Plants do not have the option of fleeing from predators. As a consequence, they have developed an elaborate set of chemical defenses to ward off insects and other creatures that want to make them into a meal.
Toxic chemicals that plants use against predators are consumed by us at low levels in fruits and vegetables. Exposure to these substances causes a mild stress reaction that lends resilience to cells in our bodies. Adaptation to these stresses, a process called hormesis, accounts for a number of health benefits, including protection against brain disorders we receive from eating broccoli and blueberries. Hormesis means that positive benefits occur when consumption is in low to modest amounts but becomes increasingly noxious at high levels. (1)
About 99.999 percent of all pesticides in the human diet are natural pesticides from plants. Tens of thousands of these natural pesticides have been discovered and every species of plant contains its own set of different toxins, usually a few dozen. Bruce Ames and colleagues at the University of California Berkeley estimate that Americans eat about 1,500 mg per person per day of natural pesticides, which is 10,000 times more than we eat of synthetic residues. They also estimate that a person ingests annually about 5,000 to 10,000 different natural pesticides and their breakdown products. (2)
When asked why eating lots of fruits and vegetables can improve health many people will point to the antioxidants in these foods. But the antioxidants story is not quite so simple. The emerging answer to why fruits and vegetables promote health has much to do with the strategies that plants have evolved over millions of years to protect themselves from pests. It is not that antioxidants have completely faded from the picture. Rather, the biochemical processes set in motion by hormetic stress seem to control when antioxidants are available to be used by brain cells, reports Mark Mattson. (1)
Further, understanding hormesis's effects may even provide new ways to prevent or treat some of the most devastating brain diseases, including Alzheimer's Parkinson's and stroke. (1)
Should we be concerned about these chemicals?
A recent analysis published in the International Journal of Food Contamination shows that pesticide residues in food are at levels far below those that would pose any health concern. (3)
In addition a research paper by University of Texas Professor Frank Cross highlights findings from a number of studies showing that the EPA's risk estimates overstate pesticide exposure by as much as 99,000 to 463,000 times actual exposure. As a result, standards are actually tens of thousands—maybe hundred of thousands—times more stringent than necessary to protect public health. (4)
So with hormesis benefits suggested by Mark Mattson and the low levels we ingest, we should not be concerned. Also, remember the words of Paracelsus, the father of toxicology, who told us 500 years ago, “All substances are poison, there is none which is not a poison, the right dose makes the difference between a poison and a remedy.”
Jack Dini
Livermore, CA
References
1. Mark P. Mattson, “What doesn't kill you,” Scientific American, 313, 41, July 2015
2. B. N. Ames and L. S. Gold, “Paracelsus to parascience: the environmental cancer distraction,” Mutation Research, 447, 3, 2000
3. Carl K. Winter, “Chronic dietary exposure to pesticide residues in the United States,” International Journal of Food Communication, 2:11, July 10, 2015
4. Angela Logomasini, “The dangerous demonization of our food,” Competitive Enterprise Institute, August 4, 2012
