Soymilk: The Super Plant Milk
A spin down the supermarket dairy aisle today looks vastly different then it did, say, 10 years ago. Crowding out the dairy milk, you’ll find an increasing variety of plant milks made from just about every grain, nut, and seed, including almonds, flax, hemp, cashew, coconut, peanuts, oats, peas, and rice. In fact, the sales of plant-based milks are up 9% in the U.S., now comprising 13% of total milk sales. (1) These days, plant milks are emblazoned with clever packages and names, such as Ripple, Malk, and Good Karma. But long before these new age plant milks sprang to life, soymilk was the standby plant milk in markets. And it was around long before that—soymilk has been part of traditional diets for centuries.
What is Soymilk?
What is the creamy, nutty liquid, which is the most widely consumed non-dairy milk worldwide? (2) Soymilk—an aqueous, white, creamy extract produced from soybeans—started as a traditional Chinese food, and is actually an important step in the making of tofu, which is an important foodstuff in China and Japan over the centuries. (2, 3) Historically, soymilk was made by soaking white soybeans in cold water, grinding them between stones into a slurry, and filtering it through a sieve to make a “milk”. (2) In Asia, this soymilk was then used to make the nutritious staple tofu, by pouring the soymilk into a kettle to heat with a coagulant. The coagulant traditionally used was nigari, a natural substance—rich in calcium and magnesium salts—obtained from salt marshes. The coagulation of the soymilk created curds, which were formed into blocks in boxes, and then rinsed and compressed into “cheese-like” tofu. (2) The modern tofu process today follows right along with this ancient technique, though with larger, more modern equipment and isolated coagulants.
As in the case for tofu-making, the current process of making soymilk is not all that different from former techniques, albeit with larger, more modern equipment. In fact, you could make soymilk in your kitchen with a blender, cheesecloth, and strainer, if you were so inclined. Today, soymilk is made by sorting soybeans to remove debris or damaged seeds, washing and soaking the soybeans for 12 hours, manually dehulling the soybeans, grinding them in a mechanical blender, and expressing the mixture in a ratio of 3:1 (water to beans, by weight). The soymilk is then formulated with additives (if they are part of the recipe), pasteurized, and packaged. (3)
The History of Soymilk
You can trace soymilk back to 1365 in China, when it was first documented by Han Yi under the name doufujiang (soymilk), according to William Shurtleff and Akiko Aoyagi, who have spent a lifetime recording the history of soymilk for the Soyinfo Center in California in a nearly 3000-page 2013 sourcebook. In this book, they report a timeline for the history of soymilk, which I share here. Only in China has soymilk long been used as a beverage, and it was probably in regular use there by the Qing Dynasty in 1640. It wasn’t until 1704 that the word soymilk appeared in English by the missionary Domingo Fernandez Navarrete in his book A Collection of Voyages and Travels. In 1896, Henry Trimble first referred to soymilk in the U.S. in the American Journal of Pharmacy; in the following year it was first referred to by the USDA as soy-bean milk. Soymilk also made its way to other Asian cultures, such as Vietnam and Japan, in the late 1800s and early 1900s. In 1909, the first soy-based infant formulas and soymilk were developed in the U.S. by a pediatrician. The world’s first soy dairy was founded in Paris in 1910, along with an application for the patent of the world’s first official soymilk. In 1917, soymilk began commercial production in New York City. In the early 1900s, the Seventh-day Adventist organization began their long-time appreciation for soymilk as part of their health message by launching La Sierra Soy Milk in California. By 1929, bottled soymilk was widely available in China, with factories churning out a thousand bottles a day. The first calcium-fortified soymilk was created in the U.S. in 1931 by Seventh-day Adventists for Madison Foods. Sobee—the world’s earliest known soy-based infant formula—was produced in Evansville, Indiana in 1936. By 1950, soymilk had entered the modern era, as it was marketed in bottles much like soft drinks. Those familiar Tetra Paks used for soymilk were launched in 1967, eliminating the need for refrigeration. By the 1970s and 1980s, soymilk became a popular beverage through out Asia, Europe, Australia, and U.S. During this period, processing became refined to a “milk-like” taste and appearance by numerous manufacturers, such as Alpro, Eden Foods, Vitasoy, Westbrae, Edensoy, and Pacific Foods—by 1991 there were at least 35 processors or marketers in the U.S., with production of 9.8 million gallons, and annual growth of up to 20%. By 1993, more than 200 scientific journal articles about soymilk had been published in English, and at least 80 patents had been issued. In 1996, the beverage made inroads when Silk by White Wave was the first U.S. soymilk to be sold in the dairy case in a milk carton, becoming the superstar of the soymilk world. (2)
Soymilk, Part of Traditional Diets
In China, soymilk was traditionally served hot, ladled from a cauldron for breakfast, sweetened, or used as a base for a soup. It was not used as an infant food. (2) Sherene Chou, MS, RD, a plant-based dietitian and sustainable food and nutrition consultant based in Los Angeles, says, “Soymilk is a big part of breakfast in Chinese culture traditionally and present day, which tastes completely different than what you find in U.S. grocery stores. The soymilk served traditionally is from soybeans soaked overnight, blended and strained, much like how homemade nut milks are made. It can be served hot or cold and sweet or savory.”
