Utilization of Isoflavones in Soybeans for Women with Menopausal Syndrome: An Overview

Abstract

Based on their nutrient composition, soybeans and related foods have been considered to be nutritious and healthy for humans. Particularly, the biological activity and subsequent benefits of soy products may be associated with the presence of isoflavone in soybeans. As an alternative treatment for menopause-related symptoms, isoflavone has gained much popularity for postmenopausal women who have concerns related to undergoing hormone replacement therapy. However, current research has still not reached a consensus on the effects of isoflavone on humans. This overview is a summary of the current literature about the processing of soybeans and isoflavone types (daidzein, genistein, and S-equol) and supplements and their extraction and analysis as well as information about the utilization of isoflavones in soybeans. The processes of preparation (cleaning, drying, crushing and dehulling) and extraction of soybeans are implemented to produce refined soy oil, soy lecithin, free fatty acids, glycerol and soybean meal. The remaining components consist of inorganic constituents (minerals) and the minor components of biologically interesting small molecules. Regarding the preventive effects on diseases or cancers, a higher intake of isoflavones is associated with a moderately lower risk of developing coronary heart disease. It may also reduce the risks of breast and colorectal cancer as well as the incidence of breast cancer recurrence. Consumption of isoflavones or soy foods is associated with reduced risks of endometrial and bladder cancer. Regarding the therapeutic effects on menopausal syndrome or other diseases, isoflavones have been found to alleviate vasomotor syndromes even after considering placebo effects, reduce bone loss in the spine and ameliorate hypertension and in vitro glycemic control. They may also alleviate depressive symptoms during pregnancy. On the other hand, isoflavones have not shown definitive effects regarding improving cognition and urogenital symptoms. Because of lacking standardization in the study designs, such as the ingredients and doses of isoflavones and the durations and outcomes of trials, it currently remains difficult to draw overall conclusions for all aspects of isoflavones. These limitations warrant further investigations of isoflavone use for women’s health.

Current Perspectives on the Beneficial Effects of Soybean Isoflavones and Their Metabolites for Humans

“…Long-term consumption of isoflavones is considered safe, and it has various beneficial effects, but further research is needed to determine the side effects of high isoflavone intake [318,319]. The amount of isoflavone consumed in the Asian diet may be the most reasonable, as the US FDA's recommended intake is 50 mg/day [12,101]. The effects of isoflavones on each of the health aspects dealt with in this review are still being debated and need further consideration.…”

“…Since there are various effective antihypertensive drugs already in use, isoflavones may not be considered a substitute for such drugs (Table S3). However, since estrogen is a natural antihypertensive agent, estrogenic isoflavones can also be effective in lowering blood pressure [12,101,102].…”

“…In particular, the period when menstruation completely disappears, called perimenopause or menopause is an important stage of development women, which begins around the late 40 s. Most women experience menopausal syndrome, which can include hot flushes, cold sweats, lethargy, depression, memory problems, and sleeping problems. In addition, as the secretion of the female hormone estrogen decreases, the risk of developing diseases, such as osteoporosis, dementia, and cardiovascular diseases increases [101,133,[250][251][252]. Therefore, women require proper exercise and a regular diet to lead a healthy life.…”

Pleiotropic Effects of Isoflavones in Inflammation and Chronic Degenerative Diseases

“…Isoflavones can alleviate many pathological conditions including cancer, metabolic, cardiovascular, neurodegenerative diseases, rheumatoid arthritis and adverse menopause symptoms ( Figure 1 ). Recently, various aspects of isoflavones have been overviewed in detail in the following reviews [ 3 , 9 , 10 , 11 , 12 , 13 ]. Two mechanisms are implicated to be responsible for the beneficial effects of isoflavones—the estrogen receptor-mediated signaling pathway [ 2 , 7 , 8 ] and the modulation of other intracellular signaling pathways, e.g., phospholipase C, protein tyrosine kinase and mitogen-activated protein kinase [ 3 , 7 , 14 , 15 ].…”

The role of soy in development of breast, ovarian, endometrial and prostate gland cancer

“…Soybeans have been grown as a commercial crop in Eastern countries for thousands of years [1]. Soy and soy-based food products constitute a source of vitamins, minerals, high amounts of fat, protein as isoflavones -genistein, daidzein, glycitein, which makes soy considered as a common nutritional product with health benefits [2,3].…”