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Tofu is a widely-enjoyed food made from soybeans, and it is a great example of how a simple food like soybeans can be woven into human food traditions in a way that is natural, inexpensive, and nourishing. Tofu is a surprisingly versatile form of soybeans that is made by curdling soymilk so that its proteins become coagulated and then pressed into a sliceable cake. Even though very little tofu sold in the U.S. has been fermented, it is also possible for tofu to be made not only through coagulation, but also through fermentation—i.e., through the addition of micro-organisms which can interact with the soy curds. (There are many health advantages to the fermentation of soy foods, and these advantages will be described in more detail throughout this food profile.)
In the Health Benefits section of our Soybeansfood profile, we provide an in-depth look at many of the controversial issues surrounding soy foods and their role in health. (You may want to visit that section of our website to learn more about these issues.) One of the most important things to remember about tofu is its basic whole food nature. The vast majority of soy consumed in the U.S. comes from a highly processed form of soy. The soybeans we consume have usually been genetically engineered, cracked, dehulled, crushed, and subjected to solvent extraction to separate their oils from the rest of the bean. What's left behind after oil extraction (defatted soy flour) is then further processed into animal feed, or processed to produce a protein concentrate or a protein isolate. The isolate can be used as an ingredient in low-fat soymilk, and the concentrate can be further processed (extruded) to form a textured soy protein for use in meat analog products (like soy burgers). Tofu is produced with significantly less processing than most low-fat soymilks and soy burgers, it is a soy food that is much closer to a "whole foods" category than soy protein isolates and concentrates.
While there is existing research that indicates the possibility of certain health risks from consumption of soy, we believe that a significant amount of these possible health risks involve consumption of soy in a highly processed form (like soy protein isolate or soy protein concentrate) rather than a whole food form. By contrast, we view tofu as a form of soy that is closer to soy in its whole food form.
From a health benefits standpoint, there are also benefits to tofu that has been fermented. Fermentation increases the digestibility of soy (especially its proteins), nutrient absorption from soy (including absorption of phytonutrient isoflavones like genistein and daidzein), and the concentration of bioactive peptides (formed during the breakdown of soy proteins during fermentation).
According to a recent research analysis of the U.S. population and dietary practices within this population, U.S. adults would increase their intake of folate, vitamin K, calcium, magnesium, iron and fiber if we replaced our meat and dairy intake with soy, including tofu. Replacing meat and dairy with tofu and other soy products would also lower our total cholesterol intake by about 125 milligrams per day and our saturated fat by about 2.4 grams per day. These nutritional changes, in turn, would lower our risk of several chronic diseases, including cardiovascular diseases.
Soy foods typically contain a wide variety of well-studied phytonutrients. In the case of fermented soy foods like tofu that has been fermented these phytonutrients can become more concentrated and more bioavailable as well. Below is a list of some key phytonutrients that can be found in tofu and other soy foods.
Before concluding this phytonutrient section, we think it's important to point out one nutrient-related aspect of soy processing. Phytates are substances found in soybeans (and many other foods) that can lessen the absorption of certain nutrients, especially minerals. Soy products in general (including products that are minimally processed) contain 1.4-3.0% phytates. Soy isolates (commonly used production of low-fat soy milk) usually contain a minimum of 2.89% phytates, and soy concentrates can contain up to 4.8-4.9% phytates. Forms of soy, like tofu, that are more whole food-based will do a better job of lowering your phytate exposure than highly processed forms of soy like soy protein concentrates or isolates.
We've seen very few studies of soy and cardiovascular health that are specific to tofu. However, we do know that whole food soy products provide better cardiovascular support than dietary supplements containing isolated soy components (like purified isoflavones). We also know that fermented soy foods like fermented tofu have more bioactive peptides than non-fermented soy foods, including "regular" tofu. (Peptides are smaller breakdown parts of proteins.) In the case of fermented soy foods like tofu,, two key storage proteins—glycinin and conglycinin—are broken down by molds, yeasts, and bacteria into peptide fragments that have antioxidant, anti-inflammatory, and blood pressure-lowering properties. For example, some of the peptides found in fermented tofu inhibit angiotensin-converting-enzyme (ACE) and are therefore classified as "ACE inhibitors." When this enzyme is inhibited, it is often easier for the cardiovascular system to regulate blood pressure. The antioxidant and anti-inflammatory properties of soy peptides found in fermented soy food like tofu can help protect the blood vessels from oxidative and inflammatory damage.
