Grilled tofu on a plateShare on Pinterest
The Picture Pantry/Offset Images

You’ve probably heard a lot of things about soy over the years — some positives and some negatives.

Now that you’re pregnant, you might be wondering if including soy in your diet is safe for you and your growing baby.

The good news is that you can enjoy foods that contain soy, at least in moderation.

Here’s more about what exactly this means, some benefits and potential risks of soy, and which foods are best to eat when you’re pregnant.

Soy is an ingredient found in a variety of foods. You’ve probably seen it on labels for veggie burgers, tofu, or the obvious — soy milk.

It comes from soybean plants and is considered a legume. Soybeans are a solid source of plant protein with low saturated fat and a hefty dose of dietary fiber.

Common soy foods include:

  • Edamame. Edamame are immature soybeans that can be boiled and salted before eating.
  • Tofu. Soybean curd that’s made from curdled soy milk, tofu may come packaged in bricks with different textures (silken, firm, extra firm) and can be flavored during cooking.
  • Tempeh. This is fermented soybeans mixed with rice, millet, or other grains and pressed into a cake. Like tofu, tempeh can be flavored with marinades and used in a variety of dishes.
  • Textured soy protein. Also called TSP or TVP, textured soy protein is and made from textured soy flour or soy protein concentrates. It’s high in protein and dietary fiber and must be hydrated (chewy texture) before consumption.
  • Processed faux-meat products. Veggie burgers, veggie nuggets, soy hot dogs, soy bacon, and so on are all examples of faux meat. A variety of vegetarian and vegan meat substitutes are made using soy as a base.
  • Soy milk. Refrigerated or shelf-stable soy milk is made by soaking, blending, and straining soybeans and water. Soy milk can be unsweetened, sweetened, flavored (chocolate, for example), or fortified. You may also see soy creamers and other soy dairy products, like yogurts or cheese.
  • Miso paste. This is a salty paste made with fermented soybeans. Miso paste is used in cooking for added flavor (for example, miso soup).
  • Soy sauce. You’re likely familiar with soy sauce, a salty liquid made from fermented soybeans. You may also see versions called shoyu, teriyaki, or tamari. Each sauce contains different ingredients along with the soy.
  • Soy nuts. Soy nuts are roasted soybeans with a nutty flavor. They’re high in protein and fiber. You may even see roasted soy nuts ground into a peanut butter–like paste.

You may have noticed that some of these foods are fermented. There’s evidence to suggest that fermented soy products may be easier to digest than their unfermented counterparts, according to a 2019 research review.

During the fermentation process, microbial enzymes help break down proteins and may improve the nutritional quality of the food and its ability to be absorbed by the body.

People living in Asia tend to consume more soy than people living in other parts of the world. Researchers claim in a 2020 analysis that this may be one reason these same populations tend to have a lower incidence of things like heart disease, stroke, and cancer.

But what are the benefits specific to pregnancy?

Better mood

Eating soy foods may protect against depression in pregnancy.

One particular 2018 study in Japan surveyed more than 1,700 women about their mood and consumption of soy. The food that showed the most benefit was miso paste. Soy milk, on the other hand, didn’t show much benefit.

Blood sugar control

Those with gestational diabetes may find help from soy with their blood sugar and cholesterol levels.

Participants in one 2015 study consumed 50 grams of soy each day after week 26 in pregnancy. The group was small (68 women), so researchers suggest speaking with your doctor before changing your diet dramatically.

Source of vegetarian protein

You should aim to get at least 60 grams of protein each day during pregnancy.

Soy is a good choice for plant protein and can be especially useful to vegetarians and vegans who need to boost their nutritional intake during pregnancy or otherwise.

Protection against anemia (or not)

Anemia is common in pregnancy and may cause fatigue, weakness, headache, and more.

While an older 2008 study didn’t specifically focus on pregnancy, it did associate eating tofu regularly with lower rates of anemia in both men and women.

However, data is mixed. If you do have anemia, talk with your doctor about what to do about it.

Related: 13 foods to eat when you’re pregnant

Things get a little tricky surrounding soy and a certain compound it contains, called isoflavones. These are plant estrogens (phytoestrogens).

This compound is similar to the hormone estrogen that’s typically associated with female sex development, the menstrual cycle, and pregnancy.

Experts aren’t sure whether phytoestrogens work in the body the same way that estrogen does, and research has yielded conflicting results.

