Soy foods have been a source of high-quality protein and healthy fats for decades. Their nutritional components have attracted significant attention in determining how soy can be utilized in human nutrition and health. Soybeans contain essential nutrients such as proteins, carbohydrates, vitamins, minerals, and isoflavones. Further, they produce bioactive peptides through enzymatic hydrolysis, food processing, gastrointestinal digestion, and fermentation. In addition to their significant nutritional value, soy and soy foods are essential dietary solutions for vegetarians.
History
Soybean has a long history and was first grown in China. Soya beans were first grown in China, followed by Japan, and later introduced in the United States in the 10th century and Europe in the 18th century (Chatterjee et al.,2018)”. The United States is among the last countries to raise soybeans and has used soya beans as the cash crop since 1940. According to Chatterjee et al. (2018), soybean forms over 30% of the crop’s global production. Its nutritional components and central role in reducing the risk of cardiovascular diseases have supported its growing popularity.
Soybeans have different nutritional components in varying quantities. Chatterjee et al. (2018) highlight that in 1999, the United States Food and Drug Administration approved that soybeans played a crucial role in reducing the risk of coronary heart disease. Similarly, Messina (2016) agrees that soy foods decrease the risk of developing coronary heart disease. Therefore, exploring evidence-based research to understand soy’s nutritional components and critical health benefits is essential.
Some traditional Asian soy foods are known to have various health benefits that people are seeking to obtain from soybeans. In Asia, soy is used for traditional cuisines dishes prepared in distinct ways such as heating to extract soymilk, fermentation to get Natto, or treating with magnesium chloride to get tofu (Rizzo & Baroni, 2018). Soy is frequently used in preparing traditional dishes in many Asian countries. Mainly, the cuisines prepared through fermentation, such as Tempeh, soy sauce, and Sufu, activate peptides and attain the health benefits such as anti-cancer and anti-diabetes properties.
Consumption of Soy Products
Depending on demographic, cultural, and environmental factors, population groups have varying consumption levels. The Chinese women in Shanghai had an intake of 39.9 milligrams a day and 8.7 grams of soy, soy protein and isoflavones, respectively (Rizzo & Baron, 2018). According to Rizzo and Baron (2018), the adult Japanese population reported an average intake range of between 6 to 11 grams per day and isoflavones consumption of 23–54 milligrams per day, which is a decline from the 1980s with an average of 66.8 grams, 6.5 grams, and 27.8 milligrams, respectively. Mediterranean countries have low consumption of soybeans and its products, with an average of 1% (Rizzo & Baron (2018). However, other European countries have a significantly higher rate of 149 grams per day of soy dairy substitutes with an isoflavone intake of 15–30 milligrams per day among the population group committed to the health-conscious diet. The high intake of soy foods has reduced colon and prostate cancer prevalence in China and Japan (Dimidi et al., 2019). Therefore, increasing focus on health-conscious lifestyles and encouraging soy-based diets can help people reap soy’s nutritional elements.
Nutritional Components
Proteins
Soybean has higher quality protein content than similar plants and animal proteins. Mainly, soy contains a protein digestibility-corrected amino acid PDCAAS score of 0.9-1.0 (Rizzo & Baroni, 2018). However, it varies across soy foods due to the impact of processing which alters its fibre and phytates components. Soybean’s two major storage proteins are Beta-conglycinin and glycinin, which comprise 80%- 90% of the total protein (Chatterjee et al., 2018). Soy proteins have different nutritional and psychological effects. Furthermore, the intestinal absorption of the other protein components differs based on the mode of administration or processing.
Soy Isoflavones
Isoflavones refer to the primary bioactive compounds in soybean associated with soy protein. They possess both estrogenic and anti-estrogenic components. Mostly the combination is present in soybean as glycosides, genistin, daidzin, and glycerin, although they convert into their respective bioactive forms upon fermentation or digestion (Rizzo & Baroni, 2018). The properties of the compounds antioxidant and hormonal have contributed to the majority of health interests; examples include the prevention of heart ailments, symptoms of menopause, diabetes and breast and prostate cancers (Chatterjee et al., 2018). Nonetheless, considerable variation in the isoflavones, soya beans, and soy foods shows inconsistent physiological functions. Soy saponins are the insignificant bioactive elements in soybeans, and they are amphiphilic oleanane triterpenoids having polar sugar chains attached to non-polar pentacyclic rings. Its properties which cannot be emphasized, include antimicrobial, cardioprotective effects, anti-inflammatory and anti-carcinogenic.
Carbohydrates
The carbohydrate macronutrient component of soybean is significantly low. It comprises oligosaccharides, which stimulate the growth of bacteria bifidobacteria in the colon since it is poorly digested by intestinal enzymes (Mesina, 2016). Notably, soybean oligosaccharide can be used in place of table sugar even though it can lead to flatulence. However, Mesina (2016) suggests that flatulence is not an issue in most soybeans products since their processing reduces oligosaccharides significantly. The low carbohydrate combined with high protein content makes soy products a good alternative for people with diabetes.
Fats
Soybean and entirely fatty soy foods are good sources of essential fatty acids. Soybeans comprise different types of fats in varying quantities. For instance, they contain 10%- 15% percent saturated, 19%-14% percent mono-saturated, and 42%-62% percent poly-saturated fatty acids (Mesina, 2016). The poly-saturated fatty acids, omega-6 essential fatty acids, linolenic acid and essential omega-3 fatty acids are in the ratio of 7-8:1(Mesina, 2016). Soybean oil is widely used globally. Overall, soybean accounts for a significant intake of essential fatty acids.
