If our 2019 Food and Health Survey and perhaps many conversations you’ve had yourself about food this year are any indication, plant-based protein is big and its presence in our dietary lexicon is on the rise. Soy foods have been a key player in this arena for decades, and they’re seeing even more attention as part of a new wave of plant-centric products.
Since soy is so versatile, we’re launching a four-part series on the basics of soy foods. The first article in this series focuses on whole soybean food products, the second article discusses soy-derived ingredients used in many familiar foods, and the third homes in on soybean oil. We wrap things up with our fourth article, which looks at how soy foods impact our health.
What is soy?
Soy is technically classified as a legume, a group of plants whose seeds grow in enclosed pods, like peas and peanuts. But soy’s nutritional content sets it apart from most others in the legume family: Soybeans are much higher in protein and fat and lower in carbohydrates than other legumes. In addition, unlike other plant protein sources, soy is considered a complete protein since it contains each of the essential amino acids our body needs for cell metabolism, building and repairing tissues, and providing energy. In addition to its high protein content, soy is a source of fiber, polyunsaturated fats, vitamins and minerals. It’s also a plant source of omega-3 fatty acids, which are known for their cardioprotective effects. Compared with other legumes, soybeans contain more calcium, iron, magnesium, and potassium, all of which have been identified as under-consumed nutrients in the American diet. Lastly, soy provides a high concentration of isoflavones, which are plant-derived compounds that can behave like a weaker form of human estrogen and exert positive effects on our health.
Examples of whole soybean foods
Foods made from an entire soybean can be referred to as “whole soybean foods.” Let’s look at a few common options:
- Soybeans We’ll start simple: soybeans that have been removed from their pod can be found either dried or canned. The yellow and black varieties are the most common. One half-cup serving of cooked soybeans contains about 150 calories, 16 grams of protein and 5 grams of fiber.
- Edamame The contents of the little green pods we snack on at sushi restaurants are soybeans harvested while they’re still a little immature. They’re soft and have a mild flavor. In one cup of shelled edamame there are 8 grams of fiber, which is one-fifth of the daily recommendation of fiber for men and almost one-third of the daily recommendation of fiber for women.
- Soy nuts Roasting soybeans draws out their water content, turning them into small, crunchy “nuts” that can be eaten as a snack or to add texture to a salad or trail mix. Since most of the water has been removed, a serving of soy nuts is higher in calories than the same amount of edamame or soybeans—but they’re also higher in protein and several vitamins and minerals, including calcium, iron and B vitamins. Soy nuts can also be used to make soy nut butter, an alternative to peanut butter.
- Soymilk This dairy alternative can be made in a few different ways. One is by soaking soybeans in water and then grinding, cooking, and filtering the mixture to yield a milk-like liquid. Soymilk can also be made by mixing soy flour or soy protein solids with water (more on those later). Many soymilks are also pasteurized, homogenized and/or sterilized for food safety purposes, and some have added flavors or stabilizers, which help to maintain product quality. Many soymilks are fortified with nutrients like calcium, vitamins A and D, and B vitamins. Like other soy products, they provide protein, iron, fiber and bioactive compounds like isoflavones. Soymilk is often an ingredient in soy-based yogurt, cheese alternatives, frozen desserts and many other foods.
- Tofu Of all soy foods, tofu is probably what comes to mind most often when we think of plant-based protein. It’s made by solidifying (also known as coagulating) the protein and oil in soymilk and then pressing the liquid out to get a solid block of tofu. Different types of tofu are based on how much liquid remains in the finished product: silken tofu has more water and therefore a softer shape and texture, while firm and extra-firm tofu have had more liquid removed and therefore maintain their shape better when cut and cooked.
- Tempeh Tempeh can be described as a fermented soybean cake, made by combining cooked soybeans with a mold that binds the beans together. Tempeh can be made from soybeans alone, and it is often combined with other grains like brown rice and barley.
- Miso This paste made from fermented soybeans, salt and a strain of fungus is a staple of Japanese cuisine, where it’s used for everything from miso soup to sauces and as part of main dishes. There are several different types of miso that vary based on their ingredients (strictly soybeans or the addition of other grains) and their degree of fermentation. Common varieties include white, yellow and red miso. Miso paste can contribute small amounts of vitamins and minerals, although people trying to watch their salt intake should be aware of its high sodium content.
- Soy Sauce Traditionally, this pantry staple is made by fermenting soybeans and wheat with salt and a fermenting compound like a yeast or mold. After fermentation, the mixture is pressed and the liquid is pasteurized and bottled. More often, though, it’s made through a chemical production in which soybeans are heated and mixed with an acid that breaks down the soy and wheat proteins into amino acids. Like miso, soy sauce is particularly high in sodium—just one tablespoon meets over half our daily needs.
- Natto To many, natto may be the least familiar food on this list. It’s a popular food in Japan made by fermenting soybeans with a species of bacteria called Bacillus subtilis. It has a distinct consistency best described as “slimy,” a pungent smell and a nutty taste. A one-cup serving of natto has 34 grams of protein, 9.5 grams of fiber and 15 grams of iron. It’s rich in potassium, phosphorus, magnesium and calcium, among other nutrients, and is also thought to contain probiotic bacteria.
As you can see, whole soybean foods are a diverse and nutritionally powerful group. But what about soy-derived ingredients, like soy protein isolates and concentrates, which are found in many packaged foods? We’ll explore these uses for soybeans in the next article in this series.