Fruits and Vegetables Are Trying to Kill You

Thursday, September 4th, 2014

Vegetable KnightFruits and vegetables are trying to kill you — and that only makes you stronger:

That stress comes courtesy of trace amounts of naturally occurring pesticides and anti-grazing compounds. You already know these substances as the hot flavors in spices, the mouth-puckering tannins in wines, or the stink of Brussels sprouts. They are the antibacterials, antifungals, and grazing deterrents of the plant world. In the right amount, these slightly noxious substances, which help plants survive, may leave you stronger.


The nicotine that we so prize in tobacco slows grazing insects. Beans contain lectins, which defend against insects. Garlic’s umami-like flavor comes from allicin, a powerful antifungal. These “antifeedants” have evolved in part to dissuade would-be grazers, like us.

Mattson and his colleagues say these plant “biopesticides” work on us like hormetic stressors. Our bodies recognize them as slightly toxic, and we respond with an ancient detoxification process aimed at breaking them down and flushing them out.

Consider fresh broccoli sprouts. Like other cruciferous vegetables, they contain an antifeedant called sulforaphane. Because sulforaphane is a mild oxidant, we should, according to old ideas about the dangers of oxidants, avoid its consumption. Yet studies have shown that eating vegetables with sulforaphane reduces oxidative stress.

When sulforaphane enters your blood stream, it triggers release in your cells of a protein called Nrf2. This protein, called by some the “master regulator” of aging, then activates over 200 genes. They include genes that produce antioxidants, enzymes to metabolize toxins, proteins to flush out heavy metals, and factors that enhance tumor suppression, among other important health-promoting functions.

In theory, after encountering this humble antifeedant in your dinner, your body ends up better prepared for encounters with toxins, pro-oxidants from both outside and within your body, immune insults, and other challenges that might otherwise cause harm. By “massaging” your genome just so, sulforaphane may increase your resistance to disease.

In a study on Type 2 diabetics, broccoli-sprout powder lowered triglyceride levels. High triglycerides, a lipid, are associated with an increased risk of heart disease and stroke. Lowering abnormally elevated triglycerides may lessen the risk of these disorders. In another intervention, consuming broccoli sprout powder reduced oxidative stress in volunteers’ upper airways, likely by increasing production of native antioxidants. In theory, that might ameliorate asthmatics’ symptoms.

Elevated free radicals and oxidative stress are routinely observed in diseases like cancer and dementia. And in these instances, they probably contribute to degeneration. But they may not be the root cause of disease. According to Mattson, the primary dysfunction may have occurred earlier with, say, a creeping inability to produce native antioxidants when needed, and a lack of cellular conditioning generally.

Mattson calls this the “couch potato” problem. Absent regular hormetic stresses, including exercise and stimulation by plant antifeedants, “cells become complacent,” he says. “Their intrinsic defenses are down-regulated.” Metabolism works less efficiently. Insulin resistance sets in. We become less able to manage pro-oxidant threats. Nothing works as well as it could. And this mounting dysfunction increases the risk for a degenerative disease.

Implicit in the research is a new indictment of the Western diet. Not only do highly refined foods present tremendous caloric excess, they lack these salutary signals from the plant world—“signals that challenge,” Mattson says. Those signals might otherwise condition our cells in a way that prevents disease.

Another variant of the hormetic idea holds that our ability to receive signals from plants isn’t reactive and defensive but, in fact, proactive. We’re not protecting ourselves from biopesticides so much as sensing plants’ stress levels in our food.

Harvard scientist David Sinclair and his colleague Konrad Howitz call this xenohormesis: benefitting from the stress of others. Many phytonutrients trigger the same few cellular responses linked to longevity in eukaryotic organisms, from yeasts to humans. Years of research on Nrf2 in rodents suggest that activating this protein increases expression of hundreds of health-promoting genes, including those involved in detoxification, antioxidant production, control of inflammation, and tumor suppression.”


  1. Alrenous says:

    By “massaging” your genome just so, sulforaphane may increase your resistance to disease.

    Eurgh. Mattson, you’re not smarter than evolution.

    It’s not that being too sanitized is bad for you per se, it’s because the genome doesn’t expect it. The body saves the health-promoting processes for poisonous insults, because it can’t run them all the time.

    Obviously xenohormesis is also happening, not happening instead of. We share, what, 50% of our genes with plants? Something like that? If one of them is a stress signal, then proof over: xenohormesis happens.

  2. Harold says:

    To state the obvious: while vegetables don’t “want” to be eaten, fruits do — at least by the types of animal which will spread their seeds.

    Many years ago the feature article in an issue of The New Scientist was devoted to this topic. In the article it was argued that by virtue of being chemically potent, toxins would be prime targets for evolution to co-opt and put to beneficial uses.

  3. Harold says:

    The article I mentioned above was probably by Colin Tudge. From his site:

    Some of these toxins are merely repellent, like tannins; and others are frankly poisonous. I suggest that the animals in turn have evolved mechanisms that help them — including us — not merely to cope with the toxins but eventually to make use of them.

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