The study, published in the journal Nutrition and Cancer, reports that supplementation with 30 mg of synthetic genistein daily resulted in a 7.8% decrease in levels of blood serum prostate specific antigen (PSA) in a matter of weeks. The researchers, from the University of Oslo, added that PSA levels in the placebo arm of the double blind trial increased by 4.4% in the same time.
“Genistein at a dose that can be easily obtained from a diet rich in soy reduced the level of serum PSA in patients with localized prostate cancer, without any effects on hormones ... It was well tolerated and had a beneficial effect on blood cholesterol,” said the researchers, led by Bato Lazerevic of Oslo University Hospital, Norway.
“Our results indicate a possible therapeutic effect by genistein in early CaP, producing a borderline significant serum PSA reduction and normalization of PSA expression in malignant prostate tissue,” they added.
The research, which used the synthetic genistein supplement geniVida (provided by DSM), revealed that plasma levels of total genistein in the supplement arm of the trial were significantly increased “and comparable to high consumers of soybean products.”
The researchers said that the study was performed at Oslo University Hospital, Norway, was solely financed by official grants from the hospital.
Study details
Lazerevic and colleagues conducted a placebo-controlled, randomized, double blind study in 47 men with early prostate cancer and elevated PSA levels.
They noted that although PSA is present in small quantities in the serum of men with healthy prostates, it tends to rise in the presence of prostate disorders, including prostate cancer.
The researchers reported that supplementation with 30mg of geniVida over a period of three to six weeks, was shown to reduce PSA values in serum. In addition, the supplement was seen to lower blood cholesterol levels.
The daily dose of geniVida was also shown to be well tolerated, with no effects on hormone levels, such as testosterone.
“Our results indicate that genistein normalize the intra-cellular expression of PSA in CaP epithelial cells. Furthermore, genistein was shown to reduce the level of PSA in serum,” said Lazerevic and co-workers.
“The molecular mechanisms behind this discrepancy are not known but indicate that genistein also affects the secretion of PSA,” they added.
DSM said that the findings of the study could help to explain the reduced risk of prostate cancer in men consuming a diet high in soy products, and highlights the potential benefit of a 30mg per day geniVida dietary supplement for men.
However, the researchers noted that due to the low number of participants in the current study, “the clinical significance of the finding is questionable, and a clarification requires further studies.”
“The number of patients in our study is too small to conclude on any effects by genistein on tumor grade or focality,” they said.
Source: Nutrition and Cancer
Published online ahead of print, doi: 10.1080/01635581.2011.582221
“Efficacy and Safety of Short-Term Genistein Intervention in Patients with Localized Prostate Cancer Prior to Radical Prostatectomy: A Randomized, Placebo-Controlled, Double-Blind Phase 2 Clinical Trial”
Authors: B. Lazarevic, G. Boezelijn, L.M. Diep, K. Kvernrod, O. Ogren et al