For Mice and Men, Dose Doth Make the Poison


Image by ky_olsen via Flickr

My latest Green Chain column in today’s Lake County Record-Bee:

Every day, I make my wife and myself a cup of coffee. Should I be arrested for spousal abuse? I am serving her a phenol-laced liquid, containing 826 volatile chemical substances, 16 of which are known by the state of California to cause cancer. One cup of this hot and astoundingly delicious pick-me-up contains at least 10 milligrams of known carcinogens including: caffeic acid, catechol, furfural, hydroquinone and hydrogen peroxide.[1]

In one cup, my wife and I take in more carcinogens than we would from one year’s worth of pesticide residue on fruits and vegetables. [2]

Let’s be clear: we are talking about food from plants, not just coffee; you can find naturally occurring carcinogenic chemicals in all kinds of food. Honey contains benzyl acetate. Orange juice and black peppers harbor d-limonene. Brussels sprouts, cabbages, cauliflower, collard greens, and horseradishes contain allyl isothiocyanate. And neochlorogenic acid lurks in apples, apricots, broccoli, Brussels sprouts, cabbage, cherries, coffee, kale, peaches, and pears. These are but a few; the list goes on. Whether the plant was grown without any synthetic pesticides or fertilizers is not the issue.

Just as some plants grow spines to hinder grazing, plants produce their own chemical pesticides, to combat predators and competitors. No human put them there. These natural pesticides help the plant ward off insects and animals and even other plants. That is why you will find chemicals such as allyl isothiocyanate and/or neochlorogenic acid in apples, apricots, broccoli, Brussels sprouts, cabbages, cherries, coffee, collard greens, horseradishes, kale, peaches, and pears. The plants themselves developed the chemicals.

Researchers apply the Ames test to determine if a chemical has mutagenic (potentially cancer causing) properties. Developed in the 1970s, the Ames test doses bacteria, which reproduce rapidly, with the chemical being tested to see if mutations result. At that time scientists assumed only a small number of substances would cause cancer. Instead about half of the chemicals tested, whether man-made or natural, turn up positive as being rodent carcinogens. [3] So, Dr. Ames (the man who developed the cancer tests) notes we need to “rethink what we’re doing with animal cancer testing.”

“We’re eating natural pesticides,” Dr. Ames points out, “And we eat roughly 1,500 milligrams of them per day. We eat 0.09 milligrams of synthetic pesticide residues.” [4] In other words, each day we eat over 16,600 times more natural pesticide than synthetic.

Exposure to pesticides isn’t the same as toxicity because the toxicity of a substance depends on the amount. Even that chemical which our life needs, dihydrogen oxide (H2O, water), can be poisonous if you drink too much of it. As Paracelsus, the so-called father of toxicology, noted, “All things are poison, and nothing is without poison; only the dose permits something not to be poisonous.” [5] Or, as it’s paraphrased, “Dose makes the poison.”

About a month ago in the original Peet’s Coffeehouse in Berkeley, I stood behind a woman quizzing the barista if Peet’s used chemicals to produce its decaffeinated coffee. (Never mind that the Swiss Water Process uses water, a chemical composed of two hydrogen atoms bonded to one oxygen atom.) The barista assured her the levels of the chemicals used were too low to be of concern (“Dose makes the poison”). I pointed out that coffee already has 16 chemicals known to be carcinogenic; why worry about the minuscule amount of synthetic ones. She frowned at me. I think her next purchase was to be a chemical-free chemistry set for her grandson. (You think I made that up? “Chemistry 60” with its “60 fun activities with no chemicals” costs $21.88 on [6]. Don’t the makers know that water is…oh never mind.)

The moral of this story is eating fruits and vegetables that have many of these chemicals is much healthier for you than avoiding them. The jury remains deadlocked on the coffee.

[1] Ames, Bruce N., M Profet, AND Lois Swirsky Gold, Proceedings of the National Academy of Sciences, Vol. 87, pp. 7777-7781, October 1990, Medical Sciences, “Dietary pesticides (99.99% all natural)

[2] Dr. Bruce Ames, Reason Magazine, Of Mice and Men (

[3] Ames writes in, “The main rule in toxicology is that ‘the dose makes the poison‘. At some level, every chemical becomes toxic, but there are safe levels below that.

“In contrast to that rule, a scientific consensus evolved in the 1970s that we should treat carcinogens differently, that we should assume that even low doses might cause cancer, even though we lacked the methods for measuring carcinogenic effects at low levels. In large part, this assumption was based on the idea that mutagens – chemicals that cause changes in DNA – are carcinogens and that the risk of mutations was directly related to the number of mutagens introduced into a cell.

It was also assumed that:

1. only a small proportion of chemicals would have carcinogenic potential;

2. testing at a high dose would not produce a carcinogenic effect unique to the high dose; and

3. carcinogens were likely to be synthetic industrial chemicals.

It is time to take account of information indicating that all three assumptions are wrong.”

[4] Ibid



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