I saw this press release today about genistein, a compound found in soy that has been promoted as a supplement that can prevent and treat cancer. A couple of red flags came up for me in the press release such as this;

The researchers found that a commercially available form of genistein called GCP was effective in killing canine lymphoid cells in a laboratory setting, and that GCP is "bioavailable" in canines - meaning it is absorbed into the bloodstream where it can affect cancer cells in the body. The researchers hope that their findings will lead to the use of GCP for their canine patients in conjunction with traditional cancer treatments like chemotherapy.

This by itself sounds OK, but it does not mean that the concentrations of the compound which killed the cancer cells in vitro are safe or even achievable in dogs or humans. Then comes a claim that humans use genistein as a complementary cancer therapy;

"Humans have been using soy in conjunction with traditional chemotherapy for some time as a chemo potentiator," Suter says. "This means that the GCP makes the chemotherapy work more efficiently and faster, which translates to less stress on the patient and less money spent on chemotherapy."

That is a huge leap from killing cells in a petri dish, and is not substantiated by much evidence. Indeed Genistein is know to have estrogenic effects and may actually make certain types of cancer, especially breast cancer grow more quickly.

Finally the biggest red flag in the entire press release was the last paragraph;

"Since GCP is a dietary supplement, it is harmless to patients," he adds. "Plus it's inexpensive and easy to administer in a pill form. There's really no downside here."

A product such as this is not harmless to patients, and saying so could be dangerous to patients, human or animal, who have estrogen responsive tumors. There most definitely is a downside. They have also not established any toxic effects in living animals or humans of the concentrations required to kill canine lymphoma cells.

The paper this press release is referring to was published in the February 15, 2009 issue of Clinical Cancer Research. This paper is a report of a preliminary study of Genistein that was evaluating it's effect on one specific cell type, and they were unable to achieve high enough concentrations in dogs in a 72-hour dose escalation study. The study showed a potential effect for the compound for certain cancers, but there is still a long way to go before the correct dosage is identified and genestein is proven to be a safe and effective treatment. The author's conclusions were much more modest and reasonable than the press release indicated;

The results of these studies support the notion that canine high-grade B-cell lymphoma may represent a relevant large animal model of human non-Hodgkin's lymphoma to investigate the utility of GCP in chemopreventive and/or treatment strategies that may serve as a prelude to human clinical lymphoma trials.

The press release is misleading and could be dangerous if people read it and decide that this over-the-counter product is completely safe and useful for treating or preventing any type of cancer. This is an excellent example of why dietary supplements should be regulated similarly to drugs, and not declared "harmless".