|
Here's a brief look at a most controversial subject: hormesis. The word comes from the Greek word for "excite." Hormesis is a positive influence from a small dose of a poison. Counterintuitive.
"Is Radiation Good for You? Or dioxin? Or arsenic?" is the caption of a titillating article, www.discover.com, Dec. '02. You may be thinking, "Is this a joke?" Not at all.
The article reveals the results of a detailed search for hormesis by University of Massachusetts toxicologist Edward Calabrese. "Poisons that injure or kill at high doses can have the opposite effect at low doses, he says, and the paradox holds true for every conceivable measure of health - growth, fertility, life span, and immune and mental function."
This is from a researcher who previously dogged polluters and made them live by tougher standards. But his search of tens of thousands of research papers showed that there are many documented examples of hormesis. "Worms exposed to excessive heat, rats given a little dioxin, mice and humans exposed to low-level radiation - all have lived longer, in controlled experiments, than they would have without the toxins."
Now, just this year, researchers have established a new refereed scientific journal to document this near-forgotten field of science (see www.belleonline.com). BELLE stands for Biological Effects of Low Level Exposures.
The mechanisms of hormesis are still little understood, though the results are impressive. Prof. Calabrese finds pharmacology a good model for the studies. After all, most pharmaceuticals are toxic at high dosages though they excite the body to react or over-react at proper doses. "Drugs typically lock onto receptors that signal the body to produce more of some needed chemical - a hormone say - or to remove it from circulation."
The usual criterion for toxicity is to assume it has a linear relationship with dose. So 10% of a toxic dose would be expected to produce 10% of the full toxic illness. But low doses often - not always - produce bodily reactions that stimulate a defense response (flu shots, e.g.).
I first viewed such data at a national health physics meeting. A noted researcher showed life expectancies for various groups of people exposed to radiation - from atomic bomb survivors to those living in homes with radon. At high doses the killing effect was clear. But at low doses, as someone in the audience pointed out, a positive effect seemed apparent. The speaker declined to comment. He knew.
Every toxin is not beneficial at low dosage and every person reacts differently. So caution is essential.
"While most scientists dismissed radiation treatments as quackery after World War II, a handful continued to test it as a way to prevent metastasis in cancer patients. In 1976 and 1979, two small clinical trials at Harvard found that low-dose radiation boosted four-year metastatic cancer survival rates from 40 to 70 percent and from 52 to 74 percent. Five years ago, a study at Tohoku University in Japan reported that patients who received low-dose radiation had an 84 percent chance of surviving for 12 years; those who didn't receive it had only a 50 percent chance of surviving nine years."
The Discover Magazine article and BELLE give many examples of significant hormesis benefits: low doses of mercury, carbon monoxide, arsenic, etc. that benefit.
A most impressive study of arsenic suggests that raising the national drinking water standard from 10 parts per billion to 50 would prevent 1000 cancer deaths per day!
Hormesis is not to be dismissed.
|
|
