Poultry-growing literature has recommended Benadryl to reduce anxiety among chickens, apparently because stressed chickens have tougher meat and grow more slowly. Tylenol and Prozac presumably serve the same purpose.

Researchers found that most feather-meal samples contained caffeine. It turns out that chickens are sometimes fed coffee pulp and green tea powder to keep them awake so that they can spend more time eating. (Is that why they need the Benadryl, to calm them down?)

The other peer-reviewed study, reported in a journal called Science of the Total Environment, found arsenic in every sample of feather meal tested. Almost 9 in 10 broiler chickens in the United States had been fed arsenic, according to a 2011 industry estimate.

These findings will surprise some poultry farmers because even they often don’t know what chemicals they feed their birds. Huge food companies require farmers to use a proprietary food mix, and the farmer typically doesn’t know exactly what is in it. I asked the United States Poultry and Egg Association for comment, but it said that it had not seen the studies and had nothing more to say.

What does all this mean for consumers? The study looked only at feathers, not meat, so we don’t know exactly what chemicals reach the plate, or at what levels. The uncertainties are enormous, but I asked Nachman about the food he buys for his own family. “I’ve been studying food-animal production for some time, and the more I study, the more I’m drawn to organic,” he said. “We buy organic.”

I’m the same. I used to be skeptical of organic, but the more reporting I do on our food supply, the more I want my own family eating organic — just to be safe.