Intake of soy foods (especially whole soy foods) has been associated with improved levels of blood fats in numerous research studies. However, even in the case of whole soy foods, we would not describe this improvement of blood fat levels as being "strong." A better word would be "moderate." The most consistent effect of soybean intake on blood fats has been a moderate lowering of LDL cholesterol. Some studies show other positive impacts on blood fats, like the lowering of triglycerides and total cholesterol or the raising of HDL cholesterol (the "good" cholesterol). However, these additional blood fat results have not been confirmed in all studies.
Soyasaponins are soy phytonutrients that have been especially interesting to researchers with respect to their cardiovascular benefits. There is some evidence, mostly in animal studies, that soyasaponins can lessen the rate of lipid peroxidation in blood vessels, lessen absorption of cholesterol from the GI tract, and increase excretion of fecal bile acids. All of these events would be expected to contribute to a decreased risk of cardiovascular disease. Soyasaponins are provided in many forms of soy, but fermentation of soy has been shown to increase their concentration. Increased levels of soyasaponins in fermented soy foods like fermented tofu are likely to play a role in the better track record of fermented (versus non-fermented) soy foods in the area of cardiovascular benefits.
The area of cancer prevention is a controversial area of health research on soybeans. Many studies provide us with evidence that supports the role of whole soy foods in a cancer-preventing diet. Genistein (an isoflavone phytonutrient in soy) is often a key focus in these cancer-prevention studies. This soy isoflavone can increase activity of a tumor suppressor protein called p53. When p53 becomes more active, it can help trigger programmed cell death (apoptosis) in cancer cells, and it also help trigger cell cycle arrest (helping stop ongoing cancer cell activity). Genistein has also been shown to block the activity of protein kinases in a way that can help slow tumor formation, especially in the case of breast and prostate cancer. Importantly, genistein is found in higher concentrations in fermented soy foods like fermented tofu (compared to non-fermented soy foods like soymilk, isolate soy protein, concentrated soy protein, textured soy protein—also known as TVP—and non-fermented tofu).
Even in the case of fermented soy foods and their higher concentration of isoflavones like genistein, however, the potential cancer-related benefits of soy are complicated by other real-life factors. For example, the lifecycle and metabolic status of an individual seems to make a potentially important difference in the anticancer benefits of soy (even fermented soy). In studies on soy intake and breast cancer involving women who are pre-menopausal and develop tumors that are neither estrogen receptor positive nor progesterone receptor positive, soy and genistein intake (even from fermented soy foods) does not appear to offer risk reduction. Overall dietary intake may also make an important difference in the anticancer benefits of soy. For example, without strong dietary intake of fresh fruits and vegetables, even fermented soy foods may not provide reliable anticancer benefits.
In several studies, large doses of purified soy isoflavones (obtained through dietary supplements) has been associated with increased risk of certain cancers, including breast cancer. This evidence should not be surprising. Under certain metabolic circumstances, most antioxidant, anti-inflammatory, and anti-tumor compounds can also act in a way that is pro-oxidant, pro-inflammatory, and pro-tumor (often called a "proliferative" effect that is promoting of tumor growth). We view intake of tofu (especially fermented tofu) as very different from intake of highly processed forms of soy, or intake of dietary supplements containing purified soy components. And our recommendations to you based on all of this information are as follows:
First, if you have a family history of hormone-related cancers like breast cancer or prostate cancer, we recommend that you consult with your healthcare provider before consuming very large amounts of soy in your diet (for example, 3 or more servings per day). This recommendation holds true for both non-fermented and fermented soy foods. And while this recommendation is a conservative one on our part, we believe that it's justified based on the current level of controversy in the health research on soy.
Second, we recommend that you choose whole food soybeans whenever possible, rather than highly processed versions like soy protein isolates and soy protein concentrates. Especially good choices in this context would be whole food-type soy products that have also been fermented, like fermented tofu. In general, it's worth remembering that fermented soy foods have a better track record in cancer prevention than non-fermented soy products.
There are several other areas of potential health benefit from tofu that we believe deserve special mention. First is prevention and treatment of obesity. In this context, it is some of the unique peptides (protein breakdown products) in soy that have been associated with obesity prevention and treatment. Some of these peptides have shown the ability to decrease synthesis of SREBPs (sterol regulatory element binding proteins), thereby helping decrease synthesis of certain fatty acids as well as the depositing of these fatty acids in fat cells. Since fermented soy foods like fermented tofu have increased concentrations of bioactive peptides (versus non-fermented soy foods), fermented tofu may turn out to be premier forms of soy with respect to obesity management. However, it's important to remember that this fascinating research on soy and obesity is still in a very early stage.
