For the first example below, a conflict of interest (CoI) isn't literally declared, but seems to be implied in the funding section. Additionally, the majority of the studies included have a similar CoI. For the second example, again with funding there seems to be partial CoI. Is there any credence to studies funded from food industry sources not be tolerated?
2009 Effects of soy protein and isoflavones on circulating hormone concentrations in pre- and post-menopausal women: a systematic review and meta-analysis
forty-seven studies (11 of pre-, 35 of post- and 1 of perimenopausal women)
isoflavones – soy phytoestrogen (which mimics estrogen in the body, beneficial in combating symptoms and conditions caused by estrogen deficiency)
To our knowledge, this is the first systematic review and meta-analysis to compare the endocrine effects of different soy products on hormonal status in women at different lifecycle stages. It provides weak evidence that soy and isoflavones decrease FSH and LH in premenopausal women, and a suggestion that they may increase estradiol [estrogen steroid hormone and the major female sex hormone] in post-menopausal women.
Twenty studies declared a funding source with a commercial interest in the study results; 25 did not report industry funding; and 2 were unclear.
This work was partially funded by the Soy Nutrition Institute, Inc., St Louis, MO, USA. M.J.M. consults for companies that manufacture and/or sell soyfoods, soy protein and isoflavone supplements and is a Scientific Advisory Board Member of the Soy Nutrition Institute.
Extra for 1
Letters to the Editor
These estrone levels are important because in the meta-analysis of Hooper et al. (2009) […] evidence indicates that isoflavones will not increase breast cancer risk in healthy women or worsen the survival of breast cancer patients.
2010 Clinical studies show no effects of soy protein or isoflavones on reproductive hormones in men: results of a meta-analysis
The results of this meta-analysis indicate that neither soy protein nor isoflavones affect reproductive hormone concentrations in men regardless of age or cancer status. Although the duration of most trials was <6 months, soy protein and isoflavone intake greatly exceeded typical dietary Japanese intake 2. These results suggest that consumption of soy foods or isoflavone supplements would not result in the adverse effects associated with lower T levels .
J.H.-R while a doctoral student at the University of Minnesota received some minor funding from the Soy Nutrition Institute for work on this manuscript. G.V. has nothing to disclose. S.J.D. has nothing to disclose. W.R.P. has nothing to disclose. M.S.K. occasionally consults for the Solae Company. M.J.M. regularly consults for companies in the soy food industry.
Supplement for 2
2011 Re: Clinical Studies Show No Effects of Soy Protein or Isoflavones on Reproductive Hormones in Men: Results of a Meta-Analysis
The authors performed a meta-analysis of the available literature, and conclude that soy protein or isoflavone intake had no detectable effect on free or total testosterone, sex hormone binding globulin or free androgen index. While the study does not include measurements of semen or paternity, and androgenic status does not tell the whole story of male fertility, this meta-analysis is a step in the direction that soy products are unlikely to be harmful to male reproduction.