Beyond Animal Research
By Jonathan Balcombe, Ph.D.
Mice on Soy
A recent study from the University of Colorado made headlines when it was reported that a soy-based diet worsened heart disease in male mice carrying a mutation for hypertrophic cardiomyopathy (HCM).1 In humans, HCM is a congenital heart disease involving abnormal thickening of the left ventricular walls; it is the leading cause of death in young athletes, and affects about one in 500 people.
There is a considerable body of published research concerning soy’s benefits to human health, including cancer prevention,2,3,4 lower blood pressure5 and cholesterol,6,7 and improved bone density.8,9 Even skeptical nutrition experts say that soy is beneficial if for no other reason than that it displaces less healthy fare like hamburgers and hot dogs.10 Since 1999 the U.S. Food and Drug Administration has allowed companies to tout a cholesterol-lowering benefit on soy-based food labels.
The mice in the Colorado study had to endure a harmful genetic manipulation, barren cages (which, incidentally, afford scant opportunities for exercise), and a host of painful and stressful procedures: physical restraint, abdominal injections, removal of ovaries or testicles, surgical implantation of hormone pellets into the neck, and killing (method not divulged). The question bears asking: Why are mice subjected to all this to try to shed light on effects to human health that could be addressed with reliable and ethical human clinical investigations? It adds insult to injury that the study was then published in The Journal of Clinical Investigation. There is nothing “clinical” about this study.
A dietary analysis of HCM patients would reveal any possible interaction with soy, avoiding feeble extrapolations from mice to men. My search of the PubMed database suggests that little or no effort has yet been made to address clinically any relationship between dietary soy and HCM.
The reason the University of Colorado study made a media splash is not because it makes a valuable contribution to human medicine—though sadly that is the impression many readers may get. Rather, it is that the results contradict well-established benefits of soy in humans. The lead author on the mouse study commented to the press that “I don’t think normal, healthy people should be alarmed by the results of this study.” What we should be alarmed at is that this sort of thing is still regarded as useful, ethical science.
1. Stauffer BL, Konhilas JP, Luczak ED, Leinwand LA. Soy diet worsens heart disease in mice. J Clin Invest. 2006;116:209-216
2. Dalais FS, Meliala A, Wattanapenpaiboon N, Frydenberg M, Suter DA, Thomson WK, Wahlqvist ML. Effects of a diet rich in phytoestrogens on prostate-specific antigen and sex hormones in men diagnosed with prostate cancer. Urology. 2004;64:510-515.
3. Xu WH , Zheng W, Xiang YB, et al. Soya food intake and risk of endometrial cancer among Chinese women in Shanghai: population based case-control study. BMJ. 2004;328:1285.
4. Jakes RW, Duffy SW, Ng FC, et al. Mammographic parenchymal patterns and self-reported soy intake in Singapore Chinese women. Cancer Epidemiol Biomarkers Prev. 2002;11:608-613.
5. Yang G, Shu XO, Jin F, et al. Longitudinal study of soy food intake and blood pressure among middle-aged and elderly Chinese women. Am J Clin Nutr. 2005;81:1012-1017.
6. Sirtori CR, Lovati MR, Manzoni C, Gianazza E, Bondioli A, Staels B & Auwerx J. Reduction of serum cholesterol by soy proteins: clinical experience and potential molecular mechanisms. Nutr Metab Cardiovasc Diseases. 1998;8:334–340.
7. Sirtori CR, Pazzucconi F, Colombo L, Battistin P, Bondioli A & Descheemaeker K. Double-blind study of the addition of high-protein soya milk v. cows’ milk to the diet of patients with severe hypercholesterolaemia and resistance to or intolerance of statins. Brit J Nutr. 1999;82:91–96.
8. Ho SC, Chan SG, Yi Q, Wong E, Leung PC. Soy intake and the maintenance of peak bone mass in Hong Kong Chinese women. J Bone Miner Res. 2001;16:1363-1369.
9. Spence LA et al. 2002. Effects of Soy isoflavones on calcium metabolism in postmenopausal women. J Nutr. 2002;132:581S.
10. Stengle J. Heart association derides soy claims. Yahoo!News Jan. 23, 2006. Available from: http://news.yahoo.com/s/ap/20060124/ap_on_he_me/fit_soy_health.