Can Tiny Amounts Of Poison Actually Be Good For You?
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Apple juice with 3apples
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The flap over whether there are harmful levels of arsenic in certain brands of apple juice as alleged by Dr. Mehmet Oz and Consumer Reports has elicited some bizarre commentary. Dr. Manny Alvarez, senior managing health editor of, said that arsenic levels in juice should not be tolerated at any level. “I don’t want to sound like an alarmist,” he said, “but just look at the growing levels of learning disabilities, autism spectrum disorders and other diseases that seem so prevalent today as compared to decades ago.”

He is an alarmist. Alvarez, a gynecologist, presented no evidence that arsenic has any harmful effects at the parts per billion levels at which it has been found in juices. His statement is irresponsible – especially since very low levels of toxins may actually be beneficial.

Since ancient times, it has been known that “the dose makes the poison.” In other words, the mere presence of a substance that is harmful at some level does not imply that small amounts are toxic or deleterious. All of the carbon-, potassium- and hydrogen-containing substances in our bodies contain radioisotopes of those elements, for example, and a cup of coffee contains hundreds of compounds known to be carcinogens at high levels. Other examples include a toxin called roquefortine, which is produced by a mold in … guess which French cheese; and carbon monoxide, which is lethal at high concentrations but is harmless if there is adequate ventilation and the exposure is low.
The releases of radiation related to the recent earthquake in Japan — and tsunami-related problems at Fukushima Daiichi nuclear power plant — elicited a lot of uninformed, misleading speculation. In fact, radiation at the levels detected posed a minimal threat to human health for anyone outside the immediate area of the nuclear power station. Those farther away who were exposed to low levels of radiation could have actually benefitted from it. This phenomenon is called hormesis, a non-linear dose-response relationship in which something such as a toxic heavy metal or ionizing radiation that is harmful at moderate to high doses may actually produce adaptive beneficial effects at low doses. In other words, we don’t see a completely linear relationship between the dose of the potential toxin and a deleterious effect; rather we see a curve that looks something like a check-mark with the amount of a substance or radiation on the horizontal axis and some measure of damage on the vertical axis.

Hormesis is a byproduct of evolution. From the beginnings of life on earth, organisms have been exposed to potentially harsh conditions, with individual cells commonly exposed to toxic substances such as chemicals and radiation. In order to avoid extinction, organisms developed complex mechanisms to cope with the environmental hazards, including altering the synthesis of nucleic acids and proteins to activate pathways that protect against or repair damage.

Biology professor Paul Z. Myers of the University of Minnesota describes an animal study in which fish embryos experience non-linear toxicity from alcohol, a toxin that causes severe deformities in zebrafish embryos at high doses and prolonged exposure. According to Myers, “I’ve done concentration series, where we give sets of embryos exposures at increasing concentrations, and we get a nice linear curve out of it: more alcohol leads to increasing frequency and severity of midline and branchial arch defects. With one exception: at low concentrations of about 0.5% alcohol, the treated embryos actually have reduced mortality rates relative to the controls, and no developmental anomalies.” Similarly, in experiments by Ronald Chesser, a radiation biologist at Texas Tech University, and his colleagues, mice exposed to low doses of radiation around Chernobyl for 10 to 45 days became resistant to damage from a higher, acute radiation dose delivered later in the lab.

Hormesis appears to result from a kind of overcompensation that explains the enhanced protective mechanisms elicited by small amounts of a toxin. That is, protective mechanisms are activated to a greater degree than would be necessary merely to neutralize the insult, resulting in a beneficial effect.

There are some epidemiological studies that have been touted as offering real-world illustrations of hormesis in humans, but they have palpable shortcomings. (You can read an excellent analysis of them by surgical oncologist David H. Gorski here.) His learned comments were stimulated by pundit Ann Coulter’s uninformed statements about the likely benefits from hormesis after the damage to the Fukushima Daiichi nuclear power plant. Coulter’s thesis: “With the terrible earthquake and resulting tsunami that have devastated Japan, the only good news is that anyone exposed to excess radiation from the nuclear power plants is now probably much less likely to get cancer.”

But that would only be true for radiation exposures at extremely low levels. Some of the workers who have ventured into the plant are likely to have received higher doses of radiation. Several workers actually suffered radiation burns from highly radioactive water that breached their protective footgear. And people (especially infants or children) in or near the facility exposed to high levels of Iodine-131 before they could be protected by prophylaxis might well have received cancer-inducing doses of the radioisotope to their thyroid gland.

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