Our ancient diet had a saying, "The five grains are suitable for nourishment, but without beans, they are not good" (cited from "Huangdi Neijing • Suwen"), meaning that although the five grains are nutritious, without beans, balance is lost. This shows that our ancestors had a deep understanding of the role of beans in dietary nutrition through their life practices.
There are many varieties of beans. Based on the seed coat color of soybeans, they can be divided into five major categories: yellow soybeans, green soybeans, black soybeans, other soybeans, and feed soybeans. It should be noted that black soybeans are different from black beans here.
Modern nutrition has confirmed that soybeans are rich in nutrients such as high-quality protein, unsaturated fatty acids, calcium, B vitamins, vitamin E, and dietary fiber. The protein content of soybeans is about 35%-40%. Except for methionine, the composition and ratio of other essential amino acids are similar to the protein in meat. Moreover, they are rich in lysine, which is lacking in cereal proteins, making them a natural and ideal food that complements cereal proteins.
The fat content in soybeans is about 15%-20%, of which unsaturated fatty acids account for 85%, and linoleic acid is as high as 50%. The carbohydrate content in soybeans is about 25%-30%, half of which is dietary fiber. Among them, raffinose and stachyose are fermented by intestinal bacteria to produce gas, which can cause bloating. Soybeans have a high phytic acid content, which may affect the bioavailability of mineral elements such as iron and zinc.
Soybeans are rich in phosphorus, iron, and calcium, significantly more than in cereals. The content of B vitamins such as vitamin B1, vitamin B2, and niacin in soybeans is also several times higher than in cereals, and they also contain a certain amount of carotene and rich vitamin E. Soybeans also contain various phytochemicals such as soybean saponins, soybean isoflavones, phytosterols, and soybean oligosaccharides, which are beneficial to health.
The protein content in soy milk is comparable to that of milk and is easily digested and absorbed. Its saturated fatty acid and carbohydrate content are lower than that of milk, and it does not contain cholesterol, making it suitable for the elderly and patients with cardiovascular diseases to drink. However, the calcium and vitamin C content in soy milk is much lower than in milk, and the content of zinc, selenium, vitamin A, and vitamin B2 is also lower than in milk. They have their own nutritional characteristics, so it is best to drink some milk and soy milk every day.
Soybeans are a high-quality source of protein and can eliminate the adverse health effects of excessive meat consumption.
The "Dietary Guidelines for Chinese Residents" recommends that each person should consume 30-50 grams of soybeans or an equivalent amount of soy products per day. However, in the past 20-30 years, the intake of bean foods by Chinese residents has not changed significantly.
Soy products are usually divided into two categories: non-fermented soy products and fermented soy products. Non-fermented soy products include soy milk, tofu, dried tofu, yuba (dried tofu skin), etc. Fermented soy products include douchi (fermented black beans), doubanjiang (broad bean chili paste), furu (fermented tofu), stinky tofu, douzhi (mung bean milk), etc. In terms of the protein provided, 40 grams of soybeans are equivalent to 200 grams of tofu, 100 grams of dried tofu, 30 grams of yuba, 700 grams of tofu pudding, and 800 grams of soy milk.
After soy products are fermented, the protein is partially broken down, making it easier to digest and absorb. The content of certain nutrients (such as vitamin B2 synthesized by microorganisms during the fermentation process) increases. When soybeans are made into bean sprouts, in addition to the original nutrients, they also contain more vitamin C. Therefore, when fresh vegetables are lacking, bean sprouts are a good source of vitamin C.
This article is excerpted from "Ma Guansheng Talks about Nutrition" by Ma Guansheng, authorized by Phoenix Hanzhang Books. Reproduction is strictly prohibited.