SAGE-Hindawi Access to Research Journal of Osteoporosis Volume 2010, Article ID 891058, 8 pages doi:10.4061/2010/891058 Review Article The Signiﬁcance of Soy Protein and Soy Bioactive Compounds in the Prophylaxis and Treatment of Osteoporosis Sa’eed Bawa Department of Dietetics, Faculty of Human Nutrition and Consumer Sciences, Warsaw University of Life Sciences, Nowoursynowska Street 159C, 02776 Warsaw, Poland Correspondence should be addressed to Sa’eed Bawa, halilbawa@yahoo.com Received 20 July 2009; Revised 4 December 2009; Accepted 28 January 2010 Academic Editor: Merry Jo Oursler Copyright © 2010 Sa’eed Bawa. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Osteoporosis is deﬁned as a progressive systemic skeletal disease characterized by low bone mass and microarchitectural deterioration of bone tissue, with a consequent increase in bone fragility and susceptibility to fracture. Although bone mass and quality is mainly determined genetically, many other factors, including lifestyle and nutrition also have an impact on bone health. It has been suggested that dietary protein intake may be a risk factor for osteoporosis, and high-protein diets are associated with increased bone loss. Many scientists have examined the relationship between types of protein and urinary calcium excretion, and found that although animal protein was associated with increased urinary calcium excretion, soy protein was not. There is suﬃcient evidence suggesting soy isoﬂavones may have potential beneﬁts for bone. Soy protein with naturally occurring phytoestrogens, mainly isoﬂavones protect against bone loss and synthetic soy ipriﬂavone in some studies has been shown to favorably aﬀect, but a cause and eﬀect relationship has not been established between the consumption of ipriﬂavone and maintenance of bone mineral density in post-menopausal women. Therefore it is too early to recommend it as a supplement for this group of women. 1. Introduction Osteoporosis is a skeletal disorder characterized by compro- mised bone strength, a disorder that predisposes to fractures resulting from no identiﬁable injury or from minimal trauma insuﬃcient to fracture normal bone. Bone strength is the result of two major determinants: bone mineral content and bone quality. A person’s bone mineral content is a function of the interaction of two key factors: the uppermost amount of bone achieved during youth (called the peak bone mass, PBM) in combination with the rate of subsequent bone loss. Growth in bone size and strength occurs during childhood, through adolescence and is usually completed in the 20 s. After peak bone mass is achieved during the third decade of life, bone architecture is maintained by a constant remodeling process. Osteoclasts attach to a speciﬁc area of bone, remove old bone (resorption pit), then osteoblasts move in and ﬁll this pit with new bone. The balance between these processes shifts at menopause [1] and women typically undergo a rapid phase of bone loss that begins approximately 2 to 3 years before the cessation of menses and continues for up to 5 years postmenopause [2]. Although the decreased concentrations of circulating estrogen observed during menopause and the rapid phase of bone loss are chieﬂy responsible for the process [2], many other factors are associated with increased fracture risk [3]. These factors include prior fragility fracture, advanced age, a family history of osteoporotic fracture, and the use of certain medications [1]. Additional predictors of bone loss and fracture risk in early postmenopause include prolonged low vitamin D and calcium intake and low body weight as well as high consumption of animal protein, inadequate intake of plant protein, soybean isoﬂavones and n-3 PUFA [1, 4]. Although hormone replacement therapy (HRT) is able to ameliorate the loss of estrogen at menopause and thus address the concerns related to osteoporosis, there remains substantial interest in alternatives, particularly dietary alter- natives, to HRT. It is in this regard that phytoestrogens have received considerable interest in relation to bone health. Related to isoﬂavones in particular is research showing that ipriﬂavone, a synthetic isoﬂavone, eﬀectively reduces bone loss in postmenopausal women [5]. Interest in the potential