Positive Health Online

Abstract

MCLAUGHLIN and COLLEAGUES, The Ohio State University, Comprehensive Cancer Center, Columbus, OH 43210, USA. mclaugj1@gmail.com conducted a study to determine whether dietary modifications with tomato products and/or a soy supplement affected circulating levels of insulin-like growth factor (IGF)-1 and other markers of cell signalling in postmenopausal women at risk for developing breast cancer.

Background

To determine whether dietary modifications with tomato products and/or a soy supplement affected circulating levels of insulin-like growth factor (IGF)-1 and other markers of cell signalling in postmenopausal women at risk for developing breast cancer.

Methodology

Eligible and consented postmenopausal women at high risk for developing breast cancer were enrolled in a 26-week, two-arm (tomato and soy, 10 weeks each) longitudinal dietary intervention study in which each woman served as her own control. Changes in biochemical endpoints including IGF-I, IGF-binding protein (IGFBP)-3, estradiol, sex hormone-binding globulin (SHBG), C-peptide, and insulin were measured for each intervention arm. Carotenoid and isoflavone levels were measured to assess adherence.

Results

Significant increases in carotenoid and isoflavone levels during the tomato and soy study arms, respectively, suggested that women were adherent to both arms of the intervention. The tomato-rich diet had little effect on cell-signalling biomarkers previously associated with breast cancer risk. However, results of the soy intervention showed that concentrations of IGF-I and IGFBP-3 increased by 21.6 and 154.7 mumol/L, respectively (P = 0.001 for both) and SHBG decreased by 5.4 mumol/L (P < 0.001) after consumption of the soy protein supplement. Increased soy protein intake may lead to small, but significant, increases in IGF-I and IGFBP-3. Soy consumption also led to a significant decrease in SHBG, which has been hypothesized to promote, rather than prevent, cancer growth. Previous epidemiologic studies, however, have confirmed protective effect of soy on breast cancer.

Conclusion

Additional investigation about the effect of soy on breast cancer risk and its mechanism of action is warranted.

References

McLaughlin JM, Olivo-Marston S, Vitolins MZ, Bittoni M, Reeves KW, Degraffinreid CR, Schwartz SJ, Clinton SK and Paskett ED. Effects of tomato- and soy-rich diets on the IGF-I hormonal network: a crossover study of postmenopausal women at high risk for breast cancer. Cancer Prevention Research. 4(5):702-10. May 2011.