Cox reports that in the U.S., there is an impression that everyone drinks cow’s milk, but that’s never been the case—many cultures do not drink dairy milk. Scientists believe that the ability to digest lactose—allowing early Europeans to drink milk without getting sick—first evolved in the dairy farming communities in Central Europe. However, most adults worldwide do not produce the enzyme lactase that gives them the ability to digest dairy milk. (4) Historically in Asia, livestock were considered work tools rather than a source of milk, thus dairy was not part of cultural traditions.
Soymilk has long been a staple in diets among Seventh-day Adventists, as well as vegetarians, and vegans. The trend continues, along with the rise in popularity of plant-based diets. However, today’s alternative, less-nutritious plant milks are increasingly taking the place of soymilk in these diet patterns.
Soymilk Nutrition
Soymilk has long held the reputation as a nutritious alternative to dairy milk—being very similar in nutrition value. “There are many fortified soymilk products on the market today that are almost nutritionally identical to regular dairy milk, but with the advantage of containing no cholesterol or saturated fat,” says John Westerdahl, PhD, MPH, RDN, plant-based nutrition expert and radio talk show host.
One of the most significant nutritional contributions of soymilk is protein content. “Although other plant milks may provide a variety of benefits, they do not naturally contain as much protein per serving, unless added to the milk as a blend. Soymilk contains all of the essential amino acids,” says Chou, adding that one 8-fluid ounce glass contains 7 grams of protein, compared to many plant milks that contain 0-1 grams of protein per serving.
In addition to protein, fortified soymilk can provide a good nondairy source of calcium, vitamin D, and vitamin B12 to the diet, says Westerdahl. “The key is to look for fortified soymilks that contain these nutrients,” he advises.
“Soy is unique in that it contains the antioxidant isoflavones genistein and daidzein,” says Ginger Hultin, spokesperson for the Academy of Nutrition and Dietetics, and owner of Champagne Nutrition® LLC. “These compounds have been linked to cardiovascular benefits, bone health, and even some anti-cancer benefits.” One serving of soymilk contains 25 milligrams of isoflavones.
Soymilk and Health Science
What have we learned from the research on soymilk and health? Soy expert, Mark Messina, PhD, MS, Executive Director of the Soy Nutrition Institute, says that there have been 8 reviews in the last three years on plant milks that included soymilk. (5) The bottom line, according to Messina, is that “there is nothing that makes cow’s milk superior to soymilk when fortified. Soymilk is the most nutritionally comparable plant milk to cow’s milk, which is mainly distinguished by its protein content. When you are buying something like Silk Original soymilk, there is no reason to think that in any way it is inferior from a nutritional standpoint to cow’s milk,” says Messina. “The difference is that soymilk is fortified with nutrients to make it more comparable to cow’s milk.”
When it comes to protein quality, the PDCAAS (protein digestibility corrected amino acid score) for soymilk is the same as cow’s milk, says Messina. “Cow’s milk is higher in leucine, but the latest information shows that, probably over the long-run, protein type doesn’t have much of an impact on gains in strength and lean body mass. For those wanting to increase muscle and strength, making sure protein intake is adequate is key.”
Fortified soymilks typically contain calcium and vitamin D at levels similarly found in dairy milk. Messina reports that, like cow’s milk, soymilk is fortified with vitamin D—using vitamin D2 instead of D3. “Vitamin D3 may be the more potent form, but this may not matter much from a practical consequence,” says Messina. “For calcium availability, three studies have investigated this and found that soymilk is the same as cow’s milk.”
One intriguing area of comparison is fatty acid content. Messina says that when you compare soy to whole milk—a fair comparison because consumers are choosing whole milk more often—dairy milk is higher in fat and saturated fat, but there is controversy there because fat in dairy may not adversely affect cardiovascular risk after all. “But if you assume that cow’s milk has a neutral effect, soymilk would still have an advantage because it is so high in polyunsaturated fats, which should reduce heart disease risk.”
Potassium is fairly high in both soymilk and cow’s milk, according to Messina. As for the glycemic effect of soymilk, he says that research shows similar effects as dairy milk. “Soy has some iron in it, which could be a factor, but it is a small amount. Traditionally we view nonheme iron as not well absorbed, but newer data suggest that it is better absorbed than acute studies suggest.” Interestingly, chronic consumption of a high-phytate diet mitigates the inhibitory effect of phytate on iron absorption. Also, according to Messina, much of the iron in soybean is in the form of ferritin, which may be insensitive to inhibitors of iron absorption. Messina notes that soy is loaded with phytate and oxalate, yet the calcium availability is as good as cow’s milk.
