April 2019 Issue

Soymilk’s Reign
By Sharon Palmer, MSFS, RDN
Today’s Dietitian
Vol. 21, No. 4, P. 18

Today’s Dietitian explores the history and nutritional attributes of this traditional nutrient-rich dairy alternative that continues to surge in popularity.

A spin down the supermarket dairy aisle today looks vastly different than 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, sales of plant-based milks are up 9% in the United States, 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?
This nutty liquid, which is the most widely consumed nondairy milk worldwide, is an aqueous, white, creamy extract produced from soybeans that started as a traditional Chinese food. It’s a key step in the making of tofu, which has been 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 “cheeselike” tofu.2 The modern tofu process today follows right along with this ancient technique, though with larger, more modern equipment and isolated coagulants.

As is the case for tofu making, the current process of making soymilk isn’t 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’re part of the recipe), pasteurized, and packaged.3

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 3,000-page 2013 sourcebook. In this book, they report a timeline for the history of soymilk, which Today’s Dietitian shares 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 Fernández Navarrete in his book A Collection of Voyages and Travels. Soymilk also made its way to other Asian cultures; some say it was in Vietnam as early as 1790, and Japan by circa 1900. In 1896, Henry Trimble first referred to soymilk in the United States in the American Journal of Pharmacy; in the following year, the USDA first referred to it as soybean milk. In 1909, the first soy-based infant formulas and soymilk were developed in the United States by a pediatrician. The world’s first soy dairy was founded in Paris in 1910, the same year an application was submitted 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 its 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 1,000 bottles per day. In 1931, Seventh-day Adventists created the first calcium-fortified soymilk in the United States 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 throughout Asia, Europe, Australia, and the United States. During this period, processing became refined to a “milklike” 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 United States, 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 WhiteWave was the first US 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 wasn’t used as food for infants.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 US 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.”

John Cox, executive director of the Soyfoods Association of North America, reports that in the United States, there’s an impression that everyone drinks cow’s milk, but that’s never been the case—many cultures don’t 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 don’t 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 wasn’t part of cultural traditions.

Soymilk has been a longtime staple in diets among Seventh-day Adventists, as well as vegetarians and vegans. While many individuals still drink soymilk, today’s alternative, less-nutritious plant milks are increasingly taking the place of soymilk in plant-based dietary patterns. This is unfortunate, as soymilk reigns supreme in nutrients over these plant milks.

Soymilk Nutrition
Soymilk has long held its reputation as a nutritious alternative to dairy milk, being similar in nutritional 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, CNS, FAND, a 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-oz glass contains about 7 g protein, compared with many plant milks that contain 0 to 1 g 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, Westerdahl says. “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, MS, RDN, CSO, a 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 anticancer benefits.” One serving of soymilk contains 25 mg 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 there have been eight reviews in the last three years on plant milks that included soymilk.5 The bottom line, according to Messina, is that “there’s 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’re buying something like Silk Original Soymilk, there’s no reason to think that in any way it’s inferior from a nutritional standpoint to cow’s milk. 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, Messina says. “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,” he says.

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,” he notes. “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 one compares soy with whole milk—a fair comparison because consumers are choosing whole milk more often—dairy milk is higher in fat and saturated fat, but there’s controversy there because fat in dairy may not adversely affect cardiovascular risk. “But if you assume that cow’s milk has a neutral effect, soymilk would still have an advantage because it’s so high in polyunsaturated fats, which should reduce heart disease risk,” Messina says.

Potassium is fairly high in both soymilk and cow’s milk, according to Messina. “Soy has some iron in it, which could be a factor, but it’s a small amount. Traditionally, we view nonheme iron as not well absorbed, but newer data suggest it’s better absorbed than acute studies suggest,” he says.

Interestingly, chronic consumption of a high-phytate diet mitigates the inhibitory effect of phytate on iron absorption. In addition, according to Messina, much of the iron in soybeans is in the form of ferritin, which may be insensitive to inhibitors of iron absorption. He notes that soy is loaded with phytate and oxalate, yet the calcium availability is as good as cow’s milk.

One study showed there was an approximate 5% reduction in blood cholesterol levels associated with soymilk intake compared with dairy milk, which is related to both the soy protein and fatty acid content of soymilk, according to Messina. As for the glycemic effect of soymilk, he says research shows similar effects as dairy milk.

“It also may have a hypotensive effect. There’s data that consuming soy early in life reduces risk of breast cancer later on in life. There’s a strong hypothesis that just one serving per day is all girls need to consume, as long as it is made from whole soybeans,” Messina says.

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 in 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,” Chou says.

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 effect on our environment, as they don’t 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 also can have a negative effect 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, Chou says.7

Making Recommendations
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 2015–2020 Dietary Guidelines for Americans, the Healthy Vegetarian Eating Pattern highlights that fortified soymilk can replace dairy to support a plant-based eating pattern. In addition, the USDA MyPlate allows for soymilk—the only plant-based milk listed—to replace one serving of dairy milk within that food group.

“I often recommend including unsweetened soymilk in coffee, lattes, or tea; as a base for smoothies; or in cooking and baking,” Hultin says. “You can use it just like dairy milk in cereal or even for drinking on its 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.”

— Sharon Palmer, MSFS, RDN, The Plant-Powered Dietitian, is a plant-based food and nutrition expert who recently received her master’s degree in sustainable food systems from Green Mountain College in Poultney, Vermont. She also serves as the nutrition editor of Today’s Dietitian.

References
1. Watson E. US retail sales of plant-based milk up 9%, plant-based meat up 24% YoY. FoodNavigator-USA website. https://www.foodnavigator-usa.com/Article/2018/07/30/US-retail-sales-of-plant-based-milk-up-9-plant-based-meat-up-24-YoY. Updated August 10, 2018. Accessed February 15, 2019.

2. Shurtleff W, Aoyagi A; Soyinfo Center. History of soymilk and other non-dairy milks (1226 to 2013): extensively annotated bibliography and sourcebook. 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. Int J Food Sci Nutr. 2017;2(6):66-70.

4. Milk drinking started in central Europe. University College London website. 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? J Food Sci Technol. 2018;55(1):10-20.

6. Messina M. Soy and health update: evaluation of the clinical and epidemiologic literature. Nutrients. 2016;8(12):E754.

7. Poore J, Nemecek T. Reducing food’s environmental impacts through producers and consumers. Science. 2018;360(6392):987-992.