HerbClip: Benefits of Phytochemicals in Soybeans

PDF^[?] (Download)	Chemoprevention Phytochemicals Soy (Glycine max)
Date: October 22, 1997	HC# 080277-120

Re:Benefits of Phytochemicals in Soybeans

Friedrich, Joan. Protective and Regulatory Benefits of Soy Alternative & Complementary Therapies. :.

Phytochemicals are categorized as 'non-nutritional' substances, despite the fact that many present in human diets provide significant health benefits. Soybean-derived foods are rich in health-promoting phytochemicals; the attached article discusses soy's glycolipids (saponins), isoflavones, phytic acid (inositol hexaphosphate), lignans, protease inhibitors, phytosterols, and phenolic acid. Possible health benefits conferred by these substances include hormonal regulation, cholesterol reduction, immune support, and antioxidant and anticancer protection.

Saponins, 'complex glycosidic compounds. . . consist[ing] of a steroid or triterpene group . . . linked to one or more sugar molecules,' are known for a detergent-like action that 'arises from the water-soluble carbohydrate molecules being mixed with the fat-soluble sapogenin portion.' Saponins may positively influence the body's hormonal balance. They have also been associated with cholesterol reduction, through a series of mechanisms: 1) Increased bile excretion, 2) Inhibition of cholesterol absorption through binding with cholesterol molecules in the gut lumen, and 3) increased exfoliation and proliferation of intestinal mucosal cells, which can increase fecal cholesterol excretion. Soy fiber contributes to saponin's cholesterol reduction actions by absorbing cholesterol-carrying bile acids.

The author asserts that saponins 'have also been shown to provide antioxidant and cell-protective properties, immunopotentiating benefits for both humoral and cellular responses, and antiviral activity, with suggested inhibitory actions against HIV infection.' Research continues on saponins' possible antibiotic, expectorant and anti-cancer benefits. The author notes that, although 'saponins are highly toxic if administered intravenously to mammals, oral use in mammals causes low toxicity because of its almost complete failure to pass the gut wall and enter the bloodstream.'

Research on soy isoflavones has centered on genistein and daidzein, and, to a lesser extent, equol and O-desmethylangolensin. These phytochemicals influence hormone regulation; they may offer protection against various male and female hormone-related cancers, including prostate and breast cancers (isoflavones are structurally similar to the antiestrogen tamoxifen). Isoflavones compete with and protect against high levels of endogenous estrogen and synthetic estrogens by (more weakly) attaching to estrogen receptor sites.

The isoflavone genistein has conclusively been shown to influence or arrest cancer cell growth, even prompting 'cancer cells to differentiate and return to normal cell status.'

A 1994 study indicated that a daily intake of 45 mg of isoflavones significantly lengthened the follicular phase of the menstrual cycle in normal women, which suggests one of isoflavone's protective mechanisms against breast cancer. (Japanese daily consumption of isoflavones averages 150-200 mg.) The luteal phase of the menstrual cycle involves a greatly increased rate of breast tissue mytosis, thus an increased danger of cancerous growth. If a woman spends proportionally more of her lifetime in the follicular phase, she spends that much less time in the more dangerous luteal phase. In the same way, women with lengthened cycles have less lifetime exposure to the cancer-linked hormone estrogen. Surges of gonadotropins, luteinizing hormone (LH) and follicle-stimulating hormone (FSH) are also significantly suppressed by soy protein ingestion. This, and other reactions, are similar to the results observed with tamoxifen therapy.

The author links research interest in the soy isoflavone daidzein to the prescriptive drug ipriflavone, but it is not clear in the article whether interest in daidzein grew out of the development of ipriflavone, or vice versa. Ipriflavone prevents bone mass loss in osteopoerotic patients.

Soy rich in isoflavones and other phytoestrogens has been shown to offer protection against coronary heart disease (CHD) in both male and female subjects. The author notes the relatively low CHD rate in countries with high rates of soy consumption.

Essential fatty acids (EFAs) comprise about 85 percent of soy fat. These EFAs are 50 percent linoleic (Omega 6) acid and eight percent linolenic acid. The author itemizes 12 therapeutic benefits of PPC fatty acids. They are crucial to the structure of all biologic membranes, and 'indispensable for cellular differentiation, proliferation, and regeneration.' They maintain and activate membrane-bound proteins and receptors and membrane-located enzymes, and they help transport molecules and facilitate metabolic processes across cell membranes. They emulsify fat in the gastrointestinal tract and the bile, and influence immunologic reactions on the cellular level. All of these actions on the part of PCC 'support its clinical application as a membrane therapeutic agent.' Applications may include psoriasis, neurologic diseases, lung/respiratory diseases, geriatric conditions, fat metabolism, gastrointestinal inflammation, and more.

Another compound present in soy, phytic acid may sequester important minerals, but the author adds that it 'may also suppress damaging iron-catalyzed redox reactions.' Also, 'Phytates may delay initiation of atherosclerotic lesion formation and may provide protection against colon and breast cancer.'

The author discusses lignans as a significant and beneficial component of a high-fiber diet; soy's lignan-precursor content is not defined. Lignans are a product of bacterial fermentation of certain dietary fibers in the gut. The author notes that vegetarian diets are rich in lignan, and are associated with a lower than average incidence of both breast and colon cancers. Because lignans are weakly estrogenic, it has been postulated that their presence in the intestinal tract stimulates the liver production of sex-hormone binding globulin (SHBG), which in turn reduces the levels of free hormones in the blood (possibly conferring anti-cancer benefits). This mechanism may explain the higher SHBG levels present in people consuming high-fiber vegetarian diets. The author adds that 'lignans can [also] provide specific anticarcinogenic, antiviral, bactericidal, and fungistatic benefits while yielding antioxidant activity associated with their phenolic structure.'

Protease inhibitors and phytosterols both have demonstrated anti-cancer benefits. Phytosterols act in the colon, where they 'neutralize bile acids, assist in cholesterol reduction, and provide protection against colon cancer.' They may also protect against skin cancer.

The article concludes with an interesting discussion of the theoretical interdependence of healthy gastrointestinal function (and the balance of intestinal flora), liver/bile function, and hormone regulation. - Betsy Levy

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