The first of its kind research from Shanghai indicates isoflavones may reduce risk of fractures in men.1
Even a superficial examination of the literature quickly reveals that most of the soy research focused on bone health involves women. For example, all five of the clinical trials examining bone mineral density (BMD) that were at least two years in duration involved only women.2-6 Since isoflavones are classified as phytoestrogens and women lose considerable bone mass after the cessation of ovarian estrogen production— and are more likely to suffer from osteoporosis and fractures than men— the focus on women is understandable.7 But the new study from China now puts the spotlight on men.
This new research consists of a prospective study from Shanghai involving 61,025 men aged 40–74 years at study enrollment (2002-2006) who were followed for a median of 9.5 years during which time 1.2% and 3.4% of participants experienced osteoporotic or non-osteoporotic fractures, respectively. Diet was assessed at enrollment and at three additional times. High isoflavone intake was associated with a statistically significant 27% reduction in risk of osteoporotic fracture after adjustment for a host of potentially confounding variables including age, educational level, smoking status, alcohol consumption, exercise, BMI, fracture history, calcium supplement use, calories, protein, fat, vitamin D, calcium, and magnesium intake.
Two notable strengths of this study include its large size and relatively long follow up period. Equally, if not more, important is the high isoflavone intake of the men in this study. The cutoffs (mg/d) for the four isoflavone intake quartiles were <21.7, 21.7-32.1, 32.2-45.2 and >45.2. Shanghai is one of the highest soyfood-consuming regions in the world.
In contrast to the impact of isoflavone intake on risk of osteoporotic fracture, isoflavones were unrelated to non-osteoporotic fractures. Non-osteoporotic fractures are much more common than osteoporotic fractures. Mai et al.8 found that of the 3,700 participants in the Dubbo Osteoporosis Study, only 21% and 16% of total fractures in women and men, respectively, were attributable to osteoporosis. These figures align with those from the Shanghai study in that there were nearly three times more non-osteoporotic fractures than osteoporotic fractures.2
The authors suggested that antioxidant and immune-modulating effects, anti-inflammatory activity, and anti-parathyroid hormone activity might account for the protective effects of isoflavones in this Chinese study. However, these effects are not well established in clinical trials. Nevertheless, the novel finding that isoflavone intake is associated with a lower risk of osteoporotic fracture among men warrants further exploration.
If this finding is confirmed by future research, there are considerable public health implications because each year about 80,000 American men experience osteoporotic fractures.
- Cui Y, Cai H, Zheng W, et al. Associations of dietary intakes of calcium, magnesium and soy isoflavones with bone fracture risk in men: a prospective study. JMBR Plus. 2021.
- Lydeking-Olsen E, Beck-Jensen JE, Setchell KD, et al. Soymilk or progesterone for prevention of bone loss: A 2 year randomized, placebo-controlled trial. Eur J Nutr. 2004;43:246-57.
- Alekel DL, Van Loan MD, Koehler KJ, et al. The soy isoflavones for reducing bone loss (SIRBL) study: a 3-y randomized controlled trial in postmenopausal women. Am J Clin Nutr. 2010;91:218-30.
- Tai TY, Tsai KS, Tu ST, et al. The effect of soy isoflavone on bone mineral density in postmenopausal Taiwanese women with bone loss: a 2-year randomized double-blind placebo-controlled study. Osteoporos Int. 2012;23:1571-80.
- Levis S, Strickman-Stein N, Ganjei-Azar P, et al. Soy isoflavones in the prevention of menopausal bone loss and menopausal symptoms: A randomized, double-blind trial. Arch Intern Med. 2011;171:1363-9.
- Marini H, Bitto A, Altavilla D, et al. Breast safety and efficacy of genistein aglycone for postmenopausal bone loss: a follow-up study. J Clin Endocrinol Metab. 2008;93:4787-96.
- Cawthon PM. Gender differences in osteoporosis and fractures. Clin Orthop Relat Res. 2011;469:1900-5.
- Mai HT, Tran TS, Ho-Le TP, et al. Two-thirds of all fractures are not attributable to osteoporosis and advancing age: Implications for fracture prevention. J Clin Endocrinol Metab. 2019;104:3514-20.
This blog sponsored by SNI Global and the United Soybean Board.