The health effects of antioxidants came up recently because a study found that organic food has more of them. Now science writer Moises Velasquez-Manoff has a fascinating story on a theory that upends conventional wisdom about antioxidants.

The original idea was that antioxidants were good because they sopped up molecules called “reactive oxygen species” (ROS) that are released by stress and bounce around cells, wrecking havoc. This new theory suggests that we need the stress, and it’s our bodies’ reaction to that (producing our own internal antioxidants) that really does us good.

In other words, it’s the whole system that’s important — piling on more antioxidants from outside alone basically accomplishes nothing. Here’s Velasquez-Manoff:

Exercise accelerates the burning of fuel by your cells. If you peer into muscles after a jog, you’ll see a relative excess of those supposedly dangerous ROS — exhaust spewed from our cellular furnaces, the mitochondria. If you examine the same muscle some time after a run, however, you’ll find those ROS gone. In their place you’ll see an abundance of native antioxidants. That’s because, post-exercise, the muscle cells respond to the oxidative stress by boosting production of native antioxidants. Those antioxidants, amped up to protect against the oxidant threat of yesterday’s exercise, now also protect against other ambient oxidant dangers.

Contrary to the ROS dogma, [scientist Michael] Ristow realized, the signal of stress conveyed by the ROS during exercise was essential to this call-and-response between mitochondria and the cells that housed them. To improve health, he figured, perhaps we shouldn’t neutralize ROS so much as increase them in a way that mimicked what happened in exercise. That would boost native antioxidants, improve insulin sensitivity, and increase overall resilience.

But we also see a true health benefit from eating plants. This may be because Fruits and Vegetables Are Trying to Kill You — to quote the title of Velasquez-Manoff’s piece. That is: The toxins produced by veggies stimulate the same kind of stress response as exercise and give your system a work out.

Obviously it’s still too early to make specific dietary recommendations based on this thinking (though someone will be trying to turn this into a lucrative diet fad in 5, 4, 3 …). I still stick with my don’t worry, be happy, eat veggies theory of nutrition. But check out this fascinating essay, and glory in the weirdness of the notion that we might just need toxins to keep us healthy.