Soy and cancer: an uncertain and limited preventive role , according to a U.S. report

The role of soy in the prevention of various diseases, especially cancer, is limited and uncertain , according to the findings of a U.S. government report , reported in an article published in the "Journal of the National Cancer Institute " ( JNCI ) .
Soy and Health: bad or not ?
" A government report concluded that the evidence of benefit of soy in the prevention of various diseases including cancer , was uncertain and limited , despite numerous studies have focused on the topic ," said Damaris Christensen, in the journal JNCI .

* The government report , funded by the U.S. Agency for Health Research and Quality ( Agency for Healthcare Research and Quality , AHRQ) , analyzed 178 previous studies focused on soy foods , soy milk and food supplements including soy isoflavone extracts . The researchers studied the effects of soy on various diseases and functions of the body : cancer , kidney disease , cardiovascular disease , endocrine function , reproduction, bone metabolism etc. .

The authors have shown that consumption of soy protein provides small benefits in terms of reducing the risk of heart disease by reducing low-density lipoprotein (LDL) or "bad cholesterol" . In addition , isoflavones found in soy reduce the frequency of hot flashes during menopause. On other diseases , including cancer, no result is proved successful , because " a small number of studies, poor quality and they are too short ," said a press summary of the report the AHRQ .

Several clinical studies have examined , in people with no history of cancer, the effects of soy consumption on the level of biomarkers associated with cancer : expression of receptors for estrogen and progesterone, prolactin concentration , PSA level and cortisol .

No significant effect of soy in cancer prevention
But none of these biomarkers have been clearly associated with a risk of cancer, " no study has been able to provide significant evidence of a beneficial effect of soy in the prevention of cancer ," said the author of the study , Ethan Balk , New England Medical Center in Boston ( USA) .

Conducting more rigorous studies nevertheless seems difficult due to the low number of validated biomarkers for cancer, the time required for development of the disease and the difficulty associated with the call participants a special diet over a long period .

" Experimental studies in vitro and population studies have shown an association between soy and a reduced risk of cancer," recalled Karen Collins , however , a nutritionist at the American Institute for Cancer Research in Washington.

So many epidemiological studies have suggested that high consumers of soy have a lower risk of breast , colon , endometrial and prostate cancer compared with the general population.

However, the scientists hope that further studies will better define the role of soy in preventing and treating cancer .