Tofu: Types, Nutritional Value, Health Benefits and Risks

What is Tofu?

Tofu is known for its nutritional benefits and also for its versatility. Other names for tofu are soya curd and bean curd. Soya milk is curdled with a coagulant, "Nigari", which is a by-product of the salt making process and it is rich in minerals. Basically, after the salt is extracted from the seaweed, the mineral-rich coagulant that is left over is nigari.

The magnesium chloride or calcium sulfate in these coagulants helps to solidify the milk to form a cheese-like food, which is known as tofu. It is pressed into a solid block and then cooled. The making of tofu is similar to that of traditional dairy cheese, which is also made by curdling and solidifying milk. The whey is discarded, and then the curd is then pressed so that cohesive bonds are formed.

The product actually tastes bland, hence it can easily absorb other the flavor of other ingredients. It is sold in water filled packs. If the tofu is fresh, it should be refrigerated. The water should be drained and changed daily. This will increase the shelf life of tofu. It can be refrigerated for upto three months. Freezing helps because it makes tofu chewier and also changes the texture. Tofu is gluten free. However, check the label since some companies use coagulants which contain gluten.

Tofu is entirely plant based and it is also used as a meat substitute. In many lactose free diets, low-fat diets and low-cholesterol diet plans, tofu is incorporated since it has many health benefits. Tofu is eaten by inhabitants of China, Japan, Thailand, East Asia and Southeast Asian countries and is an important part of Chinese, Asian, Korean and Japanese cuisines. 

Tofu is nutritious, versatile and affordable. It adds a new dimension to the dish when it absorbs the flavor properly of the other combined food. It is quite a complete source of proteins since it contains 8 out of 9 essential amino acids. Tofu contains fewer calories, but when it is pressed, the nutrients and calories become denser. Tofu contains less sodium. It does not contain cholesterol or animal fat and this lowers the bad cholesterol and increases and maintains the good cholesterol. It is also a good source of B vitamins.

Origin of Tofu

Tofu actually originated in China. About 2000 years ago, soy milk was accidentally curdled by a Chinese cook when he added nigari seaweed. Originally, tofu was called okabe. In the eight century, it was introduced in Japan. Until 1400, it was not called tofu. Later in 1960s, tofu was brought to the western nations. There have been many research studies to find the benefits of soya as well as tofu.

Nutritional Value

Tofu contains eight essential amino acids and is an excellent source of proteins. It also contains iron, calcium, selenium, manganese, phosphorus, copper, zinc, vitamin B1 and magnesium. From nutritional and health perspective, it is very beneficial. It is known to protect against heart diseases and cancer. 100 g of tofu contains 3.5 g fat, 1.5 g carbohydrates, 8.2 g protein and 0.9 g fiber. It can provide 70 kcalories.

Tofu also contains vitamin K, vitamin B6, folate, riboflavin, niacin, and choline. Soybeans are rich in polyunsaturated fats which is healthy, especially omega-3- alpha linolenic acid. 100 gms of tofu contains 76 calories. For people on a low-calorie diet, eating moderate amounts of soy food is not a problem. Tofu is rich in proteins and is listed in ‘complete protein’ category.

It is equivalent to the proteins found in animal sources. Hence for people who are vegetarian, tofu is the best alternative for meat and fish.

Research

Tofu contains isoflavones, whose structure is similar to female hormone estrogen and they are known to mimic the action of the female hormone by binding human cells such as breast cells to the stronger receptor sites. Hence, they can reduce the risk of breast cancer.

During menopause, the secretion of estrogen stops and menopausal symptoms are experienced. Many women who enter menopause decide to increase their intake of soy rich food such as tofu, since it contains phytoestrogen. Phytoestrogen acts as a weak estrogen and by boosting the levels slightly may help relive symptoms of menopause such as hot flushes.

Types of Tofu

The firmness of tofu determines the type. There are many varieties of soybean-based food.

• Firm tofu - It is dense. It can be cubed. Further, it can be scrambled, pickled, baked, grilled, stir-fried, barbecued, smoked, combined in soups. It is rich in proteins, calcium; fats compared to all other types. This tofu will remain dense and stay together and can be fried, without falling apart.

• Regular - It is slightly looser, but still manages to stay together. It is mostly used in many dishes.

• Soft tofu - It is suitably used in blended dishes; it may fall apart while cooking or frying. It can be used when you want to crumble it on salad, or in soups or in making sauces.

• Silken tofu- It is also used in recipes in which tofu is blended. It has a creamy structure. It is consumed along with soy sauce. This is also used in sauces, soups or other similar blended dishes.

Depending on the firmness, the protein content may vary. However, one of the least processed forms of soy milk is tofu. It is low in cholesterol, saturated fat and calories. It is rich in proteins and also contains iron, calcium, vitamin B and phytoestrogen.

Other types of tofu are extra firm, fermented, processed dried tofu, fried tofu and frozen tofu. The fermented tofu is the healthiest version. They also include the pickled ones, which consists of tofu cubes that are dried. With the help of aerial bacteria, they are fermented. Stinky tofu also is soft tofu. It is fermented in a vegetable and fish brine. If the tofu is unfermented, it should not be consumed.

It can be eaten raw; stir fried, grilled, barbecued, marinated in soy sauce or can be used as a base for desserts. In Western diet, it is substituted for meat.