One study showed that there was an approximate 5% reduction in blood cholesterol levels associated with soymilk intake compared to dairy milk, which is related to both the soy protein and fatty acid content of soymilk, according to Messina. “It may also have a hypotensive effect. There is data that consuming soy early in life reduces risk of breast cancer later on in life. There is a strong hypothesis that just one serving per day is all girls need to consume, as long as it is made from whole soybeans.”
Consumer Confusions
Despite the positive evidence on soymilk, it has come under fire in recent years. Soy consumption has been linked with reduced risks of heart disease and breast and prostate cancer, yet people are shunning it over fears that isoflavones may result in untoward health effects, such as on the breast and thyroid. (6)
“Unfortunately, there has been quite a lot of misinformation around soy, so I have seen fewer options for soymilk in grocery stores over the years as more alternatives become available. I think consumers are fearful of soy, but wrongfully so,” says Chou.
Hultin agrees, adding, “I wish these myths would end but I still hear people fearing that soy is an ‘estrogen’, and they cite fear that it causes cancer in women or feminizing effects in children or men, though all of that is completely untrue. Some of these myths come from very old research in animal studies. Animals do metabolize phytoestrogens differently than humans do.”
Eco Benefits of Soymilk
Another reason to welcome soymilk is for environmental benefits. (7) Westerdahl says, “Soymilks have a positive affect on our environment, as they do not require the amount of natural resources, such as water and food production, needed to raise dairy cows. Soymilk also eliminates the waste issues produced by dairy cows that can also have a negative affect upon our environment.” It’s no surprise then that producing a glass of dairy milk creates almost three times as much greenhouse gas emissions as soymilk, points out Chou. (7)
Making Recommendations for Soymilk
Dietitians can feel confident about recommending soymilk as part of a healthful diet for people who choose this option for numerous reasons, including personal dietary choices, plant-based eating styles, cultural food preferences, and food intolerances. According to the Dietary Guidelines for Americans 2015-2020, the Healthy Vegetarian Eating Pattern highlights fortified soymilk can replace dairy to support a plant-based eating pattern, says Chou. In addition, the USDA MyPlate allows for soymilk—the only plant-based milk listed—to replace a serving of dairy milk within that food group.
Hultin says, “I often recommend including unsweetened soymilk in coffee, lattes or tea, as a base for smoothies, or in cooking and baking. You can use it just like dairy milk in cereal or even for drinking on it’s own. I recommend soymilk over other types of plant-based beverages because I like the higher level of protein that it has over almond, rice or coconut. It has a nice, thicker consistency that mimics regular dairy milk. Anyone wanting to switch over or simply include soymilk as part of their diet should find it relatively easy to add in or replace.”
References
1. Watson E. US retail sales of plant-based milk up 9%, plant-based meat up 24% YoY. Food Navigator. https://www.foodnavigator-usa.com/Article/2018/07/30/US-retail-sales-of-plant-based-milk-up-9-plant-based-meat-up-24-YoY. Published July 30, 2018. Accessed February 15, 2019.
2. Shurtleff W, Aoyagi A. History of soymilk and other non-dairy milks (1226 to 2013): Extensively annotated bibliography and sourcebook. Soyinfo Center. https://drive.google.com/file/d/1-Ot-XUZcGeTPnY7ZIFXFFNL8rZJoK-Lx/view. Published 2013. Accessed February 15, 2019.
3. Kohli D, Kumar S, Upadhyay S, Mishra R. Preservation and processing of soymilk: A review. International Journal of Food Science and Nutrition. 2017;2(6):66-70. file:///Users/sharon/Downloads/2-6-26-996.pdf
4. Milk drinking started in central Europe. UCL. https://www.ucl.ac.uk/news/2009/aug/milk-drinking-started-central-europe. Published August 28, 2009. Accessed February 15, 2019.
5. Vanga SK, Raghavan V. How well do plant based alternatives fare nutritionally compared to cow’s milk? Journal of Food Science and Technology. 2018;55(1):10–20. https://link.springer.com/article/10.1007%2Fs13197-017-2915-y
6. Messina M. Soy and Health Update: Evaluation of the Clinical and Epidemiologic Literature. Nutrients. 2016;8(12):754. doi: 10.3390/nu8120754
7. Poore J, Nemecek T. Reducing food’s environmental impacts through producers and consumers. Science. 2018;360(6392):987-992. doi: 10.1126/science.aaq0216
Image: Super Berry Soy Chia Pudding, Sharon Palmer, MSFS, RDN
This article written by Sharon Palmer first appeared in Today’s Dietitian.