Isoflavones health benefits

The mucosa of the GIT represents an interface between the external and internal environments. The expansive surface area is necessary for the efficient hydrolysis of foodstuffs and the absorption of energy and nutrients. The mucosa also influences the systemic availability of non-nutrient compounds in the diet, both beneficial and detrimental. Digestion and absorption of glucosinolates are critical determinants of health benefits (see Chapter 4) Similarly, the bioavailability and health benefits of phytoestrogens, such as genistein (see Chapters 5 and 10) are at least partly dependent on the carrier-mediated processes of absorption associated with the GIT (Oitate et al, 2001). Moreover, the metabolic activities of the mucosa can influence the systemic concentrations and forms of dietary phytochemicals, as exemplified by research with soy isoflavones (Andlauer et al., 2000). 

Since 1999, when the Food and Drug Administration allowed the first health claim for soy-fortified foods in the USA, there has been a large increase in the sales of food products claiming to contain soy isoflavones. At the same time, over-the-counter supplements have become widely available. However, concerns have been raised about the real health benefits of such supplements in the absence of adequate information about bioavailability, pharmacokinetics and safety. To fill this gap, an extensive study on pure isoflavones and commercial soy isoflavone supplements has recently been carried out (Setchell et al, 2001). A selection of 31 commercially available supplements showed a wide variation in isoflavone composition and in the amount provided by one tablet. Furthermore, a lower isoflavone content, with respect to the claimed levels, has been observed in almost 50% of the analysed products. In one case, no isoflavones at all could be detected (Setchell et al, 2001). 

The basis for understanding the health benefits of isoflavones requires detailed knowledge on the absorption, distribution, metabolism, elimination, and bioavailability of these phytoestrogens that demands robust, precise, accurate, and affordable analyses from biological and other matrices. 

One concern raised about isoflavones, coumestanes, and stilbenes is that they have estrogenic activities. Indeed, some of the health benefit claims for these compounds... 

Numerous health benefits have been reported or claimed for flavonoids and isoflavones, such as in cancer prevention, cardiovascular effects, and relief of menopausal syndromes. However, concerns have been raised about potential adverse effects, such as enhancement of reproductive organs and anti-thyroid effects. In order to evaluate potential beneficial or hazardous health effects from flavonoids. 

Epidemiological studies (Aldercreutz et al., 1991 Aldercreutz, 1998) indicate that consumption of tofu and other soy foods may be associated with the low incidence of breast cancer in Japanese women. This discovery has led numerous researchers in recent years to search for the biochemical components in soybean that are responsible for the cancer risk-lowering effect. Aside from the potential cancer prevention effect (Wu et al., 1996 Cline and Hughes, 1998 Griffiths et al., 1998 Messina and Bennink, 1998 Stephens, 1999), isoflavones also have been found to have other potential health benefits, including heart disease prevention (Anthony et al., 1998), bone mass density increase to prevent osteoporosis (Anderson and Camer, 1997) and the reduction of postmenopausal syndromes in women (Knight et al., 1996). 

These observations lead to the hypothesis that isoflavones may be biologically active, conferring health benefits that could explain the relatively low incidence of hormone-dependent diseases in countries where soy is a dietary staple. However, the effects of soy consumption on hormonal metabolism have been inconsistent, probably as a result of methodological differences in the studies as regards the characteristics of the subjects, study design, isoflavone form and other factors [7],... 

Liu, K. Soy isoflavones chemistry, processing effect, health benefits, and commercial production. Soybeans as Functional Foods and Ingredients K. Liu, Ed., AOCS Press Champaign, IL, 2004b pp. 52-72. 

Given the inconclusive evidence base for soy protein and isoflavones, many questions abound about whether specific soy products in adequate doses may have a health benefit. As noted in the AHRQ Report, further well-conducted studies are needed to determine whether soy protein or isoflavones affect hormone-related conditions. Numerous clinical trials are underway (www.clinicaltrials.gov) to evaluate effects of soy products on multiple clinical conditions including menopause, cancer, and bone health, among others. 

Isoflavonoids also have been reported to have physiological activity in animal and human studies. Besides acting as an estro n mimic, it was reported that the isoflavones found in soybean seeds possess antihemolytic, antifungal, tumorsuppressing, and serum cholesterol-lowering effects. In addition, both epidemiological and dietary-intervention studies indicate that when isoflavones in soybean seeds and in subsequent protein products prepared from the seeds are part of the human dietary intake, those products provide many significant health benefits. - ... 

McCarty MF (2006) Isoflavones made simple - genistein s agonist activity for the beta-type estrogen receptor mediates their health benefits. Med hypotheses 66 1093-1114... 

Dietary consumption of foods and food additives containing isoflavone phytoestrogens has been associated with several beneficial properties to human health (Table 60.5), such as prevention of coronary heart disease and osteoporosis, reduction of menopausal symptoms, and prevention of distinct cancer forms (e.g., breast, prostate, and colon cancer) [19, 20]. The potential health benefits of isoflavones for humans have been the subject of several reviews that have analyzed clinical, animal, and in vitro evidence for biological activity [5]. Several studies have reported that isoflavone consumption by... 

Three major classes of secondary metabolites are involved in these phytochemicals, which are alkaloids, terpenes, and phenoUcs [16]. There are many phytochemicals recognized with health benefits such as sulfur-containing compounds of garlic family, various terpenoids, and polyphenols (anthocyanins, flavones, flavanols, isoflavones, stilbenes, ellagic acid, etc.). 

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