Soy has been termed as the wonder bean presenting as the best vegetarian protein source. But, often soy is surrounded by several controversies creating more confusion and doubts among consumers regarding the safe use of this legume native to East Asia.
Soyabean is an excellent source of high quality protein containing all the essential amino acids in readily digestible form. In non-vegetarians, Soy products can be used as meat replacers to bring down fat content since it has textural qualities similar to that of meat. Soyabean contains important compounds called isoflavones – genistein and daidzein which are phytoestrogens (plant estrogens). These are good sources of antioxidants and protective against several diseases.
Soy products A large variety of soy products such as tofu, tempeh, miso, soy flour, soy chunks, soy granules, etc are available.
Soy milk- Dry soybeans are soaked in water and grinded with water. It contains the same amount of proteins as cow’s milk but relatively lesser carbohydrates and fats. It contains zero cholesterol since it is a plant source. Soy milk contains sucrose and not lactose hence it can be safely consumed by those suffering from lactose intolerance or milk allergy.
Tofu-Soy milk is coagulated to form a soft white curd called tofu (soy paneer). It is low in calories, low in fat and contains large amounts of iron. It can be used easily as a low-calorie substitute to full fat paneer (cottage cheese).
Soy flour– Soy flour is made from ground, dehulled soy beans. The process of roasting and grinding causes release of the inhibiting factors present in raw soyabean. It can be mixed into wheat flour in 1:5 proportions to improve nutritive value of chapatti.
Soyabean oil– Soybeans are cracked and heated, then rolled into flakes and extracted in the presence of a solvent. The oil so obtained is cholesterol free and low in saturated fats. It contains good quality of fat (omega 3 fatty acids) and ideal ratio of fatty acids which are less harmful for the heart.
Soy nuggets and granules– Soy is processed to make soy nuggets and granules. These are creamish in colour and easy to digest as compared to beans and flour. These just have to be soaked in warm water before use in curries, cutlets, parathas, stir fries, pulao and various other Indian traditional recipes.
1/2 cup, cooked
|Tempeh 1/2 cup||15.7||14.1||6.4||3.8||43||77||1.9|
|Soynuts 1/4 cup||15||14.5||10.0||0.6||91||59||1.65|
|Tofu 1/2 cup||10||2.3||5.9||0.2||19||130*||—|
defatted 1/4 cup
plain 1 cup
The trouble makers in Soyabean
– It contains trypsin inhibiting factors. Trypsin enzyme is required for protein digestion and hence if its action is inhibited it may precipitate deficiency of some amino acids and gastric problems.
– Soybean contains phytates which inhibit absorption of dietary minerals like calcium, copper, magnesium, iron, and zinc
– It contains hemagglutinin which is a clot promoting substance and may lead to clotting of red cells in blood.
The processing of soyabean such as roasting, germination, and fermentation leads to release of its trypsin inhibiting factors and phytates to a large extent. However, it may be advisable to avoid using unprocessed soy foods in elderly/old age with compromised digestion capacity.
Myth: Soy foods cannot be consumed by individuals suffering from hypothyroidism
Facts: Soy has been categorized as a goitrogen indicating that it increases the risk of developing goiter which is basically an iodine deficiency disease. Animal studies have shown that in iodine deficient individuals, soy foods may inhibit its absorption further. It is advised that sufficient iodine intake should also be ensured in adult hypothyroidic patients consuming Soy foods on regular basis.
Myth: Soybeans help reduce heart disease risk
Fact: It is still unclear whether increased soy consumption helps to lower the risk of cardiovascular disease. Lignans are the fiber component of soybeans which help to bind cholesterol and throw it out of the body. Soybeans have shown to bring about small reduction in bad (LDL) cholesterol but the direct association with decrease in heart disease risk has not been proven.
Myth: Menopausal women may not benefit from soy
Fact: Small percentages of women have shown minor reductions in hot flashes using soya during menopause. Soybeans have weak estrogen-like properties. Estrogen is responsible for development of sexual characteristics in females. A decrease in this hormone levels occurs after cessation of regular menstrual cycle hence supplementation with soy and its products, especially soy milk is very important in postmenopausal women.
Myth: Men should not consume soy foods
Fact: Only very large quantities of upto 40-70mg/day of soy isoflavones through diet or supplements may reduce semen quality. Hence, caution should be exercised in administering excess soybeans to males.
Myth: Soy foods help reduce risk of cancers
Fact: It is true to some extent that due to its anti-oxidant properties, soy isoflavones may be beneficial in suppressing tumour (cancerous cells) growth. There is only weak clinical evidence of the role of genistein in reducing the risk of breast and prostrate cancer
Myth: High protein foods including soybean should be avoided in kidney patients
Fact: In chronic kidney disease there is often strict protein restriction recommended. But the required quantity of protein has to be met using high quality protein sources. The American Association of Kidney Patients (AAKP) proposed that Soy proteins form highly digestible good quality protein source that has shown to reduce loss of protein in urine (proteinuira) and excess filtration of solutes from the kidney thereby decreasing risk of complications.
While the facts about health claims related to soyabean need to be straightened out further, it is harmless to consume the soy products, which have been sufficiently processed, in moderate amounts to accrue maximum benefits of its good quality protein, fiber, fat and anti-oxidative effects.