Articles

Is Soy Dangerous?

Posted by Dan's Cancer Healing Story on

Author, Ralph W. Moss, PhD

SOY and TKIs

Does soy intake increase the risk of cardiotoxicity or even death among those taking the kind of drug known as a tyrosine kinase inhibitor (TKI)? These drugs include (listed alphabetically):

This prospect was raised by two scientists at the University of Colorado. The title of their paper was dramatic:

Interestingly, the authors state that soy isoflavones are themselves potent tyrosine kinase inhibitors (TKIs):

  • “Genistein, the most prevalent phytoestrogen in soy, is a potent tyrosine kinase inhibitor (TKI) that causes programmed cell death in many cell types. Chemotherapeutic TKIs limit cancer cell growth via the same mechanisms. However, TKIs such as sunitinib cause cardiotoxicity in a significant number of patients.”

So the implication is that patients should avoid the natural TKI, soy while taking pharmaceutical grade TKIs. This should come as great news to patients who are prescribed pharmaceutical-grade TKIs by their doctors. Not everyone wants to take the synthetic over the natural product. One important point of comparison is the price. The cost of a 150 mg tablet of Tarceva® (erlotinib) is $294.43 per pill, which comes to $8,832.76 per month, or $106,000 per year. The cost of a Soy Isoflavones 750 mg capsule is ten cents apiece! Since the label dose is one capsule per day, this could set you back $36 per year. $36 vs. $106,000, it’s your choice. Of course, the only time we are told that nutrients can function in exactly the same way as toxic and overpriced pharmaceuticals is when we are being warned away from them!

Also, these natural sources of TKIs have been consumed as a staple food in Asia for over 5,000 years. But synthetic TKIs, such as sunitinib (Sutent®), is anything but harmless. In fact, according to the above authors, “they cause cardiotoxicity in a significant number of patients.”

To return to the scary study, the mice in question were given a diet supplemented with 227 mg of genistein and 205 mg of a related compound, daidzein. But if you add the TKIs in soy to the TKIs in sunitinib you may get an increase in the toxicity (and presumably the effectiveness) of the drug.

The logical conclusion might be to utilize the safe natural forms of TKIs (such as soy isoflavones) and avoid the dangerous modern forms (such as Sutent®). But the authors, from the University of Colorado, Boulder, draw exactly the opposite conclusion:

But one commentator on this study stated,

In other words, the writers do not know that such an interaction will actually take place in people. They fear that it might, and so intend to eliminate soy from the diet on that basis.

Human Implications?

We often hear that soy is dangerous. This is based on a study of test animals in one Chinese laboratory experiment. But let’s do the math. Among American men, the average body weight is almost 200 pounds. Among American women, the average weight is 170 pounds. Thus, for an American man, the equivalent dose of genistein would have to be about 9,000 mg per day. For women, the equivalent dose would be about 7,740 mg.  But this dose is astronomically more than what human beings typically consume:

But we have to ask whether the effect in a rat receiving huge overdose of a phytochemical is likely to reflect what happens to a human being taking a relatively small dose on a daily basis? Of course not!

We certainly agree with the authors of an Italian paper that “considering the increasing interest and consumption of phytoestrogens, further studies about their interactions with drugs are urgently needed.” (edited) But such research should include the possibility that in a harmful interaction between a drug and an herb it is the drug that should be reconsidered and not the herb!

Leave a comment