Other potential issues with soy include:

Toxic minerals

There is limited research, such as a 2012 study, that suggests soy foods may contain minerals or heavy metals, like cadmium, that are considered toxic.

Researchers determined that eating tofu may lead to notable concentrations of cadmium in the urine of premenopausal women. The other major risk factor for excess cadmium is smoking.

That said, cadmium is found in other foods, including ones that contain important benefits for pregnancy, like shellfish and legumes. If you were to avoid everything that contained cadmium, you’d miss out on a lot of the good stuff, too.

A few other things to be aware of include:

  • Aluminum. Some sources, like the Deirde Imus Environmental Health Center, say that tofu and other soy foods may contain aluminum. This is concerning because aluminum may act as a neurotoxin. However, there are no studies to back up these claims. Also, aluminum is found naturally in many fruits and meats.
  • Genetically modified organisms (GMO). In the United States, some 94 percent of soy crops cultivated are GMO. Some argue that GMO crops may have negative impacts on health, like being more allergenic or toxic, or having lower nutritional content.
  • Absorption issues from phytic acid. Soy and other legumes contain phytate (phytic acid), which is considered an antinutrient. This acid may hinder the absorption of some vitamins and minerals, like iron, zinc, magnesium, and calcium.
  • More absorption issues from lecithins. Soy, beans, and peanuts also contain lecithins — another antinutrient — which may also impact the absorption of calcium, iron, phosphorus, and zinc.

There is some research, including a 2013 analysis, surrounding soy and a particular urological condition called hypospadias presenting at birth.

This condition is marked by the opening of the urethra being located on the underside of the penis instead of at the tip. It’s generally not considered dangerous and can be corrected with surgery.

And while hypospadias can be caused by hormones or exposure to chemicals during pregnancy, most cases don’t have a clear cause or may be genetic. More study is needed on soy and its potential role in this condition.

Another 2016 study on rats suggests that exposure to high levels of soy during the prenatal period may suppress a baby’s immune system. The study also showed that higher exposure to soy also meant lower birth weight.

However, this effect was only noted in female offspring. Plus, there haven’t been studies in humans to confirm that these effects are the same for people.

Last, there is some 2012 research surrounding exposure to phytoestrogens during pregnancy and infancy and their impact on the reproductive health of babies. Potential concerns surround early puberty and reproductive tract issues in both males and females.

Keep in mind that most of the significant evidence has been observed in studies on animals and not humans.

You may consume soy in moderation without needing to worry about potential risks, according to the guidance published by the American College of Obstetricians and Gynecologists and the U.S. Soybean Export Council.

However, there are no official guidelines on just how much you can eat.

Examples of moderate amounts of soy are:

  • 1 cup of soy milk
  • 1/2 cup of tofu
  • 1/2 cup of tempeh
  • 1/2 cup of soy meat substitute
  • 1/2 cup of soybeans

That said, every person is different, and your doctor may have a specific recommendation for you. If you regularly consume foods containing soy, speak with your doctor about how much is safe for you to eat during pregnancy.

You may eat all types of soy, but fermented varieties (like tempeh, miso, etc.) may be more easily digested, according to a 2019 research review.

Related: Nutritional needs during pregnancy

If soy is a new food for you, you might be wondering how to incorporate it into your diet.

Foods like tofu and tempeh are preferable to processed soy foods like veggie nuggets or soy hot dogs. Processed foods may contain added ingredients and less nutritional value than their whole food counterparts.

Ways to eat soy include:

  • baked tofu tossed into a salad with your favorite dressing
  • pan-fried tempeh in a stir-fry with your favorite sauce
  • soy milk poured into your favorite cereal
  • edamame beans added to your favorite vegetable dish
  • soy protein in place of ground beef in chili

Tofu can take on the flavor of whatever marinade or sauce you put it in. To get the most flavor infused in your tofu, you’ll want to use extra firm tofu and be sure to drain, press for 15 minutes in a tofu press, and then marinate for at least 24 hours before cooking.

Soy can be a healthy part of your pregnancy diet. If you have concerns about how much soy you should eat, speak with your doctor.

Sticking to just a serving or two per day is likely safe and may even give you some added health benefits.

Be sure to balance the rest of your diet by eating fresh fruits, vegetables, whole grains, and other lean proteins, as well as by drinking plenty of water.