The study, “does not accurately reflect current state of scientific knowledge,” and “fails to prove that the change in gene expression may translate into actual tumour growth,” said Bernard Deryckere, president of the European Natural Soyfood Manufacturers Association (ENSA).
“…this publication does nothing to challenge the well-documented view that soyfoods perfectly fit a healthy balanced diet for those with or without breast cancer.”
He said the featured results were not a primary endpoint of the study. “The two markers which indicate risk of tumour growth (cell growth, marker Ki67, and cell death, marker Cas3) are in fact the primary end point of the study. The analysis of changes in the expression of certain genes is a secondary outcome of the study.”
There were no significant differences between the soy and placebo groups, for these two primary endpoints, ENSA noted.
The study
The study suggested soy could raise levels of the isoflavone genistein which could enervate the FGFR2 gene that has been linked to cancer growth.
But lead scientist Dr Moshe Shike acknowledged ambiguity in the results that were derived from women with invasive breast cancer (adenocarcinoma).
“Soybeans contain the isoflavones genistein and daidzein,” Dr Shike said. “Genistein stimulates growth of estrogen-sensitive breast cancer (BC) cells and can block the inhibitory effects of tamoxifen. However, isoflavones have also been reported to decrease BC cell growth.”
The study also noted, “the clinical impact of the subtle changes in gene expression have not been examined.”
Deryckere pointed to work by the American Institute for Cancer Research (AICR) which found soy food was safe and furthermore, “has the potential to reduce breast cancer risk” including among breast cancer survivors.
The ENSA chief also wondered why a subset of 11 women had been selected within the study.
ENSA said the daily soy supplementation level of 51.6 g soy protein per day containing about 100 mg of isoflavones was very high - comparable to 1.7 litres of soy drink, “a portion hard to reach with normal soy food consumption.”