Hypertensive crisis associated with high dose soy isoflavone supplementation in a post-menopausal woman: a case report [ISRCTN98074661]

BACKGROUND Isoflavones are gaining popularity as alternatives to hormone replacement therapy. However, few guidelines exist to inform the public as to an appropriate dose. This case involves a postmenopausal woman who experienced a hypertensive crisis while consuming a high-dose isoflavone supplement as part of a research protocol. CASE PRESENTATION The participant was part of a placebo-controlled crossover trial to investigate the potential synergism of the antioxidant activity of soy isoflavones and vitamin C. Upon entry into the study, this healthy, well-nourished, normotensive postmenopausal woman (51 years old), consumed the first of four randomly assigned treatments (500 mg vitamin C plus 5 mg/kg body weight soy isoflavones). During this treatment, the participant's systolic blood pressure spiked to a recorded 226/117 mmHg, necessitating medical intervention and discontinuation of study participation. Two plausible mechanisms for this hypertensive crisis are discussed. CONCLUSION Due to the availability and increasing popularity of soy supplements, practitioners should be aware of the potential side effects associated with their use. Practitioners counseling clients who are consuming soy isoflavone supplements should advise them that elevated blood pressure may be a potential side-effect to consider and monitor.