A second area of potential health benefit is prevention of type 2 diabetes. In multiple animal studies, soy foods have been shown to lessen insulin resistance by increasing the synthesis of insulin receptors. However, this increased formation of insulin receptors only appears to occur in the presence of other dietary circumstances, like a moderate amount of polyunsaturated fat intake. High levels of total soy intake (approximately 200 grams per day) have also been associated with decreased risk of type 2 diabetes, but only in Asian populations thus far. We have yet to see specific studies on tofu in this regard, but we look forward to more research in this area.
Other areas of active research on soy and health include chronic obstructive pulmonary disease (COPD), periodontal disease, and neurodegenerative disease. While we have yet to see studies on tofu in these areas, we expect to learn more about potential benefits of tofu in these areas.
Originating in China well over a thousand years ago, tofu is made by curdling soymilk so that soymilk proteins become coagulated. The resulting soy curds can then pressed into a sliceable cake. "Nigari" tofu typically refers to soymilk that has been coagulated with the addition of magnesium chloride. Gypsum (calcium sulfate) is another coagulant that is widely used to curdle soymilk. Both calcium sulfate and magnesium chloride are also referred to as "salt" coagulants. ("Salt" in this case doesn't mean table salt, i.e., sodium chloride. Salt is used in this context in a chemical way to refer to any ionic compound.) "Acid" coagulants like glucono delta-lactone (GDL) are also used to coagulate tofu in a way that produces a softer version of this soy food, often referred to as "silken" tofu. Because tofu is "curded" soymilk, tofu is also often called "bean curd." In Chinese, tofu would more accurately be spelled "doufu." Today there are over 200,000 manufacturers of tofu worldwide.
The vast majority of tofu sold in the United States has not been fermented. However, many forms of fermented tofu are widely enjoyed worldwide. You will read and hear about fermented tofu being described using a seemingly endless list of terms, including: pickled tofu, preserved tofu, tofu cheese, Chinese cheese, sufu, sufu cheese, stinky curd, stinky tofu, and stinky sufu. All of these terms refer to tofu that has been fermented. Fermentation of tofu can take place using a variety of methods, including the addition of bacteria and molds as well as special brines.
There's little question in the research about the added health benefits that can come from fermentation of tofu. To understand these health benefits, however, it can be helpful to think not only about fermentation of tofu, but about fermentation of foods in general.
Fermentation of food typically involves the breakdown of a food's carbohydrates into gasses, alcohols, and other molecules by micro-organisms. These micro-organisms include molds, yeasts, and bacteria. Common examples of fermented food include beer and wine, cider, leavened bread, yogurt, and sauerkraut. Interestingly, a relatively small number of micro-organisms account for a very large percent of commercially fermented foods, and an even smaller number account for most fermented soy foods. Fermented soy foods (including fermented tofu) usually involve the activity of the molds Aspergillus, Rhizopus, Mucor, Actinomucor and Neurospora; several species of the yeast Saccharomycces; and numerous species of the bacteria Bacillus and Pediococcus.
While fermentation is usually defined in terms of the action of micro-organisms on a food's carbohydrates, many nutrients in food can be transformed during the process of fermentation. These nutrients can include the food's proteins, fats. vitamins, minerals, and phytonutrients. In fermented soy foods, for example, proteins are often made more digestible through fermentation. Minerals like calcium in soy foods can become more soluble and bioavailable through fermentation as can the bioavailability of many phytonutrients, including isoflavones like genistein and daidzein. In some cases, when fermentation changes the digestibility of protein in soy foods (and in other foods as well), smaller protein fragments are created (called peptides) that have unique health supportive properties of their own. For example, one of the important storage proteins in soybeans is called conglycinin. Conglycinin and its fellow storage protein, glycinin, account for as much as 80% of the total proteins in soybeans. During the process of fermentation, conglycinin in soy is often broken down into smaller peptides that serve as antioxidants, boost immune function, and prevent excessive inflammatory response.
In the overall picture, we believe that non-fermented soy foods like non-fermented tofu (or a non-fermented fresh green soybean food like edamame) can provide you with important health benefits. (To learn more about these overall soy benefits, please refer to our food profile for Soybeans.) We believe that these whole food-based forms of soy stand in clear distinction to highly processed versions of soy like soy protein concentrate or soy protein isolate. So we recommend that you consider adding any whole-food form of soy to your diet. At the same time, we also believe that the research support for the health benefits of soy foods is even stronger for fermented versus non-fermented soy foods. So we also encourage you to consider inclusion of fermented soy food—such as fermented tofu—among your whole soy choices.
