soybeans are a species of legume and come in many colors, shapes and sizes
Journal of Clinical Endocrinology & Metabolism To the editor [Received March 12, 2002] Dewell et al.[1] in their article (Soy Supplement: Why Is the Effect So Elusive? Journal of Clinical Endocrinology & Metabolism) did not find any effects with 150 mg of soy-derived isolated isoflavones. Their results appear in contradiction with the bulk of data that have shown a beneficial effect of soy on lipid parameters, although these results were mostly obtained with soy preparations containing isoflavones rather than isoflavones alone in tablet form. One of the possible explanations, as the authors correctly pointed out, is the fact that other components of soy, rather than the isoflavones alone, may be required for the effect of soy on cholesterol. There is also a second possibility. Once nutrients are isolated in tablet form, they become in all effects a pharmacological preparation. Tableting compounds may drastically influence their bioavailability, and hence, influence clinical effects. A lot of resources are invested in testing bioavailability, stability, and absorbability of drugs, but supplements are not usually submitted to such rigorous testing. This is usually because of the lack of adequate resources. Thus, it is conceivable that if a compound is present but is not absorbed, it will not be clinically effective. Hence, the apparent contradictory effect is observed in clinical studies with supplements.[2] Dewell et al.[1] correctly state the amount of isoflavones present in both the glycone and aglycone form but fail to give an indication whether any of these compounds were actually absorbed and in what levels. Bioequivalence is the effect of different pharmaceutical formulations of identical compounds. An example may be two preparations of calcium chemically identical but pharmaceutically different. They may not be bioequivalent precisely because they may not have identical bioavailability. The source factors include associated ligand anti-absorbent, the pharmaceutical formulation that includes a broad range of physical and chemical factors involving the granulation of excipient; the coating, the hardness, and disintegration potential of the final formulation; and finally the size of the ingested load.[3] There are important factors to keep in mind when both performing clinical trials and advising patients on the use of these substances. Too often, results from food studies are used to support the marketing of isolated nutrients in tablet form. This is clearly unacceptable. Given the variability of food and the lack of standardization, results of clinical trials refer only to the compound tested and cannot be extrapolated even to preparations that are apparently similar, such as tablets containing isolated nutrients. Above all, when using isolated nutrients such as isoflavones in tablet form, it is important to assess their bioavailability first, before attempting to assess clinical efficacy. A lot of these phytoestrogen preparations may in fact just be very expensive pellets that once ingested are, literally speaking, going down the drain! This lack of rigor will, if allowed to persist, ultimately undermine the credibility of the whole field of phytoestrogens among both scientists and consumers alike, thus dooming compounds that could potentially have extremely attractive health giving properties. Paola Albertazzi MD References 1. Dewell A, Hollenbeck CB, Bruce B. The effects of soy-derived phytoestrogens on serum lipids and lipoproteins in moderately hypercholesterolemic postmenopausal women. J Clin Endocrinol Metab 87:118–121 2. Albertaizz P, Purdie DW The nature and utility of phytoestrogens: a critical review of the evidence? An unconventional approach to postmenopausal health. Maturitas, in press 3. Heaney RP 2001 Factors influencing the measurement of bioavailability, taking calcium as a model. J Nutr 131:1344S–1348S
Soybeans are a vegetable crop species of legume. The seeds (called beans) contain significant amounts of phytic acid, alpha-Linolenic acid, and the isoflavones genistein and daidzein. Genistein is an estrogen-like phytochemical and is included in the isoflavones group of Phytoestrogens. Soybean seeds come in a variety of colors and shapes.
Each bean, by weight, is about 40% protein, 35% carbohydrate, 20% oil, and 5% ash. The selection of soybean seeds shown in the photo, depict variations in their color, size, and shape.
Source: National Soybean Germplasm Collection http://www.ars.usda.gov/is/graphics/photos/k5267-7.htm
Centre for Metabolic Bone Disease
Hull Royal Infirmary (Hull, UK)
EFFECT OF HIGH-DOSE SOY ISOFLAVONES
ON POST-MENOPAUSAL WOMEN
CONTEXT: Recent interventional studies indicate that post-menopausal hormone replacement therapy is associated with an increased risk of cardiovascular mortality and breast cancer. Isoflavones, a class of plant estrogens, have structural similarities to estradiol. Hence, isoflavones may exert beneficial estrogenic health effects in post-menopausal women with fewer adverse effects.
