A Review of the Clinical Effects of Phytoestrogens.
A Review of the Clinical Effects of Phytoestrogens.
Year: 1996
Authors: D C Knight, J A Eden.
Publication Name: Obstet. Gynecol.
Publication Details: Volume 87; 897.
Abstract:
The objective of the present study was to review the sources, metabolism, potencies, and clinical effects of phytoestrogens in humans. The MEDLINE data base for the years 1980-1995 and reference lists of published articles were searched for relevant English language papers related to phytoestrogens, soy products, and diets with high phytoestrogen content, including lignans from flaxseed. Using this study selection, 861 articles covering human cell line studies, human epidemiological studies (case-control or cohort), randomized trials, and review articles were included. Animal studies related to phytoestrogens were included when no human data were available in an important clinical area. The studies that were reviewed dealt with topics in the areas of growth and development, menopause, cancer, and cardiovascular disease. The authors noted that lignans exist as constituents required for the formation of lignin in plant cell walls. Flaxseed produces amounts of mammalian lignans 100 times that of any other plant studied to date. The results of the extensive review process undertaken by the authors indicated that all studies included concurred that phytoestrogens are biologically active in humans or animals. Lignans have both weak estrogenic and anti-estrogenic effects, and have been found to exhibit anti-viral, anti-fungal and anti-bacterial actions. Phytoestrogens inhibit the growth of different cancer cell lines in cell culture and animal models. Human epidemiological evidence supports the hypothesis that phytoestrogens inhibit cancer formation and growth in humans. Foods containing phytoestrogens such as soybeans and flaxseed reduce cholesterol levels in humans. The results of cell line, animal, and human studies indicate that phytoestrogens have beneficial effects in treating osteoporosis. The authors state that their review suggests that phytoestrogens are among the dietary factors responsible for protection against cancer and heart disease noted in vegetarians. Epidemiological and cell line evidence support the need for intervention studies to further assess the clinical effects of phytoestrogens. The authors indicate that scientific research has established a beneficial role for phytoestrogens (such as lignans from flaxseed and isoflavonoids from soybean) in the diet as a means to reduce the risk of cancer and cardiovascular disease. They conclude by stating that, as an intervention with such enormous potential advantages (with few side effects and easy to tolerate), elucidation of the properties of phytoestrogens should be expedited.