Along with miso, tofu was a favored food as early as the 12th century AD in Japan, regularly enjoyed by military rulers (Shoguns) and at Zen Buddhist temples throughout the country. In fact, tofu became one of the primary ingredients in "Zen Temple Cookery" (Shojin Ryori) during this time period. Tofu provided a common bond of sorts between common persons, monks, and other officials whose lives were more closely connected with the world of and monasteries. To this day, tofu is viewed as a common food that is both nourishing and inexpensive and can be enjoyed by all.
Tofu is available refrigerated in individual packages or in bulk, or non-refrigerated in aseptically sealed containers. Packaged tofu should feature expiration dates, which you can use as a guideline for how long of a shelf life it will have. Tofu varies in texture from soft to firm to extra-firm. Soft tofu has a smoother texture and is therefore better suited for salad dressings, sauces, and desserts. Firm and extra-firm tofu are best for baking, stir-frying, and grilling.
While aseptically packaged tofu need not be refrigerated until it is opened, all other forms of tofu should be refrigerated in their container. Once their packages are open, all types should be rinsed well, kept in a container covered with water, and placed in the refrigerator. Changing the water daily will help keep the tofu fresh for up to one week.
Tofu can also be frozen in its original packaging and will keep this way for up to five months. This process will actually alter its texture and color, making it more spongy and absorbent, and more yellowish in color. This change in physical properties is actually very suitable for certain recipe preparations.
If you are selecting tofu on the basis of fat content, the firmer tofus are usually the highest in fat, and the softest tofus, often called silky or silken, are the lowest.
If you are looking for tofu with higher calcium content, look for products that specifically say "calcium-precipitated" on the label or that include calcium sulfate in their ingredient list. This method of tofu manufacturing uses calcium to help coagulate the soy milk. You'll also sometimes find the word "gypsum" being used to describe tofu coagulants, and this word refers to calcium sulfate as well.
If you are looking for tofu with higher magnesium content, look for products that say "nigari tofu" or "prepared from nigari flakes" on the label. In this context, "nigari" usually refers to a magnesium chloride coagulant that has been used to curdle the soymilk.
Finally, if you are looking for a tofu that is more easily digested and more likely to contain nutrients in forms that are better absorbed, look for fermented tofu. As described earlier, you will find a wide variety of terms being used to describe fermented tofu, including pickled tofu, preserved tofu, tofu cheese, Chinese cheese, sufu, sufu cheese, stinky curd, stinky tofu, and stinky sufu.
If you would decide that you would like to have your tofu available at a later date, or if you decide that you would like to remove some of the moisture from your tofu to help it soak in sauces and flavors, you can freeze it. Freezing tofu is also called "pressing" it. First, take the tofu out of its package and place it on a cutting board to allow the packaging fluids to drain off. This step will help keep too much ice from forming around your tofu when you freeze it.
Next, place the tofu on some paper towels, and cover the top of the tofu with some paper towels as well. Then find some slightly heavy object (like a small book) that can be placed on the tofu's top paper towel layer. The goal here is to find an object that is heavy enough to press down on the tofu and cause its fluid to be pushed out without actually crushing or collapsing the tofu. Leave the object on top of the tofu for 15 minutes.
After 15 minutes, remove the object and all paper towels from the tofu, and place the drained tofu in a freezer bag. Make sure you run your hand over the tofu and bag to remove all the air pockets before sealing the bag. Then just place it in the freezer.
Your tofu should be fine for at least 2-3 months when frozen in this way. When you are ready to use it, just remove and thaw. Some tofus will change color slightly after being frozen (usually to a slightly more yellowish color) and most will also have a slightly different texture (usually a little more "chewy").
For some of our favorite recipes, click Recipes.
Although allergic reactions can occur to virtually any food, research studies on food allergy consistently report more problems with some foods than with others. It's important to realize that the frequency of problems varies from country to country and can change significantly along with changes in the food supply or with other manufacturing practices. For example, in several part of the world, including Canada, Japan, and Israel, sesame seed allergy has risen to a level of major concern over the past 10 years.
In the United States, beginning in 2004 with the passage of the Food Allergen Labeling and Consumer Protection Act (FALCPA), food labels have been required to identify the presence of any major food allergens. Since 90% of food allergies in the U.S. have been associated with 8 food types as reported by the U.S. Centers for Disease Control, it is these 8 food types that are considered to be major food allergens in the U.S. and require identification on food labels. The 8 food types classified as major allergens are as follows: (1) wheat, (2) cow's milk, (3) hen's eggs, (4) fish, (5) crustacean shellfish (including shrimp, prawns, lobster and crab); (6) tree nuts (including cashews, almonds, walnuts, pecans, pistachios, Brazil nuts, hazelnuts and chestnuts); (7) peanuts; and (8) soy foods (such as tofu).