Benefits of Tofu

Tofu is a plant-based food and plant-based foods have been linked to lower risk of health conditions. Such foods decrease the likelihood of obesity, diabetes mortality, and heart diseases. Also, they promote increased energy, healthy hair and complexion, and lower the weight, overall. The isoflavones in tofu contribute towards the health.

• Rich in nutrients - Tofu has proteins and B-vitamins. It can therefore be used in vegetarian as well as meat recipes. Even though soy milk does not contain calcium, tofu is rich in calcium which it gets from the coagulant. This calcium helps prevents osteoporosis. During the manufacturing process, the fiber from soybean is removed which makes tofu extremely easy to digest.

• Reduces cholesterol - Tofu reduces the risk of heart diseases by lowering the bad LDL cholesterol. It also maintains the level of good cholesterol.

• Rich in isoflavones - Isoflavones are known to reduce the risk of osteoporosis and bone fractures. They also lower the risk of certain types of cancers such as breast cancer and prostrate cancer. They reduce symptoms of menopause such as hot flushes and mood swings. The isoflavones genistein and daidzein of soy remain bounded to the soy proteins of soy during the making of tofu. Thus tofu gets these isoflavones. Per 100g tofu contains 35mg of isoflavones. 

• Cardiovascular diseases - Tofu decreases the level of bad cholesterol. This reduces the risk of high blood pressure and atherosclerosis. As an alternative to animal protein, vegans can consume tofu for protein.

• Cancer - The isoflavone that is predominant in tofu is genistein. It inhibits the growth of cancer cells. However, in estrogen-sensitive breast tumor, women should avoid tofu. There has been confusion in the past since the chemical structure of isoflavones and estrogen is similar. Moderate amounts of tofu would be safe for consumption. If soy products are consumed regularly, then the recurrence of breast cancer decreases, but evidence is not yet strong enough, hence not all breast cancer survivors are recommended to have tofu.

• Type 2 Diabetes - Kidney disease is very common in people with type 2 diabetes. In the urine, the body eliminates excess amount of protein. Study has shown that those who consumed soy protein excreted less amount of protein.

• Osteoporosis - It has been reported that tofu increases bone mineral density during menopause and decreases bone loss. Also, it reduces the symptoms of menopause.

• Liver damage - Liver damage happens due to free radicals. Studies have shown that all types of tofu can help prevent liver damage.

• Brain diseases- Studies have shown a link between tofu consumption and incidences of age-related mental disorders. It has been observed that those who consumed greater amount of soy products had lesser chances of age-related mental disorders.

• Weight loss- Tofu has been found to be beneficial in weight loss.

• Enhances function of the brain- Tofu enhances brain functions and memory. This is attributed to the isoflavones found in tofu.

• Improves skin health- Skin elasticity is improved and wrinkles are reduced by daily intake of soy.

Selection, Storage and Safety

Tofu needs to be refrigerated. It can be sold in bulk or individual packets and it may also be sold in sealed containers. If they are sold in sealed containers, then they need not be refrigerated till they are opened. Once they are opened, the water needs to be drained, changed and refrigerated. Tofu is versatile and can work with many types of foods and flavors. Its taste is neutral. Soy products such as tofu contain large amounts of oxalate. Those with kidney stones and history of oxalate should avoid such products. Those who have estrogen-sensitive breast tumors should also restrict their intake.

Tofu can also be made at home. Outside, it may come as freeze-dried, canned, jarred or dehydrated. Rinse tofu before using it. Tofu in packaged form remains fresh upto 5 months, hence check the package and do not buy tofu which is more than five months old. If possible, make fresh tofu at home.

Health Risks

There is some confusion about consumption of soy food, especially in patients with breast cancer. However, there has been evidence that the isoflavones in tofu or soy can contribute to breast cancer. Early studies in rats had shown that higher intake of soy increased tumor growth. However, further research showed that the metabolism of soy in rats is completely different, which made the study invalid.

Hence, it was concluded that moderate amounts were safe and would not affect the growth of tumor cells or increase the risk of breast cancer. Taking 10 mg of soy on a daily basis could prevent the recurrence of breast cancer by 25 percent. Tofu contains goitrogen, hence should not be taken by women with thyroid issues. The isoflavones in tofu is not good for infants. It may disrupt the reproductive organs that are developing. Also, some reports have suggested that fertility could be affected by soy products.

Tofu contains antinutrients which may weaken the metabolism and functions of digestion. Antinutrients may inhibit the action of trypsin which aids in the digestion of proteins. The lectin protein in tofu which is an antinutrient may cause nausea and bloating. Soy also contains phytates which may reduce the ability of minerals to be absorbed. However, these antinutrients become ineffective while cooking, fermenting or soaking. Hence, soybean should be sprouted before making tofu out of it. It eliminates many problems and increases the content of proteins.

Further studies in animal subjects have shown a positive link between tumor growth and the processing of isoflavone-based product. Hence, it is better to consume soy products that have undergone minimal processing.

Adding Tofu to Diet

You can decide whether tofu is good for you or not, since you know its nutritional information and value. Tofu readily absorbs the flavor of the food that it is combined with, hence it is mostly loved by many people. As it is versatile and a flexible option, it is used in wide range of recipes.