OBJECTIVE: To evaluate the effect of high-dose isoflavones on self-reported quality of life, cognition, lipoproteins and androgen status in post-menopausal women.
DESIGN AND SUBJECTS: Double-blind, randomized, placebo-controlled, 12-week trial of 93 healthy, ambulatory, post-menopausal women (mean age 56 yr). The study was conducted at a tertiary care center in the United States.
INTERVENTION: Participants were randomly assigned to receive 20 g of soy protein containing 160 mg of total isoflavones vs taste-matched placebo (20 g whole milk protein). Both soy and the placebo were provided in the form of a powder to be mixed with beverages.
MAIN OUTCOME MEASURES: Quality of life was judged by the Menopause-specific Quality of Life (MENQOL) questionnaire while cognitive function was assessed with standard instruments. Total, free, and bioavailable testosterone, gonadotropins, SHBG, and fasting lipids were measured.
RESULTS: Eighty-four women (90%) completed the study (active=38, placebo=46). There was a significant improvement in all 4 quality of life subscales (vasomotor, psychosexual, physical, and sexual) among the women taking isoflavones, while no changes were seen in the placebo group. No significant changes in cognition, serum androgens or plasma lipids were seen within any of the groups. However, at the end of the study, a group-by-time interaction was observed such that total testosterone and HDL levels were significantly lower in the isoflavones compared to placebo groups.
CONCLUSION: High-dose isoflavones is associated with improved quality of life among women who have become menopausal recently. Hence, the timing of isoflavone supplementation with regards to the onset of menopause appears to be important. The use of isoflavones, as an alternative to estrogen therapy, may be potentially useful and seemingly safe in this group of women who are looking for relief from menopausal symptoms.
[Department of Internal Medicine, Division of Endocrinology and Metabolism, Johns Hopkins University School of Medicine, Baltimore, Maryland]
Basaria S, Wisniewski A, Dupree K, Bruno T, Song MY, Yao F, Ojumu A, John M, Dobs AS. Effect of high-dose isoflavones on cognition, quality of life, androgens, and lipoprotein in post-menopausal women (Abstract). Journal of Endocrinological Investigation, Feb 2009.
Pilot Study: EFFECTS OF HIGH DOSE ISOFLAVONES ON THE COMPLICATIONS OF PROSTATE CANCER THERAPY
PURPOSE: The profound hypogonadism due to androgen deprivation therapy for prostate cancer results in complications such as sexual dysfunction, poor quality of life, vasomotor symptoms and altered cognition. Since estrogen is associated with cardiovascular risks, phytoestrogens are being increasingly evaluated as a potential treatment for these adverse effects. We evaluated the effects of high dose isoflavones, equivalent to that consumed by Asian populations, on the aforementioned consequences of androgen deprivation therapy.
MATERIALS AND METHODS: A total of 33 men undergoing androgen deprivation therapy for prostate cancer were enrolled in this randomized, double-blind, placebo controlled, 12-week pilot trial. Participants were randomly assigned to receive 20 gm soy protein containing 160 mg total isoflavones (17) vs taste matched placebo, that is 20 gm whole milk protein (16). The study was performed at a tertiary care center in the United States.
RESULTS: At baseline the groups were well matched in demographic parameters, sleep quality, cognition and overall quality of life. However, men in the isoflavone group had a higher baseline prevalence of hot flashes and poor intercourse satisfaction compared to those on placebo. At 12 weeks there were no significant differences between the 2 groups in any outcome measure.
CONCLUSIONS: This pilot study of high dose isoflavones in androgen deprived men showed no significant improvement in cognition, vasomotor symptoms or any other aspect of quality of life measures compared to placebo. Future studies should use variable doses of isoflavones for a longer period before ruling out beneficial isoflavone effects in this population.
[Georgetown University, Washington, DC]