These foods do not need to be eaten in their pure, isolated form in order to trigger an adverse reaction. For example, yogurt made from cow's milk is also a common allergenic food, even though the cow's milk has been processed and fermented in order to make the yogurt. Ice cream made from cow's milk would be an equally good example.
Food allergy symptoms may sometimes be immediate and specific, and can include skin rash, hives, itching, and eczema; swelling of the lips, tongue, or throat; tingling in the mouth; wheezing or nasal congestion; trouble breathing; and dizziness or lightheadedness. But food allergy symptoms may also be much more general and delayed, and can include fatigue, depression, chronic headache, chronic bowel problems (such as diarrhea or constipation), and insomnia. Because most food allergy symptoms can be caused by a variety of other health problems, it is good practice to seek the help of a healthcare provider when evaluating the role of food allergies in your health.
Along with the increasing presence of soy foods (such as tofu) in grocery stores and on restaurant menus has come increasing controversy over soybeans and thyroid health. We're not surprised to find strong conflicting opinions in this area because scientific research on thyroid and soy is both complicated and inconclusive. We have written an extensive review of what we know—and what we don't know—about this important issue at this point. You find the article Soy Food and Thyroid Health here.
Genetically modified (GM) soybeans have reached 90% market penetration in the United States, and if you are purchasing non-organic soy products, including tofu, you are likely to be consuming soy that has come from a genetically modified plant. Since 1998, nearly a dozen patents have been approved for genetic modification of soybeans, mostly to increase their resistance to herbicides and pesticides that growers expect to spray on the plants during cultivation. If you are wanting to decrease your exposure to GM foods, choose certified organic tofu since the current USDA (U.S. Department of Agriculture) organic regulations prohibit any use of genetic modification. You may find some versions of tofu in the marketplace that are not certified organic but contain the words "GMO free" on the packaging. This labeling information would also indicate the absence of genetic modification in the soybeans used to prepare the tofu. For more on this subject, see this Q+A.
A wide range of unique proteins, peptides, and phytonutrients contained in soy foods, including tofu. Examples are flavonoids and isoflavonoids (daidzein,genistein, malonylgenistin, and malonyldaidzin); phenolic acids (caffeic, coumaric, ferulic, gallic and sinapic acids); phytoalexins (glyceollin I, glyceollin II, and glyceollin III); phytosterols (beta-sitosterol, beta-stigmasterol, campestrol); unique proteins and peptides (defensins, glycinin, conglycinin, and lunacin); and saponins (soyasaponins from group A and group B, and soyasapogenols).
Tofu is an excellent source of calcium and a very good source of manganese, copper, selenium, protein, and phosphorus. In addition, tofu is a good source of omega-3 fatty acids, iron, magnesium, zinc, and vitamin B1.
For an in-depth nutritional profile click here: Tofu.
|
Tofu, firm
4.00 oz 113.40 grams
Calories: 164
GI: very low |
||||
| Nutrient | Amount | DRI/DV (%) |
Nutrient Density |
World's Healthiest Foods Rating |
|---|---|---|---|---|
| calcium | 774.51 mg | 77 | 8.5 | excellent |
| manganese | 1.34 mg | 67 | 7.3 | very good |
| copper | 0.43 mg | 48 | 5.2 | very good |
| selenium | 19.73 mcg | 36 | 3.9 | very good |
| protein | 17.89 g | 36 | 3.9 | very good |
| phosphorus | 215.46 mg | 31 | 3.4 | very good |
| omega-3 fats | 0.66 g | 28 | 3.0 | good |
| iron | 3.02 mg | 17 | 1.8 | good |
| magnesium | 65.77 mg | 16 | 1.8 | good |
| zinc | 1.78 mg | 16 | 1.8 | good |
| vitamin B1 | 0.18 mg | 15 | 1.6 | good |
| World's Healthiest Foods Rating |
Rule |
|---|---|
| excellent | DRI/DV>=75% OR Density>=7.6 AND DRI/DV>=10% |
| very good | DRI/DV>=50% OR Density>=3.4 AND DRI/DV>=5% |
| good | DRI/DV>=25% OR Density>=1.5 AND DRI/DV>=2.5% |
In-Depth Nutritional Profile for Tofu
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