1. ¹Department of Surgery, Royal Free and University College London Medical School, London, UK
2. ²Department of Medicine, Queen's University Belfast, Belfast, UK
3. ³Dept of Chemical Pathology, University College London Hospitals, London, UK
4. ⁴Department of Medical Biochemistry, Tenovus Building, University of Wales College of Medicine, Heath Hospital, Cardiff, UK

Correspondence: JV Woodside, Department of Medicine, Queen's University Belfast, Mulhouse Building, Grosvenor Road, Belfast, BT12 6BJ, UK. E-mail: j.woodside@qub.ac.uk

Guarantor: JV Woodside.

Contributors: MJ Campbell was involved in protocol design, sample analysis, interpretation of the findings and preparation of the manuscript, and carried out all the subject recruitment and sample processing. JV Woodside was involved in protocol design, sample analysis, statistical analysis, interpretation of the findings and preparation of the manuscript. JW Honour advised on the final stages of the protocol and was involved in the isoflavone analysis and in the interpretation of the study findings. MS Morton advised on the final stages of the protocol, directed the isoflavone analysis and was involved in the interpretation of the study findings. AJC Leathem advised on protocol development and preparation of the manuscript.

Received 17 October 2002; Revised 20 February 2003; Accepted 21 February 2003.

Abstract

Background: Isoflavones are estrogen-like plant compounds that may protect against cardiovascular disease and endocrine-responsive cancer. Isoflavones may, because of their ability to act as selective estrogen receptor modulators, alter insulin-like growth factor (IGF) status.

Objective: The aim of this study was to assess the effect of 1-month isoflavone supplementation (86 mg/day red clover-derived isoflavones) on IGF status.

Design and subjects: Healthy pre- (n=16) and postmenopausal (n=7) women were invited to take part in a randomised, placebo-controlled crossover study with a minimum 2-month washout period.

Results: For premenopausal subjects, the change in IGF-1, IGF-BP1 and IGF-BP3 assessed at different points of the menstrual cycle did not differ between isoflavone and placebo phase. However, the change in IGF-1, when examined pre- and post-supplementation, was nonsignificantly reduced (P=0.06) on the isoflavone supplement compared to placebo. For postmenopausal subjects, the change in IGF-1, IGF-BP1 and IGFBP-3 concentrations over the supplementation period did not differ between isoflavone or placebo phase. Isoflavones increased HDL in postmenopausal women compared to placebo (P=0.02) but did not alter either cholesterol or triacylglycerol concentrations, and had no effect on antioxidant status.

Conclusions: This study shows that 1-month supplementation with red clover isoflavones has a positive effect on HDL cholesterol, but at most a small effect on IGF status in premenopausal and no effect in postmenopausal subjects. Further studies are required to ascertain the role these dietary compounds may have to play in breast cancer prevention.

Sponsorship: The isoflavone and placebo supplements were kindly supplied by Novogen (North Ryde, Sydney, Australia). This study was supported by Action Against Breast Cancer registered charity number 1020967.