Tofu
Tofu is a food made of condensed soy milk that is pressed into solid white blocks in a process quite similar to cheesemaking. It is also know as bean curd. It originated in China. A cook discovered tofu more than 2,000 years ago by accidentally mixing a batch of fresh soy milk with nigari. Nigari is what remains when salt is extracted from seawater. It is a mineral-rich coagulant used to help tofu solidify and keep its form.
Most of the world’s soybeans are currently grown in the US, and a very large proportion is genetically modified (GMO). Be sure you verify that the tofu you buy is non-GMO and organic.
One 3.5-ounce serving of tofu has:
- Protein: 8 grams
- Carbs: 2 grams
- Fiber: 1 gram
- Fat: 4 grams
- Manganese: 31% of the RDI
- Calcium: 20% of the RDI
- Selenium: 14% of the RDI
- Phosphorus: 12% of the RDI
- Copper: 11% of the RDI
- Magnesium: 9% of the RDI
- Iron: 9% of the RDI
- Zinc: 6% of the RDI
In this serving size, there are 70 total calories, which makes tofu a highly nutrient-dense food. The micronutrient content of tofu can vary depending on the coagulant used. Nigari adds more magnesium while precipitated calcium increases the calcium content.
Like most plant foods, tofu contains several anti-nutrients.
- Trypsin inhibitors: These compounds block trypsin, an enzyme needed to properly digest protein.
- Phytates: Phytates can reduce the absorption of minerals, such as calcium, zinc, and iron.
Soaking or cooking soybeans can inactivate or eliminate some of these antinutrients. Sprouting soybeans before making tofu reduces phytates by up to 56% and trypsin inhibitors by up to 81% while also increasing protein content by up to 13%.
Fermentation can also reduce antinutrients. For this reason, fermented, probiotic soy foods, such as miso, tempeh, tamari, or natto, are low in anti-nutrients.
Soybeans contain natural plant compounds called isoflavones. These function as phytoestrogens, meaning that they can attach to and activate estrogen receptors in your body. This produces effects similar but weaker to the hormone estrogen. Tofu contains 20.2–24.7 mg of isoflavones per 3.5-ounce serving.
Scientists have also discovered that soy isoflavones can reduce blood vessel inflammation and improve their elasticity. One study found that supplementing with 80 mg of isoflavones per day for 12 weeks improved blood flow by 68% in people who were at risk of stroke.
Taking 50 grams of soy protein per day is also associated with improved blood fats and an estimated 10% lower risk of heart disease. In postmenopausal women, high soy isoflavone intake is linked to several heart-protective factors, including improvements to body mass index, waist circumference, fasting insulin, and HDL cholesterol.
Research shows that women who eat soy products at least once a week have a 48–56% lower risk of breast cancer. This protective effect is thought to come from isoflavones, which have also been shown to positively influence the menstrual cycle and blood estrogen levels.
Tofu contains saponins, compounds thought to have protective effects on heart health. Animal studies show that saponins improve blood cholesterol and increase the disposal of bile acids, both of which can help lower heart disease risk.
In fact, research shows that women who ate soy products at least once a week throughout adolescence and adulthood had a 24% lower risk of breast cancer, compared to those who ate soy during adolescence alone.
One frequent criticism of tofu and other soy products is that they may increase breast cancer risk. However, a two-year study in postmenopausal women who consumed two servings of soy per day failed to find an increased risk. Other studies report similar findings, including a review of 174 studies, which found no link between soy isoflavones and increased breast cancer risk.
One study observed that higher intakes of tofu were linked to a 61% lower risk of stomach cancer in men. A second study reported a 59% lower risk in women. A recent review of several studies in 633,476 people linked higher soy intake to a 7% lower risk of cancers of the digestive system.
Several recent test-tube and animal studies show that soy isoflavones may boost blood sugar control. In one study of healthy postmenopausal women, 100 mg of soy isoflavones per day reduced blood sugar levels by 15% and insulin levels by 23% For postmenopausal women with diabetes, supplementing with 30 grams of isolated soy protein lowered fasting insulin levels by 8.1%, insulin resistance by 6.5%, LDL cholesterol by 7.1%, and total cholesterol by 4.1%.
In another study, taking isoflavones each day for a year improved insulin sensitivity and blood fats while reducing heart disease risk.
- Bone health: Scientific data suggests that 80 mg of soy isoflavones per day may reduce bone loss, especially in early menopause
- Brain function: Soy isoflavones may have a positive influence on memory and brain function, especially for women over 65.
- Menopause symptoms: Soy isoflavones may help reduce hot flashes. However, not all studies agree.
- Skin elasticity: Taking 40 mg of soy isoflavones per day significantly reduced wrinkles and improved skin elasticity after 8–12 weeks.
- Weight loss: In one study, taking soy isoflavones for 8–52 weeks resulted in an average weight loss of 10 pounds (4.5 kg) more than a control group.
Eating tofu and other soy foods every day is generally considered safe. That said, you may want to moderate your intake if you have:
- Breast tumors: Due to tofu’s weak hormonal effects, some doctors tell women with estrogen-sensitive breast tumors to limit their soy intake.
- Thyroid issues: Some professionals also advise individuals with poor thyroid function to avoid tofu due to its goitrogen content.
However, a recent report from the European Food Safety Authority (EFSA) concluded that soy and soy isoflavones pose no concerns for thyroid function or breast and uterine cancers. Nevertheless, researchers agree that infants should not be exposed to soy isoflavones, which may disrupt the development of reproductive organs.
Although this has not been studied well in humans, some animal studies suggest that high amounts of soy may interfere with fertility.
If you have concerns, discuss soy consumption with your doctor.
How to Buy
Tofu can be purchased in bulk or individual packages, refrigerated or not.
You can also find it dehydrated, freeze-dried, jarred, or canned
Heavy processing is unnecessary to make tofu, so choose varieties that have short ingredients lists. You can expect to see ingredients like soybeans, water, coagulants (such as calcium sulfate, magnesium chloride, or delta gluconolactone) and maybe some seasoning.
How to Store
Once opened, tofu blocks need to be rinsed prior to use.
Leftovers can be kept in the refrigerator for up to one week by covering with water, as long as you change the water often. It is best to use filtered water.
If you will have to store it longer than a week, tofu can also be frozen and will last for up to three months. Cut it into chunks and freeze on a parchment-lined baking sheet until solid, then transfer to an airtight freezer container or bag. Defrost in the refrigerator and squeeze out any excess liquid before cooking. Tofu that has been previously frozen will have a sturdier, spongier texture that many cooks prefer, especially if you plan on marinating it.
How to Cook
- Crispy Tofu – Pan-frying is the easiest, least fussy way to cook tofu
- Stir-Fried Tofu – add it to veggies
- Baked Tofu – use a marinade
- Grilled Tofu – with herbs
- Scrambled Tofu – treat it like an egg