Soybeans are also high in phytic acids or phytates, an organic acid. These are present in the bean or fruit of all seeds, which block the uptake of essential minerals (calcium, magnesium, iron, and especially zinc) in the intestinal tract. Although not a household word, phytates have been extensively studied.
SOY BEAN: THE WONDER BEAN AND ITS NUTRITIONAL VALUES
Soy bean was declared by the Chou dynasty as one of the five sacred grains together with barley, wheat, rice, and millet. However, it was never used as food. Early Chinese history shows that soybean was valuable to them as a crop rotation since soybean fixes the nitrogen of the soil.
It was only used as food when fermentation techniques were stumbled upon during the Chou dynasty (1134-245 BC). So as early as that period, the ancient Chinese enjoyed the flavor of soy sauce, tempeh, natto and miso.
Much later, in the 2nd century BC, Chinese scientists discovered that a purse of cooked soy beans could precipitate with calcium sulfate, what we know now as (plaster of paris) or Epsom salt. This makes a smooth pale curd called tofu, or bean curd. Being expert traders, Chinese brought this fermented products in the Japanese and Indonesian markets.
The Chinese did not use to eat soybeans like other legumes because then it contained large amount of harmful substances. Topping the list is the potent enzyme inhibitors which block the action of trypsin and other enzymes needed for protein digestion. These “anti-nutrients” are not completely deactivated during ordinary cooking and can produce serious gastric distress, reduce protein digestion, and chronic deficiencies in amino acid intake. In test animals, diets high in trypsin inhibitors cause enlargements and pathological conditions on the pancreas, including cancer.
Soybeans also contain hemaglutinin, clot-promoting substance that cause red blood cells to lump together. Trypsin inhibitors and hemaglutinin have been tightly leveled “growth depressant substances.” They are deactivated during the process of fermentation. The precipitated products, enzyme inhibitors concentrate in the soaking liquid rather in the curd. Thus, in tofu and bean curd, these enzyme inhibitors are reduced in quantity but not completely eliminated.
Soybeans are also high in phytic acids or phytates, an organic acid. These are present in the bean or fruit of all seeds, which block the uptake of essential minerals (calcium, magnesium, iron, and especially zinc) in the intestinal tract. Although not a household word, phytates have been extensively studied. Scientists generally agreed that grain and legume base diets high in phytates contribute to wide spread mineral deficiencies in the Third World countries. Analysts show that calcium, magnesium, iron and zinc are present in the plant foods eaten in these areas, but the high phytate content of soy and rice diets prevent their absorption.
The soybean has a higher phytate content than any other grain or legume that has been studied. Furthermore, it seems to be highly resistant to many phytate reducing techniques such as long, slow cooking. It is only through a long period of fermentation that phytate content of soybeans will be significantly reduced. Thus tempeh, miso, and soy sauce will are all fermented products provide nourishment that easily assimilated. But this put into question the nutritional value of tofu, or “tauho” and soy milk, which are high in phytates.
Nutritional values of soybeans
Soybeans are very rich in nutritive components. Besides the very high protein content, soybeans contain a lot of fiber and are rich in calcium, magnesium. The soy protein has a high biological value and contains all the essential amino acids.
Soybeans are rich in unsaturated fatty acids and low in saturated fatty acids, which need to be avoided.
Nutritional values of soybeans (per 100g):
Water 8.5 g
Energy 416 kcal
Energy 1741 kJ
Protein 36.5 g
Fat (total lipid) 19.9 g
Fatty acids, saturated 2.9 g
Fatty acids, mono-unsaturated 4.4 g
Fatty acids, poly-unsaturated 11.3 g
Carbohydrates 30.2 g
Fiber 9.3 g
Ash 4.9 g
Isoflavones 200 mg
Calcium, Ca 277 mg
Iron, Fe 15.7 mg
Magnesium, Mg 280 mg
Phosphorus, Mg 704 mg
Potassium, K 1797 mg
Sodium, Na 2.0 mg
Zinc, Zn 4.9 mg
Copper, Cu 1.7 mg
Manganese 2.52 mg
Selenium, Se 17.8 µg
Vitamin C (ascorbic acid) 6.0 mg
Thiamin (vitamin B1) 0.874 mg
Riboflavin (vitamin B2) 0.87 mg
Niacin (vitamin B3) 1.62 mg
Panthotenic acid (vitamin B5) 0.79 mg
Vitamin B6 0.38 mg
Folic acid 375 µg
Vitamin B12 0.0 µg
Vitamin A 2.0 µg
Vitamin E 1.95 mg
[Source: USDA Nutrient Database for Standard Reference]
When precipitated soy products are consumed with meat, the mineral blocking effects of the phytates are reduced. The Japanese traditionally eat tofu as part of mineral rich fish broth. Vegetarians also consume tofu and bean curd as a substitute for meat and dairy products risk severe mineral deficiencies. The result of calcium, magnesium, and iron deficiency are well-known; those of zinc are less so. Zinc is called the intelligence mineral because it is needed in optimal development and functioning in the brain and nervous system. Phytates found in any soy products interfere more with zinc absorption then with other minerals. Literature extolling from soy products tend to minimize the role of zinc in human physiology, and to gloss over the deleterious effects of diet high in phytic acid.
Milk drinking is given the reason that second generations Japanese in America grow taller than the native ancestors. Some investigators postulate that the reduced phylate content of the American diet – whatever may be its other deficiencies – is the true explanation, pointing out that Asian and Oriental children who do not get enough meat and fish products to counteract the effects of a high phylate diet, frequently suffer rickets and stunted growth. The current climate of medical opinion in America has cast a cloud of disapproval on tallness based on substituting tofu for other dairy products.
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