Vitamins and Minerals
Soybeans are rich in various vitamins and minerals. However, different soy products contain varying levels of the respective nutritional subcomponents. For example, potassium is a predominant vitamin in soybean and is relatively high in iron and calcium (Chatterjee et al., 2018). Mesina (2016) suggests that soy-based calcium absorption is relatively good. However, the mineral status of soy products remains questionable due to concerns over the absorption efficiency of minerals from plant-based diets.
Soy Bioactive Peptides
Research studies are increasingly focusing on soy bioactive peptides, their properties, and their physiological impacts that inform their wide adoption to reduce the risk of cardiovascular diseases and other health conditions. Some benefits include hypercholesterolemia, hypotriglyceridemic, and anti-obesity, which include lipid-lowering besides anti-cancer, anti-inflammatory, anti-diabetes, and antioxidant benefits (Cao et al., 2019). Soy peptide has a hypolipidemic attribute which is among the most studied property lowering cholesterol and triglycerides, whose primary function is reducing the synthesis and storage of fats.
Soy peptides have anti-diabetic properties due to their hypolipidemic function. An example is the hypocholesterolemic soy peptides which enhance glucose metabolism by adding the uptake of glucose in cultured hepatic cells by glucose transporters (Chatterjee et al., 2018). In addition, soy protein and Isoflavones are connected with reduced serum glucose volume and increased insulin secretion in diabetic rodent models. The soybean peptide vglycin also has an anti-diabetic function in type II diabetes as it returns to regular fasting glucose volume. It also reinstates insulin, indicating pancreatic functions, and improves the sensitivity of insulin (Rizo & Baroni, 2019). Therefore, soy foods can have similar impacts on people with diabetes, which benefits their health.
Antihypertensive Peptides
The hypertensive peptides task is angiotensin-converting Acetyl-CoA carboxylase (ACC), whose responsibility is modulating the rennin angiotensin system in regulating blood pressure. Soy protein is hypertensive and significantly effective in reducing blood pressure by 2-5mmHg. Further, it reduces the risk of stroke and coronary heart disease by 6%- 14 % and 5%-9 %, respectively (Messina, 2016). Consumption of soybean also reduces artery stiffness. The rigidity of the arterial wall depends on the aspects such as elastin and proteoglycans.
Bone Health
Soybean has also been considered a significant contributor to improved bone health. Mainly, soy foods promote bone health in postmenopausal women through reduced fracture risk resulting from reduced estrogen levels and consequential loss of bone mass. Notably, their effect on bones is attributed to the estrogen-like consequence of isoflavone. According to Messina (2016), soybeans significantly reduce about one-third of fracture risk among menopausal women if taken substantially. Additionally, the consumption of soy milk among older women is associated with a reduced d risk of developing osteoporosis. The effect is attributable to either the calcium or isoflavone content of soybean.
Moderate doses of isoflavones are more effective in promoting bone than larger doses. Cao et al. (2019) suggest that human and animal soy fermented with LAB can mitigate osteoporosis. Thus, soy foods can promote bone health. Natto, a traditional Japanese food fermented from soybeans, is key to promoting healthy bones. According to Cao et al. (2019), consuming dietary Natto lowers the prevalence of hip breakages by increasing the strength of bones. The positive impact is attributable to increased isoflavone aglycone concentrations and bioavailability and increased soluble calcium and vitamin D levels in LAB-fermented soymilk (Chatterjee, 2018). However, there is a need for clinical trials to prove the applicability of experimental laboratory outcomes.
Other health benefits associated with Natto are related to improved gastrointestinal health. Most bioactive factors such as Vitamin K2,dipicolinic acids and nattokinase are all produced by Natto. Further, it contains high amounts of isoflavone genistein, which prevent inflammatory and metabolic disorders better than other non-fermented soy products (Dimidi et al., 2019). The recent increased consumption of soy products is attributable to the realized potential health benefits and the augmented need to address lifestyle diseases.
Conclusion
Soybeans are a high-quality protein with a rich history as a traditional cuisine among Asians and Americans. In Asia, soy has been an essential part of a daily diet for thousands of years; the West embraced the food ingredient around one hundred years ago. Different research studies seek to establish its benefits to different population groups, especially in managing specific health conditions related to age, cardiovascular issues, and diabetes. Soy product peptides are essential in regulating blood pressure and fatty acids. The increasing recognition of the plant product, changing attitudes to health-conscious lifestyles, and a shift to embracing vegetarian diets have promoted improved consumption of soy products.
References
Cao, Z. H., Green-Johnson, J. M., Buckley, N. D., & Lin, Q. Y. (2019). Bioactivity of soy-based fermented foods: A review. Biotechnology Advances, 37(1), 223–238. https://doi.org/10.1016/j.biotechadv.2018.12.001
Chatterjee, C., Gleddie, S., & Xiao, C. W. (2018). Soybean bioactive peptides and their functional properties. Nutrients, 10(9), 1211. https://doi.org/10.3390/nu10091211
Dimidi, E., Cox, S. R., Rossi, M., & Whelan, K. (2019). Fermented foods: Definitions and characteristics, impact on the gut microbiota and effects on gastrointestinal health and disease. Nutrients, 11(8), 1806. https://doi.org/10.3390/nu11081806
Messina, M. (2016). Soy and health update: Evaluation of the clinical and epidemiologic literature. Nutrients, 8(12), 754. https://doi.org/10.3390/nu8120754
Rizzo, G., & Baroni, L. (2018). Soy, soy foods and their role in vegetarian diets. Nutrients, 10(1), 43. https://doi.org/10.3390/nu10010043
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